Several methods exist for analyzing samples. The most common method is to treat the sampling filter with an appropriate acid solution, thereby releasing the entrained nickel for subsequent analysis by atomic absorption. The definitive method has been described by the International Union of Pure and Applied Chemistry (IUPAC) (Brown et al., 1981). X-ray spectrometry of the filter is a simple and accurate alternative if the equipment is available. In samples with relatively high concentrations of nickel (µg/g or µg/dl range) Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) allows multi- element detection including the reliable analysis of nickel ions.
Speciation currently is used only as a research procedure since it is time consuming and expensive. As the importance of speciation has already become more widely recognized by researchers and regulators alike, it may become more commonplace, or even mandatory, to analyze samples for specific species. Alternatively, it may be considered adequate first to characterize the workplace atmosphere by a detailed species analysis (Zatka et al., 1992) and then use conventional methods to measure total nickel and apportion the results to specific species.
In selecting a method, an important consideration is the requirements of the applicable regulations. These regulations may require that the laboratory conducting the analysis participate in a qualification or certification program to ensure accurate results. If no regulations exist, then the objectives in sampling should help determine the choice of analytical methods. Evidence of effective quality control will be essential. Contacts and resources for additional guidance are listed in Appendix A. Whenever possible, the selected sampling procedure should be discussed with the laboratory that will perform the analysis prior to sampling. Frequently, the laboratory can also provide valuable guidance on potential interferences, the number of samples and field blanks needed, sample storage, and transportation.