||Nitrofurans have been widely used either in waterbath or feed additives for the prevention and treatment of aquatic products. The European Union was able to assign a maximum residue limit and prohibited nitrofurans used to animals in 1995, because of the potential carcinogenic effects of their residues on human health. This study is focusing on the analytical method of four kinds of commonly used nitrofurans and corresponding residual metabolites by LC-MS/MS. The detection limits of furazolidone, furaltadone, nitrofurazone and nitrofurntoin were 6.11, 3.63, 4.52 and 6.20 μg kg-1,respectively. The detection limits of AOZ, AMOZ, SC and AH were 0.23, 0.30, 0.36, 0.53 μg kg-1, respectively. The lightness is the main factor to cause the decomposition of nitrofurans. It is not significant for temperature to depredate nitrofurans. The adsorbtion of metabolites by the plastic tube was in the extraction procedure. Equipments in glass are suggested to be used for the sample pretreatment and plastic meterials are averted to be exercised.|
About the comparation of determination of AOZ by ELISA and LC-MS/MS. The result demonstrated that the ELISA method might overestimate the residual AOZ content at low concentrations. The detection limit and recovery of the known addition were 0.05 μg kg-1 and 108% for the LC-MS/MS method and 0.31 μg kg-1 and 305% for the ELISA method, respectively.
The amounts of residual nitrofurans and metabolites in muscle, liver, gill and skin tissue of tilapia which were treated in different conditions were compared. The depletion data of bathing treatment group obtained showed similar be haviors of furazolidone, furaltadone, nitrofurazone, nitrofurantoin in tilapia which the residual time was less than 24 hr. The amounts of residual nitrofurans appeared the highest concentration in gill and the lowest concentration in muscle. Bonded residues of metabolites can be detected for at least 4 weeks after administration in muscle, skin, liver and gill. The concentrations of residual bonded metabolites were higher than non-bonded metabolites in gill and muscle besides liver during depletion periods. After bathing medication, there were more residual nitrofurans and corresponding metabolites in sea water tilapia than fresh water group, because sea water fish survives in high osmotic condition to reduce their urination. Nitrofurans and metabolites were deconstructed by enzyme in gills, livers, intestines and muscles. Then tissues of fish accumulated nitrofurans and metabolites soon after medication. The maturity of fish is one of facters to effect different residual concentration during depletion periods. Liver is the main tissue to deconstruct nitrofurans and metabolites for the bathing medication and intestine is the major tissue to decompose antibiotics for the feeding medicaton.
In this research, we built a completed way to determine nitrofurans and corresponding metatbolites. Comparation of fish in different conditions and different medicative ways were in this investigation. These results could be helpful for aquacultures and government institutions.