Supercritical Fluids - Free Essay Example

Sample details Pages: 29 Words: 8556 Downloads: 6 Date added: 2017/06/26 Category Statistics Essay Did you like this example? I. ABSTRACT (ENGLISH) The experimental determination of the yield of pyrethrins from the Chrysanthemum cinerariaefolium flower is usually carried out with Chromatographic Techniques. A lot of methods about this have been reported over the years [Z-M. ChertY.H. Wang (1996)]. These include HPLC [13 -22], GC [22-26] and SFC [B. Wenclawiak, A. Otterbach (2000) methods. Because of the need for only analyzing the pyrethrins (not reporting for the individual six pyrethrins but analyzing for total pyrethrins), GC was selected as a method of choice. The yield reported from literature usually ranges from 0.91 1.30% of the dry weight [Kolak et al., 1999], 0.60 0.79% [Bakari (2005)], 0.75 1.04% [Bhat (1995)], Don’t waste time! Our writers will create an original "Supercritical Fluids" essay for you Create order 1.80 2.50% [Morris et al. (2005), Bhat and Menary, (1984); Fulton, (1999)], 0.50 2.0% [Kiriamiti et al. (2003)], and 0.90 1.50% [Pandita and Sharma (1990)]. However, Casida and Quistad (1995) in their book: Pyrethrum Flowers: Production, Chemistry, Toxicology and Uses (pp123-193), states that it is possible to obtain pyrethrin yield of 3.0% or even more. We obtained, with hexane extraction in a water bath at controlled temperatures and vigorous stirring (with three magnetic stirrers at a speed of 30rpm); pyrethrin yields varying from 0.85 3.76% of the dry weight. To our knowledge, this is the first time to report of pyrethrins yield above 3% envisaged by Casida and Quistad. Key words: Supercritical Fluid Extraction, Supercritical Carbon Dioxide, Pyrethrins, Solvent extraction, Extraction Yield, Gas Chromatography, Pyrethrin concrete, Crude Hexane Extract. III. ABBREVIATIONS AND SYMBOLS GC Gas Chromatography HPLC High Performance Liquid Chromatography SFC Supercritical Fluid Chromatography SCF Supercritical Fluid SCFs Supercritical Fluids SFE Supercritical Fluid Extraction SC-CO2 Supercritical Carbon Dioxide SC Supercritical CO2 Carbon Dioxide et al et alii (and others) pp page % percentage CHE crude hexane extracts BC Before Christ PY pyrethrin PYI pyrethrin 1 PYII pyrethrin 2 C1 cinerin 1 C2 cinerin 2 J1 Jasmolin 1 J2 Jasmolin 2 P1 pyrethrin 1 P2 Pyrethrin 2 A1 area of pyrethrins 1 A2 area of pyrethrins 2 WHO world health organization Fig Pc critical pressure Tc critical Temperature Cp critical point Cm centimeters ~ Approximately oC degree centigrade MPa mega Pascal FID flame ionization detector n-hexane normal hexane mL milliliters /min per minute Soc. Society Eds editions Sci. Science m meters mm millimeters tR retention time k Retention factor R2 Pearson correlation coefficient LOQ limit of quantification LOL limit of linearity LOD limit of detection BOD beyond limit of detection IS internal standard k response factor f relative response factor m micro meters L micro liters rpm revolutions per minute 1.0. CHAPTER 1: Introduction and Literature Review 1.1.0 Supercritical Fluids (SCF) When a fluid is forced to a pressure and temperature above its critical point (Fig. 1), it becomes a supercritical fluid. Under these conditions, various properties of the fluid are placed between those of a gas and those of a liquid. The supercritical state of a fluid is thus defined as one whose liquid and gas are indistinguishable from each other, or one in which the fluid is compressible (i.e. behaves as a gas) while having a density similar to a liquid and, therefore, similar solvating power. Their low viscosity and relatively high diffusivity gives them better transport properties than liquids, can diffuses easily through solid materials and hence faster and better extraction yields. The most important properties of a SCF are its density, viscosity, diffusivity, heat capacity and thermal conductivity. Higher densities of SCFs contribute to greater solubilization of compounds, while low viscosities enable Easy penetration into solids and facilitate flow with fewer hindrances. Manipulating the temperature and pressure above the critical points affects the properties of SCFs and enhances their ability to penetrate and extract targeted molecules from the source materials [1]. Since density is directly related to solubility, by altering the extraction pressure, the solvent strength of the fluid can be modified to exhibit desirable transport properties that enhance its adaptability as a solvent for liquid extraction processes. The density of a SCF is closer to that of liquids and its viscosity is comparable with gases, hence high diffusivity and faster dissolution of solute particles (the diffusivity of SCFs is ~10-4 cm2 s-1 while that of liquid solvents is ~10-5 cm2 s-1). This has contributed to the increasing use of SCF as solvents for extraction purposes. 1.2.0 Supercritical Fluid Extraction (SFE) Supercritical Fluid Extraction (SFE) is a separation technology that uses supercritical fluid as the solvent. Every fluid is characterized by a critical point, which is defined in terms of the critical temperature and critical pressure. Fluids cannot be liquefied above the critical temperature regardless of the pressure applied, but may reach a density close to the liquid state as mentioned earlier. The consumer and public awareness of the health, environmental and safety issues emanating from organic solvents use in chemical processes and above all, the possibility of contaminating the final products with the solvent are forces to reckon with in recent times. This has driven the chemical industry looking for the best separation technologies to obtain natural compounds from high purity and healthy products that are of excellent quality [2]. The high cost of organic solvents, environmental regulations, and new requirements in the medical fields, for all time purer and highly valuable products have also revitalized the need for the development of new but clean technologies for products processing [3]. 1.3.0 Supercritical Carbon Dioxide (SC-CO2) SFE with Carbon dioxide (CO2), for this and many reasons is most unique and is able to save both time and money while retaining an overall extraction precision and accuracy. CO2, therefore, compressed to pressures above its critical pressure [4]; isothermally shows effective solubility powers in the region of its critical temperature [5-6]. Though a lot of SCFs can be adapted as solvents, CO2 is by far, the most extensively used due to its non-toxic, inert and non-flammable nature. It is also inexpensive and is generally environmentally accepted substance [7]. Biological products are often thermally labile, lipophilic, and non-volatile and as such required to be kept and processed at around room temperatures. CO2 has a critical temperature of 31oC which makes it particularly an attractive medium for this task. Other fluids show critical temperatures in the vicinity of critical state but are often difficult to handle and to obtain in pure state, may be toxic, explosive or ecologically unsafe. For such logical reasons, SFE using CO2 has emerged as an attractive unit operation for processing biomaterials. However, its limitations include the difficulty of extracting polar analytes, owing to the non-polar character of CO2, the different recoveries obtained from spiked and natural samples, and the frequent need for clean-up steps after extraction. Poor thermodynamic description of Supercritical (SC) solvent-solute mixtures, high capital cost for its extraction processes and an almost absence of engineering data to facilitate scale-up and design are also the prime factors that limits the use in industrial and commercial scales. For an excellent engineering design requires reliable data on the transport of a given biomaterial into the SC-CO2; such as the thermodynamic properties, fluid-liquid or fluid-solid equilibrium data of the biomaterial in the region of the temperatures and pressures where processing is technically and economically viable. Also, the measurements for the biomaterial plus SC-CO2 mixture in this condition, any mass transfer limitations for the bulk material into the SC solvent and the selectivity for the desired chemical species with the rest of the solubles in the biomaterial is paramount. Nonetheless, SFE with CO2 has great potential in the field of biomaterial processing as evidenced by the many papers published and the communications presented at the recent symposia on Supercritical fluid Technology [8]. CO2 is a good solvent for extracting lipid-soluble compounds and enables a high level of recovery [9]. CO2 is supercritical above 31.10C and 7.38 MPa, which makes it an ideal solvent for extracting thermally sensitive materials such as pyrethrins. 1.4.0 Set-Up and Principle A Pilot plant equipped with two fractionation cells. (1) CO2 pump; (2) modifier pump; (3) solid samples extraction cell; (4) fractionation cell 1; (5) fractionation cell 2; (6) valve. A fluid (CO2) is brought to a specific pressure-temperature combination, which allows it to attain supercritical solvent properties for the selective extraction of active ingredients from the sample matrix of a biomaterial (in this case Pyrethrum). The sample is exposed to the SC- CO2 under controlled conditions; time, temperature, and pressure that allow dissolution of the active ingredients (Pyrethrins) from the sample in the SCF. The dissolved active ingredients will then be separated from the supercritical solvent by a significant drop in solution pressure [10]. Several guiding principles can be utilized to effect the extraction of these ingredients, particularly the quantitative extraction. This ideal extraction method would afford total recovery and high purity of the isolated desired ingredients (Pyrethrins). Due to the inherent variability in density, chemical composition etc, many substances that can be extracted by SFE, modification of the extraction conditions; specificall y temperatures, pressures, and extraction time, may be necessary to obtain maximum extraction yield. In addition to being used for total active ingredient (Pyrethrins) quantification, the pressure-temperature-time variables in this case would be manipulated to allow selective extraction of minute quantities of polar or non-polar analyses from the Pyrethrum sample matrices. This will help attain the optimum extraction time for the process. 1.5.0 Pyrethrum Pyrethrum flowers come from the Chrysanthemum genus. Due to the size, shape, and colour of the petals; and the daisy-like appearance, they are often called painted daisies or painted ladies. Other names given to it are Buhach, Chrysanthemum Cinerariaefolium, Ofirmotox, Insect Powder, Dalmatian Insect Flowers, and Parexan. According to Visiani (1842-1852), it was first recorded in Dalmatia [11]. Other writers [Bakari P. (2005)] believe that the Pharmacist Antun Drobac (1810-1882) from Croatia was the first to prove its insecticidal activity [12]. Yet there are claims that it was first identified to possess insecticide properties in Asia around 1800 or about 300 B.C.[ Jeanne Roberts]; and that the Crushed and powdered plants were used as insecticides by the Chinese as early as 1000 BC. The Pyrethrum contains about 1-2% pyrethrins by dry weight, but approximately 94% of the total yield is in the seeds of the flower [Casida J.E., Quistad G.B. (1995)] [13]. From literature [14] [Coomber H.E. (1948)], the chemical structures of the active ingredients, pyrethrin I and pyrethrin II was identified in 1924 by a German chemist Herman Staudinger and a Croatian scientist Lavoslav Ruika. Kenya is the worlds main producer today, producing more than 70% of the global supply [Casida (1973)]. [15-17] 1.6.0 Pyrethrins Pyrethrins are the natural active ingredients of the chrysanthemum. Pyrethrin I, cinerin I and jasmolin I are esters of the chrysanthemic acid, and cinerin II, pyrethrin II, and jasmolin II are esters of the pyrethric acid. The three chrysanthemic acid esters are referred to as pyrethrins I (PYI), and the pyrethric acid esters as pyrethrins II (PYII) [Essig K., Zhao Z. J. (2001)]. Pyrethrins I, though insoluble in water, are soluble in some hydrocarbons and organic solvents [WHO (1975)]. According to Todd et al. (2003), they are non-volatile at ambient temperatures, non-toxic to mammals and other worm-blooded animals; and highly unstable in light (photodegradable) [Chen and Casida, (1969)], biodegradable [WHO (1975)], but toxic to aquatic animals. They are mainly used for biological crop protection and as domestic insecticides; and are the major formulations of synthetic pyrethroids. Pyrethrins when used in sufficient amounts are very effective in killing many insects. Although pyrethrins are soluble in a number of organic solvents such as hexane, acetone, benzene, petroleum ether, methanol, chlorinated hydrocarbons, etc; other considerations as practical, economic and environmental concerns limit the use of many of these solvents. This reduces the options to just a few. One of the qualities of Hexane in the extraction of pyrethrins is that it can dissolve the active ingredients effectively without dissolving all the other natural contaminants (pigments, waxes, fatty acids, etc), which are present and must be removed. Removing it from the concrete is also possible at lower temperatures, which limits degradation due to prolonged heating. Its low boiling point is also an added quality. Again, it can be recovered for recycling and reduces the weight of the concrete. Above all, it is inexpensive, accessible and environmentally friendly. It is non-toxic, non-corrosive, non-reactive, and non-flammable. 1.7.0 Pyrethrin Extracts Although pyrethrins are soluble in a number of organic solvents such as hexane, acetone, benzene, petroleum ether, methanol, chlorinated hydrocarbons, etc; other considerations as practical, economic and environmental concerns limit the use of many of these solvents. This reduces the options to just a few. Normal Hexane (n-hexane) is the solvent for the extractions. One of the qualities of Hexane in the extraction of pyrethrins is that it can dissolve the active ingredients effectively without dissolving all the other natural contaminants (pigments, waxes, fatty acids, etc), which are present and must be removed. Removing it from the concrete is also possible at lower temperatures, which limits degradation due to prolonged heating. Its low boiling point is also an added quality. Again, it can be recovered for recycling and reduces the weight of the concrete. Above all, it is inexpensive, accessible and environmentally friendly. It is non-toxic, non-corrosive, non-reactive, and non-flammable. The Hexane is heated above ambient temperature, considering its boiling point (pyrethrum is 170 oC 200 oC) [23] as the upper limit; for efficient extraction but raising the temperature has an effect. It promotes and aids degradation of the active ingredients. The concentration of pyrethrins in the concrete is expected to be 30 10% by weight with contaminants. Organic compounds that have lower molecular weights (ester, ether, etc) are soluble in liquid carbon dioxide. Some constituents of pyrethrum are partially soluble in liquid CO2, while others are not. Fatty acids, alkanes, triterpenols, Water, are those slightly soluble yet inorganic salts, amino acids, sugars, carotenoids, and fruit acids are insoluble [Marc Sims, (1981)]. Pyrethrins are very soluble in liquid CO2 due to the lone ketone and at least one or ester in its molecules. The rest of the molecule is hydrocarbon. Normally, GC analysis of the Pyrethrin components is difficult because Pyrethrin I and II undergo thermal isomerization to form isopyrethrin I and II at temperatures above 200oC [24-27]. These temperatures can neither be avoided in split or splitless injection systems nor in the elution from capillary columns. This brings about a transition of the isopyrethrins continuously and lead to improper integration of Pyrethrin I and II the peaks. The use of very short thin film columns combined with an on-column injection system17 will reduce this thermal conversion. Yet even with such columns the capacity and the separation performance will be insufficient. It also means that the natural Pyrethrins will appear together but the overall detection of the total amount of the pyrethrins is therefore feasible. 1.8.0 Properties Pyrethrum is very important due to these key properties: 1.8.1 Action: It attacks rapidly, the nervous system of the insects providing knockdown and killing effects eventually. 1.8.2 Immunity: In fact, there are beliefs that insects developing resistance to Pyrethrum is not practicable due to the complex nature of its structure 1.8.3. Toxicity: For a long time, it has proven to be safe for humans and other warm blooded animals but some claim it is toxic for cats [PetEducation.com], but toxic to aquatic animals even at as 2 parts per trillion [Bhanoo, Sindya (2010)] Green Inc. Energy, Environment, and the Bottom Line. New York Times, https://greeninc.blogs.nytimes.com 1.8.4 Activity: It has a vast spectrum of activity and can be used against any insect species. This is because of its closely related group of compounds (PYI and PYII). 1.8.5 Repellency and inhibition/jamming: Pyrethrum is also used to repel insects in food and grain during storage and personal protection. Beside this, it is also used to inhibit insects biting efficiency [ ] or jam their biting ability 1.8.6 Flushing: It is considered to have the greatest flushing action than any insecticide. It disturbs and flashes out the insects in their hiding outs. 1.8.7 Environment: Pyrethrum is photodegradable and as such is environmentally friendly (half-life of 12 days in soil) [www.ehow.com]. It also decomposes in air and relatively high temperatures and therefore presents no hazards due to persistence [NPTN Fact Sheet]. National pesticide telecommunications network 1.9.0 Pyrethroids Pyrethroids are man-made (synthetic) but chemically stabilized form of natural pyrethrins. Their structures are adapted and resemble that of pyrethrins and as such have similar activities. They are altered to improve their stability and potency.There are two kinds. Type I include tetramethrin, Allethrin, bioresmethrin, resmethrin and permethrin. Some type II pyrethroids are cyfluthrin, cypermethrin, deltamethrin, fenvalerate, cyphenothrin, and fluvalinate. They are persistent compounds (cypermethrin, permethrin and deltamethrin) and are resistant to degradation by air and light and therefore, are appropriate for use in wide applications, but they have higher significant mammalian toxicities (Morgan, 1989). 1.10.0 Synergist Despite the potency and safety of pyrethrum, it has few limitations. Some insects are able to recover from the knockdown effect. Again, because it breaks down in air and sunlight, it looses its effectiveness quickly in outdoor use. These are combated by treating pyrethrum extract with a liquid called Synergist. This has the ability to protect the pyrethrum from breaking down in the insects system. Small quantities of pyrethrum are mixed with these chemicals to effectively and efficiently control insect populations. The most popular of there are MGK-264 and Piperonyl butoxide. 1.8.0 Experiments 1.8.1. Objective The purpose of this experiment is to determine, compare the efficiency and provide a method by which pyrethrins are obtained in an appreciably pure and at the same time stable form (yet economical) from pyrethrum flowers by extracting 1) with an organic solvent (n-hexane) in a Soxhlet extraction and finally obtaining the pyrethrins from the concrete using sc.CO2 (proposed method); and 2) Directly with SC.CO2 and finally dissolving the concrete in organic solvents (methanol, petroleum ether and n-hexane) to obtain the pyrethrins (Factory method). 1.8.2. Chemicals Grounded chrysanthemum cinerariaefolium, Hexane, CO2 SFE grade 1.8.3. Instruments Soxhlet apparatus, burner, and flask, filter paper 1.8.9. SFE apparatus A self built apparatus with the following parts will be used: the pump, cylinder, oven, flow valves, pressure gauges, and thermometers. 1.9.0. Normal (Organic) Solvent Extractions 1.9.1. Water bath Extraction of the pyrethrins from 100g of the grounded pyrethrum flowers with hexane would be conducted in a water bath (YUHUA, DF-101S) in batches at temperatures of 35oC, 40 oC, 45 oC, 50 oC, 60 oC and 70 oC in 3hrs, 4hrs, 5hrs, 6hrs and 7hrs; in a 1000mL round bottomed flask. Agitation would be achieved by stirring vigorously with three big size magnetic stirrers at a speed of 20rpm. The hexane would then be removed with a rotary evapourator (YUHUA, RE-2000B) at a temperature of 25 oC and at a speed of 180rpm; to obtain the pyrethrin concrete (20mL) also called Crude Hexane Extract (CHE). 1.9.2. Chromatographic Conditions A Gas Chromatogram with flame ionization detection (FID); Agilent., HP-5 capillary Column, 30mm 0.25mm id., 0.25um lm thickness would be used. Each run required about 50mins. The instrument would be calibrated with multiple-point standard additions calibration method using the six individual standard samples to be prepared. The peak area of each component in the sample solutions would be fitted within the linear range of the standard. The split/split less injector, in the ratio 20:1, would be kept at 250 C. Nitrogen would be the carrier gas at a ow rate of 1.6L/min with an injection volume of 0.1L. The temperature program would start at 180 oC, kept for 11 minutes, heated at 10C/ min to 200 C, kept for 8 minutes; heated to 210 C at 10 C/min, kept for 18 minutes, then heated to 245C at 30C/min, staying at this temperature for 4 minutes. 1.9.3. SFE Conditions The carrier gas will be Hexane with a constant flow rate of 2mL/min, pressure would be between 13-25Mpa. The temperature program would be from 35-45oC. Contact time would be within 3hrs to 6hrs. References 1) Dunford, N.T., Teel, J.A., King, J.W., 2003, A continuous counter current supercritical fluid deacidification process for phytosterol ester fortification in rice bran oil. Food Research International 36, 175-181. 2) Ravents, M., Duarte, S., Alarcn, R., 2002, Application and possibilities of supercritical CO2 extraction in food processing industry: an overview. Food Science Technology International 8 (5), 269-284. 3) Mohamed, R.S., Mansoori, G.A., 2002. The use of supercritical fluid extraction technology in food processing, featured article food technology magazine, June, The World Markets Research Centre, London, UK. 4) The pressure of a fluid in its critical state; i.e. when it is at its critical temperature and critical volume, source: Answers.com 5) The temperature above which a gas cannot be liquefied, regardless of the pressure applied, source: Answers.com 6) The solubility of naphthalene in supercritical ethylene., J. Am. Chem. Soc 7) Extraction with supercritical Gases, Verlag Chemie, Deerfield Beach, FL 8) Present state of extraction of natural materials with supercritical fluids and development trends in supercritical fluid science and technology, eds, K. P. Johnston and J. M. Penninger, ACS symposium series No. 406, pp. 478-498; Performance of a packed column for continuous SC-CO2 processing of anhydrous milk fat. Biotech, Progress, 9) Awasthi, A., Trivedi, R.K., 1997: A review on supercritical carbon dioxide extraction of natural products, Chemical Engineering World Feature/Article; Fattori, M., Bulley, N.R., Meisen, A., 1988. Carbon dioxide extraction of canola seed: oil solubility and effect of seed treatment. Journal of the American Oil Chemists Society 65, 968-974. 10) Food analysis second edition: crude fat analysis. Purdue University, West Lafayette, Indiana, pp. 203-214 11) Visiani R. (1842-1852). Flora Dalmatica 12) Bakari P. (2005), Buha prirodni insekticid. Gospodarski list 17: 41-45 13) Casida J.E., Quistad G.B. (1995). Pyrethrum flowers: Production, Chemistry, Toxicology, and Uses. Oxford University Press, New York. 14) Coomber H.E. (1948). The chemical evaluation of Pyrethrum flowers, Pyrethrum Post 1 (1): 16-19 15) Chandler S.E. (1948), The Origin and Early History of the Production of Pyrethrum in Kenya. Pyrethrum Post 1 (1): 10-13 16) Mocatta G. (2003). Pyrethrum- from ancient discovery to advanced agriculture; Agriculturalist, Botanical Resources Australia. 17) Jones, G. D. G. Pyrethrum production, In Pyrethrum; The Natural Insecticide. J. E. Cadisa (eds.). Academic Press. New York, NY. 1973. pp 17-21. 18) Essig K., Zhao Z. J. (2001b). Preparation and characterization of a Pyrethrum extract standard. LC/GC 19(7): 722-730 19) Head S.W. (1966). A study of the insecticidal constituents in Chrysanthemum cinerariaefolium. (1) Their development in the flower head. (2) Their distribution in the plant. Pyrethrum Post 8(4): 32-37 20) WHO (World Health Organization). 1975. Data Sheet on Pesticides No. 11; Pyrethrins. www.inchem.org/documents/pds/pds/pest11_e.htm 20) Todd, G. D., Wohlers, D., and Citra, M. Toxicology Profile for Pyrethrins and pyrethroids. Department of Health and Human Services. Agency for Toxic Substances and Disease Registry. Atlanta, GA. 2003. 21) Chen, Y-L., and Casida, J. E. 1969. Photodecomposition of pyrethrin I, allethrin, phthalthrin, and dimethrin. J. Agr. Food Chem. 17: 208-215. 22) W.H.T. Pan, C.K. Liu, L. Y. Chou and M.H. Lee, J. Chin. Med., 5 (1994) 71 23)M. MATSUMOTO, Jpn Patent 119,682, 1974 24) L.W.Levy, Br. Patent 870, 456, 1961 25) G. Foget , J. Toxicol.Environ. Health, 32 (1991) 11 26) V.M.Valentine, Veterinary Clinics of North America-Small Animal Practice, 20 (1990) 375 27) D.A. Otieno, I.J. Jondiko, P.G. McDowell, and F.J. Kezdy, J. Chromatogr. Sci. 20, 566 (1982). 28) Technical Data sheet, Wefco marketing international cc; www. Wefco.co.za 29) Zong-Mao Chen, Yun-Hao Wang, chroma. Methods for the determination of pyrethrin and pyrethroids pesticides in crops, foods and environmental samples; journal of chrom. A. 754 (1996) 367-395 30) Ernesto Reverchon, Iolanda De Marco, Supercritical fluid and fractionation of natural matter; J. of suppercrit. Fluids, 38 (2006) 146-166 31) Carlo Bicchi, Claudio Brunelli, Mario Galli, Abino Sironi, Conventional inner diameter capillary columns: an approach to speeding up GC; J. of chrom. A, 931 (2001) 129-140 32) Thomas J. Class and Joachim Kintrup, pyrethroids as household insecticides: analysis, indoor exposure and persistence; Fresenius J. Anal Chem (1991) 340: 446-453 33) B.W. Wenclawiak, M. Krappe, A. Otterbach, In situ transesterification of the nat. pyreth; J. of chrom. A, 785 (1997) 263-267 34) Wynn H.T. Pan, Cheng-Chin Chang, Tien-Tsu Su, Fong Lee, Ming-Ren Steve Fuh: prep. supercrit. Fluid extract. Of pyreth I and II from Pyrethrum flower; Talanta 42 (1995) 1745-1749 35) Amrith S. Gunasekara, environ. Fate of pyrethrins; depart. Of pesticide regulation 1001 I street, Sacremento, CA 95812: novenmber 2004, revised 2005 36) Martina Gardisa, Klaudija Carovic-Stanko, Ivan Kolak, Zlatko Satovic; Morphological and biological diversity of Dalmatian pyre. Review article. Croatia 37) Ken Essig and Zhouming J. Zhao; Aventis environ. Sci, 95 chestnut ridge road, Montvale, new jersey 07645 38) .[ Jeanne Roberts, www.celsias.com: Insecticide Treated Mosquito Nets and Malaria Prevention: Weighing the Benefits, Naming the Benefactors] 2.0. CHAPTER 2: Report on GC analysis and Organic (Normal) Extractions 2.1.0 Objective The objective of this section of the experiment was to establish standard curves, by gas chromatographic techniques; for pyrethrins 1 (PYI) and pyrethrins 2 (PYII); the two groups of the six essential ingredients (Cinerin 1, Jasmolin 1, Pyrethrin 1; and Cinerin 2, Jasmolin 2, Pyrethrin 2) of the chrysanthemum (with the standard sample provided by the company), and to determine the percentage yields (and global yield) after Hexane (normal) extractions. 2.2.0 Background In analytical chemistry, the accuracy of quantitative measurements of the constituents of samples, using standard samples of known composition usually requires calibration. It is usually, but not automatically, done with samples and standards dissolved in appropriate solvents. This is due to the ease of preparing and diluting accurately, mixture of standard samples. Several standard solutions are prepared and analysed or measured, a line or curve is drawn (fit) to the data points and the obtained equation is used to translate values from the unknowns into corresponding concentrations. It has the advantage that random errors in the preparation and readings of standard solutions are averaged over many standards. Again, non-linearity can be seen and eliminated by fitting into the linear sensitivity range by dilution. Yet still, this can be compensated for by using non-linear curve fitting methods. It is usually, but not limited to a first-order of measured fit signal (area) on the y-axis against concentration on the x-axis. The model equation is: y (signal) = m (slope) * x (concentration) + c (intercept) (1) It is the most common and straightforward method, but its main drawback is that it cannot compensate for non-linearity. A minimum of two data points are needed to construct the curve. The concentration, x of the unknown sample is given by x = (y-c)/m.. (2) Where y is the measuredsignal, m is the slope and c is the intercept from the curve (straight line fit). The value of c is zero if the curve is forced through the origin: then x = y/m.. (3) 2.3.0 Gas Chromatography Gas Chromatography (GC) is a means by which separations, quantifications and identifications of analytes of a given solution or mixture is done. The essentials required for this method are an injection port where samples are placed. There is also a column on where separations of the components are done; a carrier gas whose flow is regulated to carry the samples all along the instrument, and a detector for the identification of analytes as well as a data processor. By this tool, a sample is brought to the vapour form and a carrier gas sends the sample into a column. The carrier gas should be inert; chemically. The choice is often governed by the type of detector which is used. With a gas-liquid chromatography, the column is normally packed with a solid stationary phase. Once the sample moves along the column, the analytes that interact strongly with the phase spend more time in the stationary and the moving gas phases, hence will require more time to travel along the column. There are generally two types of columns: packed and capillary (sometimes called open tubular). Packed columns are 1.5 10m in length and have about 2 4mm internal diameter. Capillary columns are coated with liquid stationary phases or lined with thin layer which adsorb the stationary phase. They are more efficient than packed columns. After exiting the column the analytes once separated are detected by a detector and their response recorded for analysis. The time from injection of a sample to the time an analyte is detected is defined as Retention time tR. The boiling point of the sample is vital in determining retention time. Those with higher volatility (lower boiling points) tend to have shorter retention times as they spend more time in moving from the gas phase. Each analyte (component) will have a different retention time. Retention factor, k, (or capacity factor) is a term used to describe the travel rate of an analyte on a column. If the retention factor is less than one, elution will be quick such that to determine accurately the retention time is difficult; otherwise elution takes a very long time. The retention factor for an analyte is usually between one and five. For optimum efficiency, the volume must not be very large, and must be put in the column as a vapour plug. The most common injection method is the use of a micro syringe to inject the sample. For effective separations, peaks must symmetrical, sharp and hence no band broadening and trailing must be present. The greatest constraint of gas phase chromatography is the vaporization of the solid and liquid samples on the column in the gaseous state. This limits its use usually to the study of thermo stable and sufficiently volatile compounds (1) www.chromatographyonline.com 2.4.0 Determination of the Standard/Calibration Curve A calibration curve provides the relationship between a signal produced by an instrument and the concentration of the analytes being measured. Different analytes produces different and unique signals. The measurements (signals) of an analyte of unknown sample are commuted, from the standard curve into concentrations. Quantitative analysis with GC is based on comparative methods. The Concept is that the sample with the analyte and a standard Sample that has the same concentration of this analyte will produce similar results, using an instrument with the same conditions. Several standards of known are prepared and their concentrations calculated. Then a standard curve is established from the values of the analytical result (in this case; area) as a function of analyte concentration. This standard curve is then used to find the concentration of an unknown sample. Usually, the abscissa (x-axis) corresponds to the concentration and ordinate (y-axis) of the signal result (area). 2.4.1. Regression analysis The import of this analysis is to provide an equation that relates the instrument results to the concentrations used, such that with a given result the corresponding unknown concentration can be determined. The model of the function is y = f (x), defining y. The errors in calculating the concentrations would be acceptable (less) if the signal of the unknown are in the range (middle) of the signals of the standards. 2.4.2. Simple linear regression Once the results of the detectors are linear as a function of the measured variable, then the goal now is to obtain the parameters of a straight line of best fits. The least squares regression line, which reduces the sum of the square or the error of the data points; is represented by the linear equation, y = mx + c.. (4) x is the independent variable, and y is the dependent variable. The term c is the y-intercept or regression constant (c is the value when x = 0), and the term, m; is the slope (sensitivity) or regression coefficient. The Pearson correlation coefficient R2 gives a measure of the reliability of the linear relationship between the x and y values. If R2 = 1, the linear relationship between x and y exists and is exact. Values of R2 close to 1 indicate excellent linear reliability. If the correlation coefficient is far away from 1, the relationship is less reliable. A straight line suggests that the errors in y follow the law of normal distribution and usually, the experimental error is considered to affect the y value only but not the x value (concentration recorded). If the response of any unknown falls outside the range of the standard, then additional work is required. Likewise if it falls below the Limit of Detection, then the sample needs to be concentrated and must be diluted if it lies above the Limit of Linearity. 2.4.3 Calibration Methods There are about three methods for the determination of the standard/calibration curve. These are explained below. 2.4.3.1 External standard method This method involves the comparison of two chromatograms obtained successively but with the same control conditions. The first chromatogram is acquired from a standard solution (reference solution) of known concentration in a solvent, for which a known volume is injected and the corresponding area in the chromatogram is measured. The second chromatogram results from the injection of the same volume of the sample in a solution containing an unknown concentration of the compound to be measured. Since the same volumes of both samples are injected, the ratio of the areas is proportional to the ratio of the concentrations which depend upon the masses injected. For precision, several solutions of varying concentrations are used in order to create a calibration curve. 2.4.3.2 Internal standard method With internal standardization, a second compound, often related to the analyte but never found in the sample, is added at a known concentration to every sample and calibrator. It is the ratio of the analyte to internal standard that is the critical measurement in an internally standardized method. The calibration curve data are generated by injecting calibration samples of different concentrations, that all contain the same concentration of internal standard. The ratio of the analyte area to the internal standard area is calculated and plotted as the y-value against the concentration of the calibrator in x-axis. This compensates for any imprecision resulting from the injected volumes, which is the main drawback of the External standard method. This method relies on the relative response factor of each compound to be measured against the standard. It requires two chromatograms, one to calculate the relative response factors of the compounds of interest, and the other for analysis. The idea of relative response factors arises because the detector does not respond to each analyte in a mixture the same way. The areas of peaks could directly be used, if this was so; to obtain the total composition. This is done by dividing the peak area of each by the total area of the peaks. Hence, every peak area should be multiplied by an appropriate factor known as the response factor, (k) to compensate that. The compensated areas are then what are used to calculate the total mixture composition. Each response factor is then ratioed to that of a chosen component and this is termed relative response factor (f). The relative response factors then enable the determination of the total composition of any unknown mixture of similar components. The regression equation is rearranged as in equation (3), which allows calculation of the unknown concentration. 2.4.3.3. Method of Standard Additions Usually, in both the external and internal standard methods, matrix-based standards are prepared. This implies that the standard to be used for the calibration must not have any traces of the analyte. By this, reduces the likely signal stifling or interference of the matrix. To be exact, a blank matrix sample is analysed to ensure that no interfering peaks exist. Unfortunately sometimes, it is not possible to have an analyte without interfering peaks (free matrix). In such cases, this method is employed. A series of standards are obtained in several different concentrations. The standards are so added to portions of the sample. Several concentrations of the reference sample may be prepared (if available), without an internal standard. Thereafter, the samples are assayed and the corresponding results appropriately plotted. 2.5.0 How to determine an unknown concentration Determination of the unknown concentration of any sample can be done in two ways: 2.5.1. Graphically: Once the signal of the unknown is obtained, a horizontal line is drawn from the signal on the y axis (0.068) to meet the calibration curve and then a vertical line drawn straight down to the concentration on the x-axis (shown with blue arrows). The value at this point (estimated as 0.32M) is the concentration of the unknown sample as shown below. 2.5.2. Mathematically: The equation of the calibration curve is fitted to the data, and solved for concentration as a function of the signal (y). Then, the signal for each unknown is substituted into this equation and the corresponding unknown concentration calculated for. This gives more accurate concentration values compared with the graphical method. The fit equation is as in equation (1) and it is expressed mathematically as in equation (4) above. Solving equation (4) for Concentration (x) yields either equation (2) or (3) depending on whether the fit is forced through zero or intercept at c. i.e. x = (y c)/m (2) Or x = y/m (3) x is the unknown concentration to be calculated. 2.6.0 GC Analysis My first problem was to determine a set of experimental analysis conditions that give a better separation of the six analytes in a pure solution prepared from the standard sample provided by the company, in a reasonable time frame. Several conditions were tested until this particular one below chosen. Identification of the individual peaks was based on the similarities between the peaks produced and those from literature (B.W. Wenclawiak et al, 1997) with different conditions though. Analyses with these conditions were repeated three times for accuracy and reproducibility. Six standard solutions prepared were injected and chromatograms obtained. Replicate injections of each solution were made for precision and accuracy. The peaks from these chromatograms were compared with those found in literature for the identification of the individual analytes and their corresponding retention times noted. After this, the peak areas for PYI and PYII of all the six solutions were calculated by the software and recorded. A plot of these peak areas and the concentrations calculated earlier gave the standard curve for the analysis. 2.7.0 Experimental Procedure 2.7.1 Chemicals and Reagents Hexane: 110-54-3C6H14 97.0%86.18M Ethanol64-17-5 C2H5OH99.7% (46.07M) Ethyl dodecanoate: Filter papers (7cm and 15cm): Finel: filters (0.45m): Syringes (1mL): All the solvents were analytical-reagent grade. Hexane and Ethanol were purchased from Sinopharm Chemical Reagent Co., Ltd and used without any pre-treatment. 2.7.2 Equipment and Apparatus 2.8.0 Samples The grounded chrysanthemum (light green with a characteristic smell) was provided by the company in as well as two samples of the pyrethrum concrete (yellowish in colour). The first sample contained 50% of pyrethrins (i .e. 29.5% of pyrethrins 1 referred to as PYI and 20.5% of pyrethrins 2, called PYII); and the second one had 85.15%, comprising of 46.33% PYI and 38.82% PYII. 2.9.0 Conditions The conditions finally chosen as the best, after a series of conditions tried was: The split/split less injector, in the split ratio 20:1, was kept at 250 C. Nitrogen was used as carrier gas at a ow rate of 1.6L/min. The injection volume was of 0.1 L. The temperature program was started at 180 C kept for 11 minutes, heated at 10C/ min to 200 C, kept for 8 minutes; heated to 210 C at 10 C/min, kept for 18 minutes, then heated to 245C at 30C/min, staying at this temperature for 4minutes. The chromatographic analysis was performed in a gas chromatograph with an FID detector, Agilent GC, HP-5 Column, 30mm 0.25mm id., 0.25 m lm thicknesses. This column was chosen because it gives the best resolution, identication and quantication for products containing OH and C=O. (Rosana, Vanessa, 2003; Analytica Chimica Acta 505 (2004) 223-226). 2.10.0 Standard Curve Once the conditions were established, 2g of the PY concrete was transferred into a 100mL volumetric flask and Ethanol was filled to the mark and shook to mix. Knowing the mass, the concentration of the PY solution (20mg/mL) was then calculated using the relation: Concentration (mg/mL) = mass (mg)/Volume (mL) . (5) The concentration of PYI (9.266mg/mL) and PYII (7.764mg/mL) was calculated keeping in mind the % of each group in the sample provided (i.e. 46.33% and 38.82% respectively). Six standard aliquots; 1mL, 2mL, 4mL, 8mL, 16mL and 32mL of this PY solution was then transferred into a 50mL flask each and diluted with Ethanol again to the mark and mixed. The concentration of each standard portion and the PYI and PYII concentrations were then calculated appropriately. Pure PY sol PY conc.(mg/ml) PYI conc.(mg/ml) PYII conc.(mg/ml) pure sol 20 9.266 7.764 1ml 0.4 0.1853 0.1553 2ml 0.8 0.3706 0.3106 4ml 1.6 0.7413 0.6211 8ml 3.2 1.4826 1.2411 16ml 6.4 2.9651 2.4845 32ml 12.8 5.9302 4.969 Table 1: Concentrations of each standard portion calculated With a micro syringe, 0.1L of each of these solutions were injected into the GC for analysis. The elution times and the corresponding peak areas were noted and recorded. See the table below. Comp. 1ml 2ml 4ml 8ml 16ml 32ml Elution (min) Peak area Elution (min) Peak area Elution (min) Peak area Elution (min) Peak area Elution (min) Peak area Elution (min) Peak area Cinerin1 19.86 20.01 19.87 42.79 19.87 81.28 19.87 174.29 19.88 260.04 19.91 618.90 Jasmolin1 23.11 11.94 23.11 12.86 23.11 24.18 23.11 58.79 23.12 87.79 23.13 209.17 Pyrethrin1 24.27 56.51 24.29 121.83 24.29 227.91 24.31 487.30 24.34 722.69 24.43 1711.29 Cinerin2 38.44 24.09 38.46 37.92 38.47 75.19 38.48 161.23 38.51 238.44 38.57 581.32 Jasmolin2 42.06 19.06 42.07 29.42 42.06 48.35 42.07 114.08 42.07 161.40 42.09 390.64 Pyrethrin2 42.91 4.22 42.91 3.60 42.91 8.09 42.91 18.14 42.92 26.26 42.96 57.89 Table 2: Elution times and peak areas of analytes in standard sample The concentrations and the peak areas are then tabulated to construct the overall standard curves for PYI and PYII respectively. Soln. PY(mg/ml) PYI(mg/ml) A1 PYII (mg/ml) A2 pure sol 20 9.266 4436.5566 7.764 1790.7451 1ml 0.4 0.1853 88.4592 0.1553 47.3710 2ml 0.8 0.3706 177.4739 0.3106 70.9374 4ml 1.6 0.7413 333.3663 0.6211 131.6275 8ml 3.2 1.4826 720.3725 1.2411 293.4468 16ml 6.4 2.9651 1070.5243 2.4845 426.1003 32ml 12.8 5.9302 2539.3593 4.969 1029.8515 Table 3: concentration and corresponding peak areas The Pearson correlation coefficient R2 in each of the curves is about 0.99. From literaturechromatography online, this indicates the measure of the reliability of the linear relationship between the x (concentrations) and y (peak areas) values. Therefore, the standard curves could be used for the determination of corresponding unknown concentrations given their peak areas. 3.0 CHAPTER 3: Organic (Normal) solvent Extraction 3.1.0 Objective and Procedure The main objective of this extraction process is to obtain a light coloured Product with a high recovery rate of the six pyrethrin active ingredients [Kiriamiti et al. 2003]. Extraction essential components with an organic solvent is the simplest, commonest and most importantly, economic technique in modern Chemical industry Wikipedia. The desired samples are submerged completely and agitated in an organic solvent. This agitation (with or without heat) helps to dissolve the desired compounds needed. Hexane, dimethyl ether, methanol, ethanol are some of the most common organic solvents used for these kinds of extractions. However, not only the desired components are extracted during this process. Other soluble substances (waxes and pigments) that are hydrophobic are also extracted. The solvent is removed from the extract by vacuum processing at lower temperature, for re-use. The process can last for hours or weeks, or even more. After the solvent removal, the waxy thick mass left is the concrete. This is composed of essential oils and other oil soluble (lipophilic) materials (Wikipedia). The concrete is too thick (viscous), coupled with the presents of undesired components; to be used directly. A further treatment, usually with another solvent that only dissolve the desired compounds from the concrete is necessary. This solvent is again removed leaving behind the absolute (substance). 3.2.0 Sample Preparation For all chemical analyses, the analyte to be measured must be in a sufficient quantity and in a suitable form for the GC analysis. Usually, samples require pretreatment. This has an influence on the end result. Sample preparation is therefore an essential step in analysis just as measurements. Then appropriate extraction methods are employed. A 100g of the grounded chrysanthemum material containing the desired analytes was weighed out and placed inside a 500mL round bottom flask and a bottle of normal Hexane (as extraction solvent) was poured in to submerge the sample completely. This was then transferred into a water bath. The set up was then equipped with a condenser, to condensate the liquid vapour and connected to water source. The temperature program was set and the system was heated at various temperatures (40 oC, 50 oC, 60oC and 70 oC) each at times 5hrs and 7hrs. Magnetic stirrers were used to maintain equal distribution of heat and solvent and the rotation was set at 20rpm in each case. Each solution was filteredfilter paper-7cmwith the aid of a rotary evapourator after the set time and the extracted solid discarded. The filtered solution was condensed to 10ml each with a rotary evapourator to remove the solvent. This system has the advantage that the solvent is repeatedly recycled and also the temperature can be controlled (since the sample is thermo labile). Each concentrated sample was thereafter, filtered (0.45m) and 0.1L of each analysed in the GC. The results are below. Cp Art 40C (5Hrs) 50C (5Hrs) 60C (5Hrs) 70C (5Hrs) t A t A t A t A C1 19.91 20.88 23270.3 20.24 5483.71 20.25 5039.21 20.30 5921.06 J1 23.13 23.80 10711.0 23.33 3043.60 23.33 2753.30 23.39 3258.92 P1 24.43 25.44 19810.3 24.86 8830.62 24.87 7989.68 24.95 8956.26 C2 38.57 39.55 4121.32 39.16 3328.70 39.19 3132.16 39.35 3767.63 J2 42.09 42.289 1125.67 42.23 2075.81 42.25 1956.50 42.29 2505.47 P2 42.96 43.237 215.407 43.18 329.54 43.20 304.55 43.25 1030.98 Ttl 191.09 190.27 389.82 193.01 23091.95 193.09 21175.4 193.53 25440.32 Table 4: results for 5hrs analysis Cp Art 40C (7Hrs) 50C (7Hrs) 60C (7Hrs) 70C (7Hrs) t A t A t A t A C1 19.91 20.19 4175.84 20.13 3015.38 20.16 3069.10 20.96 21666.50 J1 23.13 23.31 2341.50 23.27 1642.98 23.32 1651.68 23.87 10253.00 P1 24.43 24.80 6795.98 24.72 5034.69 24.76 4946.84 25.51 18905.40 C2 38.57 39.08 2675.11 38.98 1841.87 39.06 1896.36 39.73 3905.71 J2 42.09 42.21 1638.08 42.18 1097.48 42.22 1206.58 42.34 1616.78 P2 42.96 43.16 284.72 43.11 182.52 43.15 187.01 43.28 167.43 Ttl 191.09 192.75 17911.23 192.39 12814.92 192.7 12957.57 195.69 56514.82 Table 5: results for 7hrs analysis The average elution time for each analyte was calculated within each time frame. Component Standard sample At 5hrs At 7hrs Cinerin 1 19.91 20.43 20.36 Jasmolin 1 23.13 23.46 23.44 Pyrethrin 1 24.43 25.03 24.95 Cinerin 2 38.57 39.31 39.21 Jasmolin 2 42.09 42.26 42.24 Pyrethrin 2 42.96 43.22 43.18 Total 191.09 193.71 193.38 Table 6: average retention times With the peak areas from Table 4, the concentrations and yields for PYI and PYII within these times was calculated as well. Concentrations (mg/ml) Num Comp Pyret Stand 5hrs 7hrs 40 50 60 70 40 50 60 70 1 C1 PYI 9.27 1175.54 379.33 344.90 396.34 290.94 211.83 211.27 1110.71 2 J1 3 P1 4 C2 PYII 7.76 247.65 259.97 244.51 331.15 208.46 141.52 149.16 257.96 5 J2 6 P2 Total PY 17.03 1423.19 639.30 589.41 727.49 499.40 353.35 360.43 1368.67 Table 7: concentrations of PYI and PYII Yields Num Comp Pyreth Stand 5hrs 7hrs 40 50 60 70 40 50 60 70 1 C1 PYI 0.46 1.18 0.38 0.34 0.40 0.29 0.21 0.21 1.11 2 J1 3 P1 4 C2 PYII 0.38 0.25 0.26 0.24 0.33 0.21 0.14 0.15 0.26 5 J2 6 P2 Total PY 0.85 1.42 0.64 0.59 0.73 0.50 0.35 0.36 1.37 Ratio (PYI : PYII) 1.21 4.75 1.46 1.41 1.20 1.38 1.50 1.40 4.27 Table 8: yields and ratio for PYI and PYII The areas of PYI and PYII for the various temperatures from the analysis (Tables 4 and 5), gave higher concentrations (Table 7). These exceeded the range set for the standard. The range for PYI is 9.27mg/ml and that of PYII is 7.79mg/ml. Yet the lowest concentrations for PYI and PYII (Table 7) are 211.27mg/ml and 141.52mg/ml respectively. The total PY concentration in the standard (range) is 17.03mg/ml and the highest PY concentration from the analysis (extractions) is 142.32mg/ml (since PYI and PYII have the same volume, their concentrations could be added). Therefore, and for accurate results, these concentrations should be diluted (mix with more solvent) to fit into the range before proceeding with the analysis. This can be done by ways: 1) Finding the Dilution Factor. This in a way will tell how many times the initial volume (before the analysis) should be diluted to fit into the range. For such cases, the concentrations gotten from the reading on standard curve should be multiplied by the dilution factor. Therefore, the dilution factor, Df = final concentration/initial concentration (6) The final concentration is 1423.19mg/ml and the initial concentration is 17.03mg/ml Therefore, Df = 1423.19(mg/ml)/17.03(mg/ml) Df = 83.56958 This show a that the initial concentrated volume of 10ml should be multiplied almost 84 (i.e. about 850ml) times. This is too much solvent to use, hence not economical. 1) By taking a portion (aliquot) of the concentrated concrete and diluting it with an amount of solvent. The concentration of the concentrated concrete, Cc = 142.32mg/ml and that of the diluted concrete is Cd. The volume of the concentrated concrete taken is Vc and that of the dilution targeted is Vd Using the dilution equation Cc * Vc = Cd * Vd.. (7), the diluted concentration, Cd can be calculated. Cc = 1432.19mg/mL, if Vc = 1mL and Vd = 50mL. Cd = ? Cd = 1432.19 x 1 / 50 (mg/mL) = 14.3219mg/mL This new diluted concentration falls within the range of 17.03mg/mL Therefore, after concentrating the extract to 10mL, 1mL aliquot is moved into a 50mL flask and solvent topped to the mark before the GC analysis. 2) Eliminating the use of the rotary evapourator. Since a bottle of Hexane (500mL) is used for the extraction each time, it is not necessary to concentrate the solution after filtration but top up with some hexane to 500mL (some hexane will escape during the extraction process) mark before the GC analysis. 3.3.0 Optimum Extraction Temperature Table 8 shows the extraction temperatures and the corresponding yields between 5hrs and 7hrs. The result in this case suggests that the optimum temperature is at 40oC. This is because pyrethrins are thermo labile and therefore degrade after 40oC [E. Stahl, 1998; C. Gourdon, 2002; W.H.T.Pan, 1994]. At 40oC, targeted PY components are extracted more but after this temperature (with the increase) more undesirable components are extracted at the expense of the pyrethrins components which decompose. Again, at 40oC 5hrs gave a better yield than 7hrs. This suggests that with prolong heating, even at a safer extraction temperature (40oC), the PY yield is affected negatively. Therefore, an investigation into the optimum time and yield at this temperature (40oC) was done and the results, by fitting into the concentration range this time, before GC analysis are below: Num Comp Pyret Stand 40oC 3hrs 4hrs 5hrs 6hrs 1 C1 PYI 9.27 4.23 5.72 3.77 3.59 2 J1 3 P1 4 C2 PYII 7.76 1.03 1.81 0.83 0.70 5 J2 6 P2 Total PY 17.03 5.26 7.53 4.60 4.29 Table 9: Concentrations at various times at 40oC The results show that the concentrations are fitted into the range such that all the concentrations less than the maximum range set (17.03). Even more, they are within half of the range. This is important because the errors in the concentrations will be minimal if the signal (area) from the unknown lies in the middle of the signals (areas) of all the standards (chromatography online). Num Comp Pyreth Stand 40oC 3hrs 4hrs 5hrs 6hrs 1 C1 PYI 0.46 2.12 2.86 1.88 1.80 2 J1 3 P1 4 C2 PYII 0.38 0.52 0.90 0.41 0.35 5 J2 6 P2 Total PY 0.85 2.64 3.76 2.29 2.15 Ratio (PYI: PYII) 1.21 4.10 3.16 4.56 5.15 Table 10: Yields and ratio of PYI and PYII 3.4.0 Results and Discussions The percentage yields I obtained are not out of place comparing with literature. In some cases, the yield of PY varies from 0.91 to 1.30% of the dry weight [Kolak et al., 1999; Casida and Quistad, 1995]. According to Bakari (2005), the yield is between 0.60 0.79%. Bhat (1995) reported content ranging from 0.75 to 1.04%. However, Morris et al. (2005), reported yields of approximately 1.80 to 2.50%. Still according to Kiriamiti et al. (2003) the yield ranges between 0.50 and 2.0% while Pandita and Sharma (1990) gave yields varying from 0.90 to 1.50%. Above all Casida and Quistad (1995) states that it is possible to obtain pyrethrin yield of 3.0% or more. Therefore, the yield from my analysis of 0.85 to 3.76% conforms to literature. From this analysis, the optimum extraction conditions with Hexane are at 40oC in 4 hours (yield 3.76) but is this the real optimum extraction conditions (especially the temperature)? Since PY does not decompose between 20oC and 40oC, is it possible to have the optimum temperature at 25oC, 30oC or even 35oC? With this in mind, a further investigation was carried out in the same time frame (4hrs) beginning with 30oC such that if the result gave more yield than the one at 40oC, then the next would be 25oC and possibly 20oC. On the other hand, if the result gave fewer yields then the next would be 35oC and possibly 45oC. This would confirm the optimum conditions for the extraction process. 3.5.0 Conclusion References 1) Wikipedia 2) chemical analysis book 3) www.chromatographyonline.com 5) B.W. Wenclawiak et al, 1997 6) Rosana, Vanessa, 2003; Analytica Chimica Acta 505 (2004) 223-226 7) Kolak et al., 1999; Casida and Quistad, 1995 8) Bakari (2005) 9) Bhat (1995) 10) Morris et al. (2005) 11) Kiriamiti et al. (2003) 12) Pandita and Sharma (1990) 13) Casida and Quistad (1995) 14) Journal of chemical education vol. 75, no. 9, September 1998 Pyrethrins are well separated on polar columns but their analysis with a conventional (normal) column takes about 1 h. This is unacceptable but with a short OV-1 column, analysis time is reduced and thermal decomposition is also drastically limited; since the residence time is shorter and the elution temperature of pyrethrins I and II is lower. [Recommendation] A cold-on-column injection system and a high constant flow rate can further reduce pyrethrin degradation and elution temperatures and as a consequence their isomerization. [Recommend]

The Subjugation Of The African American Race - 879 Words

Priscilla Takyi Composition 6’ Simon Bolivar The Subjugation of the African American Race: Living in Poverty/ Health Effects In America, it is to no surprise that a large percentage of the African American race has and still is struggling financially. Many African-Americans are subjected to live in poorer areas where sanitation isn’t as heavily emphasized compared to more prosperous neighborhoods. Due to this blatant divide there has been many detrimental effects this has to minority communities. In specifically predominantly black communities the effects are seen heavily. Over the years the most frequent illnesses affecting African-American’s are high blood pressure, obesity, diabetes, stroke, kidney failure and cancer. Racism and classism are contributing factors to this environmental crisis’ because of the where toxic waste is disposed, where pollutive industries are located, and the financial challenges African-Americans face. Where toxic waste is disposed of is one of the reasons why racism and classism leads to environmental factors. As referred in an article called †Emelle, Alabama:Show MoreRelatedColonization Of The United States1097 Words   |  5 Pagesconnected the US to other nations and allowed Settler Colonialism and Chattel Slavery to affect more groups of people. The unequal material conditions of land and labor that resulted from these processes benefited the US to the detriment of other races. Christopher Columbus came to the Americas with the ideas of Whiteness and the Doctrine of Discovery. With Early European settlers began the long and ongoing process of settler colonialism. They forced or coerced the Indians out of their lands andRead MoreRacism - A History : The Color Of Money1063 Words   |  5 Pagessix short episodes explore and chronicle centuries of European attitudes and practices regarding race and the transatlantic slave trade of Africans. It underscores how economics served as the driving force behind slavery. The documentary highlights that although slavery existed for several centuries prior to the slave trade, the concept of racism is rooted in the enslavement and exploitation of Africans for labor and capital gain. The documentary describes how the British’s development of the transatlanticRead MoreThe Slavery Of The Black Race1508 Words   |  7 PagesTocqueville anticipated the future these three races. For the Native Americans, Tocqueville anticipated that they were bound to vanish. With a specific end goal to survive, they should be acculturated or begun a fight were one of the two races could vanish. What s more, Tocqueville anticipated that they will be secluded by the whites. For the Negros, he anticipated the racial blend will extend Negros race everywhere throughout the country. Additionally, they will be more acknowledgeable of theirRead MoreThe Source Of Racism And White Supremacy Essay1718 Words   |  7 Pagesgives color to eyes, skin and hair. Legendary scholar, author and psychiatrist, Dr. Frances Cress Welsing argues that African albinos, rejected by their parents, alienated from their communities and sensitive to the African sun, were forced to migrate northward to Europe. This as a consequence resulted in inbreeding amongst the exiles led to the birth of the White or European race. Racism and white supremacy functions both on a microcosmic and macrocosmic level. Similar to a massive bureaucracy, whiteR ead MoreEvolution Of Slavery Throughout Colonial America1336 Words   |  6 Pagesstories from our past. Slavery began when African Slaves initially arrived in the North American settlement of Jamestown in 1619. These slaves helped with the creation of profoundly lucrative products such as tobacco. In this manner, it was absolutely a rural undertaking that would later provoke the presence of one of the chronicled treacheries done particularly to the African migrants. The issue took course during the sixteenth and eighteenth century American colonies. Although it was not their uniqueRead MoreDiscrimination, Anti Feminism, And Gender Inequality1455 Words   |  6 PagesMovements. Gender and race has been the target of numerous discriminatory laws that have persisted throughout time. Two major films have portrayed the endurance of women on issues of gender discrimination and discriminatory laws. The Color Purple, based on the same novel by Alice Walker, discusses the suffering of A frican American women through anti-feminism. On the other hand, The Help, based also on the novel by Kathryn Stockett, deliberates the struggle of African American women during the JimRead MoreA Reading Of Micheaux s Within Our Gates1418 Words   |  6 Pages A Reading of Micheaux’s Within Our Gates (1920) In 1920, pioneering African American film director Oscar Micheaux released his second picture, Within Out Gates. The film is a silent drama that revolves around a young professional woman, Sylvia Landry, her quest to fund an opening rural school for black children, and her past experience of violent racism in the South. It is a work largely concerned with African Americans as being at a sort of impasse in history and, furthermore, with the positingRead MoreSlavery And The Civil War1527 Words   |  7 Pagesrailroad lines, and guaranteed 630,000 lives? Numerous elements drove the country into disarray in 1861. Key political causes incorporate the moderate breakdown of the Whig Party, the establishing of the Republican Party, and, most vital, the 1860 race of Abraham Lincoln as president. Religious restriction to servitude expanded, upheld by priests and abolitionists, for example, William Lloyd Garrison. Topographical clash over the spread of servitude into western domains and sta tes—zones with neitherRead MoreAnalysis Of Toni Morrison s Beloved Essay1634 Words   |  7 PagesBeloved is one of the best and most well-known books of writing in the African-American society published in 1987. The novel, for the most part, discusses the black community that is unwilling to incite their past and in this way, irritated by its incarnation (Abdullah 25). Toni Morrison does not dissent suppression. Rather, she is pained by its effect on the souls of the black individuals. Nevertheless, the novel approves Toni Morrison s ability in creating the free awareness of various individualsRead MoreThe Contrasting Views of Pro-Slavery vs. Abolitionist Essay1244 Words   |  5 Pages Throughout the history of mankind, slavery has existed in one form or another. Since the times of ancient civilizations to modern era subjugations, there have forces who feel strongly of its necessity and purpose, while others have devoted themselves to seeing the ideas and acts of slavery abolished. America is not an exception to the concept of slavery and during the nation’s early history, parties from both sides have been made famous for their beliefs in the continuation or the denouncement

Art Conclusive Essay Free Essays

â€Å"All the best stories are but one story in reality – the story of escape. It is the only thing which interests us all and at all times, how to escape. † – AC Benson The concept of escape is central to the development of the theme in my work, We escape the mundane reality and boring routine of our daily lives through our dreams and ambitions. We will write a custom essay sample on Art Conclusive Essay or any similar topic only for you Order Now We dream to be different. We dream to be truly alive, in such a way that we can look back at our lives on day and think that we have truly reached our full potential and made the most out of each opportunity. However, often it is people’s and sometimes even our own perceptions of ourselves that keep us in â€Å"the box† and that â€Å"clip our wings† and thus prevent us from reaching our goals. We often live up to the stereotypes placed upon us because of our race, gender, financial standing, culture, nationality etc. To achieve our full potential, we must try to fly above these false perceptions and escape from that which prevents us from chasing our dreams – the banality of reality. ESCAPING THE BANALITY OF REALITY THROUGH NON-TRADITIONAL ART MEDIUMS Brian Dettmer, an American artist1, is an expert at transforming what is perceived and giving it new, true meaning. He is best known for his detailed and innovative sculptures with books and in recent years has established himself as one of the leading contemporary artists working with books today. His work deals with the concept of how information, material and history of our age is being lost, eroded and slipping away from us because it is no longer ‘real’ – it is virtual, digital information. He said, â€Å" In the tangible world we are left with a frozen material but in the intangible world we may be left with nothing. †2 Books, according to society have lost their relevance in their physical form and yet it’s richness and depth is universally respected but the book’s intended function has decreased. Dettmer thus alters the physical form and physical function as well as shifting the preconceived functions to allow new and unexpected roles to emerge. Much like my theme, he is taking away the frame that contains the ideas of the book and changing it to allow it’s true form to be revealed. He meticulously excavates or concisely alters the book so as to dissect communicative objects or systems and allows for its content to be recontextualised and new meanings and interpretations to emerge. The book, in essence thus breaks free and escapes from it’s bindings – its reality. From Dettmer, I investigated the idea of using paper as a medium. However, like Dettmer I wanted to portray the concept of â€Å"escape† through my medium. Naturally, â€Å"escape† makes me think of birds flying from a cage – but how to represent the birds and how represent the cage according to my theme? According to my theme it is perceptions that are trapping us and our dreams and ambitions that are freeing us, and perceptions are all in the mind. I thus decided to make a white head from Plaster of Paris with my own face on, to make my work more personal. The white represents the dry, yeastless factuality that is reality and from the cranium I attached a wire spiral. In the dream world, nothing is realistic and as it seems – much like the way Dettmer represents the content of his books, and thus the birds shouldn’t be realistic. Wanting to make the unrealistic birds from paper, I opted to make origami cranes from bright optimistic colours. The colours represented the hope, joy and how vivid are dreams are, but mostly how full of life. To add further to the idea that the birds are escaping with our memories, i decided to use photographs from my Lomography film photographs to make the cranes at the the top of the spiral and have them unfolding out into one photograph with a drawing of a bird flying into the distance. the work contributes to the theme of reality being â€Å"ripped apart† and the dreams coming together to reach new heights for the individual – perceptions being shed along the way. THE SYMBOLIC BALANCE BETWEEN THE LIVING AND THE â€Å"PRE-FABRICATED† EXPRESSED THROUGH METAPHORICAL VECTORS Sandrine Pelletier3, an artist I was drawn to because she borrows her creative and production processes from folk arts, from arts and crafts, ranging from their most worthy to their most trivial forms, as well as from DIY in order to conceive a body of free-standing works, all of which are underpinned by the notion of subversion and experimentation with the limits of materials. I loved how she made simple arts and crafts into exquisite works of art. I had always wanted to thread a form of tapestry – in the traditional way my grandmother did it, but wanted to incorporate my themes of perceptions, dreams and reality. I thus decided on the image of a ballerina – always perceived to be graceful, gentle, quiet women who were not outspoken or loud, but just polite. I could resonate with this concept on a personal level as when I was little people called me â€Å"Nina pretty ballerina† (from the ABBA song) and I despised it and to break away from the name I did karate. The ballerina is a wonderful symbol of being stereotyped and placed â€Å"in the box†. Pelletier did a piece titled â€Å"Flash Dance†4, I was greatly inspired by that represented two ballerina pumps worn on the tips with a trail of blood on material protruding from the back. This specific artwork made me think of the realities and difficulties of being a ballet dancer and all the physical and emotional strain they must take. This coincided with my theme in the way that it is not always easy to break away from the perceptions placed upon you and sometimes it takes blood, sweat and tears to achieve your goals and to make your dreams come true. As I wanted to create a link between what was â€Å"real† and â€Å"living† and the materialistic nature that is the perceptions of people (my threaded material ballerina tapestry), I decided to place the ballerina within an old bird cage. Inspired by Pelletier’s work, â€Å"The Goodbye Horses†5, I decided to hang threads from the bottom of my work. From the cage, I suspended many old keys at the bottom of the cage to represent the concept of escape. I also sketched realistic birds on material which I hung inside and around the cage to represent the freedom of one’s true inner self. My piece is more an introspective one that calls upon the viewer to reflect on him/herself and about who they really are as opposed to the person people see on the outside – the person they are perceived to be. In this way my work is like Pelletier’s in that her works free itself of all its tautology and escapes all systematic interpretation. It deconstructs conscious contexts and endows Pelletier to redefine her own work and to the answer the question of the function of art through logical means and to question the function if perceptions and stereotypes. It also implements an intuitive and automatic writing, in an attempt to capsulate her own perception of the world and it’s relation to the real world, to memory, to emotion, to identity, to the invisible.? PROCESS AND HOW IT STITCHES IDEAS TOGETHER Briann Dettmer starts with an existing book and seal its edges, creating an enclosed vessel full of unearthed potential. He cuts into the surface of the book and dissect through it from the front. He works with knives, tweezers and surgical tools to carve one page at a time, exposing each layer while cutting around ideas and images of interest. Nothing inside the books is relocated or implanted, only removed. Images and ideas are revealed to expose alternate histories and memories. His work is a collaboration with the existing material and its past creators and the completed pieces expose new relationships of the book’s internal elements exactly where they have been since their original conception. In this way, his process is much like mine regarding the folding of the origami cranes – I started by folding from existing paper the origami cranes. Origami is the Japanese art of paper folding and is a form of sculpting paper without the use of cutting or gluing7 – like Dettmer, I added nothing but only worked with the unearthed potential. The folds must be extremely precise. I then made the Plaster of Paris head using my own face as a mould. The piece was extremely time consuming, but all the planning was complete, so I had a rough guideline to work from. With my thematic piece, I had to develop my concepts a lot more as initially I wanted to suspend my threaded ballerina within a canvas. I however, developed my theme of escape more and thus came up with the old bird cage idea within which I suspended the ballerina along with the material birds as well as hanging the antique keys. This piece was even more time consuming as I didn’t realise how much work had to be put into my tapestry. Both my work required skills I had to learn – the threading of the tapestry and the folding of the origami cranes. It took a lot of patience and practice to correct the techniques and make sure each individual aspect was as near perfect as could be. In the end I have created two art pieces that encouraged more personal growth than anything else, I hope however that the viewer will be able to my themes and be able to resonate with the message of my works. More than that, I hope the viewer will walk away feeling inspired to chase their dreams regardless of perceptions placed upon them and to break away from the weight of reality. I hope they will take flight in heart and soul and feel lighter and happier after seeing my works and to take reach for and take hold of their dreams. â€Å"Anyone can escape into sleep, we are all geniuses when we dream, the butcher’s the poet’s equal there. † – Emile M Cioran Bibliography http://www. maskara. ch/index. php? /projects/flash-dance/ http://www. maskara. ch/index. php? /projects/goodbye-horses/ http://briandettmer. com/ http://en. wikipedia. org/wiki/Origami How to cite Art Conclusive Essay, Essay examples