Determination of cadmium, chromium and copper in high salt samples by LA-ICP-OES after electrodeposition-preliminary study

A novel method is presented for determination of heavy metal ions in a high-saline matrix. It is based on the electrodeposition of the ions and subsequent laser ablation coupled to inductively coupled plasma optical emission spectrometry (LA-ICP-OES). Three arrangements for electrodeposition were worked out, two of them with stationary working electrodes. Materials for use in the working electrodes, and conditions for electrodeposition of Cd, Cr and Cu (pH, deposition current, time of electrolysis) were studied. Nickel was found to be the best electrode material. The metals accumulate on the surface of electrode and were then evaporated/ablated with a Nd:YAG laser focused into the ICP-OES spectrometer. The detection limits are 0.13 mg L-1 for Cd, 0.15 mg L-1 for Cu, and 1.9 mg L-1 for Cr in case of a stationary bottom working electrode, and 0.25 mg L-1 for Cd, 0.05 mg L-1 for Cu, 0.8 mg L-1 for Cr when using a rotating electrode. The relative standard deviation is in range from 3.8 to 10.3%. Waste water was analyzed in this way by the standard addition method.