电感耦合等离子体原子发射光谱法测定重晶石中碳酸钡和硫酸钡

通过采用不同的样品处理方法,对电感耦合等离子体原子发射光谱法(ICP-AES)测定重晶石中碳酸钡和硫酸钡含量的方法进行了探讨。采用不同浓度醋酸对纯硫酸钡进行溶解试验,结果表明,采用1.7mol/L醋酸常温溶解1h,硫酸钡的溶出率与用水进行溶解时保持一致。因而采用以下流程对样品中碳酸钡进行测定:采用水溶解样品,并用ICP-AES对样品溶液中钡进行测定,得到样品中水溶性钡的含量;采用1.7mol/L醋酸溶解样品,并用ICP-AES对样品溶液中钡进行测定,得到样品中水溶性钡、以碳酸钡形式存在的钡的含量总和;将后者减去前者可得到以碳酸钡形式存在的钡的含量,再进一步换算为碳酸钡含量,实现了ICPAES对重晶石中碳酸钡含量的测定。采用1.0mol/L盐酸加热煮沸30min处理样品,可有效溶解氯化钡、碳酸钡等含钡杂质,而采用1.0mol/L盐酸对纯硫酸钡的溶解试验表明,1.0mol/L盐酸对硫酸钡的溶出率为0.090%,与重晶石样品中硫酸钡质量分数(大于10%)相比可忽略不计。因而采用以下流程对样品中硫酸钡进行测定:样品经1.0mol/L盐酸处理后,过滤,采用过氧化钠熔融-碳酸钠溶液浸提的方法处理沉淀,并采用ICP-AES对浸取液中钡进行测定,可得到以硫酸钡形式存在的钡的含量,将其换算为硫酸钡含量,实现了ICP-AES对重晶石样品中硫酸钡含量的测定。考虑到重晶石样品中碳酸钡的含量较低而硫酸钡的含量较高,分别选择灵敏度最高的Ba 455.403nm谱线和灵敏度较低的Ba 230.424nm谱线为分析谱线对二者进行测定,其对应钡的校准曲线线性相关系数分别为0.999 1~0.999 9和0.999 5~1.000 0。按照实验方法测定重晶石样品中碳酸钡和硫酸钡,碳酸钡方法检出限为0.001%,硫酸钡方法检出限为0.003%;碳酸钡和硫酸钡测定结果的相对标准偏差(RSD,n=12)分别不大于21%和1.0%。实验方法用于样品中碳酸钡测定并加入碳酸钡进行加标回收试验,其回收率为90%~110%。实验方法用于测定重晶石矿石成分分析标准物质中硫酸钡,测定值与认定值相吻合。

Determination of barium carbonate and barium sulfate in barite by inductively coupled plasma atomic emission spectrometry

The determination method of barium carbonate and barium sulfate contents in barite by inductively coupled plasma atomic emission spectrometry (ICP-AES) was discussed with different sample treatment methods. Pure barium sulfate was dissolved with different concentration acetic acids. The results showed that when it was dissolved with 1.7mol/L acetic acid at room temperature for 1h, the dissolution rate of barium sulfate was consistent with that obtained with water for dissolution. Therefore, the following procedures were adopted for the determination of barium carbonate in sample: the sample was dissolved with water, and the content of barium in sample solution was determined by ICP-AES, thus the content of water soluble barium in sample was obtained; the sample was dissolved with 1.7mol/L acetic acid, and the content of barium in sample solution was determined by ICP-AES, thus the content sum of water soluble barium and that in the form of barium carbonate in sample was obtained; then the content of barium in the form of barium carbonate could be calculated by subtraction from the latter from the former, thus the content of barium carbonate could be obtained by further conversion. Therefore,the determination of barium carbonate in barite by ICP-AES could be realized. The sample was treated with 1.0mol/L hydrochloric acid by heating and boiling for 30min, the barium-containing impurities such as barium chloride and barium carbonate could be effectively dissolved. The dissolution tests of pure barium sulfate with 1.0mol/L hydrochloric acid showed that the dissolution rate of barium sulfate by 1.0mol/L hydrochloric acid was only 0.090%, which could be ignored compared to the mass fraction of barium sulfate in barite (higher than 10%). Therefore, the following procedures were adopted for the determination of barium sulfate in sample: the sample was treated with 1.0mol/L hydrochloric acid; after filtration, the precipitate was treated by sodium peroxide fusion-sodium carbonate solution for leaching; the content of barium in leaching solution was determined by ICP-AES to obtain the content of barium in the form of barium sulfate; then it was converted to the content of barium sulfate, realizing the determination of barium sulfate in barite sample by ICP-AES. Considering that the content of barium carbonate in barite sample was low while the content of barium sulfate was relatively high, Ba 455.403nm with highest sensitivity and Ba 230.424nm with low sensitivity was selected as analytical line for the determination of barium carbonate and barium sulfate, respectively. The linear correlation coefficients of calibration curves were 0.9991-0.9999 and 0.9995-1.0000, respectively. The content of barium carbonate and barium sulfate in barite sample was determined according to the experimental method. The detection limit was 0.001% and 0.003%, respectively. The relative standard deviations (RSD, n=12) for barium carbonate and barium sulfate were less than 21% and 1.0%, respectively. The experimental method was applied for the determination of barium carbonate in sample. Meanwhile, barium carbonate was added for standard addition recovery test. The recoveries were between 90% and 110%. The proposed method was applied for the determination of barium sulfate in certified reference material of barite for composition analysis. The results were consistent with the certified values.