| Clenbuterol (CLB) is a beta-adrenergic drug and can enhance the lean meat/fat ratio and increase the efficiency of feed conversion by inhibiting fat synthesis, improving muscular mass, and decreasing adipose tissue deposition in livestock production. CLE is still illegally used in meat industry although many countries including China, the United States and most European countries have forbidden the use of CLB as feed additivesln. This study, a convenient one-pot miniemulsion copolymerization method has been used to synthesize sulfonated polystyrene magnetic nanobeads. The new magnetic adsorbent based magnetic dispersive solid phase extraction method (MDSPE) was developed for rapid enrichment of CLE in pork and CLE immunochromatographic strip coupled with MDSPE method was proposed for rapid, sensitive and quantitative analysis of CLE residue in pork samples.This study includes three parts discribed as follows:1) Synthesis of functionalized magnetic nanobeadsFe3O4 nanoparticles were prepared by chemical coprecipitation method, and subsequently modified by oleic acid and undecylenic acid. Then polystyrene magnetic nanobeads with high surface density of sulfonic acid groups were synthesized by one-pot miniemulsion copolymerization with the optimization of the mass proportion of styrene and sodium styrene sulfonate. The prepared magnetic nanoparticles were characterized by transmission electron microscopy (TEM) and potentiometric titration. The results showed that the magnetic nanobeads had a varied size of about 110～150 nm, and the surface density of sulfonic group was 4.8 mmol/mg.2) MDSPE method for enrichment of clenbuterolA magnetic dispersive solid phase extraction method based on sulfonated polystyrene magnetic nanobeads for enrichment of CLE in water was proposed by optimization of adsorption and desorption. The factors affecting the adsorption of CLE such as pH value, salt ions and methanol concentration have been investigated. then increased rapidly with the further increase of the NaCl concentration to higher than 90% at 3 mol/L NaCl; The adsorption could be inhibited by methanol, and CLE could not be adsorbed on magnetic beads when the concentration of volume percent of methanol was 40%. The CLE adsorbed on the surface of megnetic nanobeads can be effectively eluted with 5% ammoniated methanol. The study of adsorption isotherm of CLE used megnetic nanobeads under optimum adsorption conditions at 25℃ has shown that the adsorption behavior followed the Langmuir model, and the maximum adsorption capacity was 0.41 mg/g, the Langmuir adsorption equilibrium constant KL was 147.90 L/mg。3) CLE immunochromatographic strip coupled with MDSPE method for quantitative detection of CLE in pork samplesT/C ratio based immunochromatographic strip coupled with MDSPE method was developed for quantitative detection of CLE residue in pork samples. The detection limit of the proposed method was 0.10 ng/g, and the quantification limit was 0.24 ng/g. The average recoveries of CLE for spiked pork at 0.25 ng/g、0.5 ng/g and 1.0 ng/g were 97.7%±12.7%,93.0%±7.8% and 95.9%±3.1%, respectively, and the inter-day and intra-day precision were 3.2%-13.0%(n=3) and 9.2%-12.1%(n=3) To validate the accuracy of the developed method,9 CLE positive pork samples which were confirmed by LC/MS/MS method were re-analyzed, the results revealed that the values gained from the two methods were in strong agreement. |
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