Sample preparation, generally contamination controls

At present there is no universally accepted Standard Method for Preparation of Samples from Contaminated Sites and few laboratories operate strictly comparable sample preparation methods. So it is important that the methods used for initial sample preparation are verifiably/// for their analytical purpose and applied by trained staff under an appropriate level of quality control. The design of sample preparation methods is generally constrained by the need to produce powders or finished samples with uniform physical characteristics by the most rapid method, whilst preventing the loss or alteration of any part of the sample by contamination, cross-contamination or chemical reaction. 

Other aspects that should be checked throughout development include matrix interferences (Section 9.6.3), contamination (either general laboratory sources or arising within the sample preparation process itself) and carryover (Section 9.7) all of these can be evaluated by appropriate use of extracts of analyte-free control matrix. 

In the previous paper, we have outlined the general means of preparation of samples convenient for ESCA studies. Of the methods discussed, It is clear that the pressing of films to some extent offers many advantages both in terms of convenience and of limiting the possibility of contamination (e.g. from solvent). Our previous studies of PTFE films produced by this process reinforces the conclusion that under carefully controlled conditions it should be possible to produce uncontaminated films of polyethylene suitable for direct ESCA examination and for the fluorination experiments. 

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