微波等离子体炬质谱直接分析水中镉的研究

Direct Detection of Cadmium in Aqueous Solution Using Microwave Plasma Torch Coupled with Quadrupole Mass Spectrometry

建立了一种测量水中痕量镉的质谱电离新方法。以微波等离子体炬（MPT）为离子源,结合质谱仪器可直接分析水样而无需任何样品预处理。水样直接通过雾化器雾化形成气溶胶,气溶胶经加热冷却循环及浓硫酸干燥后,由MPT中心管道引入等离子体,产生的离子采用四极杆质谱仪（QMS）检测,得到镉的MPT特征质谱。根据镉的特征质谱进行定量分析。结果表明,114Cd的信号强度与溶液中镉离子浓度在300~3 000ng/L范围内呈良好线性关系,相关系数可达0.994 96,检出限（LOD）为72.7 ng/L。对实际水样（自来水、太湖湖水、赣州龙南井水、矿泉水）进行分析,加标回收率为90.6%~112.2%,10次测量的相对标准偏差（RSD,n=10）为7.1%~21.5%,单个样品测试可在2~3 min内完成。因此,MPT质谱法对水中有害金属镉的快速测量具有一定优势,作为传统ICP质谱检测的有力补充,可以发展成为在线分析方法,应用于环境水、生活水质量监控等领域。

A new ionization mass spectrometry method was established for the detection of trace cad- mium in water. Microwave plasma torch （MI~） as the ion source, combined with a mass spectrome- ter can be directly used to analyze water samples without any sample pretreatment. Water sample was transformed into aerosol by directly atomizing nebulizer. The aerosol after heating - cooling cycles and drying of concentrated sulfuric acid, was introduced into the plasma through the MPT central conduit, generating ions detected with quadrupole mass spectrometer（QMS） to afford cadmium MPT features MS. Quantitative analysis was carried out based on the characteristics of cadmium mass. The results showed that the signal intensity 114Cd had a good linearity with the solution of cadmium ion concentra- tion within 300 - 3 000 ng/L with a correlation coefficient of 0. 994 96, the detection limit （LOD） was 72. 7 ng/L. Actual water samples（tap water, Tai Hu Lake water, Gan Zhou Long Nan well wa- ter, mineral water） were analyzed. The recoveries ranged from 90. 6% to 112. 2% with relative standard deviations（RSDs, n = 10） of 7.1% -21.5%. The detection for a single sample could be completed within 2 -3 min. Therefore, as a powerful complement to traditional ICP mass spectrome- ter, the fast MPT mass spectrometry dection of hazardous metals cadmium in water has certain advan- tages, and could be developed as a line analysis method for environmental water, tap water quality monitoring, etc.