Determination of sodium in aluminum fluoride by flame atomic absorption spectrometry with lithium metaborate fusion and ultrasonic leaching

The acid dissolution method is typically used for determining sodium in aluminum fluoride, but often fails to completely decompose the sample due to its highly stable chemical properties, leading to insufficient accuracy. To address this, lithium metaborate fusion was employed. Using anhydrous lithium metaborate as the flux, complete decomposition was achieved by fusion at 850 ℃ for 30 min. The resulting melt was then efficiently dissolved via ultrasonic leaching at 55 ℃ using a mixture of 10 mL of nitric acid (1+1) and 10 mL of water, thereby overcoming the decomposition challenge. A method based on lithium metaborate fusion followed by ultrasonic leaching and flame atomic absorption spectrometry (FAAS) was established for sodium determination. Matrix interference was eliminated by using calibration curves prepared with matched acidity, lithium, and aluminum concentrations. The calibration curve showed good linearity, with a correlation coefficient greater than 0.999. The limit of detection and limit of quantification for sodium were 0.000 63% and 0.010% (mass fraction), respectively. When applied to aluminum fluoride samples, the method yielded results with relative standard deviations (RSD, n=9) not more than 4.0% and spike recoveries between 98% and 99%.