A multicommuted fluorescence-based sensing system for simultaneous determination of Vitamins B2 and B6 Original Research Article

A multicommuted flow-through optosensor based on the direct fluorescence measurements of Vitamins B2 and B6 using a non-polar sorbent (C18 silica gel) as solid sensing zone (to accomplish the separation and subsequent preconcentration/detection of the target analytes) have been developed. The proposed flow system was controlled by Java-written home-made software and designed using three-way solenoid valves for independent automated manipulation of sample and carrier solutions. The native fluorescence signal was simultaneously monitored at two pairs of excitation/emission wavelengths (450/519 and 294/395 for B2 and B6, respectively). The separation of the analytes was performed in the detection flow cell, using the differences in the sorption/elution process on the solid support between the two vitamins, due to their different polarity. Using an optimised sampling time, the analytical signal showed linearity in the range 0.01–0.4 and 0.15–3 μg ml−1 with detection limits of 0.003 and 0.045 μg ml−1 for B2 and B6, respectively, obtaining R.S.D. (%) values better than 2% for both analytes. The proposed methodology was applied to different pharmaceutical preparations, obtaining remarkably good results with recoveries ranging from 96 to 107.5%.