Confirmatory method for sulfamethazine residues in cattle and swine tissues, using gas chromatography--chemical ionization mass spectrometry.

A gas chromatographic (GC) method has been reported for the determination of sulfamethazine residues in cattle and swine tissues. The extracts from this procedure were found to be directly amenable to examination by gas chromatography-mass spectrometry (GC-MS), allowing positive confirmation of an apparent residue of sulfamethazine. Chemical ionization mass spectrometry (CIMS) was chosen as the MS technique because it generated an ion indicative of intact sulfamethazine and fragment ions indicative of the amine functionality and sulfanil moiety. Positive ion (PI) chemical ionization mass spectrometry was adequate by itself for a confirmatory technique. Negative ion (NI) chemical ionization mass spectrometry alone could not be used for the confirmatory analysis of sulfamethazine, but it did offer a means to check the quantitative data from the positive ion analyses and provided complementary confirmatory data. Satisfactory recoveries were obtained for sulfamethazine in swine and cattle tissues at the tolerance level of 0.1 ppm. Apparent sulfamethazine residues in control tissues were less than 0.01 ppm.

Citrus artifact interference in aflatoxin M1 determination in milk.

Dried citrus waste was fed to dairy cows, their milk was extracted, and aflatoxin M1 was quantitated by using both high pressure liquid chromatography (HPLC) and thin layer chromatography (TLC). Results indicate that a compound from the citrus waste, which is excreted into the milk, interferes with the HPLC determination of aflatoxin M1 in milk and causes a false positive test. This interference can be overcome by using TLC with proper selection of developing solvents.