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PubMed1991

Determination of sulfonamides by liquid chromatography, ultraviolet diode array detection and ion-spray tandem mass spectrometry with application to cultured salmon flesh.

Ion-spray mass spectrometry was investigated for the analysis of 21 antibacterial sulfonamide drugs. All of the sulfonamides analyzed gave positive ion mass spectra with abundant protonated molecules and no fragmentation. Tandem mass spectrometry (MS-MS) using collision-induced dissociation provided structural information, allowing the identification of common fragmentation pathways and the differentiation of isomeric and isobaric sulfonamides. A reversed-phase high-performance liquid chromatographic method was developed, using gradient elution and ultraviolet diode-array detection (DAD), enabling the separation of 16 of the sulfonamides. Combined liquid chromatography (LC)-MS was accomplished using the ion-spray interface. Analyses of a mixture of sulfonamide standards were performed with gradient elution and the mass spectrometer configured for full-scan acquisition, selected-ion monitoring, or selected-reaction monitoring. Procedures for the analysis of sulfadimethoxine (SDM), a representative sulfonamide used in the aquaculture industry, are described. The presence of SDM in cultured salmon flesh was confirmed at levels as low as 25 ng/g by a combination of LC-DAD and LC-MS-MS.

Animals↗
PubMed2002

Micellar liquid chromatography: suitable technique for screening analysis.

The screening capability of micellar liquid chromatography (MLC) is discussed using the reported chromatographic data of several sets of compounds (amino acids, beta-blockers, diuretics, phenethylamines, phenols, polynuclear aromatic hydrocarbons, steroids and sulfonamides) and new results (sulfonamides and steroids). The chromatographic data are treated with an interpretive optimisation resolution procedure to obtain the best separation conditions. Usually, the pH and the concentration of surfactant (sodium dodecyl sulfate, SDS, or cetyltrimethylammonium bromide) for the optimal mobile phase were 2.5-3 and < 0.12 M, respectively. The nature and concentration of organic solvent depended on the polarity of the eluted compounds: a low volume fraction of propanol (approximately 1%, v/v) was useful to separate the amino acids, with log P(o/w) < -1 (where P(o/w) is the octanol-water partition coefficient). A greater concentration of this solvent (approximately 5-7%) was needed for compounds in the range -1 < log P(o/w) < 2, as with the studied diuretics and sulfonamides, and a high concentration of propanol (approximately 15%) or a low concentration of butanol (< 10%) had to be used for less polar compounds with 1 < log P(o/w) < 3, such as the beta-blockers. Pentanol (< 6%) was more suitable for the even less polar compounds with log P(o/w) > 3, such as the steroids. For basic drugs such as the phenethylamines (0 < log P(o/w) < 1.7), eluted with a micellar eluent of anionic SDS, propanol was too weak. A study is also shown for mixtures of sulfonamides (log P(o/w) = -1.2 to 1.7) and steroids (log P(o/w) = 3.0-8.1) eluted from conventional C18 columns with SDS mobile phases containing acetonitrile and 1-pentanol, respectively, which are compared with classical acetonitrile-water and methanol-water mixtures. The results complement a previous study on beta-blockers (log P(o/w) = -0.03 to 2.8) and reveal that MLC is a very competitive technique for the screening of compounds against conventional RPLC, due to its peculiar behaviour with regard to the selectivity and elution strength. The concentration of organic solvent needed to obtain sufficiently low retention times (even for highly hydrophobic steroids with log P(o/w) = 7-8) is also appreciably smaller for MLC, which reduces the environmental impact of the mobile phases.

Chromatography, Liquid↗
PubMed1996

Catalytic asymmetric aminohydroxylation provides a short taxol side-chain synthesis.

The p-toluenesulfonamide derivate of the C-13 side-chain of taxol was prepared on a one third mole scale in a single step from methyl cinnamate. The process employed is catalytic asymmetric aminohydroxylation (catalytic AA). In the present case, there is no work-up other than filtration of the pure product which is insoluble in the reaction mixture. The sulfonamide protecting group is removed by acidic hydrolysis.

Cinnamates↗