Sample Treatment and Storage

Gomez-Ariza, J.L., Morales, E., Giraldez, I., Sanchez-Rodas, D. Sample treatment and storage in speciation analysis. In Ebdon, L., Pitts, L., Comelis, R., Crews, H., Donard, O. F.X., Quevauviller, P. (eds.) Trace Element Speciation for Environment, Food and Health, pp. 51-80. RSC, Cambridge (2001)... 

Here the discussion focuses on the analytical procedure adopted to determine trace metals concentration in sea water in the dissolved phase. Particular attention will be given to the procedures preceding the analytical measurement (sampling, sample treatment and storage), the analytieal determination of total concentration by DPASV and Inductively Coupled Plasma Mass Speetrometry (ICP-MS) the contamination control procedure will also be discussed. The direct DPASV procedure for determining metal complexation in sea water is reported in detail and after a discussion of theoretical aspects an outline of the experimental procedure is presented. Finally, an overview of the distribution in the Southern Ocean of some metals of particular interest is examined and the evaluation of traee metals distribution is carried out also by comparison with results obtained in different geographical areas. 

Samples containing PAHs are obtained from air, soil (and sediment), or water so collection procedures to ensure the validity of the sample obtained are very important. For the sample analyzed to represent the true composition of the environmental matrix, sampling must be quantitative, no artifacts should be formed during sample collection, and all sample treatment and storage before analysis must be free from interferences and losses. 

In analysis of marine samples by AAS problems are encountered in sampling procedure, sample storage, sample treatment and measurement procedures. Analytical difficulties arise from the low concentration of most elements and complex matrices in marine samples. In this chapter, a general discussion on marine analysis by AAS will be provided in terms of seawater, marine organisms and sediments. 

Quality assurance is about getting the correct result. In environmental analysis and monitoring, this involves several steps, including sample collection, treatment and storage, followed by laboratory analysis. A complete environmental protocol is shown in Figure 2.1. It is likely that the variation in the final measurement is more influenced by the work external to the analytical laboratory than that within the laboratory. Two important terms in quality assurance are accuracy and precision. 

A number of esturial waters, from in and around Tampa Bay, Florida, area were analysed by this method for tin content. All samples were analysed without pre-treatment. Samples which were not analysed immediately were frozen until analysis was possible. Polyethylene bottles, 500mL volume, were used for sample acquisition and storage. The results of these analyses appear in Table 15.19, and the average total tin content of estuarine waters was 12ng L . Approximately 17-607o of... 

Table I. Double bond conversion as measured by solid state NMR spectroscopy for pTrMPTrA samples with various storage and treatment conditions...

During the last twenty years, food chemists have been using an increasing number of analytical instruments to analyse several samples quickly and obtain, in a short time, a great deal of chemical information from each sample. At the same time, they have increased their knowledge of the chemical composition of natural foods and of the changes due to storage and treatments, and also of market and customer requirements. 

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