Determination of sulphathiazole and sulphanilamide by photochemically induced fluorescence and first-derivative fluorescence

Paper-based analytical device for sensitive colorimetric determination of sulfonamides in pharmaceutical samples

Sulfa drugs are frequently used to treat infections, particularly in antibiotic resistant people. There are several techniques available to determine sulfa drugs, however, they are laborious operation, reagent consumption, expensive, and need specialized types of equipment. Here, a new, very simple and inexpensive paper-based analytical device described for the determination of five sulfa drugs: sulfacetamide, sulfadiazine, sulfamerazine, sulfamethoxazole, and sulfathiazole in pharmaceutical preparations. The method is a one-step reaction, based on the colorimetric reaction between acid-hydrolyzed sulfa drugs and 4-dimethylaminobenzaldehyde. Using a smartphone, the RGB value of color intensity was used as an analytical signal. The paper-based device displayed linear ranges of 0.10-5.00 µg mL-1, linear correlations ranging from 0.9903 to 0.9972, limits of detection 0.0030 to 0.0082 µg mL-1, and RSD of ≤0.258 under optimal conditions. The suggested approach was applied for determining five sulfa drugs in pharmaceutical formulations. This approach is appropriate for pharmaceutical applications since it is inexpensive, simple to utilize, sensitive, and selective.

Electrooxidation of sulfanilamide and its voltammetric determination in pharmaceutical formulation, human urine and serum on glassy carbon electrode

For the first time, sulfanilamide (SFD) was determined in otologic solution, human urine and serum by electroanalytical techniques on glassy carbon electrode (GCE). The cyclic voltammetry (CV) experiments showed an irreversible oxidation peak at +1.06 V in 0.1 mol/L BRBS (pH = 2.0) at 50 mV/s. Different voltammetric scan rates (from 10 to 250 mV/s) suggested that the oxidation of SFD on the GCE was a diffusion-controlled process. Square-wave voltammetry (SWV) method under optimized conditions showed a linear response to SFD from 5.0 to 74.7 μmol/L (R = 0.999) with detection and quantification limits of 0.92 and 3.10 μmol/L, respectively. The developed SWV method showed better results for detection limit and linear range than the chronoamperometry method. It has been successfully applied to determine SFD concentration in pharmaceutical formulation, human urine and serum samples with recovery close to 100%.

Flow-through optosensor combined with photochemically induced fluorescence for simultaneous determination of binary mixtures of sulfonamides in pharmaceuticals, milk and urine

A sensitive and selective flow-through optosensor implemented with photochemically induced fluorescence (PIF) is proposed for the simultaneous determination of mixtures sulfamethoxazole/sulfanilamide and sulfathiazole/sulfanilamide. The resolution was accomplished by placing in the flow system a minicolumn filled with an appropriate solid support. Whereas one of the sulfonamides is not retained in the minicolumn and is determined by measuring its native fluorescence on the solid surface of the sensing microbeads in the detection area, the other one is retained and, after its elution, it is photochemically converted into a strongly fluorescent photoproduct which is transitorily retained on the sensing support in the flow cell and monitored. Linear calibration graphs were obtained over a concentration range of 2-3 orders of magnitude. The detection limits for the determination of sulfamethoxazole, sulfanilamide and sulfathiazole are 8.1, 2.9 and 5.7 ng mL(-1), respectively. The method was applied to pharmaceuticals, milk and human urine. The recovery of sulfamethoxazole from pharmaceuticals was 102.5% indicating no interference from trimethoprim which is not photochemically active. The recoveries for urine and milk samples fortified with sulfonamides at levels between 0.1 and 0.7 microgmL(-1) agreed within 95.0-107.5% of spiked levels.