Sub-picomole high-performance liquid chromatographic/mass spectrometric determination of glutathione in the maize ( Zea mays L.) kernels exposed to cadmium

Abstract

Changes in fresh weight, total protein amounts (Bradford’s method), cadmium concentration (DPASV) and glutathione content (HPLC/MS) were studied in maize kernels cultivated for 5 days at three different cadmium concentrations (0, 10 and 100 μmol l −1 CdCl 2). A highly sensitive HPLC/MS method was used for the determination of glutathione on a reversed-phase Atlantis dC 18 chromatographic column ( 150 mm×2.1 mm , 3 μm particle size). An isocratic mode with acetonitrile–0.01% TFA (5:95, flow rate 0.1 ml min −1 and 30 °C) was applied. The m/ z spectra and the data for the selected ion monitoring (SIM) mode were recorded at m/ z for glutathione 308→179. Cadmium concentration was measured by a differential pulse adsorptive stripping voltammetry (DPASV) after deposition on a hanging mercury drop electrode (HMDE) at potential −0.7 V (accumulation time 180 s, acetate buffer of pH 3.6, 22 °C). An AUTOLAB with a VA-Stand 663 and a three-electrode system consisting of the HMDE as a working electrode with area 0.4 mm 2, an Ag/AgCl/3 mol l −1 KCl as a reference electrode and a Pt-wire as an auxiliary electrode was employed. The maize kernels exposed to the highest cadmium concentration (100 μmol l −1) germinated formerly and much better. A rapid increase of the fresh weight probably relates with more intensive uptake of water in order to decrease cadmium concentration. An intensive preservation of homeostasis of Cd 2+ ions in the germinating plants by defending mechanisms might explain differences of uptake rate of cadmium. The linear increase of GSH content with the exposure time at all studied concentration suggests the defending mechanisms might be triggered by concentrations of a heavy metal.