Analytical quality control, environmental analysis

In this section a concise overview of the most widely used analytical procedures for the determination of PCBs in environmental matrices (namely, air, sea water, snow/firn/ice, sediment/soil and biota) is given. Regardless of the nature of the sample, the following steps are generally included in an analytical procedure i) sample collection and storage ii) sample preparation (extraction of the analytes and cleanup of the extract) iii) instrumental analysis iv) data evaluation, including analytical quality control. 

In subsequent chapters, we provide an overview of SPMD fundamentals and applications (Chapter 2) the theory and modeling which includes the extrapolation of SPMD concentrations to ambient environmental concentrations (Chapter 3) study considerations such as the necessary precautions and procedures during SPMD transport, deployment, and retrieval (Chapter 4) the analytical chemistry and associated quality control for the analysis of SPMD dialysates or extracts (Chapter 5) a survey and brief description of bioassays-biomarkers used to screen the toxicity of SPMD environmental extracts (Chapter 6) discussions on how HOC concentrations in SPMDs may or may not relate to similarly exposed biomonitoring organisms (Chapter 7) and selected examples of environmental studies using SPMDs (Chapter 8). In addition, two appendices are included which provide... 

MS delivers both information about the mass and the isotope pattern of a compound and can be used for the structural analysis upon performance of MS/MS experiments. Therefore, it is a valuable tool for the identification and characterization of an analyte as well as for the identification of impurities. Potential applications are the identification of IL in fhe quality control or in environmental studies. Unwanted by-products formed during the s)mthe-sis or by the hydrolysis of components of the ILs can be identified by this method. The analysis of fhe IL itself is also a prerequisite for the analysis of compounds dissolved in fhese media, as will be ouflined in the section 14.4. Beside the identification of fhe ILs, a characterization of different properties like water miscibility and the formation of ion clusfers, providing valuable information abouf fhe molecular structure of the IL, can be performed by means of MS techniques. The majority of studies reported up to now have dealt with ILs encompassing substituted imidazolium or pyridinium cations, therefore fhe following discussion concentrates on these compounds unless otherwise stated. 

Acceptance criteria for precision depend very much on the type of analysis. For pharmaceutical quality control, precision of better than 1 % RSD is easily attained, while for biological samples the precision is more like 16% at the detection limit and 10% at higher concentration levels. For environmental and food samples, the precision is very much dependent on the sample matrix, the level of the analyte, and on the analytical method, being in the range of 2% to more than 20% RSD. Acceptable precision values as a function of the analyte concentration have been suggested (11) by the Association of Official Analytical Chemists (AOAC) peer-verified methods program (Table 25.1). 

The analysis of chemical pollutants in the environmental matrices has entered a new phase in the last decade. Modifications in instrumentation, sampling, and sample preparation techniques have become essential to keep up with the requirements of achieving ppt to low ppb detection levels, as well as to achieve a faster speed of analysis. In addition, more stringent quality-control (QC) requirements in analytical methods have become necessary to obtain high data quality. This has led to the many new methodologies that are different from the conventional macro and semicmicro analytical approach. 

The major quality parameters to be addressed during sample preparation are listed in Table 1.4. These are accuracy, precision, extraction efficiency (or recovery), and contamination control. These quality issues also need to be addressed during the analysis that follows sample preparation. Accuracy is determined by the analysis of evaluation samples. Samples of known concentrations are analyzed to demonstrate that quantitative results are close to the true value. The precision is measured by running replicates. When many samples are to be analyzed, the precision needs to be checked periodically to ensure the stability of the process. Contamination is a serious issue, especially in trace measurements such as environmental analysis. The running of various blanks ensures that contamination has not occurred at any step, or that if it has, where it occurred. As mentioned before, the detection limits, sensitivity, and other important parameters depend on the recovery. The efficiency of sample preparation steps such as extraction and cleanup must be checked to ensure that the analytes are being recovered from the sample. 

Generally, the analysis of environmental pollutants is considered as a necessary expense that is performed solely if stated by law. With less expensive screening methods and automated modern equipment to analyze suspect samples, the cost of analysis will become much lower. Hence, the attitude towards QA would most probably be more positive and the analytical work much more reliable for the customers. This also strengthens the international competitiveness of European producers. The credibility of the entire monitoring chain (screening methods, reference and standardized methods, as well as CRMs for the quality control of these methods) lies in the adequacy and integration of all three levels of the system. The adequate development and validation of methods is a prerequisite for a harmonized measurement system [80]. 

CRM for road dust (BCR-723) containing 81.3 2.5 Jg/kg Pt, 6.1 1.9 ig/ kg Pd, and 12.8 1.3 Jg/kg Rh, was introduced [49, 228]. It is widely used for quality control of results obtained in the analysis of environmental materials (e.g., airborne particulate matters, dusts, soils, and sediments). Comparison of results obtained using different analytical procedures and interlaboratory studies are recommended when there is a lack of suitable CRM (e.g., in examination of clinical samples). The use of standards based on real matrices (e.g., saliva, plasma, ultrafiltrates, and lung fluids) instead of synthetic solutions is recommended in such analyses. Difficulties with the identification and quantification of different metal species in examined samples make the reliability of results of great importance. The use of various instrumental techniques for examination of particular samples can be helpful. The application of chromatography, mass spectrometry, and electrochemistry [199] HPLC ICP MS and HPLC MS/MS [156] ESI MS and MALDI [162] micellar electrokinetic chromatography, NMR, and MS [167] AAS, ESI MS, and CD spectroscopy [179] SEC IC ICP MS and EC ESI MS [180] and NMR and HPLC [229] are examples of such approaches. 

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