Determination of Al, Cr, Fe, Zn, Cd, Pb and Bi in crude drugs by inductively coupled plasma atomic emission spectrometry after coprecipitation with yttrium phosphate

A novel method that combines inductively coupled plasma atomic emission spectrometry (ICP-AES) with a coprecipitation technique to determine trace and sub-trace elements in crude drugs is described herein. Yttrium phosphate quantitatively coprecipitated seven elements (Al, Cr, Fe, Zn, Cd, Pb and Bi) at pH 6 in a solution prepared from microwave-digested samples of crude drugs. Some matrix elements such as Na, K, Mg and Ca were effectively removed by this process. The thus coprecipitated elements were then determined by ICPAES with yttrium as an internal standard element. The detection limits (3σ, n = 10) were 0.17 mg/kg for Al, 0.004 mg/kg for Cr, 0.03mg/kg for Fe, 0.13 mg/kg for Zn, 0.004 mg/kg for Cd, 0.19 mg/kg for Pb and 0.06 mg/kg for Bi. The proposed method was successfully utilized to determine the concentration of the above-mentioned seven elements in standard reference materials [National Institute of Standards Technology (NIST) SRM1515, SRM1547 and SRM1575a] and seven kinds of crude drugs.