Detection and quantification of ppb level potassium in biological samples in the presence of high sodium by ion chromatographic method

Employing a silica gel column modified with carboxyl groups and an eluent consisting of 4.0 mM tartaric acid and 0.75 mM dipicolinic acid in 2% acetone, an otherwise difficult quantification of K+ at ppb level in presence of 6000 ppm NaCl was achieved by incorporating 0.75 mM 18-crown-6 ether in the mobile phase and subtracting the blank NaCl signal from each chromatogram. Optimized analytical conditions were established in terms of relative standard deviation (%) of retention time, peak area and calibration equations, and also by peak asymmetry factor. The net efflux of K+ into the gastric lumen under in vitro conditions of acid secretion was investigated in Ussing chamber model. The effects of the physiological secretagogue histamine and the antisecretory agents cimetidine, omeprazole and SCH28080 were studied. The decline of K+ efflux in presence of cimetidine, and the rise of the same in the presence of omeprazole and SCH28080 were conspicuously discernible, thereby validating the usefulness of ion chromatography based K+ quantification method under biological experimental conditions.