Trace analysis of oxytetracycline and tetracycline in milk by high-performance liquid chromatography

Abstract

A high-performance liquid chromatographic (HPLC) method for the determination of oxytetracycline (OTC) and tetracycline (TC) residues in milk a t levels as low as 10 ppb has been developed. Milk was acidified a t pH 2.7 and extracted with acetonitrile. The extract was partly purified by treatment with ammonium sulfate solution and concentrated into a phosphate buffer, pH 8.2. Following addition of tetrabutylammonium reagent (TBA), tetracyclines were extracted as ion pairs with TBA into dichloromethane, reextracted into acid, and analyzed on a reversed-phase CIS, 5 pm, column. Overall recovery was found to be 72.7 f 1.2% for OTC and 85.1 f 1.3% for TC. The linearity was excellent for both compounds in the range examined (r = 0. 9996, r = 0.09995, ppb of TC in milk). Precision data based on within-day and among-days variation suggested an overall relative standard deviation of 5% for OTC and 4.2% for TC.

Sample preparation followed by HPLC under harmless 100% aqueous conditions for determination of oxytetracycline in milk and eggs

“…Previous papers reported that the extraction of OTC from milk was not quantitative or repeatable, unless the sample had been acidified at values lower than pH 3 [33]. Possibly, the dissociation of OTC from milk proteins is incomplete at higher pH values.…”

“…OTC is stable in acid solution and decomposes rapidly in basic solution [32,33]. Previous papers reported that the extraction of OTC from milk was not quantitative or repeatable, unless the sample had been acidified at values lower than pH 3 [33].…”

Multiresidue determination of tetracyclines, sulphonamides and chloramphenicol in bovine milk using HPLC-DAD

“…For protein precipitation different solutions have been recommended in the literature for the determination of tetracyclines in milk: succinic acid (Andersen et al, 2005), ACN (Fletouris, Psomas, & Botsoglou, 1990), 1 mol L À1 hydrochloric acid (Moats & HarikKahn, 1995;Zhao, Zhang, & Gan, 2004) and McIlvaine buffer/EDTA (Abete, Genta, & Squadrone, 1997;Brandsteterova et al, 1997) and for sulphonamides: ACN (Van Rhijn et al, 2002) and 20% TCA (Furusawa, 1999). The procedures have not been harmonised for the same antimicrobial group and considering that compounds from three different groups would be evaluated in this work, protein precipitation conditions were studied.…”

Magnetic solid phase extraction based on phenyl silica adsorbent for the determination of tetracyclines in milk samples by capillary electrophoresis

“…During recent years, the problems caused by antimicrobial residues in food have stimulated the development of analytical methodologies for the determination of TC residues at g kg −1 or g l −1 levels, such as microbiological assays [7], spectrophotometry [8,9], chemiluminescence [10][11][12], high performance liquid chromatography (HPLC) [13][14][15] and capillary electrophoresis (CE) [16,17]. These techniques can be used individually or sequentially according to the complexity of the samples, the nature of the matrix and the target analytes.…”