微小膜濃縮/黒鉛炉原子吸光法による鉛の高感度定量

Ultra-trace amounts of lead were determined by graphite-furnace AAS (GF-AAS) after miniature-membrane filter (MF) concentration/dissolution. Lead was concentrated as a pyrrolidinedithiocarbamate (APDC) chelate on a miniature MF, which was 5mm in diameter, 2mm in effective filtering diameter and 0.2 μm in pore size. After collection of the lead chelate on MF, the MF was cut so as to be 3mm in diameter using a punch. This tiny MF was dissolved in 100 μl of a dissolution solvent (methyl cellosolve), which resulted in a high concentration efficiency. When 10 ml of a sample was used, the concentration ratio was 100. The addition of 5 × 10(-5) M Zephiramine to the sample solution before chelation was effective for collecting lead; the recovery was almost 100%. The filtering time was 15 min for a 10 ml sample solution. The detection limit was 10 ppt when a 10 ml of sample solution was concentrated in 200 μl of methyl cellosolve. Measurements by GF-AAS were carried out using 40 μl of a methyl cellosolve solution. The relative standard deviation for 40 ppt of lead was 4.51% (n= 4). This method was applied to both river- and tap-water samples.

極微量の鉛イオンを定量するための濃縮法として,膜濾過捕集系を改良し,微小膜捕集濃縮/溶解法を用い,黒鉛炉AASにより測定する鉛の高感度定量法を開発した.試料溶液に3.5×10(-5)Mゼフィラミンを加えた後,鉛イオンをピロリジンジチオカルバミン酸イオンと錯形成させ,微小メンブランフィルター(MF)を用いて濾過し,膜捕集濃縮する.用いたMFは膜直径5mm,濾過有効径2mm,孔径0.2μmのニトロセルロース製であり,鉛キレートを捕集後,MFをポンチで3mmにカットして用いた.これにより,膜溶解溶媒であるメチルセロソルブの量を100μlまで減少させることができ,高倍率濃縮を達成することができた.試料量10mlの濾過時間は15分であった.試料10mlを用い,メチルセロソルブ200μlに溶解したときの鉛の定量下限は,10 pptであり,鉛40pptを含む試料を用いたときの相対標準偏差は4.51%(n=4)であった.本法により,水道水,河川水中の鉛を定量した.