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Title: LIQUID CHROMATOGRAPHIC DETERMINATION OF B-LACTAM ANTIBIOTICS IN MILK - A MULTIRESIDUE APPROACH

Author
item Moats, William - Bill
item Harik Khan, Raida

Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: This method is the first reported multiresidue chromatographic procedure for B-lactam antibiotics in milk which uses a single extraction and cleanup procedure for all compounds of the group. It equals or exceeds the sensitivity of screening tests used for detection of B-lactam antibiotics. It is thus of key importance as a reference method for validating screening gtests and has already been used for that purpose in a cooperative study with FDA. It can also be used to confirm results of screening tests run on producer milk.

Technical Abstract: In the United States, testing of all milk for residues of B-lactam antibiotics is now mandatory. Although a number of screening tests for determination of B-lactam antibiotic residues have been proposed, few reference methods of the required sensitivity (<10 ppb) are available. Methods for determination of several B-lactam antibiotics using an automated HPLC cleanup have been described recently. This paper describes the integration of these methods into a single extraction and cleanup procedure. Milk was deproteinized with 0.2M Et4NCl and acetonitrile. The resulting filtrate was evaporated to about 1 ml, made to 4 ml and filtered through a disposable filter cartridge. For cleanup, 2 ml of filtrate was loaded on a bonded C18 HPLC column in 0.01M KH2PO4 (A) and eluted with an acetonitrile (B) gradient using program of 100 A : 0B (0-3 mins) to 60A : 40B (30 mins). The B-lactams were separated from each other into narrow bands. A fraction corresponding to each compound of interest was collecte and rechromatographed for analysis. The procedure has been applied successfully to determination of ampicillin, amoxicillin, cephapirin, penicillin G, penicillin V, ceftiofur, and cloxacillin. It is in principle applicable to determination of any B-lactam antibiotic or metabolite thereof by collecting appropriate fractions.