title: Sulphate radical generation through interaction of peroxymonosulphate with Co(II) for in-line sample preparation aiming at spectrophotometric flow-based determination of phosphate and phosphite in fertilizers.
abstract: An advanced oxidative process relying on the interaction of peroxymonosulphate and cobalt(II) was implemented for generating the sulphate radicals in flow analysis, in order to accomplish in-line sample preparation thus improving the spectrophotometric determination of phosphate and phosphite in liquid foliar fertilizers. To this end, a flow-batch system with a heated chamber was designed. The sample was handled twice, with and without the step of phosphite oxidation to phosphate, and the formed orthophosphate was quantified after interaction with the vanadate-molybdate reagent. Phosphite was determined as the difference in analytical signals corresponding to sample handling with and without the oxidation step. Influence of Co(II) on the peroxymonosulphate activation, reagent concentrations and added volumes, acidity, temperature and heating time were investigated like aiming at to improve analytical recovery and measurement repeatability, as well as the and system ruggedness. The 6.6-20.0mgL(-1) P2O5 standards were in-line prepared from a single stock solution. Detection limits were estimated as 0.8 and 0.1mgL(-1) for P2O5 and P-PO4. Twenty-four samples are were run per hour, and results are were in agreement with those obtained by the official procedure.
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Carla C
authors.initials: CC
authors.lastname: Crispino
authors.affiliation: Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Marcos Y
authors.initials: MY
authors.lastname: Kamogawa
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, SP, Brazil; The Regional South Research Centre, Agriculture Secretary, Piracicaba, SP, Brazil.
authors.forename: José R
authors.initials: JR
authors.lastname: Ferreira
authors.affiliation: Centre for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, SP, Brazil. Electronic address: ezagatto@cena.usp.br.
authors.forename: Elias A G
authors.initials: EAG
authors.lastname: Zagatto
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D005308:Fertilizers / Q000032:analysis*; D010545:Peroxides / Q000737:chemistry*; D010710:Phosphates / Q000032:analysis*; D017905:Phosphites / Q000032:analysis*; D013053:Spectrophotometry / Q000295:instrumentation / Q000379:methods; D013431:Sulfates / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D010545:Peroxides; D010710:Phosphates; D017905:Phosphites; D013431:Sulfates; C069025:sulfate radical; C038288:peroxymonosulfate; D003035:Cobalt
keywords: Advanced oxidative process; Flow analysis; Flow-batch system; In-line peroxymonosulphate activation; Sulphate radical