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The growing demand for enhanced food productivity to meet the needs of the global population has led farmers to use sophisticated agricultural technology in which pesticides play a crucial role. Pesticide use has a positive and dramatic impact on agricultural production through protection of crops against insects, pests, and disease, but every effort must be made to ensure that application is safe and, more importantly, to assure safety for human and environmental health. Since our initial review (1), global usage of pesticides has increased and knowledge regarding the biological significance of bound pesticide residues has expanded. The fact that more reports are appearing in the literature signifies an increased awareness of the presence of bound pesticide residues and indicates that a greater number of scientists are attempting to establish the potential toxicologic consequences of this pesticides residue fraction. Rico (2), in a review in 1990, concluded that covalently bound residues in edible animal tissues were not carcinogenic, were not readily bioavailable, and hence produced little, if any, adverse effects. Whether this conclusion is applicable to the presence and consequences of bound pesticide residues in plants and food commodities remains unanswered. Thus, the aim of this updated review is not simply to list studies on bioavailability of bound pesticide residues in grains subsequent to the review in 1992 (1) but also to establish the toxicological impact of this chemical fraction on health.

A rapid, accurate, environmentally friendly and cost-effective microwave extraction technique was developed for the extraction of spiked and incurred salinomycin from chicken tissues (kidney, liver, muscle, ovarian yolk and fat). Extraction of salinomycin from various tissues was achieved by irradiating the sample in absolute ethanol and 2-propanol (15 + 2) for 9 sec. in a common household microwave oven. The extract was analysed without further cleanup by HPLC on a C18 column (5 microns) and detected at 592 nm via post-column reaction with 4-dimethylaminobenzaldehyde (DMABA) in a heated reactor coil at 86 degrees C. Recoveries of salinomycin from spiked tissues at 30 ng/g level ranged between 87 and 100%. The limit of quantitation was found to be 10 ng/g. The developed method was applied for the analysis of incurred tissues and ovarian yolk of laying chickens given sodium salinomycin in feed at different levels for 14 consecutive days followed by withdrawal periods. Residues were detected in all tissues and ovarian yolk at 0 withdrawal time but declined during the withdrawal period. Highest residue were found in fat and ovarian yolk.

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