Tissue residue regulatory method for the determination of lasalocid sodium in cattle liver using high-performance liquid chromatography with fluorometric detection

Determination of the ionophoric coccidiostats narasin, monensin, lasalocid and salinomycin in eggs by liquid chromatography/tandem mass spectrometry

A sensitive and selective liquid chromatographic tandem mass spectrometric method (LC/MS/MS) for the simultaneous detection of the ionophoric coccidiostats narasin, monensin, lasalocid and salinomycin in whole eggs has been developed. A very simple sample preparation consisting of an extraction with an organic solvent was carried out. Sample extracts were injected into the LC/MS/MS system on a C18 column and an isocratic elution was performed. Nigericin was used as internal standard. The precursor ions produced by electrospray positive ionisation were selected for collisional dissociation with argon into product ions. Validation of the methods was performed based on Commission Decision 2002/657/EC.1 CC(alpha) was found to be 1 microg/kg for all four compounds. Monitoring of Belgian egg samples in 2004 revealed that residues of salinomycin, lasalocid and monensin could be found.

Periodicity in collision-induced and remote-bond activation of alkali metal ions attached to polyether ionophores

The collision-induced dissociation of lasalocid and monensin A bound to alkali metal cations has been investigated using electrospray MS/MS. The binding affinity for the metal cations, as measured with collision-induced dissociation, was found to depend on their ionic radius, decreasing with increasing radius. Monensin A was observed to have a greater binding affinity for alkali metal cations than lasalocid acid.

Development of Monoclonal-based Enzyme-Linked Immunosorbent Assay and Immunochromatographic Assay for Lasalocid and Semduramicin

Monoclonal antibodies (MAbs) against lasalocid and semduramicin were prepared using keyhole limpet hemocyanin conjugates for the immunization of mice. With these MAbs, we developed quantitative enzyme-linked immunosorbent assay (ELISA) methods for lasalocid and semduramicin. The ELISAs were quantitative in the ranges of 0.1-50 ng/mL for lasalocid and 0.05-12.5 ng/mL for semduramicin, and showed 50% inhibition concentrations of 1.2 ng/mL for lasalocid and 0.5 ng/mL for semduramicin. The coefficient of variations (CV%) of lasalocid were 0.3-4.4% for intra-assay and 0.5-5.1% for inter-assay and those of semduramicin were 0.1-4.6% for intra-assay and 0.3-5.2% for inter-assay. The detection limits for lasalocid and semduramicin were 10 ng/g and 5 ng/g in chicken liver and muscle, respectively. Based on the immunochromatographic method, rapid test kits for lasalocid and semduramicin were also developed. With these kits, the detection limits of lasalocid were 50 ng/mL for standard solution and 125 ng/g for chicken muscle, and those of semduramicin were 10 ng/mL for standard solution and 100 ng/g for chicken muscle.

Determination of ionophores in the tissues of food animals by liquid chromatography

A liquid chromatographic method for determining residues of ionophores in bovine, porcine, and avian tissues is described. Tissues were extracted with iso-octane-ethyl acetate and the extracts purified on silica solid-phase extraction columns. Monensin, narasin and salinomycin were detected by UV absorbance following post-column derivatization with vanillin, and lasalocid was detected underivatized using fluorescence. In muscle, kidney and fat, all drugs were determined from a single sample extract. In liver, a separate extraction was done to determine lasalocid. The detection limit for lasalocid, narasin and salinomycin was 5 ppb; for monensin it was 2 ppb. Average recoveries were: lasalocid-71.0%; monensin-94.3%; salinomycin-97.2%; narasin-94.1%.

Determination of lasalocid in eggs using liquid chromatography-electrospray mass spectrometry

A method is presented for the determination of the polyether ionophore, lasalocid, in eggs. Samples are extracted under acidic conditions using acetonitrile and the extracts are cleaned up using a simple liquid-liquid extraction step. Lasalocid is detected and quantified using liquid chromatography-electrospray mass spectrometry on a quadrupole bench-top instrument. The technique is highly sensitive, with a detection limit of about 0.5 ng g-1 of lasalocid in homogenized egg samples.

Development of an ELISA for lasalocid and depletion kinetics of lasalocid residues in poultry

Polyclonal antibodies against the coccidiostat, lasalocid, were raised in sheep. The antisera were applied in an enzyme-linked immunosorbent assay (ELISA) for lasalocid, which was validated for chicken serum, liver and muscle. Bridge homology in the ELISA was overcome by absorbing unspecific antisera onto a conjugate between salinomycin and chicken serum albumin, which was immobilized onto Biosilon beads. The described assay is highly specific for lasalocid, and is capable of detecting lasalocid at concentrations of less than 0.15 ng/g, depending on the tissue. Residual concentrations of lasalocid in broilers fed medicated feed containing 90 mg/kg lasalocid were measured during a 7 day withdrawal period. The half-life of lasalocid was 11, 36 and 41 h in serum, liver and muscle, respectively. Lasalocid concentrations in liver were approximately 10 ng/g 7 days withdrawal of the medicated feed.

Improved high-performance liquid chromatographic procedure for the determination of lasalocid in chicken tissues and egg using polymeric and porous graphitic carbon columns

A high-performance liquid chromatographic (HPLC) method for the determination of the ionophore coccidiostat lasalocid in poultry muscle and eggs was developed. The drug was extracted from tissue with acetonitrile. The extract was partitioned between saturated salt and carbon tetrachloride and the organic layer evaporated to dryness. Clean-up was by solid-phase extraction on a silica column. HPLC analysis was carried out on either a polymeric PLRP-S or a porous graphitic carbon Hypercarb column with a basic mobile phase and fluorescence detection with excitation at 310 nm and emission at 420-430 nm. Average recoveries from poultry muscle at the 0.002, 0.010 and 0.050 mg kg-1 levels were 65.7, 72.0 and 77.9%, respectively. Average recoveries from egg at the 0.010 and 0.100 mg kg-1 levels were 76.2 and 76.4%, respectively.

Improvement of chemical analysis of antibiotics. XI. Simultaneous fluorodensitometric determination of polyether antibiotics

A simultaneous determination of three polyether antibiotics, salinomycin, monensin and lasalocid, was established by silica gel and RP-18 high-performance thin-layer chromatography (HPTLC) using 18,19-dihydrosalinomycin and 18,19-dihydro-20-ketosalinomycin as internal standards. Fluorescent derivatives of the polyethers were prepared by reaction of their sodium salts with 1-bromoacetylpyrene and Kryptofix 222 in acetonitrile. A silica gel HPTLC plate with carbon tetrachloride-ethyl acetate-acetonitrile (50:5:10) as a solvent system and a RP-18 HPTLC plate with dichloromethane-ethyl acetate-acetone-acetonitrile (15:2:1:55) gave satisfactory separations of the five pyrenacyl esters of salinomycin, monensin, lasalocid, 18,19-dihydrosalinomycin and 18,19-dihydro-20-ketosalinomycin. Under these conditions the internal standard 18,19-dihydrosalinomycin was found to be suitable for the simultaneous determination of salinomycin and monensin, and 18,19-dihydro-20-ketosalinomycin for lasalocid. A linear relationship was obtained between the fluorescence intensity and the amount of each antibiotic in the range 2-14 ng. The detection limit of the three antibiotics was 100 pg.

Determination of penicillin G and cloxacillin residues in beef and pork tissue by high-performance liquid chromatography

Tissues were homogenized and then deproteinized with acetonitrile. The acetonitrile extract was partitioned between dichloromethane and pH 2.2 buffer and then extracted with pH 7 buffer. After addition of ammonium sulfate to the aqueous solution, it was mixed with acetonitrile. The acetonitrile extract was separated and evaporated, and the residue was taken up in water. The aqueous solution was analyzed by high-performance liquid chromatography (HPLC) on a C18, 10-microns particle size, reversed-phase column using gradient elution with 0.01 M orthophosphoric acid-acetonitrile (from 80:20 to 40:60 in 20 min) at a flow-rate of 1 ml/min and UV absorbance detection at 220 nm. Recoveries were generally greater than 90% with all tissues. Data on incurred residues from a treated cow showed recoveries of penicillin which were frequently several times higher by HPLC than by bioassay. Sensitivity limits in muscle were about 0.05 ppm for both penicillin G and cloxacillin, but higher in liver and kidney because of interferences. The method is suitable for other monobasic penicillins but not for dibasic or amphoteric penicillins.