試料の直接導入-金属炉原子吸光光度分析による土壌中重金属のスクリーニング Screening of Heavy Metals in Soil by Direct Sampling/Metal Furnace Atomic Absorption Spectrometry

土壌試料中のSeとCd，Hg，Pbをタングステン炉上で直接原子化して原子吸光光度法でスクリーニング分析する方法を検討した．粒径が106 μm以下になるように粉砕した土壌粉末に分光分析用のカーボン粉末を1対1の割合で混合し測定試料とした．土壌認証標準物質JSAC 0461〜0466を用いて原子化条件・マトリックスモディファイア・試料分け取り量などを最適化した．0.2〜4 mgの試料をタングステン皿に分け取ってタングステン炉上で所定の加熱条件で原子化した．グラファイトを土壌試料に1対1で添加混合することにより残査のガラス化が抑制できた．各測定元素について試料粉末量と吸光度の関係線は良い直線が得られ，その勾配は標準溶液を用いた検量線とよく一致した．土壌認証標準物質JSAC 0461を用いてPbの定量値を比較したところ，認証値は24.4 mg kg−1に対して分析値25 mg kg−1で，得られた測定結果はよく一致した．分析した本邦産の8土壌中のPbの濃度範囲は10〜62 mg kg−1であり，相対標準偏差は1.0〜8.0％（n＝5）であった．

A method of direct sampling/tungsten furnace electrothermal atomic absorption spectrometry combined with mixtures of soil and graphite powder has been developed for the determination of trace amounts of Se, Cd, Hg, Pb in soil samples, where these samples are mixed with graphite powder, and are applied to a furnace. Soil samples containing hazardous metals (Se, Cd, Hg and Pb) were mixed with graphite powder at a 1 : 1 ratio in an agate mortar. These mixtures were weighed in a tarred W dish and atomized according to an optimized heating program. These heavy metals in soil samples were determined by using calibration curves obtained with aqueous standard solutions. For measuring Hg in an aqueous standard solution, Pd(NO3)2 was used for matrix modification. The limits of detection corresponding to three-times the standard deviation for 5 measurements were as follows : Se 1.6 mg kg−1, Cd 0.026 mg kg−1, Hg 2.2 mg kg−1, Pb 0.041 mg kg−1. The relative standard deviations for the proposed method for soil samples were in the range from 1.7% for 71 mg kg−1 of Pb, to 19% for 0.11 mg kg−1 of Cd.