Membrane electrodes for the determination of glutathione

Four glutathione (GSH)-selective electrodes were developed with different techniques and in different polymeric matrices. Precipitation-based technique with bathophenanthroline-ferrous as cationic exchanger in polyvinyl chloride (PVC) matrix was used for sensor 1 fabrication. β-Cyclodextrin (β-CD)-based technique with either tetrakis(4-chlorophenyl)borate (TpClPB) or bathophenanthroline-ferrous as fixed anionic and cationic sites in PVC matrix was used for fabrication of sensors 2 and 3, respectively.β-CD-based technique with TpClPB as fixed anionic site in polyurethane (Tecoflex) matrix was used for sensor 4 fabrication. Linear responses of 1 × 10⁻⁵ to 1 × 10⁻⁴ M and 1 × 10⁻⁶ to 1 × 10⁻³ M with slopes of 37.5 and 32.0 mV/decade within pH 7-8 were obtained by using electrodes 1 and 3, respectively. On the other hand, linear responses of 1 × 10⁻⁵ to 1 × 10⁻² and 1 × 10⁻⁵ to 1 × 10⁻³ M with slopes of 47.9 and 54.3 mV/decade within pH 5-6 were obtained by using electrodes 2 and 4, respectively. The percentage recoveries for determination of GSH by the four proposed GSH-selective electrodes were 100 ± 1, 100.5 ± 0.7, 100 ± 1 and 99.0 ± 0.8% for sensors 1, 2, 3 and 4, respectively. Determination of GSH in capsules by the proposed electrodes revealed their applicability for determination of GSH in its pharmaceutical formulations. Also, they were used to determine GSH selectively in presence of its oxidized form (GSSG). Sensor 4 was successfully applied for determination of glutathione in plasma with average recovery of 100.4 ± 1.11%. The proposed method was compared with a reported one. No significant difference for both accuracy and precision was observed.