采用ICP-MS/MS准确测定食品中钙和氯

建立利用电感耦合等离子体串联质谱测定食品中钙和氯的分析方法。针对Ca的高丰度同位素40Ca受到来自等离子气40Ar的干扰，35Cl受到来自16O18OH的严重干扰，在MS/MS模式下，利用碰撞/反应池技术，以H₂为反应气，使40Ar+与H₂发生反应，而40Ca+不与H₂发生反应，利用H₂原位质量法消除40Ar+对40Ca+的干扰；而35Cl+则能与H₂发生质量转移反应生成H₂35Cl+，通过测定H₂35Cl+消除16O18OH+对35Cl+的干扰。Ca和Cl在0.0~100.0 μg·L-1的浓度范围内线性关系良好，线性相关系数（R2）≥0.999 9，Ca和Cl的检出限分别为0.061和2.32 μg·L-1。采用系列国家标准物质验证了对方法的准确性和精密度，其测定结果与标准参考物质的认定值基本一致，表明方法的准确性好、精密度高。所建立的新方法可实现食品中钙和氯的准确测定。

Accurate Determination of Calcium and Chlorine in Food with Inductively Coupled Plasma Tandem Mass Spectrometry

An analytical method for the determination of Ca and Cl elements in food was established with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). The most abundant isotope 40Ca of Ca is suffering from intense interferences from the 40Ar among the argon plasma gas, and 35Cl is subjected to interference from 16O18OH. To avoid the interference, in the MS/MS mode, collision/reaction cell (CRC) was adopted using H₂ as the reaction gas, so that H₂ will reach with 40Ar+ instead of 40Ca+, A H₂ on-mass method was used to eliminate the interference of 40Ar+ on 40Ca+. As mass shift reaction could take place between 35Cl+ and H₂ to generate H₂35Cl+, thus the interference of 16O18OH+ on 35Cl+ can be eliminated by determining H₂35Cl+. Ca and Cl showed good linearity in the concentration range of 0.0～100.0 μg·L-1 with linear correlation coefficient (R2)≥0.999 9, and the detection limits of Ca and Cl were 0.061 and 2.32 μg·L-1, respectively. The accuracy and precision of this method were verified by series of national standard materials. The results of this method were basically consistent with the certified values of the reference materials, indicating that the method of good accuracy and high precision. The new method can be used to achieve the accurate determination of Ca and Cl in food.