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Determination of Heavy Metals in Tea Through Coprecipitation Separation and Enrichment Combined with Partial Least Square-Spectrophotometry
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摘要: 以铜试剂为共沉淀剂, 在pH值为10.0的条件下, 共沉淀分离富集茶叶中痕量金属离子Ni2+、Pb2+、Cd2+和Cu2+, 并分析了铜试剂与金属离子形成配合物的最佳沉淀条件.用4-(2-吡啶偶氮)间苯二酚(PAR)作为这4种重金属离子的显色剂进行分光光度测定, 采用偏最小二乘-紫外可见光度法同时测定了四组分金属离子的模拟混合试样, 并在茶叶中进行上述金属离子含量的测定.方法操作简便、结果可靠, 对茶叶中重金属测定有一定实用价值.Abstract: Using the copper reagent as the coprecipitator under the alkaline condition of pH 10.0, the rapid coprecipitation enrichment of trace metal ions Ni2+, Pb2+ and Cd2+ and Cu2+ in tea had been carried out, and the optimal conditions for the formation of complexes of copper reagent with metal ions were analyzed. 4-(2-pyridylazo) resorcinol (PAR) was used as the color developing agent for the four heavy metals, in the spectrophotometric analysis. Partial least square-UV-visible spectrophotometry was used to determine the simulate mixed sample of the four components of the metal ions at the same time, with those in tea. This method is simple, the result is reliable, and is of certain practical value to the determination of heavy metals in tea.
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Key words:
- coprecipitation separation and enrichment /
- partial least squares /
- tea /
- heavy metal
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表 1 人工合成试样校正组质量浓度组成
Table 1. Mass concentration of the rectified group of synthetic sample
样品序号 质量浓度/(μg/mL) Pb2+ Cu2+ Ni2+ Cd2+ 1 6.00 7.20 8.00 6.40 2 6.00 6.40 7.20 7.20 3 6.00 8.00 6.00 8.00 4 8.00 7.20 7.20 8.00 5 8.00 6.40 6.00 6.40 6 8.00 8.00 8.00 7.20 7 7.20 7.20 6.00 7.20 8 7.20 6.40 8.00 8.00 9 7.20 8.00 7.20 6.40 
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表 2 人工合成试样预报组质量浓度组成、PLS预测值及误差分析
Table 2. Mass concentration of the rectified group of synthetic sample, PLS predicted value, error analysis
(μg/mL) 样品序号 预报组质量浓度 PLS预测值 Pb2+ Cu2+ Ni2+ Cd2+ Pb2+ Cu2+ Ni2+ Cd2+ 1 6.40 8.00 6.40 6.00 6.30 8.10 6.31 6.04 2 6.40 6.00 8.00 8.00 6.33 6.00 8.01 7.95 3 6.40 7.20 7.20 7.20 6.41 7.21 7.20 7.10 4 8.00 8.00 8.00 7.20 8.00 8.0 7.93 7.30 5 8.00 6.00 7.20 6.00 8.10 6.10 7.30 5.93 6 8.00 7.20 6.40 8.00 8.15 7.20 6.40 7.94 7 5.60 8.00 7.20 8.00 5.61 7.92 7.20 7.90 8 5.60 6.00 6.40 7.20 5.55 6.10 6.36 7.11 9 5.60 7.20 8.00 6.00 7.10 7.24 7.92 5.93 平均误差/% 37.6 6.98 6.02 10.73 RPEs/% 7.50 0.91 14.52 1.11 回收率/% 103.0 100.5 99.7 99.4
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表 3 样品测定结果
Table 3. Analytical results of samples
样品序号 质量分数/(mg/kg) Pb2+ Cu2+ Ni2+ Cd2+ 苦丁茶 37.8 756.5 130.2 未检出 绿茶 51.2 503.5 112.8 1.2 普洱茶 87.8 1 133.0 205.8 3.0 乌龙茶 42.5 405.2 176.0 未检出 铁观音 77.5 1 006.5 203.5 0.8 菊花茶 3.2 485.0 137.5 未检出 砖茶 89.5 1 397.8 159.2 3.5 茉莉花茶 8.8 955.2 120, 0 0.8
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