| Olaquindox is an antibacterial growth-promoting agent,which was synthesized from o-nitroaniline by Bayer company in 1965.Because olaquindox has the function of antibacterial and promoting protein synthesis,it can promote animal growth,improve feed conversion and utilization rate,it was widely used in the breeding of livestock animals,but long-term and massive use can easily lead to the accumulation of drug residues in animals.Olaquindox is banned as a feed additive in the United States and the European Union.The Chinese veterinary pharmacopoeia(2005 edition)explicitly prohibits the use of olaquindox in poultry and aquaculture.With the improvement of regulatory requirements,the existing methods cannot meet the needs,so it is urgent to optimize and establish a series of sensitive,reliable and well-applied detection methods from active drug to metabolite,source to circulation.In this paper,HPLC,LC-MS and colloidal gold technique established in cooperation with enterprises,which are commonly used by inspection and testing institutions,were used to screen the residues of olaquindox in feed at the source of application,MQCA metabolites in animal-derived food at the circulation link,and to optimize the methods of laboratory confirmation.On this basis,carry out the risk monitoring of MQCA of commercially sold animal-derived food.The main research contents and results are as follows:(1)An HPLC method for the rapid and accurate determination of olaquindox residues in feed was optimized.Compared with the national standard,the extraction efficiency of olaquindox is higher.The purification and concentration steps were improved to reduce the loss of the target substance and improve the efficiency.The pretreatment time was shortened from 3 h to about 40 min.The recovery rate indicated in the gb method ranged from 70% to 86%.Since the target substance is photosensitive compound and is easy to be lost under concentration,this method optimizes the key control points in the extraction process,making the recovery rate between 96% and 105%,the relative deviation of repeatability conditions less than 2.4%,and the accuracy and precision are better than the national standard.The sensitivity of the method was improved by optimizing the chromatographic conditions and selecting suitable column and mobile phase.(2)Laboratory scientific evaluation and optimization of food rapid assay kit technology(Immune colloidal gold technique),through the cooperation with relevant enterprises,the practical promotion and application of MQCA fast screening technology,screening animal food in the olaquindox metabolites residue.After the improvement,the colloidal gold strip method has higher sensitivity and specificity,and the quality performance test shows that the accuracy,stability and other indicators of the kit are better,and the operation is simple,compared with the instrument method,the cost is low,and the analysis speed is fast,about 5 to 8 min can be observed with the naked eye.It has obvious advantages in rapid sample screening and accurate qualitative analysis and is suitable for grassroots supervision.(3)LC-MS was further optimized for the determination of the residual concentration of olaquindox metabolites.Methods trypsin was used to hydrolyze the compound.Methods the extraction process of MQCA compound was improved,and the SPE column which was not suitable for concentration and purification of animal-derived samples in the national standard method was abandoned.The direct and rapid extraction was beneficial to the determination of batch samples.The national standard method for determination of MQCA lacks a clear process of fat removal,making it difficult to determine samples with high oil content and high fat content.This method adopts the method of freezing centrifugation and liquid-liquid extraction to remove fat,which has a more prominent purification effect on oil-rich samples and a good reproducibility.The recovery rate ranged from 92% to 101%,the RSD was less than 4.19%,and the actual RSD was less than 3%.By optimizing the ion source and chromatographic conditions,the target substance can peak rapidly in 4 min,and the ion channel is clean without obvious interferences.The method has high sensitivity and good specificity.(4)The risk monitoring and early warning of the residues of olaquindox in animal derived food origin were carried out.Muscle,liver and kidney tissues in chickens,ducks,pigs and cows in guangzhou 11 district were selected as monitoring objects.The results showed that from 2016 to 2017,the animal and poultry tissue parts of the quinolindox metabolite(MQCA)were pig liver and pig muscle,which did not exceed the limit standard of the quinolindox mark residues in pig muscle and liver stipulated in announcement no.235 of ministry of agriculture.As a whole,commercially available food of animal origin(chickens,ducks,pork,beef)is safe. |
