AMPEROMETRIC GLUTATHIONE ELECTRODES

Amperometric glutathione sensors based on hydrogen peroxide or Clark-t ype oxygen electrodes, coupled with a novel enzyme glutathione oxidase , have been assembled and analytically evaluated. Calibration curves w ere linear in the range 5 x 10(-6) to 10(-3) m for the H2O2-based prob e and 10(-5) to 2 x 10(-4) M for the oxygen probe. When the glutathion e analysis was carried out using the O2-based probe, a flow-through sy stem was used to maintain better control over the oxygen content of th e sample. Temperature, pH and selectivity studies were carried out and optimized. Stability studies of the enzyme electrode showed an enzyme lifetime of one month, with more than 200 analyses performed. The pre cision of both sensors was tested by making 20 measurements of glutath ione in phosphate buffer, pH 6.5. Results showed relative standard dev iations of 4-6% and 4.1%, respectively. The response time for both ele ctrodes was one or two minutes, depending on the blocking membrane use d. The analysis of glutathione in human erythrocytes has been carried out using the 02-based probe and the flow-through system. Results were in agreement with those reported in the literature.