Research For Detection Method For Ractopamine Control From Elimination Regularity In Urine And Hair Of Animals

Ractopamine belongs to Beta-agonist compounds and has been often used as growth-promoting agent to improving the feed efficiency and enhance lean meat to fat ratio in many animal species. It is a forbidden molecule as feed additive in most countries including China because of the many reported collective intoxication outbreaks in humans. For most labs, It was hard to get a high sensitivity method to control ractopamine, the cutoff is different for different method, so the Compliance rate for screening method and confirmation method was just 30～50%, this is a big comfuse for ractopamine controlling. So it is necessary to research different detection methods to control the using of ractopamine in animals.The objective of this study was to establish a practical method for Screening and confirmation of Ractopamine residues in urine and hair. The pharmacokinetics and the elimination regularity of ractopamine in urine and hair were firstly studied. This research will be a scientific guidance for ractopamine control.An efficient and sensitive Gas chromatography-mass spectrometry(GC/MS) and a higher sensitive Liquid Chromatography with Tandem Mass Spectrometric (LC/MS/MS) analytical method for detection of ractopamine in urine was developed and validated. The result showed these two methods all can used in quantitative of ractopamine in urine samples. A quantitative analytical procedure for the determination of ractopamine in pig hair has been developed; result showed that this method can be used for ractopamine detection in hair samples.To research the requirement for detection, this article set up a pharmacokinetics mode to study the elimination regularity of ractopamine in urine and hair. The concentration of ractopamine in urine and hair samples durine feeding and withdrawal period was anaylized by GC/MS and LC/MS/MS methods. Compare the changes of concentration with time, we found that the concentration of ractopamine in urine decline with time, the elimilation time was 3.5 days. The concentration in hair can get a stable and keep the same level after some decline time and the elimilation time was 22.9 days. Ractopamine of urine eliminated very fast after withdrawal drugs. In this study, we also found there are relationship between feeding time and withdrawal time with concentration, we can tracing the history of feeding drug from them.From elimination regularity of ractopamine in urine, we found concentration of ractopamine was very low and is hard to trace after withdrawal drug. To screening test, a higher sensitive immunoassay is necessary. We set up an ELISA method to screening samples for using in labs and a Fluorescence Chromatography immunoassay to screening samples on site. Data improved this two immunoassay were sensitive with 1ng/mL LOQ, and can be used in urine screening. We also try to test hair samples by this two method but we fail, but we still can sure it is possible to test ractopamine in hair.To use screening and confirmation method, we compared different method. By test different urine samples during feeding and withdrawal period, we found all method can test ractopamine from samples during feeding time. But we can test ractopamine up to 3～6 days by screening with 1ng/mL cutoff, and all positive samples can be confirmed by GC/MS and LC/MS/MS with 5ng/mL cutoff.At last part in this article, we discussed the meanings of hair test in ractopamine control. Hair test can detect ractopamine up to 30 days after withdrawal drugs, so it can be used to trace feeding history and confirm the false negative and positive result by urine.Overall, all method can used in ractopamine control for different purpose.