title: Water-soluble polymers for spectrophotometric and flow injection determination of cobalt with nitroso-R-salt.
abstract: The water-soluble polymers poly(ethylenimine), quaternized poly(ethylenimine), and poly-4-vinyl-(N-benzyltrimethyl) ammonium chloride were found to be able to change the kinetics of the reaction of cobalt with nitroso-R-salt and the optical density of the cobalt complex formed. The optimum pH range for the complex formation was a wide range from 1 to 10 and at pH 2 the reaction developed instantly. The calibration graph was linear in the range 0.005-2 mug ml(-1). The effective molar absorptivity coefficient of the complex was equal to (2.8+/-0.08)10(3). A spectrophotometric determination method for cobalt with nitroso-R-salt in the presence of water-soluble polymers (before and after membrane preconcentration) and a colorimetric flow injection method were developed. For the flow injection-based spectrophotometric determination, the calibration graph was linear in the concentration range of 0-4.0 mug ml(-1) cobalt with a regression coefficient of 0.9992. The relative standard deviation (R.S.D.) for the determination of 1.0 mug ml(-1) cobalt was 0.9% (ten replicate injections), and at all concentration measured, the R.S.D. of the data was below 5.0%. The proposed FI procedure was applied to river water samples after membrane preconcentration of cobalt. The limit of detection was 4 ng ml(-1).
authors.affiliation: Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow, Russia.
authors.forename: T G
authors.initials: TG
authors.lastname: Dzherayan
authors.forename: V M
authors.initials: VM
authors.lastname: Shkinev
authors.forename: L K
authors.initials: LK
authors.lastname: Shpigun
authors.forename: P M
authors.initials: PM
authors.lastname: Kamilova
authors.forename: K E
authors.initials: KE
authors.lastname: Geckeler