Rapid Extrelut column method for determination of levamisole in milk using high-performance liquid chromatography

Liquid chromatographic method with ultraviolet absorbance detection for measurement of levamisole in chicken tissues, eggs and plasma

The development and validation of a high-performance liquid chromatographic and UV detection method was accomplished for quantitative determination of levamisole in chicken tissues, eggs and plasma. The chromatographic separation was achieved on Luna 5 microm C(18) column using a mobile phase of 0.2% acetic acid in water:methanol (50:50 (v/v)) and Pic B-7 low UV reagent and the pH was adjusted to 7.31 with ammonium hydroxide and UV wavelength was 225 nm. Limits of quantification were 0.025 microg/g for all tissues and 0.003 microg/ml for plasma. Limit of detection was 0.001 microg/g for tissues and plasma.

Determination of levamisole in animal tissues using liquid chromatography with ultraviolet detection

An efficient and sensitive liquid chromatographic method is described for the determination of the anthelminthic drug levamisole, in muscle, liver, kidney and fat of sheep, pigs and poultry, using thiabendazole as internal standard. Samples were extracted by homogenizing with chloroform, and were applied to Supelco Si solid-phase extraction columns and eluted with methanol. Chromatographic analysis was performed on a LiChrospher 60 RP-Select B column using methanol/ammonium acetate buffer 0.05 M (55/65, v/v) as mobile phase and reading at 220 nm. The quantification limit for the assay was 4 ng/g. Mean recoveries were about 84% for liver, 85% for kidney, 89% for muscle and 84% for fat. The assay has been used for statutory testing purposes.

Quantitative analysis of levamisole in porcine tissues by high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry

This work presents the development and the validation of an LC-MS-MS method with atmospheric pressure chemical ionization for the quantitative determination of levamisole, an anthelmintic for veterinary use, in porcine tissue samples. A liquid-liquid back extraction procedure using hexane-isoamylalcohol (95:5, v/v) as extraction solvent was followed by a solid-phase extraction procedure using an SCX column to clean up the tissue samples. Methyllevamisole was used as the internal standard. Chromatographic separation was achieved on a LiChrospher 60 RP-select B (5 microm) column using a mixture of 0.1 M ammonium acetate in water and acetonitrile as the mobile phase. The mass spectrometer was operated in MS-MS full scanning mode. The method was validated for the analysis of various porcine tissues: muscle, kidney, liver, fat and skin plus fat, according to the requirements defined by the European Community. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r>0.99 and goodness of fit <10%). Limits of quantification of 5.0 ng/g were obtained for the analysis of levamisole in muscle, kidney, fat and skin plus fat tissues, and of 50.0 ng/g for liver analysis, which correspond in all cases to half the MRLs (maximum residue limits). Limits of detection ranged between 2 and 4 ng/g tissue. The within-day and between-day precisions (RSD, %) and the results for accuracy fell within the ranges specified. The method has been successfully used for the quantitative determination of levamisole in tissue samples from pigs medicated via drinking water. Moreover the product ion spectra of the levamisole peak in spiked and incurred tissue samples were in close agreement (based on ion ratio measurements) with those of standard solutions, indicating the worthiness of the described method for pure qualitative purposes.

A highly sensitive gas chromatographic determination of levamisole in milk

An efficient extraction and sensitive gas chromatographic method is described for the determination of the anthelminthic drug levamisole in milk. Levamisole was extracted from alkaline milk with ethyl acetate. Clean-up of the extract was by a series of liquid-liquid extraction steps. Levamisole residues in the extract were determined by gas chromatography with a nitrogen-phosphorus detector. This method was satisfactory for determining levamisole residues in milk as low as 0.5 ng/g. Mean recoveries of 0.5-10.0 ng/g fortified milk samples ranged from 84.5 to 95.2%. Five replicate analyses performed on a milk containing incurred levamisole residues yielded a mean of 3.34 ng/g levamisole with a CV of 3.0%.

Analytical considerations for trace determinations of drugs in breast milk

Recent scientific and regulatory interest in lacteal excretion of drugs has prompted this review of bioanalytical sample preparation techniques for milk. The composition and properties of milk are reviewed, with emphasis on how the sample preparation is affected. The most important principals of mammary gland pharmacology, including protein binding, ion trapping and liquid solubility, are described. Because adequate milk volume is difficult to obtain from some smaller rodent species, special arrangements for sample collection, control preparation and assay standardization often need to be made. Several commonly-used sample preparation approaches for drugs in milk, including direct injection, dialysis and ultrafiltration, protein precipitation, liquid-liquid extraction, solid-phase extraction and immunoaffinity extraction. Have been reported with varying degrees of success. The advantages and disadvantages of each of these approaches is discussed.

The disposition of 14C-levamisole in the lactating cow

1. 14C-Levamisole 1(-)-2,3,5,6-tetrahydro-6-phenyl[U-14C]imidazo[2,1-b]-thiazole was administered orally and subcutaneously to lactating cows (8 mg/kg body weight). Urine, faeces, milk and blood samples were collected from 0-48 h after dosing and tissues were collected 48 h after dosing. 2. 14C-Labelled residues (ppm 14C-levamisole equivalents) in blood were highest at 3 h (2.2 ppm, oral dose) or 6 h (2.1 ppm, subcutaneous dose) and then declined to less than 0.5 ppm 48 h after dosing. 3. 14C-Labelled residues in milk were highest in samples collected from 0-12 h after dosing (1.55 ppm and 1.86 ppm of levamisole equivalents from oral and subcutaneously dosed animals, respectively) and declined to 0.06 ppm in milk collected from 36-48 h after dosing. Milk collected from 0-48 h after dosing accounted for 0.2% (oral dose) and 0.6% (subcutaneous dose) of the total 14C-activity administered as 14C-levamisole. The parent compound, 14C-levamisole, accounted for 12% or less (declined with time after dosing) of the total 14C-activity in the milk. Three 14C-labelled metabolites (formed by oxidation of imidazoline ring and/or opening of thiazolidine ring) in the milk were isolated and identified. 4. Urinary excretion accounted for 83% and 84% and faecal excretion accounted for 11% and 9% of the total 14C-activity given orally and subcutaneously, respectively, as 14C-levamisole. No 14C-levamisole was detected in the urine; the major urinary metabolite (formed by opening of thiazolidine ring) was isolated and identified. 5. The 14C-activity remaining in the animals 48 h after dosing was widely distributed in body tissues; however, the concentration in the liver was substantially higher than in all other tissues examined. Less than 5% of the 14C-activity in the liver was present as 14C-levamisole.

Analytical strategies for the screening of veterinary drugs and their residues in edible products

The development of analytical strategies for the regulatory control of drug residues in food-producing animals is discussed. Analytical methods for the determination of veterinary drugs in edible products are based on microbiological, immunochemical and physicochemical principles. Because of complexity of biological matrices such as egg, milk and meat, well designed, and often sophisticated, off-line or on-line sample treatment procedures are essential, especially when utilising physicochemical multi-residue screening procedures. Since large series of samples have often to be analysed, automation is increasingly becoming important. Confirmation of the identity of drug residues and validation of the analytical results implies the use of adequate analytical methods. In its turn, this requires well established criteria for those methods and/or equivalent reference methods.

Modified on-column interface for coupled high-performance liquid chromatography-gas chromatography and its application to the determination of levamisole in milk

A modified on-column interface is reported for the coupling of high-performance liquid chromatography with gas chromatography, incorporating an adapted, commercially available multidimensional gas chromatography switching system. Novel features include cryogenic analyte focusing, total solvent exclusion from the analytical column and independent carrier gas supplies to the analytical GC column and uncoated pre-column. The instrumentation was used for the determination of the veterinary anthelmintic drug levamisole in milk with analyte detection by both flame ionisation and nitrogen-phosphorus detectors. Detection limits for the assay were 2.2 micrograms l-1 and 0.4 micrograms l-1 by flame ionisation and nitrogen-phosphorus detectors, respectively. The assay was applied to a survey of fourteen milk samples from different dairy outlets.

On-line high-performance liquid chromatographic/gas chromatographic/tandem ion trap mass spectrometric determination of levamisole in milk

On-line high-performance liquid chromatography/high-resolution gas chromatography/tandem mass spectrometry, performed on a quadrupole ion trap, has been used as a rapid method for the quantification of the anthelmintic drug levamisole in raw milk extracts following a simple extraction procedure. Detection at the 0.5 p.p.b. level and a linear response in the 10-0.5 p.p.b. range is demonstrated. Multiple-scan monitoring techniques have been used to acquire chemical ionization tandem mass spectra and electron impact mass spectra in a single chromatographic run.

Determination of levamisole and thiabendazole in meat by HPLC and photodiode array detection

An HPLC method for the analysis of levamisole and thiabendazole has been developed with recoveries varying over 63-75%. The two anthelmintics are extracted from meat with ethyl acetate, purified by liquid/liquid extraction and analyzed quantitatively on a mu Bondapak C18 column. The optimum detection is achieved by means of a photodiode array detector at 240 nm for levamisole and at 300 nm for thiabendazole. The detection limits for both compounds in meat are 25 micrograms/kg and 5 micrograms/kg, respectively.

Levamisole residues in milk from a herd of cows suffering from lungworms

A single intramuscular dose of 7 mg levamisole hydrochloride per kg body weight was administered to a herd of 42 milking cows suffering from lungworms. Levamisole was rapidly excreted in the milk, the peak concentration being found 1 h after administration. The half-life of levamisole in milk was about 5 h. Levamisole levels were below the limit of determination (0.04 microgram/ml) in all milk samples 29 h after treatment.