Simultaneous Determination of V, Cr, Ni, Ge and As in Geochemical Samples by ICP-MS Combined with Microwave Digestion Sample Preparation
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摘要: 地质样品中多种元素的分析,通常采用高压密封消解电感耦合等离子体质谱法(ICP-MS),而应用于测定地球化学样品中的V、Cr、Ni、Ge、As等元素,影响分析准确度的主要原因有:样品前处理方面,高压密封罐会释放Cr和Ni污染样品,同时Ge和As属于易挥发元素容易造成损失;质谱测定方面,多原子分子离子会产生干扰。本文针对两方面的干扰因素,对比了微波消解硝酸提取、微波消解王水提取、高压密封硝酸复溶、高压密封王水复溶四种前处理方法中待测元素的溶出效果以及污染或损失情况。结果表明,采用微波消解替代高压密封罐消解可消除引入的Cr、Ni污染,避免了Ge、As挥发损失,同时微波消解的时间短。而采用硝酸提取,由于避免了氯的引入,分析效果优于王水提取。且使用八极杆ICP-MS氦气碰撞模式消除了样品基体中的氯多原子分子离子干扰(如37Cl14N对51V干扰,35Cl16OH对52Cr干扰,35Cl37Cl对72Ge干扰以及40Ar35Cl对75As干扰等)。应用微波消解硝酸提取、ICP-MS测定岩石、水系沉积物和土壤国家标准物质,V、Cr、Ni、Ge、As的检出限分别为1.09、0.19、0.55、0.02、0.50 μg/g,精密度(RSD) < 4%,而采用高压密封消解、ICP-MS测定V、Cr、Ni的检出限为3.48、13.09、21.67 μg/g(Ge和As由于挥发无法用此法检测)。运用微波消解硝酸提取-ICP-MS氦气碰撞模式测定地球化学样品中V、Cr、Ni、Ge、As,简化了分析流程,样品消解时间仅2 h,相比于高压密封方法(消解时间48 h)具有消解快速、多元素同时测定、检出限低的特点。Abstract: A microwave digestion method to simultaneously determine V, Cr, Ni, Ge and As in geochemical samples by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is proposed. There are two main factors to influence the method accuracy: Cr and Ni released from stainless bomb could contaminate the samples by high press digestion and volatile elements, such as Ge and As, lost during pretreatment, and polyatomic molecular ions have mass influence on the determination by ICP-MS. In order to eliminate these two kinds of influences, four kinds of digestion methods were compared, including microwave digestion with nitric acid/aqua regia extraction and high pressure digestion with nitric acid/aqua regia extraction. The method by microwave digestion instead of high pressure digestion avoids the problem of contamination of Cr and Ni and loss of Ge and As with short digestion times. The nitric acid extraction, avoiding the addition of Cl-, has better analysis effect when compared with aqua regia extraction. A helium dilution technique based on the octopole reaction system ICP-MS was applied to decrease the interference of polyatomic molecular ions, such as 37Cl14N interference on 51V, 35Cl16OH interference on 52Cr, 35Cl37Cl interference on 72Ge and 40Ar35Cl interference on 75As. Based on the study of rock, stream sediments and soil national standard material by ICP-MS combined with nitric acid extraction, the results showed that the detection limits of V, Cr, Ni, Ge, and As by the proposed method were 1.09 μg/g, 0.19 μg/g, 0.55 μg/g, 0.02 μg/g and 0.50 μg/g, respectively. The RSDs were less than 4%. The detection limits of V, Cr and Ni by high pressure digestion were 3.48 μg/g, 13.09 μg/g and 21.67 μg/g, respectively. The proposed method was simple, time-saving (from 48 h to 2 h) and has the capability of simultaneous determination of multielements with low detection limits.
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Keywords:
- geochemical sample /
- V /
- Cr /
- Ni /
- Ge /
- As /
- microwave digestion /
- Inductively Coupled Plasma-Mass Spectrometry /
- polyatomic molecular ion interferences
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表 1 ICP-MS仪器工作条件
Table 1 Working parameters of the ICP-MS instrument
工作参数 设定条件 工作参数 设定条件 功率 1550 W CeO+/CeO+ 0.78% 雾化气(Ar)流量 0.75 L/min 采样深度 7 mm 稀释气(Ar)流量 0.25 L/min 雾室温度 2℃ 表 2 微波辅助消解溶样程序
Table 2 Procedure of microwave digestion
消解步骤 功率(W) 升温时间(min) 工作温度(℃) 时间(min) 1 600 3 80 5 2 900 3 120 10 3 900 3 160 10 4 900 3 200 10 表 3 方法准确度及精密度
Table 3 Accuracyandprecisiontestsofthemethod
标准物质编号 元素 元素含量(μg/g) RSD(%)(n=3) 对数误差 标准物质编号 元素 元素含量(μg/g) RSD(%)(n=3) 对数误差 标准值 测量值 标准值 测量值 GBW07105(玄武岩) V 167 162 1.5 0.01 GBW07405(黄红壤) V 166 146.1 1.5 0.06 Cr 134 127 1.1 0.02 cr 118 111.7 1.0 0.02 Ni 140 138 1.2 0.01 Ni 40 32 1.2 0.09 Ge 0.98 1.03 1.1 0.02 Ge 2.6 2.9 1.0 0.05 As 0.7 0.92 3.5 0.12 As 412 420 1.0 0.01 GBW07309(长江沉积物) V 97 86 1.7 0.05 GBW07407(砖红壤) V 245 225 1.0 0.04 Cr 85 80 0.9 0.02 Cr 410 401 0.6 0.01 Ni 32 35 1.4 0.04 Ni 276 241 0.9 0.06 Ge 1.3 1.1 1.0 0.08 Ge 1.6 1.7 1.1 0.03 As 8.4 10.0 1.5 0.08 As 4.8 6.0 3.8 0.10 GBW07105(斜长角闪岩) V 296 267 1.0 0.04 GBW07103(花岗岩) V 24 22 1.9 0.04 Cr 137 117 1.0 0.07 Cr 3.6 3.2 2.5 0.05 Ni 117 97 1.1 0.08 Ni 2.3 2.9 2.3 0.10 Ge 1.46 1.16 1.0 0.10 Ge 2.0 1.9 1.1 0.02 As 26 28 1.2 0.03 As 2.1 2.6 3.4 0.09 GBW07311(多金属矿) V 47 43 1.7 0.04 Cr 40 42 1.5 0.02 Ni 14.3 15.4 1.5 0.03 Ge 1.81 2.00 1.1 0.04 As 188 195 1.0 0.02 表 4 采用ICP-MS与ICP-AES/AFS分析实际地质样品结果对比
Table 4 Comparison of analytical results of the elements in actual samples by ICP-MS and ICP-AES/AFS methods
样品编号 元素 元素含量(μg/g) ICP-MS精密度RSD(%)(n=3) 对数误差 样品编号 元素 元素含量(μg/g) ICP-MS精密度RSD(%)(n=3) 对数误差 ICP-MS ICP-AES/AFS ICP-AES/AFS ICP-MS S-1(岩石) V 10.6 9.5 1.6 0.05 S-6(水系沉积物) V 51.4 56 1.2 0.04 Cr 50.9 46.5 1.6 0.04 Cr 10 12 1.8 0.09 Ni 68 68 1.2 0.00 Ni 19 23 1.2 0.09 Ge 0.9 1.2 3.0 0.12 Ge 0.6 0.7 3.1 0.07 As 0.7 0.7 1.5 0.02 As 100 117 1.8 0.07 S-2(岩石) V 30 30 1.4 0.00 S-7(土壤) V 19.3 19.5 1.3 0.01 Cr 13.3 14.4 2.3 0.04 Cr 82 97 1.3 0.07 Ni 14 18 1.2 0.10 Ni 62 64 1.0 0.01 Ge 0.81 0.87 3.0 0.03 Ge 1.0 1.3 3.0 0.10 As 14 18 1.2 0.10 As 62 64 1.0 0.01 S-3(岩石) V 9.9 11.2 1.4 0.05 S-8(土壤) V 47.0 49 1.2 0.02 Cr 51 52 1.9 0.01 Cr 23.0 24.8 1.0 0.03 Ni 2.1 2.7 1.5 0.11 Ni 68 68 1.2 0.00 Ge 0.84 0.97 3.2 0.11 Ge 0.7 0.7 1.5 0.02 As 2.1 2.7 1.5 0.11 As 19 22 2.1 0.06 S-4(水系沉积物) V 123.8 131 1.2 0.02 S-9(土壤) V 40 32 1.2 0.09 Cr 2.8 3.4 2.3 0.08 Cr 12.5 14.0 1.0 0.05 Ni 41 40 1.2 0.01 Ni 14 18 1.2 0.10 Ge 1.81 1.65 3.0 0.04 Ge 5.2 5.1 0.8 0.01 As 41 40 1.2 0.01 As 1.7 1.8 3.0 0.03 S-5(水系沉积物) V 69 71 1.1 0.01 S-10(土壤) V 76 84 1.0 0.04 Cr 8.2 8.5 1.8 0.02 Cr 15.5 17.2 0.9 0.05 Ni 23 25 1.2 0.03 Ni 2.1 2.7 1.5 0.11 Ge 0.96 1.13 3.0 0.07 Ge 2.3 1.8 1.2 0.10 As 23 25 1.2 0.03 As 38 37 2.0 0.02 -