Chemical methods nonpolar organic compounds

Since the nature of these chemicals in water varies from polar compounds like phenol to very nonpolar compounds such as pentachlorophenol (PCP), it is a challenge to analytical chemists to determine them collectively. Conventional analytical methods for these compounds are often extensive as they require numerous analytical steps to obtain significant results. The first and also one of the most important requirements is to find a suitable sample preparation technique that allows the separation of the substances of interest from the sample matrix. The analysis of phenols in water is normed by EPA Method 625 [9]. A main disadvantage of this time-consuming and cost-intensive method is the large sample volume required for the extraction and use of large volumes of toxic organic solvents. Therefore, current developments in the field of sample preparation aim for fast and low-cost treatment of enviromnental samples. 

Veith, G.D., Austin, N.M., Morris, R.T. (1979) A rapid method for estimating LOG P for organic chemicals. Water Res. 13, 43-47. Verschueren, K. (1977) Handbook of Environmental Data on Organic Chemicals. Van Nostrand Reinhold, New York, von Oepen, B.V., Kdrdel, W., Klein, W. (1991) Sorption of nonpolar and polar compounds to soils Processes, measurements and experience with the applicability of the modified OECD-Guideline 106. Chemosphere 22(3/4), 285-304. 

Some compounds can be easily detected by both CGC and high-pressure liquid chromatography (HPLC), for instance, cocaine, which has characteristic electron-impact mass and UV fluorescence spectra (Fernandez et al., 2009). Inert nonpolar or low-polar silicone phases have chromatographic features suitable for separation and analysis by CGC. In addition, dedicated base-treated stationary phases are now used to improve the identification and quantification of compoimds. HPLC analyses are done by reversed-phase elution with buffered water/organic solvent mixtures. In contrast, numerous native drags and almost all metabolites require chemical derivatization before analysis [e.g., with trifluoroacetic anhydride, A -methyl-7V-trimethylsilyltrifluoroacetamide, or iV-(r-butyldimethylsilyl)-Af-methyltrifluoroacetamide, which is usually used for cannabinoids] this improves the analytical performance of the method and drastically reduces the risk of misinterpretation and misidentification of the compoimds. 

Sulfur Mustard stability in nonpolar solvents has been determined by GC and GC-MS methods. The situation is more complex for Lewisite because GC methods generally involve derivatization with thiols, and are also complicated by the fact that Lewisite and its hydrolysis products give the same compound after derivatization. The solution to this problem can be found by measuring Lewisite without derivatization. In a study reported by Down in 2005 [63], toluene was selected as the extraction solvent because Lewisite slowly decomposed in other organic solvents, such as acetone and hexane. Thermal oligomerization in the injection port was prevented by on-column injection and a deactivated guard column was used to prevent the well-known problems of memory effects and column deterioration that occur with Lewisite. The extracts were analysed by GC-AED and GC-MS with both electron and chemical ionization [63]. More GC-MS techniques will be described in Chapter 4 with respect to the numerous degradation products of Sulfur Mustard. 

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