title: Orthophosphate, phytate, and total phosphorus determination in cereals by flow injection analysis.
abstract: A flow injection spectrophotometric procedure with enzymatic hydrolysis was developed for determination of orthophosphate, phytate and total phosphorus in cereal samples. Phosphorus species were extracted from cereals with 0.05 mol L(-1) potassium hydrogen phthalate buffer solution at pH 5.7. Orthophosphate was directly determined in the extracts by molybdenum blue spectrophotometric method. The phytate was hydrolyzed by the enzyme phytase coupled to a solid phase packed into an enzymatic reactor, and the resulting hydrolyzed orthophosphate was also determined by spectrophotometry at 650 nm. After optimization for phosphorus species extraction and enzymatic hydrolysis, a linear calibration graph was obtained up to 196 x 10(-6) mol L(-1) orthophosphate (P conc = -2.67 + 0.52x, r = 0.9998). Measurements are characterized by relative standard deviation of 1.6% for a standard of 72 x 10(-6) mol L(-1) orthophosphate and no baseline drift was observed during 4 h operation periods. It provides 72 measurements per hour, with 2.4 x 10(-)6) mol L(-1) and 7.9 x 10(-6) mol L(-1) as detection and quantification limits, respectively.
authors.affiliation: Grupo de Análise Instrumental Aplicada, Embrapa Pecuária Sudeste, C.P. 339, 13560-970, São Carlos SP, Brazil.
authors.forename: Edivan Carvalho
authors.initials: EC
authors.lastname: Vieira
authors.forename: Ana Rita A
authors.initials: AR
authors.lastname: Nogueira
mesh_terms: D002523:Edible Grain / Q000737:chemistry*; D017022:Flow Injection Analysis / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010710:Phosphates / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D010833:Phytic Acid / Q000032:analysis*; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D010710:Phosphates; D010758:Phosphorus; D010833:Phytic Acid