title: Novel oxidative electrophilic coupling reactions of phenoxazine derivatives with MBTH and their applications to spectrophotometric determination of residual chlorine in drinking water and environmental water samples.
abstract: Novel, sensitive and rapid spectrophotometric methods, using phenoxazine (PNZ), 2-chlorophe-noxazine (CPN) and 2-trifluoromethylphenoxazine (TPN) as chromogenic reagents for the determination of residual chlorine are proposed. The methods are based on the reduction of chlorine by an electrophilic coupling reagent, 3-methyl-2-benzothiazoline hydrazono hydrochloride hydrate (MBTH) in mild hydrochloric acid medium and subsequent coupling with PNZ, CPN or TPN. The blue color formed in the reaction showed maximum absorbance at 680-690 nm and obeyed Beer's law over the range 0.1-2.2 microg ml(-1). The molar absorptivity values with PNZ, CPN and TPN were 2.80 x 10(4), 2.67 x 10(4) and 1.91 x 10(4) l mol(-1)cm(-1) and Sandell's sensitivity values were 0.028, 0.027 and 0.028 microg cm(-2) respectively. The proposed methods were successfully applied in the determination of residual chlorine in drinking water and environmental water samples. The performance of proposed methods was evaluated in terms of Student's t-test and variance ratio F-test which indicated the significance of proposed methods over the standard spectrophotometric method.
authors.affiliation: Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India.
authors.forename: Riyad Ahmed
authors.initials: RA
authors.lastname: Al-Okab
authors.forename: Akheel Ahmed
authors.initials: AA
authors.lastname: Syed
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry*; D002713:Chlorine / Q000032:analysis*; D006835:Hydrazones / Q000737:chemistry*; D010078:Oxazines / Q000737:chemistry*; D010084:Oxidation-Reduction; D013053:Spectrophotometry / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis
chemical_list: D052160:Benzothiazoles; D006835:Hydrazones; D010078:Oxazines; D014874:Water Pollutants, Chemical; D002713:Chlorine; C039203:phenoxazine; C002536:3-methyl-2-benzothiazolone hydrazone