Analysis of Antibiotic Drug Residues in Food and Animal Tissue by LC/MS/MS

Li Huang (Ph.D., Supervisor and Research Scientist), Mary Wu, Cathy Cardinall
JR Laboratories Inc., #12-3871 North Fraser Way, Burnaby, BC, V5G 5J6
Phone: 604-432-9311, Fax: 604-432-7768
E-mail: lhuang@jrlabs.ca

Abstract

LC/MS/MS has been the most recent of the hyphenated techniques to become routine. The LC/MS/MS combination can use the capabilities and advantages of both the separation technique and the spectrometer, for the analysis of a wide range of molecules not previously amenable to mass spectrometric analysis. It is not only a very sensitive and confirmative analytical instrument but also makes the extraction process much more practical and reliable, which is especially important for our industrial analytical laboratory. We have successfully developed numerous methods using LC/MS/MS to analyze environmental, nutraceutical, and veterinary drug residue samples. Among these applications, the analysis of antibiotic residues in food and animal tissue can be an example.

In the past, analysis of antibiotic drug residue was a difficult task for their strong polarity and low UV activity. One common approach is to sillyl-methylate the hydroxy group on drug molecule and then analyze the content by GC. Since the sample hydrophilic substances undergo the same reaction, the chromatograms are usually very dirty; in addition, the conversion rate of derivatization is not stable. Now LC/MS/MS technology provides us a rapid and efficient way to solve the problem. In the presentation, we will discuss some new approach using LC/MS/MS-MRM (multi-reaction monitoring) technique to analyze tetracyclines, sulfa drugs, chloramphenical, ionophores (monensin, narasin, salinomycin, and lasalocid), fluoroquinolones (enrofloxacin, ciprofloxacin, and sarafloxacin), and other veterinary drug residues in food and animal tissue. We will compare the extraction procedure, detection limit, efficiency and reliability with the traditional analytical techniques.

Although there is no doubt that LC/MS/MS-MRM is an excellent technology for drug residue screening and confirmation, there are some obstacles to the accuracy of the quantitation. One problem is the poor repeatability of the peak intensity. The usage of the enriched isotope internal standard can perfectly solve the problem; however, they are often unavailable. Another problem is that the ion formation is very sensitive to the chemical environment. The same content of same analyte could show different response in different solution. In our presentation we will discuss our suggestion to reduce the ruggedness.