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2-ニトロソ-1-ナフトール-4-スルホン酸(ニトロソ-NW酸)の金属キレート(Fe(2+),Co(2+),Ni(2+),Cu(2+)及びPd(2+))をキャピラリー電気泳動により分離した.通常の泳動液(ニトロソ-NW酸と緩衝剤の混合液)では,Ni(2+),Cu(2+)のみが鋭いピークを与えた.泳動液中に第四級アンモニウムイオンを加えると,ブロードなピークであったFe(2+),Co(2+),Pd(2+)も鋭いピークとなった.泳動液中に添加する第四級アンモニウムイオンの種類と濃度の影響を調べたところ,疎水性のイオンほど,又高濃度ほどキレートの移動度(絶対値)は小さくなることが分かった.これは,第四級アンモニウムイオンがキレート陰イオンと一部イオン会合体を形成し,実質的電荷を下げていることによると考えられる.泳動液組成の最適化を検討した結果,テトラブチルアンモニウムイオンを用いることにより,上述の5種の金属イオンの良好な分離と同時定量が可能となった.本法により,市販ニッケル塩中の微量コバルトの定量を行った., Capillary electrophoresis study was carried out by using 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-NW acid) as a chelating and chromogenic agent. Nitroso-NW acid (H2R) reacts with Co(2+) to form the chelate anion, CoR(3)(3-) and also reacts with Fe(2+), Ni(2+), Cu(2+) and Pd(2+). However, except for Ni(2+) and Cu(2+), sharp peaks could not be obtained with a conventional carrier containing HR-and buffer components. This is probably because the metal chelates were highly charged: the chelates of Ni(2+), Cu(2+), Fe(2+), Co(2+) and Pd(2+) are expected to be CuR(2)(2-), Fe(II)R(3)(4-) Co(III)R(3)(3-), NiR(3)(4-) and Pd(OH)(2)(2) R(-), from their electrophoretic mobilities. The peaks of Fe(2+), Co(2+) and Pd(2+) were sharpend by adding a quaternary ammonium ion to the carrier. The quaternary ammonium ion in the carrier acts as a pairing cation of metal chelate anions. Of these, tetrabutylammonium ion(TBA(+)) was the best pairing ion for the metal chelates. By using a carrier containing HR(-), TBA(+) ·Br(-) and buffer components (pH 7), good separation and highly sensitive detection of the five metal ions (Fe(2+), Co(2+), Ni(2+), Cu2+and Pd2+) could be achieved within 7 min. The proposed method was applied to the determination of cobalt in nickel salts.