Sensitive kinetic-catalytic spectrophotometric method for cobalt determination using a chip coupled to a multisyringe flow injection analysis system.

The development of an automated kinetic-catalytic spectrophotometric method for cobalt determination is presented. The method is based on the catalytic effect of Co in the oxidation of hydroxybenzoic acid by HO in basic media. The method has been automated using a multisyringe flow injection system coupled to a monolithic flow conduit called chip (chip-MSFIA). All reagents and sample are simultaneously propelled into the chip to achieve an efficient mixing. The reaction product is monitored at 482nm. The reaction takes place very fast at room temperature, thus the fixed-time method is applied to quantify Co concentration in samples. Variables such as, reagents concentration, pH, flow rate and reaction time have been optimized to improve the selectivity and sensitivity of the proposed system. Under optimal conditions, Co may be determined in the range 0.02-10.00μgL achieving a limit of detection of 0.02μgL and an injection throughput of 68h. Relative standard deviations are below 3%. The method has been successfully applied to water samples and a pharmaceutical formulation. The accuracy of the method has been validated by add-recovery tests and satisfactory recoveries from 91% to 97% were obtained.