Trace analysis of chloramphenicol residues in egg powders by capillary gas chromatography-electron capture detection

Determination of chloramphenicol residues in meat, seafood, egg, honey, milk, plasma and urine with liquid chromatography–tandem mass spectrometry, and the validation of the method based on 2002/657/EC

A simple and rapid method for the determination and confirmation of chloramphenicol in several food matrices with LC-MS/MS was developed. Following addition of d5-chloramphenicol as internal standard, meat, seafood, egg, honey and milk samples were extracted with acetonitrile. Chloroform was then added to remove water. After evaporation, the residues were reconstituted in methanol/water (3+4) before injection. The urine and plasma samples were after addition of internal standard applied to a Chem Elut extraction cartridge, eluted with ethyl acetate, and hexane washed. Also these samples were reconstituted in methanol/water (3+4) after evaporation. By using an MRM acquisition method in negative ionization mode, the transitions 321-->152, 321-->194 and 326-->157 were used for quantification, confirmation and internal standard, respectively. Quantification of chloramphenicol positive samples regardless of matrix could be achieved with a common water based calibration curve. The validation of the method was based on EU-decision 2002/657 and different ways of calculating CCalpha and CCbeta were evaluated. The common CCalpha and CCbeta for all matrices were 0.02 and 0.04 microg/kg for the 321-->152 ion transition, and 0.02 and 0.03 microg/kg for the 321-->194 ion transition. At fortification level 0.1 microg/kg the within-laboratory reproducibility is below 25%.

Analysis of chloramphenicol in honeys of different geographical origin by liquid chromatography coupled to electrospray ionization tandem mass spectrometry

A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed to detect trace amounts of the antibiotic chloramphenicol (CAP) in honey. The methodology entailed a solid-phase extraction of aqueous honey solutions followed by liquid-liquid partitioning, filtration and direct injection onto the LC-MS/MS system. Honey extracts were spiked with an isotopically labelled internal standard (d(5)-CAP) to compensate for analyte loss and potential ion suppression during the MS stage. Detection of the analyte was achieved by negative ionization electrospray in the selected reaction monitoring (SAM) mode. For confirmation, four characteristic mass transitions were monitored each for the analyte and the surrogate standard. The method was validated according to the latest European Union criteria for the analyses of veterinary drug residues in food. At all three fortification levels studied (0.1, 0.2, 0.5 microg kg(-1)) the method was accurate to within 15%. The repeatability and within-laboratory reproducibilities were <12 and 18%, respectively. The decision limit (CC alpha) and detection capability (CC beta) were both <0.1 microg kg(-1). The procedure provides a sensitive and reliable method for the determination of residues of chloramphenicol in honey. Numerous raw honeys of various geographical origins were analysed, showing extensive contamination particularly those of Chinese origin.

Chromatographic analysis of antibiotic materials in food

The monitoring of food materials for antibiotic residues is an area of increasing concern and importance due to the potential impact on human health. Large-scale screening applications require methods that are rapid, accurate, provide low detection limits and are free from interference. The problem is further complicated by the wide range of chemical functionalities and modes of operation exhibited by the antibiotic materials of physiological significance in use today. As demonstrated, chromatographic methods provide many of the advantages necessary for screening applications. Judicious choice of sample preparation method, separation mode and detection strategy can provide significant immunity from problems associated with the food matrix. Gas chromatography can provide extremely high separation efficiencies, however, only a limited number of antibiotic compounds are inherently volatile enough for direct analysis by gas chromatography. Derivatization to enhance the volatility of the antibiotic is one approach to overcome this limitation. Among the methods available, reversed-phase high-performance liquid chromatography is used extensively for the analysis of many antibiotic systems as it does not require derivatization and it combines relatively high separation efficiencies with low detection limits. The diverse group of properties exhibited by the antibiotic materials in use today suggests that the choice of detection strategy is a key component in the successful development of an analysis technique. Derivatization of the antibiotic material is frequently used to add either a fluorogenic of chromogenic moiety to the antibiotic compound to enhance detection. Derivatization procedures suffer from several limitations which are problematic when making measurements in complicated food matrices. Among the different detection modes utilized for antibiotic analysis, polarimetric detection has the potential to provide extremely selective detection of most antibiotic materials, and this selective response can minimize many of the constraints placed upon the separation system by the sample matrix. Although many of the separation modes used for antibiotic analysis are well developed, separations based on capillary electrophoretic methods have much potential in the field of antibiotic analysis. Future investigations are needed to extend the generality of these techniques and expand their use into the field of food analysis.