Flow Injection On-line Photochemical Reaction Coupled to Spectrofluorimetry for the Determination of Sulfamethazine Using Sodium Sulfite as Sensitizing Reagent

Abstract

The reaction medium for photochemically induced fluorescence (PF) of sulfamethazine (SMT) was studied. Sodium sulfite was found effective to enhance the on-line photochemically induced fluorescence intensity of SMT. A flow injection on-line photochemical spectrofluorimetry (FI-PF) using sodium sulfite as sensitizing reagent was developed for the determination of SMT. The injected sample zone was on-line merged with a mixed sodium sulfite–borate buffer (pH 8.8) solution in a knotted PTFE photochemical reactor (0.5 mm i.d. × 150 cm, KR), which was freely coiled around a 6-W low-pressure mercury lamp. While passing the KR the drug was derived into an intensively fluorescent compound which was on-line detected in a flow-through cell at the emission wavelength of 345 nm and excitation wavelength of 287 nm. Compared to FI-PF without using sodium sulfite, the sensitivity of the developed system was improved by at least 6 fold. At the optimized conditions a detection limit of 3.5 μg · L−1was achieved at the sampling rate of 90 h−1. Eleven determinations of a 0.6 mg · L−1SMT standard solution gave a RSD of 1.2%. The calibration curve was linear in the SMT concentration range 0.02–2 mg · L−1. The proposed method was applied to assay the SMT content in some pharmaceutical formulations. Satisfactory results were obtained.