title: Speciation and preconcentration of vanadium(V) and vanadium(IV) in water samples by flow injection-inductively coupled plasma optical emission spectrometry and ultrasonic nebulization.
abstract: An on-line separation, preconcentration and determination system for vanadium(IV) and vanadium(V) comprising inductively coupled plasma optical emission spectrometry (ICP-OES) coupled to a flow injection (FI) method with an ultrasonic nebulization (USN) system was studied. The vanadium species were retained on an Amberlite XAD-7 resin as a vanadium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (V-5-Br-PADAP) complex at pH 3.7. Enhanced selectivity was obtained with the combined use of the formation on-line of the complexes and 1,2-cyclohexanediaminetetraacetic acid (CDTA) as masking agent. The vanadium complexes were removed from the microcolumn with 25% v/v nitric acid. A sensitivity enhancement factor of 225 was obtained with respect to ICP-OES using pneumatic nebulization (15-fold for USN and 15-fold for the microcolumn). The detection limit for the preconcentration of 10 mL of aqueous solution was 19 ng L-1. The precision for 10 replicate determinations at the 5 micrograms L-1 V level was 2.3% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the separation and preconcentration system for vanadium species was linear with a correlation coefficient of 0.9992 at levels from near the detection limits up to at least 100 micrograms L-1. The method was successfully applied to the speciation of vanadium in river water samples.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemistry, Biochemistry and Pharmacy, National University of San Luis, Chacabuco and Pedernera, P.O. Box 375, 5700 San Luis, Argentina.
authors.forename: R G
authors.initials: RG
authors.lastname: Wuilloud
authors.forename: J C
authors.initials: JC
authors.lastname: Wuilloud
authors.forename: R A
authors.initials: RA
authors.lastname: Olsina
authors.forename: L D
authors.initials: LD
authors.lastname: Martinez
mesh_terms: D017022:Flow Injection Analysis / Q000295:instrumentation / Q000379:methods; D013053:Spectrophotometry; D014465:Ultrasonics; D014639:Vanadium / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D014639:Vanadium