Environmental analysis extraction techniques

See alsa Chromatography Multidimensional Techniques. Environmental Analysis. Extraction Solid-Phase Extraction. Food and Nutritional Analysis Sample Preparation Contaminants Pesticide Residues. Forensic Sciences Drug Screening in Sport Illicit Drugs. Herbicides. Liquid Chromatography Instrumentation Clinical Applications Food Applications. Mass Spectrometry Peptides and Proteins. Pesticides. Pharmaceutical Analysis Sample Preparation. Proteomics. Sample Handling Automated Sample Preparation. Water Analysis Organic Compounds. 

Given the concerns about the use of toxic organic solvents in food chemistry, many new techniques have been developed to overcome or minimize this problem. For instance, environmentally clean extraction techniques, such as those based on the use of compressed fluids (pressurized liquids, PLE supercritical fluids, SFE and subcritical water, SWE or PHWE), are widely used as alternatives to conventional procedures, such as solid—liquid extraction (SEE), liquid—liquid extraction (LLE), and the like. These alternative processes have in common the use of lower amount of solvents (from hundred milliliters to few milliliters), the lack of toxic residues, higher efficiency extraction (in terms of yields and energy used), and the improved selectivity of the process. SFE has been used in food analysis as a sample preparation technique, mainly for lipophilic compounds, while PLE has been extensively used for many compositional food applications, because the selectivity of this technique... 

Important developments in LC-GC have been made by Grob and co-workers (79-81) and by the Brinkman group (82-87), who have mainly studied the application of this technique to environmental analysis. This coupled technique has usually been applied to water, although air and soil extracts have also been analysed. 

Recent Uses of Solid-Surface Luminescence Analysis in Environmental Analysis. Vo-Dinh and coworkers have shown very effectively how solid-surface luminescence techniques can be used for environmentally important samples (17-22). RTF has been used for the screening of ambient air particulate samples (17,18). In addition, RTF has been employed in conjunction with a ranking index to characterize polynuclear aromatic pollutants in environmental samples (19). A unique application of RTF reported recently is a personal dosimeter badge based on molecular diffusion and direct detection by RTF of polynuclear aromatic pollutants (20). The dosimeter is a pen-size device that does not require sample extraction prior to analysis. 

Desrosiers [23] has dared ranking extracting methods as follows (in order of preference) SFE, US, hot block or MAE, Soxhlet (to be phased out as quickly as possible). Munteanu [556] has evaluated extraction techniques for additives from polymers prior to chromatographic analysis (up to 1990). The analytical extraction of additives from polymers has recently critically been reviewed with emphasis on SFE, MAE and ASE [92]. Dean [272] compared modem extraction techniques, with focus on environmental analysis. 

High polarity is one of the reasons why both the ionic and amphoteric surfactants, and especially their metabolites, are difficult to detect. This property, however, is important for the application tasks of surface-active compounds, but is also the reason for their high water solubility. Due to this fact, their extraction and concentration from the water phase, which can be carried out in a number of very different ways, is not always straightforward. Furthermore, they are often not volatile without decomposition, which thus prevents application of gas chromatographic (GC) separation techniques combined with appropriate detection. This very effective separation method in environmental analysis is thus applicable only for short-chain surfactants and their metabolites following derivatisation of the various polar groups in order to improve their volatility. 

The mass of sample taken for analysis is primarily dependent on four factors (1) the amount of material available, (2) the concentration of the analyte, (3) the heterogeneity of the sample, and (4) the method of analysis. Most conventional solvent extraction techniques currently start with more sample than is required, use more extraction solvent than is necessary, and ultimately only analyze 0.1% of the material prepared, e.g., 1 pi from 1 ml. Micro-extraction techniques [468] can be used in conjunction with on-line LC-GC or LC-MS to utilize the whole extract in the final determinations. This approach can significantly reduce the size of sample required and the volume of solvent used. Many workers have reported the use of solid phase microextraction (SPME) in different environmental matrices for various pollutants [288,342,345,469 - 477]. 

Analysis of environmental or food samples containing PCBs include matrix preparation, extraction and determination [3]. In this section, some extraction methods, which can be easily coupled to an electrochemical immunosensor, are described. Such extraction techniques have to be simple, fast, useful for in situ measurements and do not require trained personnel. 

Namiesnik, J., Zabiegala, B., Kot-Wasik, A., Partyka, M. and Wasik, A. (2005) Passive sampling and/or extraction techniques in environmental analysis a review. Analytical and Eioanalytical Chemistry, 381, 279-301. 

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. 

The core development of MIMS has centered upon MS ionization techniques for the analysis of aromatic contaminants in water,47 improving membrane extraction selectivity48 and enhancing MIMS sensitivity by cooling and heating the membrane (trap and release MIMS).49 50 A dedicated review has been written on the applications of MIMS in environmental analysis.51... 

In this chapter we shall discuss LCA in the context of protocols for the analysis of polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbon (PAH) in surface water using two different extraction techniques,11 and the LCA of the utilization of different solvents.12-26 Generally speaking, this is the beginning of the use of LCA to assess the environmental impact of analytical protocols at the moment, there are not many papers on this subject, but this situation is sure to improve in the near future. 

The techniques of sample preparation, extraction (isolation), and/or preconcentration of analytes are usually applied in the analysis of trace components of gaseous, liquid, and solid samples. During this operation, transport of analytes from primary matrices (donors) to the secondary matrix (the acceptor) takes place. It should be remembered, however, that the extraction and preconcentration steps could be a source of environmental pollution. The techniques of sample preparation introduced in this chapter have the following advantages253 ... 

Copper is invariably determined by AAS in a lean air-acetylene flame, using the main resonance line at 324.7 nm. The detection limit is generally around 10 ng ml-1, which is marginally better than that generally achievable by flame AFS, and comparable to that reported for AES using a carefully optimized nitrous oxide-acetylene flame.2 Provided samples are not excessively diluted, this value is adequate for many practical applications in environmental analysis, such as the measurement of plant copper concentration or EDTA- or DTPA-extractable copper in soils. Interferences are rare, and unlikely to be a problem from concomitant elements present in most environmental samples, but matrix matching is still advisable. The sensitivity is inadequate for the direct determination of copper in natural water samples, for which a suitable preconcentration technique must be employed.1,23,24... 

Cr(VI) is a toxic element, and its environmental pollution should be monitored even in seawater. CrO - is a stable chemical species in seawater, while Cr(III) also exists in relatively high amounts. Therefore, a separation of Cr(VI) from Cr(III) is necessary in the analysis of Cr( VI). For this purpose, the solvent extraction technique can also be used, being followed by atomic absorption analysis. Many workers have investigated the solvent extraction of total Cr in seawater, where Cr was extracted with acetylacetonate, DDC, APDC and analysed by AAS [37—42]. Hiiro et al. examined in detail the separation of Cr(VI) from Cr(III) in seawater [42]. The effect of pH values on extraction of Cr(VI) is shown in Fig. 5. Cr( VI) is most effectively extracted near pH 5, while Cr(III) is increasingly extracted above pH 4. Therefore,... 

SFE is an efficient and fast extraction technique that fits well with green chemistry strategies. The broadest applications of SFE can be found in food, environmental, and pharmaceutical analysis, in industrial and biomedical laboratories, and in speciation analysis [86, 88, 93-97]. Table 6.13 presents selected examples of the use of SFE in trace analysis. 

The flow diagram in Figure 10.4 is intended as a guide and is the way the author would normally approach a new HPLC analysis. Reversed-phase chromatography is assumed and this will mean evaporation of solvent and dissolution in mobile phase if using the hquid-liquid extraction path. No mention has been made of direct aqueous injection as the times that this technique can be employed in environmental analysis are few indeed. It can be seen that the author s choice of detector is fluorescence then electrochemical then UV. 

Accelerated solvent extraction (ASE), also referred to as pressurized liquid extraction,53-55 is a relative newcomer to the battery of extraction techniques. This technique has been applied successfully to problems in environmental analysis56-58 and has recently begun to find a few applications in pharmaceutical analysis as well. Some of these applications have involved biological samples59,60 and solid-dosage forms such as transdermal patches.61... 

---