Determination of arsenic, molybdenum, tungsten and chromium by the ion chromatography method

An ion chromatography method for determination of arsenic, molybdenum, tungsten and chromium in the form of oxoanions in their simultaneous presence has been developed (chromatograph Dionex, models 10 and 14). 0.005 M solution of Na2CO3 has been used as an eluent. Electric conductivity-concentration are linear for the oxoanions determined in the concentration range of 0.05 to 500 mg/ml at the conductometer sensitivity of 1.3 and 10 μS. When determining high concentration of ions (1-500 μg/ml) the reproducibility is shown to be higher if the calculation is made with respect to the peak areas and in the case of low concentration determination (<0.5 μg/ml) the reproducibility is shown to be higher when the calculation is made with respect to the peak height. The minimum concentrations of elements under the optimum conditions are determined to be as follows: W-35 μg/l, Mo-25 μg/l, As-10 μg/l, Cr-50 μg/l. The use of concentratiesng column decreas the minimum determined concentrations by two orders of magnitude. It is established that 100-1000-multiple excess of the nearest ion, with respect to the retension time, does not interfere with the determination of each of the ions