[The occurrence of dapsone residues following a one-time oral, intramuscular and intramammary application in healthy dairy cows]. / Het voorkomen van Dapson-residuen na éénmalige orale, intramusculaire en intramammaire toepassing bij gezonde melkrunderen.

Dapsone is frequently used as a bacteriostatic drug in the treatment of mastitis, endometritis and footrot (necrotic pododermatitis). The farmer usually obtains this drug by 'non-ethical' channels. A regular scheme of checking the milk for residues of sulphonamides will be introduced in 1986. The sensitivity of the test is approximately 25 ppb for Dapsone. This will result in lower milk price in the case of positive tests. In healthy animals, it is shown that intramuscular treatment with 35 grammes (+/- 70 mg/kg-1 body weight) of Dapsone results in residues of Dapsone and its metabolite monoacetyldapsone above this detection level for more than 6 1/2 days. Within 5 days after oral treatment with 48.75 grammes (+/- 100 mg/kg-1 body weight) and 2 1/2 days after single intramammary treatment with 0.8 grammes, the concentrations of residues detected dropped below 25 ppb. The other well-known metabolite diacetyldapsone was only present in detectable quantities in the first milkings after oral treatment.

[Automated determination of 4,4'-diaminodiphenylsulfone (DDS) and acetyl metabolites (MADDS and DADDS) in milk with the FAST-LC system]. / Automatisierte Bestimmung von 4,4'-Diaminodiphenylsulfon (DDS) und Acetylmetaboliten (MADDS und DADDS) in Milch mit dem FAST-LC-System.

With the described method it is possible to determinate residues of Dapsone (DDS) and its acetylated metabolites (mono- and diacetyldapsone) in milk. The determination is being carried out with a FAST-LC system (Fully Automated Sample Treatment Liquid Chromatography). The purification is a combination of dialysing the milk against water and absorption of the nonpolar components from the dialysate on the preconcentration column of the LC-system used (RP, 40 microns). With back-flush, the concentrate is being injected into the analytical column (RP-8, 5 microns). The detection is being carried out with the help of a UV-absorbance detector, at a wavelength of 296 mm. The detection limit is approximately 2 micrograms/l (DADDS: 5 micrograms/l). The required amount of the sample is 5 ml. The recovery, reproducibility and linearity for the three components in milk are good.