Determination of yttrium in phosphorus powder from fluorescent lamps by microwave-induced optical emission spectrometry (MIP OES) after ultrasound-assisted extraction

Abstract

In this work, we propose a novel method for yttrium determination by microwave-induced optical emission spectrometry (MIP OES). It is based on the ultrasound-assisted extraction of yttrium with a diluted HNO₃ solution and was applied to yttrium determination in phosphorus powder from fluorescent lamps. The method was optimized employing a multivariate strategy, based on a Box–Behnken design, taking into account three experimental factors: mass of the sample (25 to 75 mg), sonication time (15 to 165 min) and HNO₃ concentration in the extractant solution (2.0 to 6.0 mol L⁻¹). According to the data obtained in the optimization process, only the sonication time and the HNO₃ concentration had an influence on the extraction of yttrium from the samples. The data also indicated that yttrium must be strongly linked to the matrix, since its quantitative extraction was only possible when using the maximum values of the two factors. Therefore, under optimized conditions, we could quantitatively extract yttrium from 75 mg of sample using a 6 mol per L HNO₃ solution and a sonication time of 165 min. The limits of detection and quantification for the method were 0.4 and 1.2 μg g⁻¹, respectively, and the intermediary precision (three days) was 14%. The concentration of Y in the analyzed samples varied from 5.37 ± 1.82 to 298 ± 31 μg g⁻¹, and recoveries of 91.0 ± 34.6 and 106 ± 23% were obtained in comparison to total digestion. The results obtained by the proposed method were not statistically different (at the 95% confidence level) from those obtained after the total digestion of the samples when applying the Student's t-test.