| Sulfnamides(SAs)are a group of chemical drugs with a common structure of sulfanilamide,which are used to prevent and treat bacterial infectious diseases.Because of its broad antibacterial spectrum,convenient use,low cost,good curative effect and other advantages,it is widely used in animal husbandry and veterinary clinic.However,if the drug is used for a long time or the drug is not stopped according to regulations,the residual drug components may cause potential risks to edible tissues of livestock products,thus affecting human health.In addition,the feces of these livestock that use sulfonamides excessively will also pollute the environment and then transfer from the environment to the human body,causing secondary hazards.To safeguard human health,the European Union(EU)has established a maximum residue limit(MRL)of 100 ?g/kg(or 100 ppb)for the total amount of SAs in food samples of animal-origin such as animal husbandry products.Document 235 of the Ministry of Agriculture of China also clearly stipulates that the content of sulfonamides in animal-derived products should not exceed 100 ?g/kg(SMZ should not exceed 25 ?g/kg).Therefore,it is necessary to develop simple,convenient,efficient and sensitive methods for monitoring and quantifying SAs residues.This paper explores the combination of off-line enrichment and on-line enrichment techniques with capillary electrophoresis,and the enrichment and detection methods for sulfonamides in food samples and environmental water samples were optimized.(1)A pressure-assisted electrokinetic injection(PAEKI)combined with capillary zone electrophoresis(CZE)on-line enrichment method has been developed and applied to the detection of six sulfonamides in food samples and environmental water samples,and the factors affecting separation and enrichment have been investigated.Under the optimized conditions,six SAs were separated at baseline within 8.5 min.PAEKI-CZE method was well verified and successfully applied to the determination of sulfonamides in animal products(milk,pork,eggs)and three environmental water samples(tap water,lake water and seawater).LOD of six SAs in milk,pork,eggs,tap water,lake water and seawater samples were 0.0018–0.0163?g/ml,0.0083–0.0638?g/ml,0.0052–0.0478?g/ml,0.0021–0.0152?g/ml,0.0104–0.0675?g/ml and 0.0097–0.0595?g/ml respectively,the range of EFs was 39-62,which proves that the method has good enrichment effect and low detection limit,and is suitable for separation and determination of sulfanilamide in food and environmental water samples.(2)The separation mode of capillary zone electrophoresis(CZE)is combined with sample pretreatment technology of DLLME and enrichment technology on PAEKI line to detect four SAs in environmental water samples,namely sulfamethazine(SMZ),sulfamethazine(SMR),sulfadiazine(SDZ)and sulfacetamide.The CE separation conditions,DLLME conditions and PAEKI conditions were investigated.Under the optimal conditions,the four SAs were separated at baseline within 6 min.The enrichment multiples of SAs determined by DLLME-PAEKI-CE method were 206,166,185 and 150 respectively,which were significantly higher than those determined by DLLME-CZE method(29,31,46 and 27 respectively),indicating that the double enrichment method was more sensitive.4 SAs showed a good linear relationship in the three environmental waters.the correlation coefficient(r)was greater than 0.9900.The LOD in tap water,lake water and seawater were 2.0~23.0 ng/ml,2.2~26.0 ng/ml and 4.3~63.0 ng/ml respectively,which was far lower than the maximum residue limit of animal-derived food.Finally,the methods established in this study are summarized and prospected.These two methods have the advantages of good linearity,high recovery,high precision and low cost.They are suitable for the determination of trace sulfonamide in complex substrates,there should also be more diverse combinations of pre-processing and on-line enrichment. |
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