Uranium analysis in urine by inductively coupled plasma dynamic reaction cell mass spectrometry

Abstract

Urine uranium concentrations are the best biological indicator for identifying exposure to depleted uranium (DU). Internal exposure to DU causes an increased amount of urine uranium and a decreased ratio of 235U/238U in urine samples, resulting in measurements that vary between 0.00725 and 0.002 (i.e., natural and depleted uranium's 235U/238U ratios, respectively). A method based on inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was utilized to identify DU in urine by measuring the quantity of total U and the 235U/238U ratio. The quantitative analysis was achieved using 233U as an internal standard. The analysis was performed both with and without the reaction gas oxygen. The reaction gas converted ionized 235U+ and 238U+ into 235UO2+ (m/z = 267) and 238UO2+ (m/z = 270). This conversion was determined to be over 90% efficient. A polyatomic interference at m/z 234.8 was successfully removed from the 235U signal under either DRC operating conditions (with or without oxygen as a reaction gas). The method was validated with 15 urine samples of known uranium compositions. The method detection limit for quantification was determined to be 0.1 pg U mL(-1) urine and an average coefficient of variation (CV) of 1-2% within the sample measurements. The method detection limit for determining 235U/238U ratio was 3.0 pg U mL(-1) urine. An additional 21 patient samples were analyzed with no information about medical history. The measured 235U/238U ratio within the urine samples correctly identified the presence or absence of internal DU exposure in all 21 patients.

Biologic monitoring and surveillance results for the department of veterans affairs' depleted uranium cohort: Lessons learned from sustained exposure over two decades

“…All participants signed a written informed consent document. [Ejnik et al, 2005;Gray et al, 2012]. Urine U concentrations were standardized on the basis of urine creatinine concentrations to account for urine dilution to obtain mg U/g creatinine [Karpas et al, 1998;McDiarmid et al, 2000].…”

Depleted uranium exposure and health effects in Gulf War veterans

“…The detection limit for quantifying total U in urine using the ICP-DRC-MS technique is 0.1 ng l K1 , an improvement in sensitivity of 200-fold compared to KPA analysis. Accurate isotopic analysis for calculating the U 235 /U 238 ratio in urine specimens is also possible using this quadrapole ICP-DRC-MS technique for samples with U concentrations as low as 10 ng l K1 (Ejnik et al 2005). With this capability, it is possible to calculate the amount of DU in a urine sample that also contains natural U at total U concentrations of 10 ng l K1 and above, thus providing direct evidence of DU exposure.…”

“…Other techniques developed for solving this problem involve magnetic sector high-resolution ICP-MS instruments or more extensive sample preparation to first remove the uranium from matrix constituents (Gwiazda et al 2004). A QA/QC comparative study involving multiple laboratories using either the ICP-DRC-MS or high-resolution magnetic sector instruments (Gwiazda et al 2004;Ejnik et al 2005) showed excellent correlations between these techniques for total U uranium and U 235 /U 238 ratio results at urine U concentrations as low as 10 ng l K1 .…”

“…To more accurately assess low-level exposures to DU and specifically quantify DU versus natural U exposure, a more sensitive analytical method than KPA was developed using an inductively coupled plasma dynamic reaction cell mass spectrometer (ICP-DRC-MS) (Ejnik et al 2005). The detection limit for quantifying total U in urine using the ICP-DRC-MS technique is 0.1 ng l K1 , an improvement in sensitivity of 200-fold compared to KPA analysis.…”

Oxygenation Mechanism of Ions in Dynamic Reaction Cell ICP-MS

“…[30][31][32] Oxygenation is an effective way of avoiding spectral interferences by producing an oxide ion free from interfering molecular ions or by oxygenating the isobaric interfering ions. [33][34][35][36][37][38][39][40][41][42][43] However, the effectiveness of O2 has not been evaluated sufficiently and the underlying mechanism of oxygenation in the reaction cell has not been fully elucidated, although the mechanisms underlying the use of NH3 and CH4 have been discussed by several researchers. We investigated the mechanism of oxygenation by using the bond energy and the enthalpy change (ΔH) between the ions and O, and demonstrated the usefulness of theoretical calculations for elucidating reaction mechanisms in DRCs.…”