膜去溶-电感耦合等离子质谱测定21种国际地质标样中的银

Direct Determination of Ag in 21 International Geological Reference Materials by Membrane Desolvation-Inductively Coupled Plasma-Mass Spectrometry

建立了膜去溶-ICP-MS直接测定各种地质样品中微量Ag的分析方法。详细比较了采用冷却雾室和膜去溶对降低氧化物和氢氧化物干扰的情况。结果表明：采用膜去溶进样可以很好地解决测定地质样品时Zr、Nb、Y的氧化物和氢氧化物对Ag的干扰。再结合少量N2的引入还可以进一步提高Ag的检测灵敏度（4倍）和降低氧化物和氢氧化物的干扰（50%）。在冷却雾室（2℃）ICP-MS条件下,Zr的氧化物和氢氧化物产率通常在-0.5%;而采用膜去溶-ICP-MS可以降低至约0.0005%。所以,可以采用膜去溶-ICP-MS直接测定各种地质样品中的Ag。在给定的条件下,膜去溶-ICP-MS对Ag的检出限是0.0005μg/L。结合密闭高温高压消解样品的方法,测定了21种各种类型国际地质标样,确证了本法的可行性。

A method has been developed for the direct determination of Ag in geological samples. In this work, various conditions involving optimizing the operating parameters of ICP-MS with or without membrane desolvation system were carefully investigated. In comparison to the cooling spray chamber, the interferences of ^91Zr^16O^＋,^91Zr^18O^＋ , ^90Zr16OH^＋ and ^90Zr^18OH^＋ were found to be reduced by three orders of magnitude by membrane desolvation sample introduction system. The addition of 8 mL/min nitrogen to the carrier gas flow rate in membrane desolvation-ICP-MS increases sensitivity for Ag by a factor of 4 and reduces the oxide and hydroxide interferences by about 50%. Under the given experiment conditions of membrane desolvation-ICPMS, the detection limit of Ag was 0. 0005 μg/L. The excellent agreement among the determination of Ag concentration values （r^2 = 0. 995） in various geological samples （n = 103 ） by using isotopes of ^107Ag and ^109Ag indicates negligible contributions of polyatomic interferences produced by Zr, Nb and Y at these m/z. The proposed method was successfully applied to the direct determination of Ag in a series of international geological reference materials.