Development of a multicommuted flow-through optosensor for the determination of a ternary pharmaceutical mixture

The combination of multicommutation and flow-through multioptosensing is presented in this work as a powerful strategy for the routine analysis of active principles in pharmaceuticals. By coupling methodologies, the selectivity and sensitivity of optosensors is maintained, while the use of the multicommutation approach provides additional advantages, such as low reagent consumption, low waste generation and reduced human supervision. The potential of this integration is enhanced when implemented with multiwavelength detection mode. An UV sensor is here developed for the simultaneous determination of three widely used active principles: salicylamide, caffeine and propyphenazone. The measuring wavelengths were 276 nm for caffeine and propyphenazone, and 302 nm for salicylamide. The five three-way solenoid valves used in the system are controlled by Java-written home-made software. The sensor is based on the on-line selective retention of two of the three analytes on a precolumn placed just before the sensing zone and filled with the same solid support than the flow-through cell (C18 silica gel). This approach allows the sequential arrival of the analytes to the sensing zone, so allowing their determination with only one sample injection. So, the use of C18 placed, in both the precolumn and the flow-cell combines the advantages of the increase of sensitivity and selectivity in the detection solid zone with the additional increase of the selectivity in the precolumn. The sensor was applied to the determination of the analytes in several pharmaceutical preparation of the Spanish Pharmacopoeia, obtaining satisfactory results.