Use of flow injection analysis coupled with Chemiluminescence detection for quality control of sulfonamides in pharmaceuticals

The coupling of flow injection manifolds with chemiluminescence detection (FIA-CL) is an interesting alternative in pharmaceutical quality control due to its advantages, such as, high sensitivity, easy implementation, simple instrumentation and low cost. Peroxyoxalate chemiluminescence (PO-CL) is an indirect CL in which a PO is oxidized in presence of H2O2 and imidazole as a catalyst, and an intermediate from the primary reaction transfers its energy to an energy-accepting fluorophore, which subsequently emits light. The use of POs presents some drawbacks arising from the of use organic solvents, as acetonitrile. We propose a FIA configuration based on the use of two injection valves for the introduction of both PO and derivatized analyte solutions in the flow system, avoiding the problems mentioned above, as neither special tubes nor special pumps are required. Furthermore, the use of micellar media (sodium dodecyl sulphate, SDS) as carrier and the addition of tetrahydrofurane (THF) in the PO solutions increase both the solubility and stability of POs, avoiding their rapid degradation in water. This CL-FIA system was applied to the determination of two sulfonamides for human and veterinary use: sulfadiazine (a sulfonamide mainly used in the treatment of urinary tract infections) and sulfamethoxazole (used mainly for bronchial affections) using bis[2,4,6-trichlorophenyl]oxalate (TCPO) as precursor and fluorescamine as fluorescent derivatizing agent. The optimization of instrumental and chemical variables was carried out by using experimental designs (Doehlert and 23 plus centered face star), separately for each sulfonamide. The method shows a LOQ of 379 µg l–1 (calibration range 126-2000 µg l–1) for sulfadiazine and has been successfully applied to the quantification of this sulfonamide in pills and ampoules, obtaining results according with those reported by the manufacturers. Further results will be presented for sulfamethoxazole. Acknowledgements: The National Institute of Agricultural and Food Research and Technology (INIA, Ministerio de Agricultura, Pesca y Alimentación, Project Ref. CAL03-087-C2-2) and EU founds (FEDER) supported this work. JJSC is grateful to the Fundación La Caixa and VPR to the Plan Propio of the University of Granada

Sulfonamidas em leite por cromatografia líquida de alta eficiência com derivação pré-coluna e detecção por fluorescência Sulfonamides in milk by high performance liquid chromatography with pre-column derivatization and fluorescence detection

O objetivo deste trabalho foi avaliar e validar um método para deteminação de resíduos de sulfatiazol (STZ), sulfametazina (SMZ) e sulfadimetoxina (SDM) em leite UHT integral. A extração foi realizada com diclorometano e coluna de extração em fase sólida de sílica. Os resíduos, após derivação com fluorescamina, foram quantificados por cromatografia líquida de alta eficiência com detector de fluorescência. O limite de detecção das três sulfas em amostra de leite integral foi 0,3 µg L-1 e o limite de quantificação foi 1 µg L-1 para STZ e SMZ e 2,5 µg L-1 para SDM, com coeficientes de variação entre 4,4 e 6,6%. Os valores de recuperação para STZ, SMZ e SDM foram 63,2, 91,2 e 63,2%, respectivamente. Considerando o limite máximo de resíduo estabelecido pela legislação brasileira de 100 µg kg-1 para a soma das concentrações totais de STZ, SMZ e SDM, o método descrito permite a determinação simultânea dos três analitos em amostras de leite UTH integral.<br>The objective of this work was to evaluate and validate a method for analysis of sulfathiazole (STZ), sulfamethazine (SMZ) and sulfadimethoxine (SDM) residues in milk. Extraction was carried out with diclhoromethane followed by silica solid phase extraction. The extracts were derivatizated with fluorescamine and quantified by reversed-phase high performance liquid chromatography with fluorescence detection. The detection limit for the three sulfonamides was 0.3 µg L-1 and the quantification limit was 1 µg L-1 for STZ and SMZ and 2.5 µg L-1 for SDM, with coefficient of variation ranging from 4.4 to 6.6%. The recoveries for STZ, SMZ and SDM were 63.2, 91.2 and 63.2%, respectively. Considering that Brazilian regulation sets maximum residue limit in milk of 100 µg kg-1 for total sulfonamide concentrations (STZ, SMZ and SDM), the present method is adequate to quantify the residues of three sulfonamides simultaneously in UHT milk