Flow-through sensor with Fourier transform Raman detection for determination of sulfonamides

A flow-through sensor system with Fourier transform (FT) Raman spectroscopy as detection technique is described. The molecular and structural information contained in Raman spectra together with the selective retention of the species of interest on the sorbent make the proposed methodology highly selective. The flow-through sensor allowed the direct quantitative determination of sulfathiazole and sulfamethoxazole in the presence of other species that are normally encountered with these analytes. The system used Sephadex QAE A-25 resin as packing material of a flow-through cell on which sulfonamides were temporarily retained. Samples were transported by a carrier solution of NaOH 10(-2) mol l(-1) (pH = 12), and 2 ml of a [NaCl (0.10 mol l(-1))/NaOH (10(-2) mol l(-1))] solution was employed as eluent. Using a sample volume of 1 ml, the analytical signal was linear in the range 0.5-7 g l(-1) and 0.5-10 g l(-1), for sulfathiazole and sulfamethoxazole, respectively. RSDs (%) lower than 4% were obtained for both analytes. The sensor was satisfactorily applied to several commercial pharmaceutical preparations for human and animals in different physical presentations, including capsules, syrup, tablets, powders, injectables and suspensions.