Residue analysis of glucocorticoids in bovine milk by liquid chromatography-tandem mass spectrometry.
A sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of 13 steroidal anti-inflammatory drugs in bovine milk is presented. Due to their weakly acid nature, analytes were separated by ion suppression reversed phase chromatography and detected in positive-ion mode by a high flow electrospray source. Dexamethasone-d4 was used as internal standard. The sample preparation was simple and reliable; it included acidic deproteinization of milk followed by sample enrichment and clean-up, utilizing a C18 solid phase extraction cartridge. Recoveries exceeded 70% with an intra-day precision not larger than 12%. The efficiency of the sample clean-up and internal standardization rendered negligible the matrix effect, estimated by comparing standard and matrix-matched calibration curves. A small-scale reconnaissance was carried out on several raw and whole fresh milk samples. A large number of analyzed samples showed a chromatographic peak, in the retention time window of cortisol, at levels included between its decision limit (CCalpha) and detection capability (CCbeta). As a result of a heat-induced transformation, an isomeric product of triamcinolone was observed during the extract evaporation. Since this rearrangement might occur during the milk pasteurization process, LC-MS/MS and (1)H-NMR investigations were performed out to conclusively differentiate the two isomers. One- and two-dimensional proton NMR spectra were able to identify the transformation product as 9a-fluoro-11b,16a-trihydroxy-17b-hydroxymethyl-D-homoandrosta-1,4-diene-3,17a-dione.
Caretti
Fulvia
F
Department of Chemistry, University of Rome La Sapienza, P.le A. Moro 5, P.O. Box 34, Posta 62, 00185 Rome, Italy. fulvia.caretti@uniroma1.it
Gentili
Alessandra
A
Ambrosi
Annalisa
A
Rocca
Lucia Mainero
LM
Delfini
Maurizio
M
Di Cocco
Maria Enrica
ME
D'Ascenzo
Giuseppe
G
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000032:analysis; D002853:Chromatography, Liquid / Q000379:methods; D056148:Chromatography, Reverse-Phase; D005938:Glucocorticoids / Q000032:analysis*; D008892:Milk / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry / Q000379:methods*
D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids