Prisciliano Hernández

Amperometric flow system for blood glucose determination using an immobilized enzyme magnetic reactor

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)](+)[FeCl(4)](-). 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 4.0mM 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.

Amperometric Biosensor for Oxalate Determination in Urine Using Sequential Injection Analysis

An amperometric flow biosensor for oxalate determination in urine samples after enzymatic reaction with oxalate oxidase immobilized on a modified magnetic solid is described. The solid was magnetically retained on the electrode surface of an electrode modified with Fe (III)-tris-(2-thiopyridone) borate placed into a sequential injection system preceding the amperometric detector. The variables involved in the system such as flow rate, aspired volumes (modified magnetic suspension and sample) and reaction coil length were evaluated using a Taguchi parameter design. Under optimal conditions, the calibration curve of oxalate was linear between 3.0–50.0 mg·L−1, with a limit of detection of 1.0 mg·L−1. The repeatability for a 30.0 mg·L−1 oxalate solution was 0.7%. The method was validated by comparing the obtained results to those provided by the spectrophotometric method; no significant differences were observed.

Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions.