Preliminary studies on the use of acid-soluble cellulose acetate internal capsules for workplace metals sampling and analysis.

Particles entering filter cassettes used to collect samples of aerosol can deposit elsewhere than on the filter. One suggested procedure for ensuring that those deposits are included in the analysis is to collect them within an internal capsule that can subsequently be digested along with the filter. An inter-laboratory evaluation was carried out to evaluate the use of cellulosic capsule inserts for their suitability in the determination of trace elements in workplace air samples. The inter-laboratory study (ILS) was performed in accordance with an applicable ASTM International standard practice, ASTM E691, which describes statistical procedures for investigating inter-laboratory precision. Performance evaluation materials consisted of prototype cellulose acetate capsules attached to mixed-cellulose ester filters, which were spiked with lead-containing materials (aqueous salt solutions, certified reference soil and paint) at ≈ 20 and ≈ 50 µg Pb per sample. Triplicates of each spiked capsule plus media blanks were conveyed to each volunteer laboratory; spiking levels were unknown to the participants. The laboratories were asked to prepare the samples by acid digestion and analyze aliquots of extracted samples by atomic spectrometry procedures described in applicable ASTM International standard test methods D7035 and/or D7439. Participants were then asked to report their data in units of µg per sample. Preliminary inter-laboratory precision and recovery estimates from six participating laboratories demonstrated the utility of the cellulosic capsule inserts for the measurement of sampled trace elements.