title: Hybrid sequential injection-flow injection manifold for the spectrophotometric determination of total sulfite in wines using o-phthalaldehyde and gas-diffusion.
abstract: A new automated spectrophotometric method for the determination of total sulfite in white and red wines is reported. The assay is based on the reaction of o-phthalaldehyde (OPA) and ammonium chloride with the analyte in basic medium under SI conditions. Upon on-line alkalization with NaOH, a blue product is formed having an absorption maximum at 630 nm. The parameters affecting the reaction - temperature, pH, ionic strength, amount concentration and volume of OPA, amount concentration of ammonium chloride, flow rate and reaction coil length - and the gas-diffusion process - sample and HCl volumes, length of mixing coil, donor flow rate - were studied. The proposed method was validated in terms of linearity (1-40 mgL(-1), r=0.9997), limit of detection (c(L)=0.3 mgL(-1)) and quantitation (c(Q)=1.0 mgL(-1)), precision (s(r)=2.2% at 20 mgL(-1) sulfite, n=12) and selectivity. The applicability of the analytical procedure was evaluated by analyzing white and red wine samples, while the accuracy as expressed by recovery experiments ranged between 96% and 106%.
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
authors.forename: Paraskevas D
authors.initials: PD
authors.lastname: Tzanavaras
authors.forename: Eleni
authors.initials: E
authors.lastname: Thiakouli
authors.forename: Demetrius G
authors.initials: DG
authors.lastname: Themelis
mesh_terms: D000643:Ammonium Chloride; D005740:Gases; D013057:Spectrum Analysis / Q000379:methods; D013447:Sulfites / Q000032:analysis*; D014920:Wine / Q000032:analysis*; D009764:o-Phthalaldehyde
chemical_list: D005740:Gases; D013447:Sulfites; D000643:Ammonium Chloride; D009764:o-Phthalaldehyde