Laboratory-based methods monitoring sampling

Because of these factors, the worker-exposure monitoring job is never done. It must be done on a periodic basis over the course of the entire job. Such is the case with asbestos and lead abatement work where continuous monitoring is required. Two major categories of samples collected to draw an exposure profile are normally analyzed by laboratories and are called area and personal. In general, direct-reading instruments are used to obtain area or background samples, and personal samples are obtained with laboratory-based analysis methods. 

The majority of studies utilising chromatographic separation of metals with electrochemical detection reported in the literature, refer to laboratory based determination of metals, where discrete batch methods of sampling from individually prepared samples are employed. In contrast, the concept to be reviewed in detail in this paper concerns continual automated monitoring of industrial effluents (or any stream of solution), over lengthy periods of time without any operator intervention. This review article therefore describes the development of automated on-line monitoring procedures based upon the formation, chromatographic separation and amperometric detection, of metal ions as their dithiocarbamate complexes. 

In a performance-based approach to quality assurance, a laboratory is free to use its experience to determine the best way to gather and monitor quality assessment data. The quality assessment methods remain the same (duplicate samples, blanks, standards, and spike recoveries) since they provide the necessary information about precision and bias. What the laboratory can control, however, is the frequency with which quality assessment samples are analyzed, and the conditions indicating when an analytical system is no longer in a state of statistical control. Furthermore, a performance-based approach to quality assessment allows a laboratory to determine if an analytical system is in danger of drifting out of statistical control. Corrective measures are then taken before further problems develop. 

The workhorses in national monitoring programs are multi-residue methods. Any official method collection of any EU Member State contains at least one multi-residue method. For multi-analyte and/or multi-matrix methods, it is likely to be impractical to validate a method for all possible combinations of analyte, concentration and type of sample matrix that may be encountered in subsequent use of the method. Therefore, initial validation should incorporate as many of the target analytes and matrices as practicable. For practical reasons this validation and the evaluation of other methods with limited scope often cannot be conducted in inter-laboratory studies. Other concepts based on independent laboratory validation or validation in a single laboratory have been developed and can provide a practical and cost-effective alternative (or intermediate) approach. 

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