Automated fluorimetric sensor for glutathione based on zone fluidics.

Abstract

A zone-fluidics (ZF) based automated fluorimetric sensor for the determination of glutathione (GSH) is reported. Discrete zones of GSH and o-phthalaldehyde (OPA) mix and react on-line under mild basic pH without the need of additional nucleophillic reagents, to yield a fluorescent isoindole derivative (λex/λem=340/425nm). The proposed ZF sensor was optimized (pH, c(OPA), time, instrumental variables) and validated. Cysteine, glutamate, glycine and ammonium were representatively examined in terms of selectivity and were found not to react in 10-fold excess. Linearity was proved in the range of 5-100μmolL-1 GSH, with an LOD of 1μmolL-1 at a practical sampling rate of 20h-1 and RSD<0.5% (within-day) and 4.2% (day-to-day). The dosage uniformity of commercially available GSH - containing nutraceuticals was evaluated.