Selenium, an essential trace element with many biochemical functions, shows toxic effects at elevated intake.
Therefore, it is important to monitor the selenium body status e.g. by investigating total selenium in biological
fluids like urine. Inductively coupled plasma mass spectrometry (ICPMS) is a robust technique with low limits
of detection for the determination of total selenium in body fluids. When flow injection (FI) is used to introduce
the sample to the ICPMS, low sample volumes can be investigated directly, without time-consuming digestion
steps. We describe a time-efficient method for determining total selenium in urine using a simple filtration
step for sample preparation and measurement by FI/ICPMS. Quantification was based on external calibration
without time-consuming standard addition approaches.Matrix effects occurring when urine is analysed directly
without dilution were minimized by splitting the flow of the carrier solution, by optimizing the injection volume,
and by using germanium as internal standard. Best results were obtained with 20 mM malonate 3% methanol
pH 6.0 containing 50 μg Ge L−1 as carrier solution at a flow rate of 1.5 mL min−1, whereby 15% of the carrier solution
was directed to the ICPMS by a passive splitter, and an injection volume of 5 μL. The method limit of detection
(LOD) and quantification (LOQ) in urinewere 0.07 μg Se L−1 and 0.2 μg Se L−1, respectively. The accuracy of
the methodwas evaluated by (i) the certified reference material NIES No. 18 Human urine and (ii) comparison of
FI/ICPMS results for different urine samples with target concentrations obtained by ICPMS after microwaveassisted
acid digestion. Urine samples could be stored at 4 °C for at least 4 days, before the formation of volatile
selenium compounds led to overestimated results. Intra-day precision for the determination of total selenium in
urine was about 3% (n=3) and inter-day precision about 5% (n=3). Simple sample preparation by only filtration,
a short analysis time, and the lowrequirement for sample volume makes the method very useful particularly
for large numbers of samples and samples for which only limited volumes are available.