title: Multi-wavelength spectrophotometric determination of Cr(VI) in water with ABTS.
abstract: A new method for Cr(VI) (0.025-8.00 mg/L) determination based on the reaction of Cr(VI) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) in aqueous solutions was developed. The colorless ABTS reacted with Cr(VI) under strong acidic conditions ([H+] = 3.0 or 6.0 M) producing a stable colored radical ABTS+, which could be measured spectrophotometrically at 415, 649 or 732 nm. The absorbance increase at these three wavelengths for ABTS+generation were all linear (less than 1.0% deviation) with respect to the amount of added Cr(VI) and the sensitivity were 1.099 × 105, 3.720 × 104, and 4.150 × 104M-1cm-1of added Cr(VI) at 415, 649 or 732 nm, respectively. Cr(VI) of 0.025 mg/L below the discharge standard of drinking water could be detected with the method quantitatively and 0.002 mg/L Cr(VI) was determined qualitatively. The molar absorptivity of ABTS+generated was determined to be (3.69 ± 0.01) × 104M-1cm-1at 415 nm and the reaction between Cr(VI) and ABTS had a stoichiometric factor of 1:3 in excess of ABTS. The absorbance of generated ABTS+was found to be stable in deionized water or wastewater and Cr(VI) spiked in wastewater could be determined accurately. The ABTS method also had a good anti-interference performance against Co(II) ions. Moreover, the ABTS method could be successfully used in the Cr(VI)-S(IV) system for Cr(VI) determination.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: fanwj0916@163.com.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Fan
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China. Electronic address: qiaoqiao@tongji.edu.cn.
authors.forename: Junlian
authors.initials: J
authors.lastname: Qiao
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Guangzhou Key Laboratory of Environmental Exposure and Health, School of Environment, Jinan University, Guangzhou 510632, China. Electronic address: guanxh@tognji.edu.cn.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Guan
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry*; D002857:Chromium / Q000032:analysis* / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D013451:Sulfonic Acids / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D002857:Chromium; D013451:Sulfonic Acids; D062065:Wastewater; D014874:Water Pollutants, Chemical; C074702:chromium hexavalent ion; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
keywords: ABTS; Cr(VI); Determination; Oxidation