LC-MS/MS measurement of ampicillin residue in chicken tissues at 2 days after in-feed administration.

We assessed ampicillin (ABPC) concentrations of liver, kidney and skin at a 2-day withdrawal period in ten male and ten female White Leghorn chickens fed the diet containing ABPC (ABPC medicated feed 40 mg/kg body weight/day) for a week. The ABPC residues were measured with liquid chromatography-tandem mass spectrometry and the mean recoveries and quantitation limits ranged from 93.0% to 102.7% and from 0.1 to 1.4 ng/g, respectively. The residual ABPC concentrations were ≤7.82 ng/g for the skin and ≤0.64 ng/g for the kidney, suggesting below the Japanese provisional maximum residue limits. These results revealed that the analytical method is developed for residue ABPC and that the withdrawal period is appropriate.

Measurement of ampicillin residue levels in chicken eggs during and after medicated feed administration by LC-MS/MS.

A simple and sensitive LC-MS/MS method was developed and validated for the determination of ampicillin (ABPC) in chicken eggs. Residues were extracted by reverse-phase solid-phase extraction. Chromatographic separation was performed using a reverse-phase column with an elution gradient. The limits of detection and quantification were 0.01 and 0.1 ng g(-1), respectively. For the 0.1-50 ng g(-1) concentration range, mean recovery and accuracy values were 93.9-98.5% and 100.2-118.0%, respectively. ABPC residue concentrations in eggs before, during and after 7 days of medicated feeding of maximum dosage (40 mg kg(-1) body weight day(-1)) of ABPC were determined with the LC-MS/MS method. The maximum concentration of ABPC in eggs was 3.6 ± 1.7 ng g(-1) (mean ± SD) on the last day of the administration period. Residue concentrations of ABPC in eggs during and after ABPC administration were not over the Japanese maximum residue limit of 0.01 mg kg(-1).

LC-MS/MS measurement of ampicillin residue in swine tissues at 5 days after in-feed administration.

We assessed ampicillin (ABPC) concentrations of kidney, muscle and intestine after a 5-day withdrawal period in 2 male and a female young Large White pigs fed the diet containing ABPC (ABPC medicated feed, 24 mg/kg/day) for a week. The ABPC residues were measured with liquid chromatography-tandem mass spectrometry, and the mean recoveries and quantitation limits ranged from 91.8 to 97.2% and from 0.1 to 0.12 ng/g, respectively. The residual ABPC concentrations were ≤1.18 ng/g for the muscle, ≤0.53 ng/g for the kidney and ≤1.93 ng/g for the intestine, suggesting below the Japanese provisional maximum residue limits. These results reveal that the analytical method is developed for residual ABPC and that the withdrawal period is appropriate.

Pharmacokinetics of metoclopramide in calves with renal dysfunction.

To clarify the effect of renal dysfunction on pharmacokinetics of the prokinetic agent metoclopramide (MCP), we administered intravenously 0.4 mg/kg MCP to healthy calves and calves subjected to right kidney vessel ligation (ligation) without or with a subsequent left nephrectomy (ligation plus removal). Plasma MCP concentration, glomerular filtration rate (GFR) and plasma prolactin level were measured by liquid chromatography-tandem mass spectrometry, simplified equation using iodixanol and enzyme-linked immunosorbent assay, respectively. Only in calves with ligation plus removal, plasma MCP concentrations were increased significantly 6, 8 and 12 hr after injection, showing that a negative correlation was observed between the plasma MCP concentrations and GFR value. A tendency to increase in plasma PRL concentration was noted also in these calves. In conclusions, plasma MCP concentrations depend on the GFR mode in calves, and its critical GFR value was estimated.

Simple and sensitive method for measurement of metoclopramide in cattle plasma by LC-MS/MS using a multimode chromatography.

A quantitative assay method using LC/ESI-MS/MS for simultaneous determination of MCP in cattle plasma was developed and validated. Chromatographic separation was carried out using a multimode column (2 × 150 mm, 3 µm) with gradient elution (0.05% formic acid/methanol with 0.05% formic acid). MCP and levosulpiride (internal standard) were analyzed in the precursor/product ion pair of m/z 300.1/226.9 and 342.0/112.0, respectively. Linear calibration curves were obtained in the range of 2.5-500 ng/ml (R(2)>0.999) with a lower limit of quantification of 0.05 ng/ml. Mean recoveries were 96-103%, and the coefficient of variation was less than 6.5%. Plasma MCP concentrations after intravenous administration at 0.4 mg/kg to 12 cattle were determined by the LC-MS/MS method.

[Determination of glycarbylamide based on formation of nickel chelate].

A new and simple analytical method for glycarbylamide (GB) based on the formation of nickel chelate was developed. The proposed method is as follows: sample solution is mixed with 0.08 mmol/L nickel nitrate in 0.2 mol/L carbonate buffer (pH 9.0), and the absorbance is measured at 290 nm. Under the optimal conditions, GB could be determined in the concentration range from 0.13 microg/mL to 2.6 microg/mL (r = 0.9999). Using this method for HPLC post column reaction, GB levels in chicken liver extracts could be determined. The recovery of GB was 79.4% (RSD=2.6%, n=3) and the quantitation limit was 30 ng/g. The apparent molar extinction coefficient (epsilon) of the GB-nickel complex was 8.5 x 10(3). The molar ratio of the complex is GB: nickel ion = 2:1.

[Residue analysis of metoclopramide in bovine and swine tissues by HPLC and administration experiment].

A reversed-phase ion-pair HPLC method with ultraviolet detection has been developed for determination of metoclopramide (MCP) in bovine and swine muscle, liver, kidney, fat and intestine. MCP was extracted from samples with acetonitrile, and the extracts were cleaned up on an Oasis HLB cartridge (60 mg) after liquid-liquid extraction. The limit of detection of MCP was 0.002 microg/g and the limit of quantitation was 0.007 microg/g. Recoveries of MCP spiked at 0.03 ppm ranged from 74.1 to 93.3% for bovine tissues and from 86.1 to 92.7% for swine tissues. The present method was used for the analysis of bovine and swine tissues 1 day after withdrawal following drug administration. The MCP concentrations in all tissues were lower than the Japanese provisional MRLs.

[Determination of glycarbylamide residues in chicken tissues by HPLC with post-column reaction].

A newly developed HPLC method for determination of glycarbylamide (GB) in chicken liver was applied to other tissues (muscle, fat and kidney). The recoveries of GB in muscle, fat and kidney were 87.2% (CV 0.5), 91.3% (CV 4.7), 79.7% (CV 1.0), respectively. The detection limit of GB was 0.01 ppm. GB concentrations were determined by this method in tissues (muscle, fat, liver and kidney) from chickens sacrificed 5 days after oral administration of GB mixed in feed at 60 mg/kg of feed for 7 days. GB was not detected in these chicken tissues.

[Residue analysis of spectinomycin in tissues of chicken and swine by HPLC].

A reversed-phase HPLC method with ultraviolet detection using p-nitrophenyl hydrazine as a pre-column derivatizing reagent was investigated for the determination of the antibiotic spectinomycin (SPCM) in muscle, liver, kidney and fat of chicken and swine. SPCM was extracted from samples with 10% trichloroacetic acid saturated with EDTA-2Na, and then cleaned up with coupled Sep-Pak Plus PS-2 cartridges. The detection limit of SPCM was 0.02 microgram (potency)/g. Recoveries of SPCM ranged from 77.4 to 97.4% for chicken tissues and from 74.5 to 91.8% for swine tissues. The present method was used for the analysis of chicken tissues after the 11th day of withdrawal (SPCM-medicated drinking water: 500 mg (potency)/L, for 7 days), and swine tissues after the 14th day of withdrawal (SPCM-medicated feed: 100 mg (potency)/kg, for 7 days). Results showed that SPCM concentrations were lower than the MRLs in all tissues.