Quantification of Cr in Natural Sparkling Mineral Waters by Inductively Coupled Plasma-Mass Spectrometry
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摘要: 含气天然矿泉水含有高浓度的HCO3-和CO2,其中元素Cr的浓度在电感耦合等离子体光谱(ICP-AES)的检出限附近甚至更低,应用电感耦合等离子体质谱(ICP-MS)测定又容易形成多原子离子40Ar12C,对52Cr的测定形成干扰,致使ICP-MS不能直接准确测定含气天然矿泉水中的Cr元素。本文对水样进行前处理,加热煮沸2 min后放置至室温,加入硝酸调节水样酸度为5%,促进HCO3-与H+反应生成大量的CO2迅速释放出来,消除了40Ar12C对52Cr产生的质谱干扰,实现了ICP-MS能够直接准确分析Cr的含量,方法检出限为0.23 ng/mL,加标回收率为92.3%~93.7%,相对标准偏差(RSD)小于10%。此方法简单实用,精确度和准确度能够满足天然矿泉水分析测试的要求,还可同时测定此批前处理水样中的锌铜砷镉铅等痕量元素。
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关键词:
- 含气天然矿泉水 /
- 铬 /
- 电感耦合等离子体质谱法 /
- 40Ar12C
Abstract: Natural sparkling mineral water contains high concentrations of HCO3- (about 1500 mg/L) and CO2(about 400 mg/L) and the concentration of Cr is equal to or lower than the detection limit of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Moreover, it is easy to form the polyatomic ion 40Ar12C, which interferes with the determination of 52Cr in the water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Therefore, it is not possible to accurately quantify Cr in natural sparkling mineral water by ICP-MS. In this paper, a new method is described to quantify Cr in natural sparkling mineral water. The water is heated to 100℃ for 2 minutes, cooled to room temperature, and the acidity of the samples is adjusted to 5% (volume ratio) with nitric acid,which promotes HCO3- and H+ reactions to generate CO2 gas, thus being rapidly released. The interference of 40Ar12C on 52Cr is eliminated by this pretreatment of the natural sparkling mineral water, and the accurate determination of Cr in the water was conducted by ICP-MS. The detection limit of this method is 0.23 ng/mL. The results were satisfactory with the recoveries from 92.3% to 93.7%. This method is not only simple and practical, but can also be used to simultaneously and accurately quantify Ni, Cu, As, Cd and Pb in the water samples by ICP-MS. Its precision and accuracy meet the requirements of natural mineral water analysis. -
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表 1 仪器工作参数
Table 1. Operating parameters of the ICP-MS instrument
工作参数 设定条件 功率 1350 W 冷却气(Ar)流量 13.0 L/min 辅助气(Ar)流量 0.75 L/min 雾化气(Ar)流量 1.0 L/min 采样锥(Ni)孔径 1.0 mm 截取锥(Ni)孔径 0.7 mm 测量方式 跳峰 扫描次数 50 停留时间/通道 10 ms 每个质量通道数 3 总采集时间 20 s 表 2 含气天然矿泉水样中主要离子的含量
Table 2. The concentration of main ions in natural sparkling mineral water samples
离子 ρ/(mg·L-1) Na+ 102 Ca2+ 341 Mg2+ 94.5 K+ 6.32 SO42- 35.2 Cl- 33.7 HCO3- 1671 CO2 460 表 3 测定Cr的加标回收率
Table 3. Recovery test of the method for Cr determination
溶液编号 ρ(Cr)/(ng·mL-1) 回收率/% 加标量 测定值 溶液 1 0.00 2.76 - 溶液 2 4.00 6.45 92.3 溶液 3 6.00 8.38 93.7 表 4 方法精密度
Table 4. Precision tests of the method
ρ(Cr)/(ng·mL-1) RSD/% 法分次测定值 平均值 2.75 2.46 2.67 2.59 7.85 2.24 2.91 2.51 2.47 2.77 2.53 -
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