Multi-pumping flow system for the determination of boron in eye drops, drinking water and ocean water

A novel automated method for the determination of boron based on the use of pulsed flows was developed and applied to the determination of this element in samples of tap water, ocean water and eye drops. The method was implemented by means of a multi-pumping system consisting of three solenoid micropumps and a photometric detector and exploits the reaction of azomethine-H in the presence of boron. The system runs under control of an open-source microcontroller. The main operational parameters were optimized. Given the particular kinetics of the reaction, a stopped-flow period (1 or 5min) was included to allow for color development. The method presents linearity in the range 0.35-3.0mgL^-1, good precision (s_r<3%), and detection and quantification limits of 0.10 and 0.35mgL^-1 respectively. Samples of tap water or eye drops could be successfully analyzed employing a 1-minute stop time, providing a maximum sampling frequency of 32 samples h^-1. In order to overcome matrix effect caused by the high saline concentration, ocean water samples required stop times of 5min, providing a sampling frequency of 10 samples h^-1. Recoveries of 102% (eye drops), 94% (drinking water) and 93% (ocean water) were obtained. The method was considered accurate and fit for the purpose.