Organic compounds determination, water samples

The analytical procedures for determining organic compounds in water samples usually involve a number of steps, such as solvent extraction, chemical fractionation, sample cleanup, and solvent reduction, before the final analysis is undertaken. Regardless of the complexity of the analytical procedure, however, almost all water samples are stored in a container for some time between... 

Ketola, R.A., V.T. Virkki, M. Ojala, et al. 1997. Comparison of different methods for the determination of volatile organic compounds in water samples. Talanta 44 373-382. 

Staniszewska M, Wolska L, NamiesnikJ. Advantages and limitations of methods for determination of volatile and semivolatile organic compounds in water samples. Pol Wiadomosci Chemiczne 2003 57 185-222 (in Polish). 

Nielen, M. W. F., Frei, R. W., and Brinkman, U. A. Th., Online handling and trace enrichment in liquid chromatography. The determination of organic compounds in water samples. In Selective Sample Handling and Detection in High-Performance Liquid Chromatography, Frei, R. W. and Zech,... 

This is an alternative technique to headspace analysis for the identification and determination of volatile organic compounds in water. The sample is purged with an inert gas for a fixed period of time. Volatile compounds are sparged from the sample and collected on a solid sorbent trap—usually activated carbon. The trap is then rapidly heated and the compounds collected and transferred as a plug under a reversed flow of inert gas to an external gas chromatograph. Chromatographic techniques are then used to quantify and identify sample components. 

High-resolution GC equipped with an appropriate detector is the most common analytical technique for determining the concentrations of 1,2-dibromoethane in air, water, wastewater, soil, leaded gasoline, and various foods (e.g., grains, grain-based foods, beverages, and fruits). The choice of a particular detector will depend on the nature of the sample matrix, the detection limit, and the cost of the analysis. Because volatile organic compounds in environmental samples may exist as complex mixtures or at very low concentrations, concentrations of these samples prior to quantification are... 

A review of high-performance liquid chromatographic (HPLC) instrumentation, techniques, and methodologies for the determination of trace organic compounds in water is presented. The review includes approaches to sample cleanup or analyte isolation for those compounds likely to be candidates for analysis by HPLC. Column technology, as it contributes to the use of HPLC for trace organic analyses, is discussed. Finally, various techniques for quantitative and qualitative detection of analytes are discussed. 

Special care must always be exercised in the study of parts-per-billion concentrations of organics in water to ensure minimal losses due to sample degradation, adsorption or absorption to process materials, and other similar losses. These issues were addressed by dividing the measurement procedures into two parts (1) sample preparation and (2) analytical method, or finish. Because well-defined sample preparation steps were not available from the literature for the quantitative determination of parts-per-billion concentration levels of most of the model organic compounds in water, a considerable amount of effort was placed on the development of appropriate procedures for such measurements. In particular, each method was developed with the indent to have a procedure that could verify the presence of appropriate concen-... 

In the determination of organic compounds in biological samples drastic methods such as ignition cannot be used. Physicochemical methods such as extraction, distillation and all types of chromatographic methods are more convenient for separating the substance to be determined from the interfering components. For compounds that will only dissolve in water with difficulty, either mixtures of water and organic solvents (e.g., alcohols, dioxan, acetone) or anhydrous solvents (e.g.. 

The newly developed solid-phase microextraction (SPME) technique, first reported by Pawliszyn in 1989, is increasingly used for the gas chromatographic determination of a wide variety of volatile and semivolatile organic compounds in water or aqueous extracts of different substrates. Basically, it involves the extraction of specific organic analytes directly from aqueous samples or from the headspace of these samples in closed vials. The extraction is achieved onto a fused-silica fiber coated with a polymeric liquid phase. After equilibration, the fiber containing the absorbed or adsorbed analyte is removed and thermally desorbed in the hot injector port of a gas chromatograph or in an appropriate interface of a liquid chromatograph. ... 

One of the most important problems in the analysis of phthalates from water samples is the detection of these compounds in the samples used as blanks. Phthalates have been detected in purified water commonly used in laboratories, including water distilled in a glass distillation apparatus, MUli-Q water, and commercially available water specially for VOC (Volatile organic compounds) determination. Therefore, special caution should be taken with the experimental use of water in laboratories. Some authors have reported the levels of phthalate esters found in the purified water employed in its studies (see Table 28.4). The concentrations found are frequently... 

COD is defined as the quantity of a specified oxidant that reacts with a sample under controlled conditions. The quantity of oxidant consumed is expressed in terms of its oxygen equivalence. COD is expressed in mg/L O2. In environmental chemistry, the chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers), making COD a useful measure of water quality. 

EKC separations of synthetic dyes include buffered SDS systems and polymeric electrolytes, modified by organic solvents. Examples of the determination of azo dyes, mono-and disulfonated compounds in water samples, as well as synthetic dyes in spiked water and soil... 

Headspace analysis has also been used to determine trichloroethylene in water samples. High accuracy and excellent precision were reported when GC/ECD was used to analyze headspace gases over water (Dietz and Singley 1979). Direct injection of water into a portable GC suitable for field use employed an ultraviolet detector (Motwani et al. 1986). While detection was comparable to the more common methods (low ppb), recovery was very low. Solid waste leachates from sanitary landfills have been analyzed for trichloroethylene and other volatile organic compounds (Schultz and Kjeldsen 1986). Detection limits for the procedure, which involves extraction with pentane followed by GC/MS analysis, are in the low-ppb and low-ppm ranges for concentrated and unconcentrated samples, respectively. Accuracy and precision data were not reported. 

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