Abstract:

In this paper, according to the regulation that boric acid and borate should not be detected in talcum powder for children （under 3 years old）, an inductively coupled plasma mass spectrometry （ICP-MS） method was explored to determine trace boron in children’s talcum powder. In exploratory stage, operation parameters of ICP-MS, microwave digestion pre-treatment, interference of coexisting ions were studied. By optimizing the microwave digestion system, HNO₃-H₂O₂ digestion solvent system was selected, and the temperature of the digestion procedure was raised to 185 ℃ for 30 minutes. In the process of optimizing instrument conditions, Nogas analysis mode was selected as the instrumental analysis mode, and yttrium （Y） was used as the internal standard element. Meanwhile, the test of interference with coexisting ions indicated that the common coexisting ions in talcum powder such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Al³⁺, Pb²⁺, Zn²⁺ had no effects on the determination of boron. Under the best experimental conditions, the boron in the range of 0-20 ng/mL can be quantified accurately. The linear correlation coefficient （r） of the method is 0.999 9. The detection limit of boron is as low as 0.02 µg/g and the limit of quantitation of boron is 0.07 µg/g. The recoveries of boron range from 99.2% to 101.4% at low, medium and high mass concentration spiked levels with 2, 4, 20 times of the quantitative concentration. The specific spiked concentrations are 25, 50 and 250 ng and the relative standard deviations （RSDs） （n=3） of recovery experiments are between 2.2% and 5.4%. The RSD （n=6） of positive samples is 1.3%. The data above show that the method is accurate, reliable and sensitive. Applying the method to control quality of 30 batches of children’s talcum powder available in the market, trace boron are detected in 24 batches of the products. Boric acid is obtained through the conversion of the mass number of boron. The results are in accordance with the requirement of current standards. This method can be used for the accurate quantification of trace boron, which is conducive to strengthen the risk control of boric acid and borate in children’s talcum powder.

Key words: microwave digestion, ICP-MS, talcum powder, boron