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比较了强酸性、强碱性、弱酸性、弱碱性和两性等5种离子交换纤维对Cr(Ⅲ)和Cr(Ⅵ)的分离能力,结果表明,强酸性和强碱性离子交换纤维对Cr(Ⅲ)和Cr(Ⅵ)的分离效果最好.分离后的Cr(Ⅲ)和Cr(Ⅵ)可用电感耦合等离子体原子发射光谱法(ICP-AES)测量.优化了纤维柱分离Cr(Ⅲ)和Cr(Ⅵ)的条件.pH 3.0的含铬试液以2～6 mL/min的流速上柱,当采用强酸性纤维柱进行分离时,用10 mL pH 1.0的硝酸预淋洗Cr(Ⅵ),再用10 mL2.0 mol/L硝酸洗脱Cr(Ⅲ);当采用强碱性纤维柱进行分离时,试液需先加入5 mL 0.005 mol/L EDTA溶液掩蔽Cr(Ⅲ)后上柱,用10mL pH 1.0的稀盐酸预淋洗Cr(Ⅲ),再用10 mL 3.0 mol/L硫酸洗脱Cr(Ⅵ).采用强酸性纤维柱时Cr(Ⅲ)和Cr(Ⅵ)检出限分别为1.06 ng/mL和0.60 ng/mL;采用强碱性纤维柱时Cr(Ⅲ)和Cr(Ⅵ)检出限分别为1.03 ng/mL和1.15 ng/mL.该方法成功应用于分离和测定管网水、池塘水样和土壤提取液中的Cr(Ⅲ)和Cr(Ⅵ).加标回收实验表明,采用强酸性纤维柱进行分离时,Cr(Ⅲ)的回收率为90.0%～108%,相对标准偏差为0.3%～5.3%,Cr(Ⅵ)的回收率为91.7%～107%,相对标准偏差为0.3%～4.4%;采用强碱性纤维柱进行分离时,Cr(Ⅲ)的回收率为93.1%～105%,相对标准偏差为0.4%～5.0%,Cr(Ⅵ)的回收率93.8%～105%,相对标准偏差为0.1%～6.2%.

A comparison for the capability to separate Cr (Ⅲ) from Cr (Ⅵ) is made between strong acid cation, strong basic anion, weak acid cation, weak basic anion and amphoteric ion exchange fibers. The result shows that strong acid cation exchange fiber and strong base anion exchange fiber have the best separation efficiency. These two exchange fibers are applied to separate Cr (Ⅲ) from Cr (Ⅵ) in water samples for the determination by inductively coupled plasma atomic emission spectrome-try. The separation conditions are optimized. Chromium(Ⅲ) and chromium(Ⅵ) can be separated by the two fiber columns completely when the test solution at pH 3.0 flows through the columns at the rate of 2-6 mL/min. For strong acid cation exchange fiber column , Cr(Ⅵ) is eluted by 10 mL of nitric acid at pH1. 0, and Cr(Ⅲ) is eluted by 10 mL of 2.0 mol/L nitric acid; For strong base anion exchange fiber column, 5 mL of 0. 005 mol/L EDTA solution is added for masking Cr(Ⅲ) before test solution flows through the column, and then Cr(Ⅲ) is eluted by 10 mL of hydrochloric acid at pH 1.0, while Cr(Ⅵ) is eluted by 10 mL of 3.0 mol/L sulfuric acid. In applying strong acid cation exchange fiber column, the detection limits of Cr(Ⅲ) and Cr(Ⅵ) are 1.06 ng/mL and 0. 60 ng/mL, respectively. In applying strong base anion exchange fiber column, the detection limits of Cr(Ⅲ) and Cr(Ⅵ) are 1.03 ng/mL and 1.15 ng/ mL, respectively. The proposed method has been applied to separate and determine Cr(Ⅲ)/Cr(Ⅵ) in the tap and pond water samples and extracting solution from soil. When strong acid cation exchange fiber column is used, the recovery and RSD are 90.0%-108% and 0.3%-5.3% for Cr(Ⅲ), and 91.7%-107% and 0. 3%-4. 4% for Cr(Ⅵ), respectively, when strong base anion exchange fiber column is used, the recovery and RSD are 93.1%-105% and 0.4%-5.0% for Cr(Ⅲ), and 93.8%-105% and 0. 1%-6.2% for Cr(Ⅵ), respectively.