在（37±2）℃下，样品经0.07 mol·L^-1盐酸溶液于pH 1.0~1.5避光振荡提取后，用2，6-吡啶二甲酸在100℃、pH 6.8条件下与提取液中的三价铬进行衍生化反应，衍生后的溶液经过IonPac CS5A分析柱（250 mm×4 mm）与IonPac CG5A保护柱（50 mm×4 mm），将三价铬衍生物和六价铬分离，再用1，5-二苯碳酰二肼作为衍生试剂在离子色谱柱后与六价铬进行衍生化反应，用紫外-可见检测器在波长365，530 nm处分别测定三价铬和六价铬。三价铬和六价铬的线性范围分别为10~500，0.1~5.0 μg·L^-1，检出限（3s）分别为10，0.1 μg·L^-1，加标回收率为80.0%~106%，测定值的相对标准偏差（n=7）为0.52%~5.7%。

The sample was extracted through oscillation under dark with 0.07 mol·L^-1 of hydrochlorc acid solution (pH 1.0-1.5) at (37±2)℃, then Cr(Ⅲ) in the extract was derivatized with 2,6-pyridinedicarboxylic acid (PDCA) at 100℃ under pH 6.8. Cr(Ⅲ) derivative and Cr(Ⅵ) in the solution were separated on IonPac CS5A analytical column (250 mm×4 mm) and IonPac CG5A guard column (50 mm×4 mm), and Cr(Ⅵ) was derivatized with 1,5-diphenyl-carbazide (DPC) as a post-column derivative reagent. The derivatives of Cr(Ⅲ) and Cr(Ⅵ) were detected by an UV-Vis detector at 365, 530 nm respectively. The linearity ranges of Cr(Ⅲ) and Cr(Ⅵ) were 10-500, 0.1-5.0 μg·L^-1 respectively, with detection limits (3s) of 10, 0.1 μg·L^-1 respectively. Recoveries for Cr(Ⅲ) and Cr(Ⅵ) obtained by standard additon method were 80.0%-106%, and RSDs (n=7) were 0.52%-5.7%.