高压密闭消解-电感耦合等离子体质谱法测定海洋沉积物中稀土元素

样品用HNO3-HF高压密闭消解,电感耦合等离子体质谱测定海洋沉积物中15种稀土元素。研究了消解方法、酸体系和质谱干扰对稀土元素测定的影响。结果表明,相比于电热板消解和微波消解,高压密闭消解具有酸用量少、消解完全、消解过程损失少等优点;HNO3-HF体系能有效地分解海洋沉积物样品;利用干扰离子校正方程,能有效地校正Ba和轻稀土元素所形成的多原子离子干扰。15种稀土元素的方法检出限为3～15 ng/g。使用水系沉积物标准物质GBW 07309和GBW 07311、海底沉积物标准物质GBW 07313进行验证,测定值与标准值基本吻合,相对标准偏差和相对误差均低于5%。方法用于长江口沉积物样品的测定,精密度(RSD,n=6)小于5%,加标回收率为95.8%～104%。该方法检出限低,精密度和准确度高,适用于大批海洋沉积物样品的分析。

Determination of Rare Earth Elements in the Marine Sediments by Inductively Coupled Plasma-Mass Spectrometry with High-pressure Closed Digestion

Using a HF-HNO₃ system with high-pressure closed digestion, a method to determine concentrations of fifteen rare earth elements (REEs) in marine sediments was studied by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Experimental conditions such as mass spectrum interferences, digestion methods and acid systems have been investigated. Compared to electric heating plate digestion and microwave digestion, high-pressure closed digestion has the advantages of using less acid, achieving complete digestion and causing less damage to the digestion process. The correction equation effectively calibrated polyatomic ions interferences formed by Ba and light rare earth elements. The marine sediment samples were dissolved completely by HF-HNO₃ system, and the relative error (RE) was less than 5%. The method detection limits were 3-15 ng/g. The proposed method was validated by the marine sediment reference materials GBW 07309, GBW 07311 and GBW 07313. The results were consistent with certified values, and the relative standard deviation (RSD) and relative error were both less than 5%. The determination precision (RSD, n=6) of the Yangtze River estuary sediment samples was less than 5%, and the recoveries were 95.8%-104%. This method has a low detection limit with high precision and accuracy, all of which meet the requirements to analyze a large number of marine sediment samples.