title: Bienzymatic amperometric sensor for protein assay in milk.
abstract: A new bienzymatic amperometric sensor is proposed for the assay of the protein content of milk. The sensor is based on two enzymes: carboxypeptidase A and L-amino acid oxidase. The response characteristics obtained for this sensor (detection limit of 1.5 micromol/L, linear concentration range between 1.8 and 2.8 micromol/L), as well as high selectivity over possible interferences from milk, made it applicable as a detector in flow injection analysis (FIA). The response characteristics obtained in the non-equilibrium conditions (FIA system) are: detection limit of 1.5 micromol/L and linear concentration range between 2 and 3.5 micromol/L. Without FIA, the average recovery of proteins from milk and milk products is 99.06 +/- 0.07% and, by utilization of FIA, it increased to 99.73 +/- 0.03. The sensor proved a good reliability for the assay of proteins in milk and milk products.
authors.affiliation: Department of Chemistry, University of Pretoria, South Africa. raluca.stefan@chem.up.ac.za
authors.forename: Raluca-Ioana
authors.initials: RI
authors.lastname: Stefan
authors.forename: Makhapa A
authors.initials: MA
authors.lastname: Makhafola
authors.forename: Jacobus Koos F
authors.initials: JK
authors.lastname: van Staden
mesh_terms: D000594:Amino Acid Oxidoreductases; D000818:Animals; D015374:Biosensing Techniques; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D004563:Electrochemistry / Q000379:methods; D050830:L-Amino Acid Oxidase; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*
chemical_list: D008894:Milk Proteins; D000594:Amino Acid Oxidoreductases; D050830:L-Amino Acid Oxidase; D002268:Carboxypeptidases; D043422:Carboxypeptidases A