Trace organic compounds environmental samples

High-Performance Liquid Chromatography for Determination of Trace Organic Compounds in 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. 

Graham and Garrison (17) evaluated on-line trace enrichment for the determination of trace organic compounds in aqueous environmental samples. These workers were primarily interested in nonvolatile and thermally labile compounds that were not readily analyzed by GC methodology. A 2-mm i.d. X 70-mm long stainless steel precolumn was packed with 30-75 pm diameter octadecyl-derivatized silica. This precolumn was substituted for the sample loop in a conventional, high-pressure, six-port valve. Water samples, 10-100 mL, were pumped directly on the precolumn. After loading, the valve was switched to... 

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... 

An attempt has been made to survey the current status of technology in HPLC as it applies to the analysis of trace organic compounds in aqueous environmental samples. No doubt, some developments relative to this topic have been overlooked, but the overall assessment should provide a glimpse of what has been done and also of what is possible. 

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 ... 

The types of examples that use ion exchange include general chemistry (salt conversions and preparation of deionized water), purification of organic compounds, environmental applications (trace enrichment and interference removal), food and beverage samples (sample clean-up), pharmaceutical and biological samples (trace enrichment), metal ions (trace enrichment), and humic substances (hydrogen saturation), to name but a few. These examples are explained in the following sections. 

A specific application of environmental SPE is sample preparation of extra-large volumes (from 10 to 100 L). This work was pioneered in the early 1970s by Junk and co-workers (1974) for the analysis of trace organic compounds in water using styrene-divinylbenzene copolymers (XAD-2 resin from Rohm and Haas) and by Thurman and Malcolm (1981) and Leenheer and Stuber (1981) for the analysis of natural organic substances in water (humic substances). One can obtain the XAD resins from Supelco (Appendix Products Guide) and still follow the protocol of this early work for the isolation of contaminants and humic substances from large volumes of water (10-1000 L of water). 

The deteraiination of trace organic compounds in environmental samples requires getting them separated from the sample matrix prior to measurement, and usually involves extraction of some sort. Common trace organics include aliphatic and... 

Throughout this book the use of a number of standard analytical samples is recommended in order that practical experience may be gained on substances of known composition. In addition, standard reference materials of environmental samples for trace analysis are used for calibration standards, and pure organic compounds are employed as standard materials for elemental analysis. 

Hennion MC, Coquart V. 1993. Comparison of reverse-phase extraction sorbents for the on-line trace enrichment of polar organic compounds in environmental aqueous samples. J Chromatogr 642 211-224... 

Early studies using resins for isolation and analysis of trace organics, such as pesticides, PCBs, and organic acids, from small volumes of water showed excellent recovery and the potential of easy application to environmental samples. Isotherm studies in distilled water were used to define the sampling parameters for quantitative analysis of these compounds. Later, studies using resin samplers for large-volume environmental samples were extrapolated from the early low-volume resin work of Junk et al. (5,14) and Thurman et al. (27) (see Table I). 

Different analytical methods used for the analysis of samples collected under the requirements of different environmental laws are discussed in Chapter 2.4. Although many of these methods target the same analytes, their calibration requirements are different. Tables 4.5, 4.6, and 4.7 summarize the differences in calibration requirements for organic compound and trace element analysis. (Inorganic analyte methods and techniques have a range of requirements that cannot be summarized in a concise manner we should refer to specific methods for this information). 

Stir bar sorptive extraction (SBSE), an approach theoretically similar to SPME, was recently introduced [141] for the trace enrichment of organic compounds from aqueous food, biological, and environmental samples. A stir bar is coated with a sorbent and immersed in the sample to extract the analyte from solution. To date, reported SBSE procedures were not usually operated as exhaustive extraction procedures however, SBSE has a greater capacity for quantitative extraction than SPME. The sample is typically stirred with the coated stir bar for a specified time, usually for less than 60 minutes, depending on the sample volume and the stirring speed, to approach equilibrium. SBSE improves on the low concentration capability of in-sample solid-phase microextraction (IS-SPME). 

Another example of ultrasound use is leaching of organic impurities from different kinds of samples. The main analytes of interest are PAHs, which are widespread in soil, sediment, dust, and particulate samples [55]. USE is recommended as a fast, efficient, and direct environmental sample preparation method for determination of PCBs, nitrophenols, pesticides, or polymer additives. Organometallic and biologically active compounds (such as vitamins A, D, and E) present in samples in trace quantities, can be extracted from animal and plant tissues with the aid of ultrasonic wave energy [59]. Table 6.6 presents some typical applications of USE in trace analysis of biological and environmental samples [60]. 

Zenker, A., Schutz, H., Fent, K. Simultaneous trace determination of nine organic UV-absorbing compounds (UV filters) in environmental samples. J. Chromatogr. A 1202, 64-74 (2008)... 

An on-line technique coupling preconcentration via a precolumn packed with PGC and LC with a PGC analytical column has been applied to the trace-level determination of some polar and water-soluble organic pollutants from environmental waters.As these analytes are much more retained by the graphite surface than by silica Cig, preconcentration on the PGC precolumn cannot be coupled on-line with a widely used and more efficient Cjg silica analytical columns. In this study, applications were presented for the trace-level determination of 2-chloro-4-aminophenol, chloroanilines, amino-phenols, and cyanuric acid these organic compounds are included in the EC environmental priority pollutant list. The influence of the sample matrix was investigated with drinking and river water samples. 

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