Detection of Dapsone in Muscle By Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Introduction:  Dapsone is a sulphonamide with bacteriostatic and bactericidal activity. It is used as an antibiotic and to prevent diseases. The administration of dapsone in livestock is prohibited in the European Union in accordance to the Directive 90/2377/EC so it is necessary to check the illegal use of this substance according to the Decision no. 2002/657 / EC.

Purpose: A rapid screening method for the analysis of dapsone by U-HPLC-MS/MS is described and it is able to reveal the dapsone recommended concentration of 5µg kg ^-1.

Methods: Samples are extracted with 0.1 M EDTA and acetonitrile, which is then evaporated under a stream of nitrogen and reconstituted in 0.1% formic acid in deionized water. An aliquot is analysed by U-HPLC-MS/MS using positive electrospray ionisation and multiple reaction monitoring. Mobile phases used are 0.1% formic acid in water and 0.1% formic acid in methanol. Validation is according to Commission Decision 2002/657/EC and was carried out for bovine and porcine species.

Results: Sulphadimetoxin-d6 is used as internal standard. Molecular weight of Dapsone is 249 kDa. The product ions are 156 (qualifier) with 14 of collition energy and 92 (quantifier) with 24 of collition energy. The specifity of the method was tested analizing twenty blank samples. A result of r²> 0.99 indicated a good linearity in the concentration range studied (2.50-050 µg/L). Trueness and precision were evaluated analyzing recovery on fortified blank samples spiked with dapsone.

Significance: A rapid method was developed for the survey of dapsone. It can be used on bovine and porcine tissue samples using liquid chromatography tandem mass spectrometry. This method is in accordance with Commission Decision 2002/657/EC.