Environmental sample preparation

Much of the current interest in using analytical-scale SFE systems comes from the need to replace conventional liquid solvent extraction methods with sample preparation methods that are faster, more efficient, have better potential for automation, and also reduce the need for large volumes of potentially hazardous liquid solvents. The need for alternative extraction methods is emphasized by current efforts to reduce the use of methylene chloride as an extraction fluid for environmental sample preparation [158]. The potential for applying SFE to a wide variety of environmental and biological samples for both qualitative and quantitative analyses is widely described in reviews [159-161] and the references therein. Analytical-scale SFE is most often applied to relatively small samples (e.g., several grams or less). 

The chapter reviews the literature on the individual stages of environmental sample preparation up to the stage of final determinations with regard to analytes occurring in low concentrations. Special attention is paid to... 

The solvent extracts can be cleaned up by traditional column chromatography or by solid-phase extraction cartridges. This is a common cleanup method that is widely used in biological, clinical, and environmental sample preparation. More details are presented in Chapter 2. Some examples include the cleanup of pesticide residues and chlorinated hydrocarbons, the separation of nitrogen compounds from hydrocarbons, the separation of aromatic compounds from an aliphatic-aromatic mixture, and similar applications for use with fats, oils, and waxes. This approach provides efficient cleanup of steroids, esters, ketones, glycerides, alkaloids, and carbohydrates as well. Cations, anions, metals, and inorganic compounds are also candidates for this method [7],... 

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]. 

Wells, M. J. M. and Michael, J. L. 1987. Reversed-phase solid-phase extraction for aqueous environmental sample preparation in herbicide residue analysis, J. Chromatog. Sci., 25 345-350. 

The field of environmental sample preparation has undergone a revolution in the last twenty five years. What was essentially a series of basic methods and procedures has developed (and continues to develop) into a new exciting area with a strong influence from instrumental approaches. This book essentially covers the traditional approaches of environmental sample preparation for both metals and organic compounds from a range of matrices. 

Finally, I should like to give a special mention to all of the students (both past and present) who have contributed to the development of interest in the field of environmental sample preparation. The achievements have been many and varied across a broad area of environmental sample preparation, but it has all been worthwhile. 

Various applications of environmental sample preparation for chromatographic analysis are shown in Table 2.7 to Table 2.10. In these tables recent applications of the new sample preparation techniques are shown classified in order of the different analytes. This compilation of applications is a representative overview of recent applications and new trends of sample preparation in the field of chromatographic techniques applied to environmental analysis. This compilation is not exhaustive it is only a brief selection of the more significant works recently published. 

HOW IS AN ENVIRONMENTAL SAMPLE PREPARED TO DETERMINE TRACE CYANIDE ... 

Internal methods of quality assessment should always be viewed with some level of skepticism because of the potential for bias in their execution and interpretation. For this reason, external methods of quality assessment also play an important role in quality assurance programs. One external method of quality assessment is the certification of a laboratory by a sponsoring agency. Certification is based on the successful analysis of a set of proficiency standards prepared by the sponsoring agency. For example, laboratories involved in environmental analyses may be required to analyze standard samples prepared by the Environmental Protection... 

Before sample preparation, surrogate compounds must be added to the matrix. These are used to evaluate the efficiency of recovery of sample for any analytical method. Surrogate standards are often brominated, fluorinated, or isotopically labeled compounds that are not expected to be present in environmental media. If the surrogates are detected by GC/MS within the specified range, it is... 

Application of rotating coiled columns has become attractive for preparative-scale separations of various substances from different samples (natural products, food and environmental samples) due to advantages over traditional liquid-liquid extraction methods and other chromatographic techniques. The studies mainly made during the last fifteen years have shown that using rotating coiled columns is also promising for analytical chemistry, particularly for the extraction, separation and pre-concentration of substances to be determined (analytes) before their on-line or off-line analysis by different determination techniques. 

Analysis of soils is an important task in the environmental researches. Reliability of ICP-MS results of soil analysis mainly depends on chemical sampling. Recently microwave systems are widely used for preparation of different samples. Influence of microwave radiation on sample ensures a complete decomposition of sample, greatly increases the mineralization, and allows possible losses of volatile elements to be minimized. In the given study to intensify decomposition of soils we applied the microwave sample preparation system MULTIWAVE (Anton Paar, Austria and Perkin-Elmer, USA) equipped with rotor from 6 autoclaves with TEM reaction chambers of 50 ml volume. 

One of trends of development of thin-layer chromatography implies that replacement of aqueous-organic eluents by micellar surfactants solution. This is reduces the toxicity, flammability, environmental contamination and cost of the mobile phases, reduce sample prepar ation in some cases. 

J. Henion, E. Brewer and G. Rule, Sample preparation for LC/MS/MS analyzing biological and environmental samples . Anal. Chem. 70 650A-656A (1998). 

V. Pichon, M. Bouzige, C. Miege and M. C. Hennion, Immunosorbents natural molecular recognition materials for sample preparation of complex environmental matrices . Trends. Anal. Chem. 18 219-235 (1999). 

Separation and detection methods A survey on determination of tin species in environmental samples has been published by Leroy et al. (1998). A more detailed overview of GS-MS methodology has been published by Morabito et al. 1995) and on sample preparation using supercritical fluid extraction has been described by Bayona (1995)- The techniques are now under control, so that routine procedures are available at a relatively low cost (Leroy et al. 1998). 

Fodor, P. and Molnar, E. (1993). Honey as an environmental indicator Effect of sample preparation on trace element determination by ICP-AES. Microchim. Acta 112,113-118. 

LC/MS/MS is the preferred means of detection, quantitation, and confirmation of sulfonylurea herbicides in biological and environmental matrices. Therefore, recommendations for establishing and optimizing LC/MS/MS analyses common to all matrices are given first, followed by specific rationales for methods and sample preparation techniques for plant, soil, and water matrices. 

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

During the last few years, miniaturization has become a dominant trend in the analysis of low-level contaminants in food and environmental samples. This has resulted in a significant reduction in the volume of hazardous and expensive solvents. Typical examples of miniaturization in sample preparation techniques are micro liquid/liquid extractions (in-vial) and solvent-free techniques such as solid-phase microextraction (SPME). Combined with state-of-the-art analytical instrumentation, this trend has resulted in faster analyses, higher sample throughputs and lower solvent consumption, whilst maintaining or even increasing assay sensitivity. 

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