Wu et al. (13) have described a protocol for detection of PCC in urine using spot tests. The indicator solution contains 10 gm/L of 1,5-diphenylcar-bazide in methanol. The indicator detects the presence of chromium ion and is colorless when prepared. Two drops of indicator solution is added to 1.0 mL of urine. If a reddish-purple color develops, the test is positive. Ferslew et al. (21) tested 36 urine specimens suspected of adulteration for the presence of chromate using a 1,5- diphenylcarbazide color test with detection of chromate ion using capillary ion electrophoretic analysis. The colorimetric chromate assay revealed a mean chromate concentration of 929 ^g/mL, whereas the capillary ion electrophoresis showed a mean chromate concentration of 1009 ^g/mL. The authors concluded that the colorimetric test could be used as a screening test, and the presence of chromate can be confirmed by using capillary electrophoresis.
Other simple and rapid spot tests have been described for detection of chromate in suspected adulterated urine (22). Addition of four to five drops of 3% hydrogen peroxide in approx 200 ^L of urine adulterated with PCC (approx six to seven drops from a transfer pipet) causes rapid formation of a dark brown color, and a dark brown precipitate appears on standing. In contrast, unadulterated urine turns colorless after addition of hydrogen peroxide. One percent potassium iodide in distilled water can also be used as an indicator solution for detection of chromate in urine. Addition of six to seven drops of urine adulterated with chromate to a few drop of 1% potassium iodide solution followed by adding a few drops of 2 N hydrochloric acid result in liberation of iodine from potassium iodide solution. Shaking this solution with «-butanol results in the transfer of iodine to the organic phase. If no chromate is present, the potassium iodide solution remained colorless. No interference was observed in these color tests from high glucose or ketone bodies.
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