A sensitive Bi/MWCNTs (multi-walled carbon nanotubes ) composite film modified electrode was fabricated by two-step electrodeposition . First , the MWCNTs were electrodeposited instead of dropping coated on the glass carbon electrode (GCE) ,and the bismuth film was then deposited on the MWCNTs/GCE .A protocol used for the determination of total chromium and hexavalent chromium in water by square wave cathodic adsorptive voltammetry in the presence of cupferron (N-nitroso-N-phenylhydroxylamine ammonium salt ) was proposed .In the presence of cupferron ,Cr(Ⅲ ) can form the complex with cupferron and be accumulated on the surface of the modified electrode by adsorption at a potential of -0.35 V ,and then is reduced with the cathodic scan from -0.35 V to -1.10 V .An accumulation time of 2 min results in a detection limit of 0.05 μg/L Cr(Ⅵ) and a relative standard deviation of 5.2% (n=75) for 10μg/L . Application to river water samples is demonstrated . The total chromium can be directly determined by standard addition of Cr(Ⅲ) or Cr(Ⅵ);the Cr(Ⅵ) can be separated with Cr(Ⅲ) by using an anion trapping column and then determined by standard addition of Cr (Ⅵ ) . T he results are consistent with those detected by ICP-MS (inductive coupled plasma mass spectrometry ) .T he attractive behavior of the new “mercury-free” chromium sensor holds great promise for on-site environmental and industrial monitoring of chromium .%通过两步电沉积方法制备了一种灵敏的铋/多壁碳纳米管复合膜修饰电极．首先用电解代替滴涂法将多壁碳纳米管沉积到玻碳电极表面，然后再把铋膜沉积到多壁碳纳米管上．提出了利用方波阴极吸附溶出伏安法分别测定水中总铬和六价铬的分析方法．在铜铁灵试剂的存在下，Cr （Ⅲ）和铜铁灵形成的络合物在-0.35 V时通过吸附富集在修饰电极的表面，然后在阴极扫描（-0.35～-1.10 V ）过程中被还原．可以利用Cr（Ⅲ）或Cr（Ⅵ）的标准加入法直接测定水中总铬含量，也可以利用阴离子富集柱将Cr（Ⅵ）与Cr（Ⅲ）分离后单独测定水中Cr（Ⅵ）含量，分析结果与电感耦合等离子体质谱法（ICP-MS）相吻合．本法的检测下限在富集时间2 min时为0.05μg/L ，相对标准偏差为5.2％（n＝75）．
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