Determination of chromate adulteration of human urine by automated colorimetric and capillary ion electrophoretic analyses

Abstract

Various chemicals can be added to urine specimens collected for drug analysis to abnormally elevate ionic concentrations and/or interfere with either immunoassay urine drug-screening procedures or gas chromatographic-mass spectrometric confirmation techniques. One such adulterant, "Urine Luck" (formula 5.3), has been identified in our previous research to contain potassium dichromate. Screening of suspected adulterated specimens and confirmation of the adulterant are important for forensic drug screening. The application and comparison of automated colorimetric and capillary ion electrophoretic techniques for the detection, confirmation, and quantitation of chromate adulteration of urine specimens were the purpose of this investigation. Thirty-six urine specimens suspected of adulteration were analyzed for chromate by colorimetric analysis with diphenylcarbazide. Duplicate aliquots were analyzed for chromate by capillary ion electrophoresis. Results of the colorimetric chromate analyses revealed a mean chromate concentration of 929 μg/mL with a standard error of 177 μg/mL and a range of 30 to 5634 μg/mL. Results of the capillary ion electrophoresis chromate analyses revealed a mean chromate concentration of 1009 μg/mL with a standard error of 218 μg/mL and a range of 20 to 7501 μg/mL. The correlation coefficient between the capillary ion electrophoretic and colorimetric chromate results was r = 0.9669. Application of the automated diphenylcarbazide colorimetric technique provides rapid determination of chromate adulteration of a urine specimen. Capillary ion electrophoresis offers a separation technique to confirm the presence of chromate in suspected adulterated specimens. The excellent correlation between these methods substantiates their application to forensic testing as screening and/or confirmation techniques.