Determination of Thorium and Potassium Oxide in Geological Samples by Inductively Coupled Plasma-Optical Emission Spectrometry
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摘要: 同时测定地质样品中的钍和钾，可为放射性矿产资源勘探、天然放射性生态环境评价提供重要依据。对于钍，传统方法使用碱熔法分解试样分光光度法测定，此方法前处理冗长、复杂且不利于多元素的同时测定。而氧化钾一般采用酸溶法消解样品火焰原子吸收分光光度法测定，此方法测定浓度高的溶液需要稀释，检测效率较低。钍和氧化钾的分析涉及了两种配套方法。本文根据地质样品的化学成分特征，筛选出了用硝酸、氢氟酸和高氯酸为溶剂溶解样品，硝酸提取定容后，用电感耦合等离子体发射光谱法（ICP-OES）分别在波长401.913nm和766.490nm处，采用径向观测方式同时测定了钍、氧化钾的含量。钍、氧化钾的标准曲线相关系数均大于0.999，方法检出限分别为0.69μg/g、0.008%，标准物质的测定值与认定值基本一致，二者的对数误差绝对值小于0.1，相对标准偏差（RSD，n=6）小于6.0%，加标回收率在96.0%~104.0%之间，符合《地质矿产实验室测试质量管理规范》的要求。Abstract:
BACKGROUNDSimultaneous determination of thorium and potassium in geological samples can provide an important basis for exploration of radioactive mineral resources and evaluation of the natural radioactive ecological environment. The thorium in geological samples is usually digested by alkali fusion in traditional methods and determined by spectrophotometry. The traditional method is long, complex and not suitable for simultaneous determination of multiple elements. The potassium oxide in geological samples is digested by acid and generally determined by flame atomic absorption spectrometry, which requires diluting the solution with high concentration and has low detection efficiency. The determination of thorium and potassium oxide involves two different analytical methods and analytical instruments. OBJECTIVESTo establish an analytical method for simultaneous determination of thorium and potassium oxide in geological samples. METHODSChemical solvent which consists of nitric acid, hydrofluoric acid and perchloric acid, was identified according to the characteristics of the chemical composition of the geological samples. The geological samples were dissolved with this solvent and extracted with nitric acid. The content of thorium and potassium oxide in geological samples was measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) at wavelengths of 401.913nm and 766.490nm, respectively by radial observation mode. RESULTSThe correlation coefficient of the calibration curve of thorium and potassium oxide was greater than 0.999 and the detection limit of this method was 0.69μg/g and 0.008%, respectively. The measured value of the standard substance was consistent with the identified value, and the absolute logarithmic error of the two values was less than 0.1. The relative standard deviation was less than 6.0% and the recovery ranged from 96.0% to 104.0%. CONCLUSIONSThis method meets the requirements of the testing quality management standard for geological and mineral laboratories. -
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表 1 不同混合酸消解样品中钍和氧化钾的测定结果比较
Table 1. Comparison of analytical results of Th and K2O in samples dissolutied with HCl-HNO3-HF-HClO4 and HNO3-HF-HClO4 acid digestion
样品处理方法 GBW07309 GBW07312 Th
(μg/g)K2O
(%)Th
(μg/g)K2O
(%)盐酸-硝酸-氢氟酸-高氯酸(方法1) 14.13 2.00 22.39 2.87 硝酸-氢氟酸-高氯酸(方法2) 14.32 1.97 23.26 2.91 认定值 12.4±0.7 1.99±0.06 21.4±1.1 2.91±0.04 
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表 2 钍和氧化钾的最佳分析谱线
Table 2. Analytical spectral lines for thorium and potassium oxide determination
测定次数 GBW04120 GBW04121 Th(μg/g) K2O(%) Th(μg/g) K2O(%) 283.730
nm401.913
nm766.490
nm283.730
nm401.913
nm766.490
nm1 11.08 3.82 0.93 43.11 24.63 6.19 2 10.00 3.92 0.95 52.84 23.59 6.17 3 12.10 3.70 0.90 48.53 23.14 6.15 测定平均值 11.06 3.81 0.93 48.16 23.79 6.17 认定值 3.4±0.1 0.84 21.7±0.5 6.08 相对误差(%) 225.29 12.16 10.32 121.94 9.62 1.48 RSD(%) 9.49 2.89 2.72 10.12 3.21 0.32 相关系数 0.9993 0.9999 0.9998 0.9993 0.9999 0.9998
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表 3 准确度和精密度测定结果
Table 3. Accuracy and precision tests of the method
测定次数 GBW07409 GBW07404 GBW07310 GBW07302a Th(μg/g) K2O (%) Th(μg/g) K2O (%) Th(μg/g) K2O (%) Th(μg/g) K2O (%) 1 13.57 1.94 30.13 1.07 6.24 0.102 37.27 5.36 2 13.10 1.94 30.04 1.08 6.20 0.104 38.99 5.44 3 13.03 1.88 29.12 1.09 5.99 0.110 37.74 5.23 4 12.11 1.94 31.59 1.05 5.45 0.119 37.72 5.64 5 12.32 2.06 29.47 1.05 5.92 0.108 38.12 5.42 6 12.68 1.97 29.32 1.04 6.12 0.115 37.53 5.28 测定平均值 12.80 1.96 29.95 1.06 5.99 0.110 37.90 5.40 认定值 12.8±1.6 1.98±0.05 27.0±2 1.03±0.06 5.0±0.3 0.125±0.013 38±3 5.34±0.11 ∆lgC 0.00 0.01 0.04 0.01 0.08 0.06 0.00 0.01 标准偏差 0.540 0.059 0.900 0.020 0.290 0.006 0.605 0.144 RSD(%) 4.2 3.0 3.3 1.9 5.8 5.2 1.6 2.7
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表 4 加标回收率试验
Table 4. Spiked recovery tests of the method
称样量
(g)Th K2O 测定值
(μg/mL)加入量
(μg)回收率
(%)测定值
(μg/mL)加入量
(μg)回收率
(%)0.1436 0.076 0 - 95.92 0 - 0.1325 0.128 1.5 96.0 166.11 2000 97.0 0.1526 0.159 2.0 98.0 232.88 3000 102.0 0.1462 0.174 2.5 97.0 237.50 3500 104.0 0.1452 0.198 3.0 101.0 253.67 4000 99.0
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