Determination of the isotopic composition of uranium in urine by inductively coupled plasma mass spectrometry.
A simple method based on inductively coupled plasma mass spectrometry (ICP-MS) was developed to identify exposure to depleted uranium by measuring the isotopic composition of uranium in urine. Exposure to depleted uranium results in a decreased percentage of 235U in urine samples causing measurements to vary between natural uranium's 0.72% and depleted uranium's 0.2%. Urine samples from a non-depleted uranium exposed group and a suspected depleted uranium exposed group were processed and analyzed by ICP-MS to determine whether depleted uranium was present in the urine. Sample preparation involved dry-ashing the urine at 450 degrees C followed by wet-ashing with a series of additions of concentrated nitric acid and 30% hydrogen peroxide. The ash from the urine was dissolved in 1 M nitric acid, and the intensity of 235U and 238U ions were measured by ICP-MS. After the samples were ashed, the ICP-MS measurements required less than 5 min. The 235U percentage in individuals from the depleted uranium exposed group with urine uranium concentrations greater than 150 ng L(-1) was between 0.20%-0.33%, correctly identifying depleted uranium exposure. Samples from the non-depleted uranium exposed individuals had urine uranium concentration less than 50 ng L(-1) and 235U percentages consistent with natural uranium (0.7%-1.0%). A minimum concentration of 14 ng L(-1) uranium was required to obtain sufficient 235U to allow calculating a valid isotopic ratio. Therefore, the percent 235U in urine samples measured by this method can be used to identify low-level exposure to depleted uranium.
Ejnik
J W
JW
Armed Forces Radiobiology Research Institute, Bethesda, MD 20889-5603, USA. ejnik@mx.afrri.usuhs.mil
Carmichael
A J
AJ
Hamilton
M M
MM
McDiarmid
M
M
Squibb
K
K
Boyd
P
P
Tardiff
W
W
D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D015203:Reproducibility of Results; D012588:Scintillation Counting; D012680:Sensitivity and Specificity; D014501:Uranium / Q000652:urine*
D014501:Uranium