Ion-selective electrodes for the determination of l-carnitine. Application in dissolution testing of a dietary supplement

l -Carnitine selective electrodes were developed using polymeric membranes containing a lipophilic cation exchanger (potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) and plasticized with three different plasticizers: bis(2-ethylhexyl) sebacate, tricresyl phosphate, and 2-nitrophenyl octyl ether. The response of the electrodes was evaluated in terms of calibration parameters (slope, limit of detection, and linear range), reproducibility, selectivity profile, and pH influence. The electrodes were applied to the dissolution testing of a dietary supplement containing l -carnitine in water and in HCl (pH = 3) by direct potentiometric monitoring. Graphical abstract