Workplace exposure to chromium species presents significant health risks. While some of
the current analytical methods can measure total chromium and Cr(VI) at the threshold limit
values (TLV®)s, there remains a need for validated methods that can reliably quantify both
Cr(III) and Cr(VI) at 0.1 × TLV® from a single sample to meet WorkSafe BC's goal for
enhanced monitoring requirements. This is particularly important for the 2020 ACGIH TLV® of
0.0002 mg/m³ for Cr(VI). A novel sequential analytical procedure was developed for the
quantification of soluble Cr(III), soluble Cr(VI), and insoluble chromium species from a single
air sample using Disposable Inhalable Samplers (DIS)s. The method combines ion
chromatography and inductively coupled plasma mass spectrometry (IC-ICP-MS) with EPA
Method 6800 speciated isotope dilution mass spectrometry (SIDMS) to enable precise
quantification and correction of species interconversion. An insoluble chromium microwave
digestion method was developed using nitric acid, sulfuric acid, and hydrogen peroxide for
difficult-to-digest chromium oxides.
Method validation demonstrated detection limits below 0.03 × TLV for soluble
chromium species and insoluble chromium. The use of EPA 6800 SIDMS improved method
precision for soluble species, with recoveries of 99-109% for Cr(VI) at concentrations ranging
from 0.1 to 2 × TLV. The standalone insoluble chromium digestion achieved 90-105% recovery
across all concentration levels. Matrix effect studies revealed that soluble iron(III) (Fe(III))
reduced Cr(VI) recoveries to 52-64%, but this interference could be corrected using isotope
dilution techniques. The sequential procedure showed promising results but indicated potential losses during
filtration, with insoluble chromium recoveries of 75-80%. This work provides a foundation for
chromium speciation analysis that meets current ACGIH exposure limit requirements while
reducing analytical costs by eliminating the need for multiple samples.
