A FLOW ANALYSIS SYSTEM FOR THE RAPID DETERMINATION OF SULFONAMIDES USING A SOLID PHASE PHOTOMETRIC SENSING ZONE

ABSTRACT

A flow injection analysis system with solid phase spectrophotometric transduction has been developed for the assay of different sulfonamides: sulfanilamide (SN), sulfacetamide (SC), sulfamethoxazole (SM) and sulfadiazine (SD). The sensor consists in a monochannel system using Sephadex QAE A-25 resin as a microsensing zone (inside a flow-through cell) where sulfonamides are temporarily retained. The measurements of the intrinsic absorbance of sulfonamides were made at 263 nm for SC, SD and SM, and 258 nm for SN. Using a NaOH (10⁻³ mol l⁻¹)/NaCl (0.02 mol l⁻¹) solution as carrier, the determination of sulfonamides was carried out for 40 and 600 µl of sample volume, being the carrier itself the desorbing solution. The detection limits were found to be less than 0.1 and 0.02 µg ml⁻¹ for both sample volumes, respectively, and the linear dynamic range extended between 1–45 µg ml⁻¹ (40 µl) and 0.2–10 µg ml⁻¹ (600 µl). The relative standard deviations (n = 10) lower than 2.3%. A study of the potentially interfering species was carried out, included trimethoprim. The method shows good results on determination of sulfonamides in pharmaceutical preparations and urine.

Keywords:

• Flow injection analysis
• Solid phase spectrophotometric
• Pharmaceuticals
• Urine

ACKNOWLEDGMENTS

The authors are grateful to the Ministerio de Educación y Cultura de España, Dirección de Enseñanza Superior e Investigación Científica (Project No. PB98-0301), for financial support.