Microbiological and bioassays have historically served to screen foods for the presence of antibiotics. While these assays have proven to be quite sensitive and inexpensive they are far too nonspecific and cause too lengthy a delay in obtaining data. This delay may allow antibiotic contaminated animal-derived foods to be marketed and consumed with drug detection being accomplished after the fact. This policy is inherently inadequate but has arisen from the limitations of the available analytical technologies. In this sense, bioassays and other methodologies that require lengthy waiting periods and prolonged and complex ana lytical procedures cannot meet the increasing need to perform rapid drug screening and confirmation on more samples for more drugs.
The advent of more specific, sensitive, and simple to perform immunoassays should overcome many of the problems of performing rapid screening and early detection of antibiotic contamination in animal-derived foods. In this regard, simple elisa, card, or test-strip assays that are suitable for use at production sites, slaughterhouses, and packing plants could dramatically reduce the occurrence of antibiotic violations and preclude the problems that can arise from antibiotic contamination of the food supply.
These and other more complex immunoassay methods could be performed on milk, urine, blood, or other body fluids. However, new methods for the rapid isolation of drugs from tissues may also make such immunoassays more directly applicable to the screening of this complex sample material. Matrix solid-phase dispersion (mspd) techniques have shown promise in providing a simple, rapid, and generic method for performing drug isolations from tissues and milk. Thus the combination of ia and mspd may prove to be a useful approach to the more rapid screening and analysis of tissues and animal derived products for antibiotics as well as other drugs. A further advantage of mspd is the capability to isolate a class of drugs or several classes of drugs from a single sample. In this regard the advances in immunoassay screening technology must be matched by advances in extraction procedures. Extraction methodology that is too narrow in extraction capability leads to a need to develop a specific method for each antibiotic drug. Extraction methods that are multidrug and multidrug class specific will have the greatest utility for performing screening analyses in the future, whether such screens are conducted by immunoassay, tic, hplc, or gc.
Of these analytical techniques ia and tic will be best utilized for rapid screening, whereas hplc and gc may be the best methods for subsequent confirmation and quantitation of antibiotic residues. However, hplc methods that are capable of separating and detecting several drug residues obtained, perhaps, from a single multidrug class extraction may also prove to be useful screening techniques. The usefulness of such screens is directly related to the efficiency of recovery of a multidrug extraction method, the elimination of background interferences, and the ability of various detectors to indicate the presence or absence of a drug with adequate sensitivity.
For the antibiotics, gc will remain of limited value but should always be considered and applied where feasible. It is expected that sfc will eventually play a major role in the extraction and analysis of compounds such as the antibiotics. However, current results are less than promising and the awaited applications may be long in development.
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