Determination of N-methyl-1,3-propanediamine in bovine muscle by liquid chromatography with triple quadrupole and ion trap tandem mass spectrometry detection.

Morantel, pyrantel and their drug-related metabolites in food of animal-origin are regulated as sum of residues which may be hydrolysed to N-methyl-1,3-propanediamine (NMPA). In this study, an isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method with pentafluoropropionic acid anhydride (PFPA) derivatization was developed for the determination of NMPA in bovine muscle. A stable isotope labeled internal standard N-methyl-d(3)-3,3'-d(2)-propane-1,3-diamine (NMPA-d(5)) was synthesized as internal standard. NMPA was derivatized with PFPA to form an N,N'-bis (pentafluoroacyl) derivative (NMPA-PFPA) and analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS/MS) and liquid chromatography ion trap mass spectrometry (LC-IT-MS/MS) using negative ion electrospray ionization (ESI). Chromatographic behavior of several perfluorocarboxylic acid anhydride derivatives of NMPA and other structurally related diamines on C-18 and perfluorophenyl (PFP) columns was studied. Conversion of the parent drugs to NMPA under various hydrolysis conditions was evaluated. In addition, comparison of the matrix effect and linearity with isotopically labeled internal standard (I.S.) and analogous I.S. were performed and investigated. The method was validated using fortified bovine muscle samples. The apparent recovery (obtained after correction with an isotopically labeled I.S.) was between 89% and 97% and repeatability was less than 10%. The lowest LOD and LOQ (0.42 and 1.39µg/kg, respectively) were obtained with LC-QqQ-MS/MS.

Morantel tartrate release from a long-acting intraruminal device in cattle: pharmacokinetics and gastrointestinal distribution.

The pharmacokinetics and gastrointestinal distribution of morantel tartrate release from a sustained release trilaminate bolus in cattle were investigated over a 98-day period post-treatment. Six Holstein calves (125-150 kg) had permanent indwelling fistulae surgically inserted into the rumen, abomasum and terminal ileum. Samples of jugular blood, feces and ruminal, abomasal and ileal fluids were taken on days -3, 1, 4, 7, 10, 14 and weekly up to 98 days post-bolus administration. Morantel tartrate concentrations were measured by HPLC after extraction and clean-up. Morantel was not detected in plasma at any time after bolus administration. High concentrations of morantel tartrate were found in ruminal, abomasal and ileal fluids and feces over 98 days post-treatment. The morantel peak concentration (Cmax) was achieved at Day 1 post-administration in each of these compartments. The steady-state morantel concentration (Css) was achieved at approximately 10 days post-treatment and maintained for 91-98 days post-treatment in these gastrointestinal compartments. The morantel Cmax, Css, area under the zero (AUC) and first moment (AUMC) of the concentration-time curve were significantly higher (P less than 0.01) in feces than in other compartments. The in vivo drug release profile of this device has been determined. Steady-state concentrations for from 91 to 98 days have been confirmed.

Liquid chromatographic determination and identification of morantel-related residues as precursors of 3-(3-methyl-2-thienyl) acrylic acid (CP-20,107) in bovine milk.

A simple liquid chromatographic (LC) method was developed to determine and identify incurred morantel-related residues in bovine milk by converting them to 3-(3-methyl-2-thienyl) acrylic acid (CP-20, 107). Key techniques in this method involve short-term digestion of milk in HCl to release residues convertible to CP-20, 107, isolation and alkaline hydrolysis of these precursors to CP-20, 107, and recovery of the product for LC analysis. Photochemical conversion of CP-20, 107 to its cis-isomer and separation by LC identifies the residue. A homolog (pyrantel), which is used as an internal standard, is hydrolyzed to 3-(2-thienyl) acrylic acid. These acrylic acid isomers are readily resolved by LC. The method was evaluated over the 1-4 ppb (ng/mL) range for accuracy and precision to assess its utility for withdrawal studies. Bovine milk supplemented with morantel at 1, 2, and 4 ppb and assayed in replicate (n = 7-8) over 4 trials gave mean values and standard deviations of 1.0 +/- 0.11, 2.0 +/- 0.24, and 4.0 +/- 0.44 ppb, respectively. A milk specimen containing physiologically incurred residues of morantel assayed 2.1 +/- 0.19 ppb in replicate (n = 5).

Determination of depletion and statistical distribution of morantel-related residues in bovine milk following administration of morantel tartrate to dairy cows.

Residue depletion studies were conducted in dairy cattle to monitor morantel-related residues in milk following oral administration of morantel tartrate (Rumate. Eleven lactating cows of various ages, periods of lactation, and known milk production were orally dosed with the bolus formulation of morantel tartrate with an actual dose range of 8.4-9.8 mg/kg body weight. Representative samples of milk were collected at 10-14 h intervals post-dose, and subsamples were assayed for the major and minor hydrolysis products of morantel-related residues, MAPA and CP-20,107. Residues assayed as precursors of MAPA peaked at the second milking (24 h post-dose) and were below 25 ppb (range: less than 12-24 ppb). Precursors of CP-20,107, which confirm the identity of morantel, also peaked at 24 h post-dose (range: 2.1-3.3 ppb) and declined rapidly thereafter. A statistical model was used to project the level of residues at the upper limit of 99% of the total target animal (i.e., dairy cattle) population with 95% confidence. The calculated peak levels from this model were 50 and 5.0 ppb for morantel-related residues convertible to MAPA and CP-20,107, respectively.

Determination of morantel-related residues in bovine milk by electron capture gas chromatography.

A gas chromatographic assay was developed to determine major residues of morantel in bovine milk over a range that is suitable for monitoring residues of the drug. The method is based on hydrolysis of the N-methyl-tetrahydropyrimidine portion of morantel and its metabolites to N-methyl-1,3-propanediamine, and converting the diamine to an N,N-bis-(2-nitro-4-trifluoromethylphenyl) derivative. The addition of an internal standard, the N-desmethyl-N-ethyl homolog of pyrantel, to the milk sample circumvents any potential problem that could arise from variable reaction yields, and eliminates the true recovery as a factor affecting the accuracy and precision of the procedure. The concentrations of the derivatives are determined by pulsed electron capture gas chromatography over a linear dynamic range that is equivalent to 12.5-50 ppb morantel. The method was evaluated at the 0, 12.5, 25, and 50 ppb levels in fortified bovine milk, and in a withdrawal sample containing physiologically incurred morantel residues. Mean values of 14 +/- 1.7, 24 +/- 3.7, and 47 +/- 6.9 were found for the fortified samples, approximately 3 ppb for control milk, and 16 +/- 1.7 ppb for the withdrawal sample.

Liquid chromatographic determination of morantel tartrate in cattle feed.

A liquid chromatographic (LC) method is proposed for measuring 0.485-0.970% morantel tartrate in cattle feeds. The drug is leached from feed, diluted, separated from interfering substances on a silica column, and measured in the effluent stream by 313 nm spectrophotometric detection. Two potential degradation products, i.e., cis-isomer of morantel tartrate and N-(3-methylaminopropyl)-trans-3-(3-methyl-2-thienyl)acrylamide, and a related anthelmintic, i.e., pyrantel tartrate, do not interfere. Average recovery of drug from liquid spiked samples and laboratory blends was 98-100% with a maximum coefficient of variation (CV) of 2.3%. Results for pelleted and crumbled commercial scale feeds ranged from 94 to 102% of label claim, with a maximum CV of 1.5%.

Identification and confirmation of pyrantel- and morantel-related residues in liver by gas chromatography-mass spectrometry with selected ion monitoring.

A gas chromatographic-mass spectrometric method with selected ion monitoring (GC/MS-SIM) is described for identification of pyrantel- and morantel-related residues in swine and beef liver. Alkaline hydrolysis of tissue liberates and converts pyrantel- and morantel-related residues to 3-(2-thienyl)-acrylic acid (TAA) and 3-(3-methyl-2-thienyl)-acrylic acid (MTAA), respectively. These thienyl acrylic acids are recovered by ion exclusion chromatography and converted to methyl ester derivatives (TAAE and MTAAE) for identification by GC/MS-SIM. When the relative intensities of the molecular ion, the base peak, and a third significant ion of the sample correspond to ion intensities of the preformed or processed standards, the identity of the residue is confirmed. The method was validated by analysis of swine and beef liver samples containing incurred residues of pyrantel and morantel under withdrawal conditions.

Electron capture gas-liquid chromatographic determination of morantel-related residues in bovine liver.

A gas-liquid chromatographic assay has been developed to determine major residues of morantel in bovine liver, a target tissue, at levels of 0.2-0.8 ppm. The method is based on hydrolysis of the N-methyltetrahydropyrimidine portion of morantel and its metabolites to N-methyl-1,3-propanediamine, and conversion of the diamine to an N,N'-bis-(2-nitro-4-trifluoromethylphenyl) derivative. The addition of an internal standard, N-ethyl-1,3-propanediamine, to the tissue sample circumvents any potential problem that could arise from variable reaction yields, and eliminates the true recovery as a factor affecting the accuracy and precision of the procedure. The concentrations of the derivatives are determined by pulsed electron capture gas-liquid chromatography over a linear dynamic range equivalent to 0.2-0.8 ppm morantel. The method has been evaluated at 0, 0.2, 0.4, and 0.8 ppm levels in fortified bovine liver, and in a withdrawal sample containing physiologically incurred morantel residues. Mean values of 0.22 +/- 0.015, 0.40 +/- 0.033, and 0.79 +/- ppm were found for fortified samples, 0.02 ppm for control liver, and 0.56 +/- 0.050 ppm for the withdrawal sample.