Energy-Dispersive X-Ray Fluorescence Spectrometric Determination of Phosphate in Water Samples via a 12-Molybdophosphate–Crystal Violet Complex

摘要

A simple and eco-friendly procedure for determining total phosphate content in water has been developed by combining a miniaturized ion-associated complex-based preconcentration method with energy-dispersive X-ray fluorescence spectrometry (EDXRF). The method is based on indirect determination of phosphorus using molybdenum present in the ion-associated complex formed by 12-molybdophosphate and crystal violet. Since phosphorus is determined indirectly, via fluorescent radiation of molybdenum, the difficulties stemming from low fluorescence yield and low energy of phosphorus radiation can be successfully overcome. A good mole ratio of phosphorus to molybdenum (1:12) and a sensitive Ka line of molybdenum make it possible to determine low phosphorus concentrations. Under optimized conditions, a good linearity (up to 2 mg mL1 of phosphorus, r ¼ 0.9991), and a detection limit of 1.3 ng mL1 were achieved. The total relative standard deviation (RSD) for EDXRF determination of phosphorus, following precipitation of the ion-associated complex and its dissolution in a microdrop of 1-hexanol was 2.6%. The enrichment factor was 167. The developed method was used to determine total phosphate content in surface waters. The reliability of the proposed methodology was tested with the use of samples spiked with a known concentration of the determined element and by comparative inductively coupled plasma-optical emission spectrometry. The recovery (in the range of 93.5–97%) was satisfactory and indicates usefulness of the developed procedure.