提出了石墨消解器-电感耦合等离子体原子发射光谱法(ICP-AES)测定香皂中滑石粉含量的方法。称取两份0.5g处理好的香皂样品于两支石墨消解管中,一支加入硝酸10.0mL和30%(质量分数,下同)过氧化氢溶液2.0mL(测定除硅酸镁之外杂质镁含量),另一支加入硝酸10.0mL、30%过氧化氢溶液2.0mL和氢氟酸2.0mL(测定总镁含量),均敞口放置1h,然后于120℃消解2h。消解完毕后冷却至室温,用0.5mol·L^-1硝酸溶液定容至100mL,按照仪器工作条件分别测定镁元素的含量,以二者之差计算样品中滑石粉的含量,基质匹配法建立工作曲线。结果显示:镁工作曲线的线性范围为0.100~3.00mg·L^-1,检出限为0.002g·kg^-1;实际样品中滑石粉测定值的相对标准偏差(n=6)为0.80%~2.7%,加标回收率为97.3%~109%。按照GB 5009.269-2016中的火焰原子吸收光谱法和本法分析3个香皂样品。在95%置信水平下,3个样品的t值均小于t_0.05(4),表明两种方法的测定结果无显著性差异,而本法检出限更低、精密度更好。

A method for the determination of talc power in soap by inductively coupled plasma atomic emission spectrometry (ICP-AES) with graphite digestion tube was proposed. Two soap samples (0.5 g each) treated were put into two graphite digestion tubes, and 10.0 mL of nitric acid and 2.0 mL of 30% (w, the same below) hydrogen peroxide solution were added into one tube for determination of impurity magnesium except for magnesium silicate, and 10.0 mL of nitric acid, 2.0 mL of 30% hydrogen peroxide solution and 2.0 mL of hydrofluoric acid were added into the other tube for determination of total magnesium. The open tubes were placed for 1 h, and then the mixtures were digested at 120 ℃ for 2 h. After digestion, the solutions were cooled to room temperature, and their volumes were made up to 100 mL with 0.5 mol·L^-1 nitric acid solution. Magnesium was determined respectively according to the working conditions of the instrument, and the content of talc power in the sample was calculated by the difference between them, and the working curve was established with matrix matching method. The results showed that the linear range of magnesium working curve was 0.100-3.00 mg·L^-1, with detection limit of 0.002 g·kg^-1. RSDs (n=6) of the determined values of talc power in the actual sample were in the range of 0.80%-2.7%, and the spiked recoveries were ranged from 97.3% to 109%. Three soap samples were analyzed by flame atomic absorption spectrometry in GB 5009.269-2016 and method. At 95% of confidence level, the t values of the three samples were lower than t_0.05(4), indicating that there was no significant difference between the two methods, while the detection limit of this method was lower and the precision was better.