X-ray fluorescence analysis of the trace molybdenum in water using dibenzyldithiocarbamate

The preconcentration of the trace amount of molybdenum in water using dibenzyldithiocarbamate (DBDTC) as a chelating agent and the subsequent determination by X-ray fluorescence analysis has been studied. The proposed analytical procedure established from the results obtained under various experimental conditions was as follows. An adequate amount of sample solution containing molybdenum was taken and a given volume of DBDTC solution was added at 30 deg C after adjusting to pH 3.0. The precipitate of Mo-DBDTC chelate was allowed to stand for 15 min, collected on a membrane filter, dried at room temperature and delivered to X-ray fluorescence analysis. The results in the basic experiments are ; 1) The chelate-formation ability of DBDTC was found excellent in view of the fact that the recovery of molybdenum was 99.5 %, 2) The caliblation curve showed linear relationship between X-ray intensity and molybdenum amount in the range of 3 ∼ 30 μg/l, and 3) The standard deviation and the coefficient of variation in ten determinations were 0.21 and 2.11 %, respectively, when eleven aqueous sample solutions containing 10.0 μg/l of the element were measured. The results in seawater samples are ; 1) The value by the method mentioned above agreed with the value by the standard addition method, 2) The slope of the straight line of the standard addition method was approximately equal to that of the above calibration curve, and 3) The standard deviation and the coefficient of variation in five determinations were 0.22 and 2.24 %, respectively. These results suggest that coexisting electrolytes in seawater do not interfere with the determination of molybdenum. The recommended procedure was applied to the determination of molybdenum in a seawater sample, and obtained data (10.0 μg/l) agreed to the value of the published data. The above results indicate that this method is useful for determination of the trace amount of molybdenum in water and seawater. (author)