This study aims to establish a modified analytical method with sensitivity and reliability for streptomycin (STP) and dihydrostreptomycin (DHS) of residues level in pig tissues, plasma and urine by LC-MS/MS on the basis of previous studies. The mass parameters of quantitative and qualitative ions for STP and DHS were optimized using multiple reaction monitoring in positive mode. The separation of compounds was conducted using BEH Amide column according to material’s characteristics. The analytes in plasma were extracted with only organic solvents. In muscle and kidney, KH2PO4 buffer solution containing 2% CCl3COOH and EDTA-Na was used as extraction solvent. The WCX cartridege was selected as SPE cartridge in considering high recoveries for STP and DHS. The analytes in urine were extracted by organic solvents with acid and addition of EDTA. The limits of detection (LODs) in STP and DHS ranged 0.45~3.66 μg/kg and 0.22~0.78 μg/kg, respectively. The limits of quantification (LOQs) were 1.35~11.10 μg/kg in STP and 0.66~2.36 μg/kg in DHS. The recoveries (%) were 94.29~104.5% in STP and 92.32~108.45% in DHS except for plasma with lower values (61.45/68.5%, respectively). In the precision evaluation, the coefficient of variation (CV, %) of STP showed <10.50% on intra-day and <18.04% on inter-day. The CV (%) of DHS showed <8.42% on intra-day, whereas <17.98% on inter-day. The modified method is reliable for continuous residual monitoring in pig to ensure food safety for consumer’s health. In addition, this method could be used in study relation to residue depletion and pharmacokinetics of veterinary drug.

A reliable and selective liquid chromatography–ultraviolet detection method for determination of antiprotozoals (selamectin, doramectin and fenbendazol) has been described. HPLC separation of active constituents was achieved on various C18 columns using methanol, acetonitrile, 0.1% phosphoric acid, acetic acid and distilled water as mobile phase, with UV detection at 243, 245 and 224 nm. The analytical procedure has been successfully identified. The method was validated for specificity, linearity, accuracy, repeatability and intermediated precision. All calibration curves showed good linearity (R2 of 0.9999) within the concentrations ranges (0~200, 0~200 and 50~400 μg/mL). The accuracy and repeatability showed 99%, 100%, 100% and below 0.4%, 0.5%, 0.6%, respectively. The precision tests conducted for 3 days in three different concentrations with standard also revealed below 3.5%, 2.4% and 2.7%. The method has also been applied successfully to monitor post-market 5 veterinary products of which active ingredient are selamectin, doramectin and fenbendazol. There were no non-compliant products.

As veterinary medicine industry has grown up steadily, the government quality control of veterinary medicine in market has been performed since 1964. The result of post-market surveillance assay from 2009 to 2012 was analyzed in this study. The average violation rate of all veterinary medicines, was 3.2%, 2.8%, 2.8% and 1.4% in 2009, 2010, 2011 and 2012, respectively. The total average violation rate in the category of antibiotics, other drugs except antibiotics, biologics were 1.2%, 4.4% and 0.8%, respectively. The violations due to insufficiency of major active ingredient content occupied 76.7% among the total violations. The most frequent violated in antibiotics were ampicillin and tylosin, followed by sulfonamides, penicillins etc. In case of other drugs except antibiotics, vitamin A and glucocorticoids (dexamethasone and prednisolone) were violated frequently. The overall trend of violation rates gradually decreased from 2009 to 2012, suggesting that quality of veterinary medicines has improved according to Korea Veterinary Good Manufacturing Practice (KVGMP) system settled down in 1988.