Interlaboratory evaluation of a standardized inductively coupled plasma-mass spectrometry method for the determination of trace elements in air filter samples: preliminary results

An interlaboratory evaluation of a standardized inductively coupled plasma-mass spectrometry (ICP-MS) method for determining trace elements in workplace air samples was carried out, toward fulfillment of method validation requirements for international voluntary consensus standard test methods. The interlaboratory study was performed in accordance with an applicable ASTM International standard practice, ASTM E691, which describes statistical procedures for investigating interlaboratory precision. Performance evaluation materials, prepared by a contract laboratory, consisted of mixed-cellulose ester filters that were spiked with 21 elements of interest at levels of 0.50 or 5.0 micrograms (mu g) per filter. Triplicates of each spiked filter, plus media blanks spiked with blank reagent, were conveyed to each volunteer laboratory; spiking levels were unknown to the participants. The laboratories were requested to prepare the filter samples by one of the three sample preparation procedures (hotplate or microwave digestion or hotblock extraction) that are described in the standard test method, ASTM D7439. Participants were then asked to analyze aliquots of the prepared samples by ICP-MS using ASTM D7439, and to report their data in units of mu g per filter sample. Preliminary interlaboratory precision and recovery estimates from 20 volunteer laboratories are reported.