Spectrofluorimetric determination of glutathione in human plasma by solid-phase extraction using graphene as adsorbent

An efficient solid phase extraction-spectrofluorimetric method using graphene as adsorbent was developed to sensitively determine glutathione (GSH) in biological samples. Fluorescent probe N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl)iodoacetamide (BODIPY Fl-C1-IA) was applied for the derivatization of GSH. The procedure was based on BODIPY Fl-C1-IA selective reaction with GSH to form highly fluorescent product BODIPY Fl-C1-IA-GSH, its extraction to the graphene-packed SPE cartridge and spectrofluorimetric determination. Some factors affecting the extraction efficiency, such as the type of the eluent and its volume, sample pH, extraction time, and sample volume were optimized. Comparative studies were also performed between graphene and other adsorbents including C18 silica, graphitic carbon, and multi-walled carbon nanotubes for the extraction of analyte. The calibration graph using the pretreatment system for GSH was linear over the range of 0.5-200 nM. The limit of detection was 0.01 nM (signal-to-noise ratio=3). Relative standard deviation for six replicate determinations of GSH at 80 nM concentration level was lower than 5.0%. The developed method was applied to the determination of GSH in human plasma with recoveries of 92-108%. This work revealed the great potentials of graphene as an excellent sorbent material in the analysis of biological samples.