Cleanup aqueous environmental samples

In this chapter, the current and future capabilities of HPLC for the determination of trace organic compounds in aqueous environmental samples will be assessed. This assessment will include approaches to sample cleanup or analyte isolation for those species likely to be candidates for analysis by HPLC. Column technology, as it contributes to the use of HPLC for trace organic analyses, will be surveyed. Finally, detection of the compounds eluting from the system will be examined. The ultimate detector will always adequately identify and measure the compounds of interest. 

In the past 5 years the frequency of reports on the use of HPLC technology for the determination of trace organic compounds in aqueous environmental samples has been steadily increasing. Many innovative approaches to sample cleanup and analyte isolation have been reported. Reversed-phase separation, with its many mobile-phase adaptations, has been and continues to be the most popular HPLC separation mode. The development of fast columns and microbore columns should provide optimal configurations for particular applications. The operating characteristics of microbore columns also make... 

Organic pollutants present in aqueous-solid phase environments and discussed in the present chapter include petroleum hydrocarbons, pesticides, phthalates, phenols, PCBs, chlorocarbons, organotin compounds, and surfactants. In order to study the chemodynamic behavior of these pollutants, it is important that (1) suitable pre-extraction and preservation treatments are implemented for the environmental samples, and (2) specific extraction and/or cleanup techniques for each organic pollutant are carried out prior to the identification and characterization steps. 

Applications On-line SPE-GC and SPE-GC-MS couplings find wide application for sample cleanup of biological, environmental and industrial analysis of aqueous samples [67]. SPE-GC-AED/MS is ideally suited for the (nontarget) screening of hetero-atom-containing compounds in aqueous samples, and allows confirmation plus identification in one run [68]. Specific applications of hyphenated SPE-GC systems for polymer/additive analysis were not identified. 

Gas chromatography (GC) is the most common analytical technique for the quantitative determination of organic pollutants in aqueous and nonaqueous samples. In environmental analysis, a very low detection limit is required to determine the pollutants at trace levels. Such low detection can be achieved by sample concentration followed by cleanup of the extract to remove interfering substances. Sample extractions and cleanup procedures are described in detail in Chapter 5 of Part 1 of this text. 

MIP-SPE sorbents are stable in both aqueous and organic solvents and are very selective for the analyte of interest. Increased selectivity relative to other sorbents produces increased sensitivity because larger sample volumes can be extracted. Also, increased selectivity results in efficient sample cleanup of the analyte in the presence of complex biological or environmental matrix... 

These two examples clearly demonstrate the importance of secondary equilibria phenomena, particularly when the analyte of interest is ionizable in an environmental aqueous sample such as groundwater. Both examples exploit secondary equilibria in developing alternative methods that include LLE in extraction and in cleanup when applied to the complex sample matrices commonly encountered in TEQA. In the next section, the mathematical framework that underlies secondary equilibria will be presented. 

Solid-phase extraction (SPE) can be used to separate an organic analyte from the aqueous phase and to concentrate the analyte in a few milliliters of solvent. SPE also can be used to clean up a sample matrix and remove concomitant contaminants from the analyte. In some cleanups the analyte is absorbed onto the solid phase and the interferences pass through unretained. In the opposite cleanup strategy the solid phase retains the interferences and allows the analyte to pass through the cartridge with the mobile phase. In some environmental application, SPE performs all three roles—extraction, concentration, and cleanup. 

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