No abstract

An accurate and simple method for the determination of total arsenic, total selenium and total chromium in urine has been developed using inductively coupled argon plasma-dynamic reaction cell-mass spectrometry (ICP-DRC-MS). Determination was by external calibration, using matrixmatched standards and high purity calibration materials from a commercial vendor. Aliquots of each urine specimen were diluted (1 + 9) with 2% (v/v) nitric acid containing rhodium and iridium as an internal standard. Argon cell gas was used to remove the isobaric interferences that normally adversely affect 75 As, 78 Se and 52 Cr analysis by ICP-MS and require the use of a dynamic reaction cell (DRC). The principle isobars that interfere with these measurements are [ 40 Ar 35 Cl] + , [ 40 Ar 38 Ar] + and [ 40 Ar 12 C] + for 75 As, 78 Se and 52 Cr, respectively. The counts at m/z 75 (arsenic); 78 (selenium); 52 (chromium), 103 (rhodium), and 193 (iridium) were measured. The ratios of the counts at m/z 75 or 78 to those at m/z 193, and m/z 52 to those at m/z 103 were calculated. These ratios were compared with those from urine-based calibration standards to calculate the arsenic, selenium, and chromium concentrations in unknown specimens. The concentrations of arsenic, selenium, and chromium were calculated as mg L À1 in the sample. No creatinine corrections were made, although these could easily be made with data for urine creatinine for each specimen. The proposed method uses the same diluted urine solutions prepared for conventional ICP-MS toxic metal biomonitoring and chemical terrorism screening analysis with the same internal standards; and uses argon as the DRC cell gas. The proposed method provides the basis for an accurate method for determining total arsenic, total selenium, and total chromium in unexposed subjects, and in persons considered to be exposed to those elements through chemical terrorism, environmental, nutritional or other pathways. Approximately 100 specimens, including blanks, calibration standards and quality-control materials, can be processed in an 8 h day.

A high-throughput method has been developed for determining Lewisite [dichloro(2-chlorovinyl)arsine] exposure by measuring the urine metabolite 2-chlorovinylarsonous acid (CVAA) and the oxidized metabolite 2-chlorovinylarsonic acid (CVAOA). The rapid sample preparation included a simple dilution of 400 microL of urine with 40 microL of water and 1 mL of buffer containing an internal standard and brief centrifugation prior to analysis by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (ICP-MS). CVAOA and CVAA were eluted isocratically with retention factors of approximately 3.0 and 4.2, respectively, from a reversed-phase polar embedded column with a cycle time of 5 min per sample. The dynamic reaction cell, typically used to remove polyatomic isobaric interferences, was not required for ICP-MS analysis because of the resolution of chloride from arsenical peaks of interest. This method was used to detect CVAA and CVAOA in the urine of a rat administered Lewisite up to 24 h after exposure. The method demonstrated linearity over at least three orders of magnitude and had a method detection limit of 1.3 microg/L as CVAA (1.4 microg/L CVAOA). The relative standard deviations for quality control samples ranged from 3 to 6%. The method was sensitive and selective with no false positives in 100 different urine samples collected from individuals with no known exposure to Lewisite. Ninety-six samples could be analyzed in an 8-h day.