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A simple, effective and reliable method for the determination of eight sulfonamide antibiotics (sulfadiazine, sulfapiridine, sulfamerazine, sulfamethazine, sulfachloropiridazine, sulfamethoxazole, sulfadoxine, sulfadimethoxin) in chicken muscle and eggs by liquid chromatography and fluorescence detection has been developed and validated. Sulfonamides do not present native fluorescence, however their direct determination was achieved by on-line post-column photochemical derivatization by UV irradiation. Sample treatment was based on QuEChERS with several modifications depending on the matrix. Egg extracts were cleaned-up using PSA for the dispersive solid phase extraction step. On the other hand, a new clean-up sorbent, Supel™ QuE Z-Sep(+), has been successfully applied in chicken muscle extract and has proved to be effective for interference removal from this matrix. Under optimum conditions, recoveries from 65.9 to 88.1%, relative standard deviations lower than 10% (except for sulfachloropiridazine), and limits of quantification (LOQs) from 14 to 85 μg kg(-1) were achieved. Thus, the method complies with current European requirements., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Peroxyoxalate chemiluminescence (PO-CL) is an indirect type of CL which allows the detection of native fluorophores or compounds derivatized with fluorescent labels. We propose a flow injection analysis (FIA) configuration based on the use of a two-injection valve system for the introduction of both PO and derivatized analyte solutions in the flow system, avoiding the problems arising from the use of organic solvents, such as acetonitrile, as no special tubes nor special pumps are required. Furthermore, the use of micellar media (sodium dodecyl sulphate, SDS) as a 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. The proposed CL-FIA system has been applied to the determination of sulphadiazine (a sulphonamide mainly used in the treatment of urinary tract infections for human and veterinary use) using bis[2,4,6-trichlorophenyl]oxalate (TCPO) as CL precursor, H2O2 as oxidant, imidazole as a catalyst and fluorescamine as the fluorescent derivatizing agent. The optimization of variables was carried out by means of experimental designs and the method showed a LOQ of 379 microg l(-1) (calibration range 126-2000 microg l(-1)). It has been satisfactorily applied to the quantification of sulphadiazine in pills for human use and ampoules for veterinary use.