Isolation 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... 

Figure 1. Schematic of the strategy for the coupled bioassay-analytical fractionation of residue organics isolated from aqueous environmental samples.

Table I. Mutagenic Activity for Residue Organics Isolated from a Variety of Aqueous Environmental Samples...

Chemical and biological analyses of trace organic mixtures in aqueous environmental samples typically require that some type of isolation-concentration method be used prior to testing these residues the inclusion of bioassay in a testing scheme often dictates that large sample volumes (20-500 L) be processed. Discrete chemical analysis only requires demonstration that the isolation technique yields the desired compounds with known precision. However, chemical and/or toxicological characterization of the chemical continuum of molecular properties represented by the unknown mixtures of organics in environmental samples adds an extra dimension of the ideal isolation technique ... 

Another relatively new SPE approach originally developed for the analysis of volatile organic compounds in environmental samples is solid-phase microextraction (SPME). This technique has gained acceptance for a wide variety of additional applications for the isolation of organic compounds from aqueous solu-... 

Similarly, simple solutions may not be readily available to the real-life problems of analysis and toxicity testing of environmentally important waters. Many of these samples contain complex mixtures of many organic compounds, some of which may be present at very low concentrations. These aqueous solutions must be concentrated and/or the constituents must be isolated before most of the various organic constituents present can be chemically analyzed. This step is necessary so that a sufficient mass of chemicals can be obtained for separation and identification of individual components. An analogous situation... 

Highly hydrophobic sorbents including porous carbon and copolymers of styrene and divinylbenzene (SDB) were widely investigated for environmental applications. The particle-loaded membranes containing modified SDB particles with surface sulfonic acid groups were successfully used for recovering different alcohols, phenols, aldehydes, ketones, or esters from aqueous samples [221]. Carbon-based PLM were also used for isolation of highly polar pesticides from water [222]. 

The metal chelate LLE was much more common 25 years ago when it was the principal means to isolate and recover metal ions from aqueous samples of environmental interest. The complexes were quantitated using a visible spectrophotometer because most complexes were colored. A large literature exists on this subject (14). The technological advances in both atomic absorption and inductively coupled plasma-atomic emission spectroscopy have significntly reduced the importance of metal chelate LLE to TEQA. However, metal chelate LLE becomes important in processes whereby selected metal ions can be easily removed from the aqueous phase. 

This high and reproducible percent recovery for the isolation and recovery of lindane from water strongly suggests that RP-SPE is very appropriate as a sample preparation method for this analyte. Lindane is of continued interest to environmental and toxicological scientists. One such study, discussed next, taken from the author s work, involves the isolation and recovery of lindane from homogenized myometrial tissue suspended in an aqueous matrix. 

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