Determination of metal impurities in pure hydroxides and salts by inductively coupled plasma optical emission spectrometry

A simple analytical method sufficient for the determination of Na, K, Ca, Mg, Al, B, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, V and Zn at mg kg−1 levels in pure NaOH, KOH, NaCl and KCl using the optical emission spectrometry was developed. The results of direct determination with multi-elemental aqueous standards were compared with them obtained by the internal standardisation, by the standard addition methods and with the maximal allowable contents of above-mentioned elements in pure chemicals. The method was shown to be very sensitive and exhibits following limits of detection: Na 0.90, K 3.0, Ca 0.064, Mg 0.026, Al 0.43, B 0.13, Ba 0.015, Cd 0.023, Co 0.056, Cr 0.041, Cu 0.063, Fe 0.060, Li 0.017, Mn 0.035, Mo 0.19, Ni 0.055, Pb 0.39, Sr 0.030, V 0.065 and Zn 0.043 (all in mg kg−1). The method presents a satisfactory precision (relative standard deviation 4–11%), high analytical recoveries, linear responses of at least four orders of magnitude, accuracy and low contamination susceptibility.