Sequential SERS determination of aspirin and vitamin C using in situ laser-induced photochemical silver substrate synthesis in a moving flow cell

In this contribution, the utility of sequential injection analysis in combination with surface-enhanced Raman spectroscopy (SERS) as a detection technique was investigated for simultaneous determination of aspirin and vitamin C in their pharmaceutical dosage forms and in spiked urine samples. The silver substrate was synthesized in situ by laser-induced photochemical procedure. By focusing the laser on a flow cell at 1 ml/min of continuous flow of 0.5 mM silver nitrate and 5 mM sodium citrate mixture, an active silver spot on the inner wall of the flow cell was prepared in a few seconds. The whole setup is fully computer controlled using ATLAS software to combine the two techniques. The system allows sequential determination of aspirin concentrations ranging from 100 to 500 ng/ml and vitamin C concentrations between 10 and 110 ng/ml with good precision of relative standard deviations (RSDs) of 0.85 and 1.7 %, respectively. A comparison of these results with those of the reported procedures showed excellent results compared with t and F values, indicating good accuracy and precision. The detection limits were 32 and 3 ng/ml for aspirin and vitamin C, respectively.