Interlaboratory evaluation of trace element determination in workplace air filter samples by inductively coupled plasma mass spectrometry

Abstract

Inductively coupled plasma mass spectrometry (ICP-MS) is becoming more widely used for trace elemental analysis in the occupational hygiene field, and consequently new ICP-MS international standard procedures have been promulgated by ASTM International and ISO. However, there is a dearth of interlaboratory performance data for this analytical methodology. In an effort to fill this data void, an interlaboratory evaluation of ICP-MS for determining trace elements in workplace air samples was conducted, towards fulfillment of method validation requirements for international voluntary consensus standard test methods. The study was performed in accordance with applicable statistical procedures for investigating interlaboratory precision. The evaluation was carried out using certified 37-mm diameter mixed-cellulose ester (MCE) filters that were fortified with 21 elements of concern in occupational hygiene. Elements were spiked at levels ranging from 0.025 to 10 μg filter −1 , with three different filter loadings denoted "Low", "Medium" and "High". Participating laboratories were recruited from a pool of over fifty invitees; ultimately twenty laboratories from Europe, North America and Asia submitted results. Triplicates of each certified filter with elemental contents at three different levels, plus media blanks spiked with reagent, were conveyed to each volunteer laboratory. Each participant was also provided a copy of the test method which each participant was asked to follow; spiking levels were unknown to the participants. The laboratories were requested to prepare the filters by one of three sample preparation procedures, i.e., hotplate digestion, microwave digestion or hot block extraction, HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author Manuscript which were described in the test method. Participants were then asked to analyze aliquots of the prepared samples by ICP-MS, and to report their data in units of μg filter −1 . Most interlaboratory precision estimates were acceptable for medium-and high-level spikes (RSD <25%), but generally yielded greater uncertainties than were anticipated at the outset of the study.

Acid-Soluble Internal Capsules for Closed-Face Cassette Elemental Sampling and Analysis of Workplace Air

“…However, the large variations encountered here were not anticipated, since such variability was not obvious in a prior round-robin study where As loading levels were 0.25, 5, and 100 μg/sample. (22) However, the As levels in this study are similar to the two lowest levels in the previous study and high variation was encountered at the very lowest level in that work. Previously, two laboratories had analyzed blank cellulosic filter capsules from the same batch as used here and had reported all samples with arsenic < 0.8 or < 1.4 μg As per sample, respectively.…”

“…A minimum of six laboratories is required for evaluation per the ASTM E691. (17) The participating laboratories, many of which have been part of previous interlaboratory evaluations, (22) included those listed in Table III.…”

Preliminary Studies on the Use of Acid-Soluble Cellulose Acetate Internal Capsules for Workplace Metals Sampling and Analysis

“…The ILS results also showed excellent intra-laboratory precision-given repeatability between ≈4 and ≈7% for all but the high aqueous spikes-well below typical target maximum repeatability for interlaboratory analysis of 15-20%. (15) Even the repeatability for the high aqueous spikes (16%) is within the desired range. Results for reproducibility are similar (between ≈4 and ≈10%), although the reproducibility for the high aqueous spikes (16%) is again higher.…”

Interlaboratory evaluation of cellulosic acid-soluble internal air sampling capsules for multi-element analysis

“…Most values for precision (expressed as relative standard deviation, RSD) were <0.20 (Tables IVb-d), which compare favorably with the variability typically observed in interlaboratory multielement analysis of air filter samples by atomic spectrometric methods. (12) The results for accuracy summarized in Table V generally demonstrate the suitability of Solu-Sert capsules for multielement analysis by acid dissolution and ICP-AES. The mean accuracy estimate is ≥0.25 for only two elements: Ag and In.…”

“…(12) Since Ag + ions are light-sensitive and subject to photoreduction, it is recommended to carry out sample preparation in light-protected vessels if this element is to be analyzed. (13) Also, precipitation of AgCl in chloride-containing solutions is possible and should be considered.…”