Amperometric biosensor for oxalate determination in urine using sequential injection analysis

An amperometric flow system for glucose determination in blood serum samples after enzymatic reaction with glucose oxidase immobilized on magnetite covered with silica gel modified propylamine is described. The solid was magnetically retained on a mini-column and placed into the flow injection system preceding the amperometric detector using a modified screen printed electrode with [Fe(tris(3,5-dimetyl-1-pyrazolyl)borate)2]+[FeCl4]-. The variables involved in the system such as flow rate, enzyme concentration, injection volume and reaction coil length were evaluated using a Taguchi parameter design. Under optimal conditions, the calibration curve of glucose sample was linear between 0.24 and 6.00 mM, and with a limit of detection of 0.08 mM. The repeatability for a 4.0 mM glucose solution was 1.0%.The method was validated by comparing the obtained results to those provided by the enzymatic spectrophotometric method; no significant differences were observed.