Analyte isolation, aqueous environmental

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.

Kientz and coworkers (l6 l7) have reviewed the general application of chromatographic methods to CWC-related analysis. In our previous review of LC/MS (4), the majority of applications were concerned with environmental-type analysis of polar degradation products of CW agents. This is still the major application because LC/MS avoids the requirement to isolate polar analytes from aqueous matrices and the need for derivatization, both of which can be major sources of error in GC/MS analysis (18). More recently there have been a number... 

Modified silica with a C18 reversed-phase sorbent has historically been the most popular packing material, owing to its greater capacity compared to other bonded silicas, such as the C8 or CN types [22]. Applications of C18 sorbents include the isolation of hydrophobic species from aqueous solutions. The mechanism of interaction with such sorbents depends on van der Waals forces, and secondary interactions such as hydrogen bonding and dipole-dipole interactions. Nevertheless, the main drawbacks of such sorbents are their limited breakthrough volumes for polar analytes, and their narrow pH stability range. For these reasons, reversed-phase polymeric sorbents are also used frequently in environmental applications for the trace enrichment of soluble molecules that are not isolated by reversed-phase sorbents such as C18. 

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. 

There is an ever increasing interest in the use of liquid membranes for performing chemical separations. Emulsion liquid membrane (ELM) systems in which the targeted chemical species in an aqueous solution is extracted with a multicomponent emulsion have a variety of applications. These include isolation and concentration of valued or harmful substances in industrial chemistry, separation of substances for determination in analytical chemistry, separation of pollutants in environmental remediation, and detoxification of biological fluids by removal of harmful substances of exogenic and endogenic origins (7). 

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