Droplet method for the determination of sodium and potassium concentrations in highly saline water samples using X-ray fluorescence spectrometry

Wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF) analysis could be a useful tool for the analysis of water samples with high Na and K concentrations. In this paper, we propose the droplet method for XRF analysis with an appropriate filter substrate selected in terms of the dropping area, drying time, and constant shape. In addition, the optimal sample volume has been determined to be 10 μL. Calibration curves were generated over concentration ranges of 1000–20,000 mg/L for Na and 200–1000 mg/L for K with good relative standard deviation values. The calculated method detection limit and the limit of quantification values were 74.1 and 236 mg/L for Na and 12.1 and 38.4 mg/L for K, respectively. The accuracy of the developed droplet method was also examined using two certified standard solutions and was shown to give a reliable relative standard error with −23.3% and 7.12% error for Na and K, respectively. To verify the feasibility of the developed droplet method for WD-XRF analysis, seven water samples, including seawater and groundwater with seawater intrusion, were analyzed. Our findings indicate that WD-XRF technique is suitable for the accurate determination of water samples with high Na and K concentrations without the need for complicated sample preparation methods.