The Analytical Strategy

The analytical strategy accepted in the laboratory designated by the Organization for Prohibition of Chemical Weapons will be discussed. 

This result is important to fully understanding the biochemical and ultra-structural origin of peaks and the physiological basis for variation. It not only helps in designing the analytical strategy (e.g., in selection of cleanup columns) but, more important, in making a decision on whether the marker should be used for strain or species identification or for biodetection. For example, there are a number of low-molecular weight peptides (1500-8000 kDa) present in... 

The process by which an analyte s identity or the concentration level in a sample is determined in the laboratory may involve many individual steps. In order for us to have a coherent approach to the subject, we will group the steps into major parts and study each part individually. In general, these parts vary in specifics according to what the analyte and analyte matrix are and what methods have been chosen for the analysis. In this section, we present a general organizational framework for these parts in later chapters we will proceed to build upon this framework for each major method of analysis to be encountered. Let us call this framework the analytical strategy. 

However, no analytical method, no matter how simple or sophisticated, no matter how specialized or routine, no matter how easy or difficult, and no matter how costly, will produce the correct result if the sample is not correctly obtained and prepared. The first two steps of the analytical strategy are therefore on at least equal footing with the analytical method in terms of importance to the end result. So although the topics of sampling and sample preparation are given the space of only one chapter in this book, their critical importance should not go unnoticed. Quality sampling and sample preparation is crucial to the success of an analysis. 

FIGURE 3.1 The analytical strategy for gravimetric analysis methods. 

The ultimate goal of any titrimetric analysis is to determine the amount of the analyte in a sample. This involves the stoichiometry calculation mentioned in the Work the Data section of the analytical strategy flow chart in Figure 4.1. This amount of analyte is often expressed as a percentage, as it was for the gravimetric analysis examples in Chapter 3. This percentage is calculated via the basic equation for percent used previously for the gravimetric analysis examples ... 

Compare Figure 3.1 with Figure 4.1 and tell how the analytical strategy for gravimetric analysis differs from that for titrimetric analysis. 

Distinguish between wet methods of analysis and instrumental methods of analysis. What do the analytical strategies for the wet chemical methods and instrumental methods have in common ... 

What is different about the analytical strategy for instrumental analysis, compared to wet chemical analysis ... 

Compare the analytical strategy for GC with the general analytical strategy for instrumental methods (Figure 6.5). 

FIGURE 13.2 The analytical strategy flow chart for HPLC. 

Seven laboratories participated in the interlaboratory evaluation within the framework of the PRISTINE, SANDRINE and INEXsPORT European Union Projects [6]. The results obtained for the analysis of diverse classes of surfactants by different analytical methods are listed in Table 4.5.1. The analytical strategies were based on LC coupled to either MS or FL detection in all cases with the exception of one laboratory using a test tube ELISA kit. Samples were spiked with the surfactants NPEO, CDEA, LAS, AEO, NPEO-SO4 and SAS. 

Sometimes it is not necessary to use the selectivity of a chromatographic technique. Sensitive analysis can sometimes be achieved with selective detection in flow injection analysis (FIA). Whilst some of the detectors described below may be appropriate in themselves in favourable cases, in most cases more sophisticated detection regimes are necessary, such as post-injection derivatisation of the analyte. Strategies involving some of the derivatisation methods outlined in Section 4.9.2 may be considered. 

The analytical strategy for a continuous process is necessarily predominantly online, as summarised in Figure 8.3. However, the correlations between continuous process development and online analysis on the one hand and batch process development and off-line analysis on the other are not simple. For example, many aspects of batch process development would benefit from the availability of online analysis and monitoring. Similarly, some of the early development stages of a continuous process will utilise data from batch (i.e. non-continuous) experiments. 

Before a decision is made on the methods to be adopted, a number of questions in key areas need to be asked (Table 26.6). In seeking answers to these questions, an analytical strategy that fits Ure requirements of the customer is more likely to be achieved. Careful planning at the start will ensure that the analytical strategy is truly fit for its intended purpose. 

In Belgium, 0.1% of the slaughtered cattle and swine are screened for antibiotic residues each year. In the analytical strategy applied, meat samples are screened with a modified four-plate test followed by screening with a group-specific ELISA for the identification of the antibiotics and confirmation by specific LC methods. 

The analytical strategies for protein characterization rely heavily on high-performance liquid chromatography (HPLC) and/or electrophoretic separation of proteins/peptides, followed by other detection methods [e.g., mass spectrometry (MS)]. 

The generation of Phase-I metabolites can be considered as a preparation for the Phase-II metabolism. The detection and identification of Phase-I metabolites is important, because possibly toxic metabolites are formed. Some metabolites are even more active than the dmg itself, either in the action the dmg was administered for or in toxic side effects. Administration of a prodrag with more favourable properties is sometimes performed. The prodrag is rapidly transformed in the actual active substance. Moreover, in quite a number of cases the analytical strategy is directed at identification of the Phase-I metabohtes, even after chemical or enzymatic deconjugation of the Phase-II metabolites. 

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