First-derivative non-linear variable-angle synchronous fluorescence spectroscopy for the simultaneous determination of salicylamide, salsalate and naproxen in serum and urine Original Research Article

Derivative variable-angle synchronous fluorescence spectrometry is developed to improve the selectivity of fluorescence measurements without loss of sensitivity. The first derivative non-linear variable-angle synchronous scanning permits the rapid simultaneous determination of salicylamide, salsalate and naproxen in a mixture from a single spectrum based on a single scan. The method is based on the intrinsic fluorescence of salicylamide, salsalate and naproxen in chloroform. The analyses are performed in the organic phase, using an alkaline medium provided by the addition of 0.40 M pyrrolidine chloroformic solution. The range of application is 0.100–1.000 μg/ml for all of them. A systematic examination of the experimental data by applying an exhaustive statistical analysis is reported. The method is applied in urine and serum samples spiked with all the drugs. Serum and urine samples are extracted into chloroform–1% acetic acid solution, using in the aqueous medium a pH of 4.8 obtained by the addition of acetate buffer solution, and a basic medium is provided with pyrrolidine prior to instrumental measurement. The simultaneous determination of salicylamide, salsalate and naproxen in human serum and urine samples is performed with this technique in the extracted chloroform phase, without necessity of any re-extraction step. The validity, applicability and simplicity of the method are demonstrated.