PAPER CHROMATOGRAPHIC DETERMINATION OF LEAD AND COPPER IMPURITIES IN DRUGS

A paper chromatographic method has been developed for the detection and quantitative estimation of lead and copper as impurities in drugs. Reeve Angel No. 201 filter paper was used in this work, though Whatman No. 1 paper also gave satisfactory results. A mixture of butyl alcohol, glacial acetic acid and 0.5N nitric acid (2: 1: 1) was chosen as the developing agent. The R_F values of copper and lead at 24℃±1℃ were found to be 0.25 and 0.15 respectively. The color developing agent for copper was a 0.5% alcoholic solution of rubeanic acid. For quantitative estimation, the dark green band on the paper was compared with a series of copper standards treated in the same manner. The lead spots were located by spraying the paper with 1N potassium iodide solution. For quantitative work, the lead spot was washed off from the untreated paper with an alkaline solution of glycerine and determined colorimetrically after acidification and addition of saturated H₂S solution. This method has been tested for the determination of lead and copper impurities in glucose, sulfanilamide and tincture of valerian. It was found suitable when the amount of these impurities added on the paper was less than 20γ. In glucose samples the average deviation for lead was less than±1γ and that for copper was about-0.5γ. The average deviation was greater in the case of tincture of valerian.