Nickos A. Botsoglou

Determination of the marker residue of albendazole in milk using ion-pair liquid chromatography and fluorescence detection

Abstract A simple, rapid, and sensitive ion-pair liquid Chromatographic (LC) method for the determination of the sulphoxide, sulphone and 2-aminosulphone metabolites that comprise the marker residue of albendazole in milk has been developed. Samples are made alkaline with sodium hydroxide solution and extracted with ethyl acetate, and the extracts are cleaned-up by partition with water. Chromatographic separation of the analytes is performed isocratically in presence of both positive and negative pairing ions, while detection is carried out fluorometrically using excitation and emission wavelengths of 290 and 320 nm, respectively. The method shows accuracy and precision figures well within acceptable limits. Overall recoveries were 85.3 ± 9.0%, 96.4 ± 6.2% and 83.4 ± 7.5% for the sulphoxide, sulphone and 2-aminosulphone metabolites, respectively, while precision data, based on within- and between-days variation, suggested overall relative standard deviation values ranging from 2.9% to 6.0%. The good analytical characteristics of the method could allow limits of detection in the low ng ml −1 range to be realised. The method was successfully applied to determine total residues in milk of a dairy cow treated with albendazole and, also, to study the stability of the residues with storage.

Ion-Pair Isolation and Liquid Chromatographic Determination of Albendazole, Oxfendazole, Oxibendazole, and Thiabendazole Residues in Milk

Abstract A liquid chromatographic [HPLC] method for the determination of Albendazole (ABZ), Oxfendazole (OFZ), Oxibendazole (OXBZ), and Thiabendazole (TBZ) residues in milk at levels below 3 ppb has been developed. Samples were deproteinized with acetonitrile, defatted with hexane partition, and evaporated to constant volume. Following addition of acidified aqueous octane-1-sulfonate solution, the target benzimidazoles were selectively extracted as ion pairs into chloroform and analyzed on a reversed-phase C18, 5 μm, column. Overall recoveries were found to be 93.5 ± 2.6% for OFZ, 90.0 ± 1.3% for OXBZ, 85.7 ± 3% for ABZ, and 74.0 ± 2.6% for TBZ. Limited data on the depletion of OXBZ and ABZ in sheep milk were also generated.

Trace analysis of albendazole and its sulphoxide and sulphone metabolites in milk by liquid chromatography

Analytical methodology for determination of albendazole and its sulphoxide and sulphone metabolites in milk at levels down to 2-5 ng/ml has been developed. Extraction was carried out with ethyl acetate under alkaline conditions, and extracts were analyzed on a silica-based C18 column in the presence of positively-charged pairing ions. Accuracy data showed overall recoveries ranged from 78.4% to 100%, whereas precision data, based on within and between-day variation, suggested overall precision values better than 4.9%. The method was successfully applied to determine residues in milk of a dairy cow orally given albendazole.

Liquid Chromatographic Analysis of Multiple Sulfonamide Residues in Chicken Muscle Using Pre-Column Derivatization and Fluorescence Detection

Abstract A rapid liquid chromatographic (LC) method is described for the quantitation of sulfadiazine, sulfamethazine, sulfadimethoxine, and sulfaquinoxaline residues in chicken muscle. The sulfonamides are extracted with chloroform, partitioned into hydrochloric acid, and submitted to pre-column derivatization with fluorescamine. LC analysis of the fluorescent derivatives is performed on a C18 column using a mobile phase of acetonitrile /20 mM phosphate buffer pH 4, (34/66, v/v), containing 20 mM octanesulfonate sodium salt. Owing to the sensitivity and selectivity of the fluorescence detection, residue levels of as low as 3 ng/g for sulfadiazine, 4 ng/g for sulfamethazine, 9 ng/g for sulfadimethoxine, and 40 ng/g for sulfaquinoxaline could be readily determined in chicken muscle. Overall recoveries were found to be 77.7±4.8% for sulfadiazine, 84.6±4.2% for sulfamethazine, 92.3±4.1% for sulfadimethoxine, and 82.5±7.0% for sulfaquinoxaline. The linearity of the method was quite acceptable in the range exa...

Albendazole-related drug residues in milk and their fate during cheesemaking, ripening, and storage.

The level and nature of the albendazole residues in milk of treated cows were determined as a function of the time of milking (12-h intervals), and the fate of those residues during cheesemaking, ripening, and storage was examined when the obtained milk was used for making Teleme cheese. Ion-pair liquid chromatographic analysis with fluorescence detection showed that the albendazole sulfoxide metabolite reached its maximum (523 +/- 199 micrograms/kg) at the 1st milking and declined below the detection limit by the 4th milking. The sulfone metabolite attained its highest level (812 +/- 99 micrograms/kg) more slowly (at the 2nd milking) and declined below detection limit by the 13th milking. The 2-aminosulfone metabolite, which was present in the milk obtained at the 1st milking, reached its maximum (128 +/- 36 micrograms/kg) at the 3rd milking, and slowly declined to a level below detection limit by the 15th milking. Whey and cheese analysis revealed that about 70% of each major metabolite initially present in milk could be distributed in the whey. The remaining 30% occurred in the cheese at residue levels higher than those initially present in the milk of the 1st or 2nd milking (688 versus 445 or 450 versus 230 micrograms/kg for albendazole sulfoxide; 890 versus 608 or 1502 versus 783 micrograms/kg for albendazole sulfone; 19 versus 15 or 161 versus 105 micrograms/kg for albendazole 2-aminosulfone). Ripening and storage of the cheeses made from milks from the 1st or 2nd milkings results in a decrease of the sulfoxide metabolite (to 225 or 206 micrograms/kg), an increase of the sulfone metabolite (to 1,181 or 1,893 micrograms/kg), and no effect on the 2-aminosulfone metabolite.

Retention behavior of multiple sulfonamides in various liquid chromatographic systems

SummaryThe retention behavior of a series of sulfonamides differing in molecular size and polarity has been studied under various chromatographic conditions. The influence on retention of inorganic buffers and of negatively or positively charged pairing ions has been examined, as has the effect of column temperature. The results showed that marked improvements in selectivity with alterations in elution order can be achieved by changing the ionic state of the solutes, the concentration of the inorganic buffer, the type and concentration of the pairing ion, and the temperature of the column.

Rapid extraction and ion-pair liquid chromatographic determination of fenbendazole in poultry feeds.

A liquid chromatographic method is described for the determination of the fenbendazole anthelmintic in poultry feeds at levels as low as 0.5 μg/g. Sample is extracted with acetonitrile, and an aliquot of the extract, after partitioning with isooctane, is evaporated to dryness, reconstituted with mobile phase, and analyzed by ion pair liquid chromatography with detection at 300 nm. The method presents quite acceptable analytical characteristics yielding recoveries in the range of 95.8–99.8% for broilers, laying hens, and turkeys diets. Precision data, based on within- and between-days variation, suggested an overall relative standard deviation of 1.9%.

Chromatographic Behavior of the Anthelmintic Fenbendazole and Its Major Metabolite Oxfendazole in Various Ion-Pair Liquid Chromatographic Systems

Abstract The chromatographic behavior of fenbendazole (FBZ) and oxfendazole (OFZ) in various reversed-phase liquid chromatographic (LC) systems has been investigated. The addition of negative and/or positive charged ion-pair reagents in the mobile phase has been examined, whereas the influence of mobile phase pH, mobile phase composition, and column temperature on retention and peak height has been evaluated. The observed behavior of the analytes during the various chromatographic processes has been discussed.

ION-PAIR LIQUID CHROMATOGRAPHIC DETERMINATION OF ALBENDAZOLE IN CATTLE FEED

A liquid chromatographic method is described for the determination of albendazole in cattle feeds. Samples are extracted with acetonitrile, and the extracts, after partitioning with hexane, are analyzed by ion-pair liquid chromatography with detection at 292 nm. Albendazole is eluted from the column well resolved from its oxidation byproducts. The method shows analytical characteristics well within acceptable limits. Recovery was in the range of 98.2–100.4%, while precision, expressed as percent relative standard deviation, in the range of 1.6–3.1%. Limit of detection was estimated at 0.5 μg/g, and limit of determination at 1.0 μg/g.

Retention behaviour of the sulphoxide, sulphone and 2-aminosulphone metabolites of albendazole in ion-pair liquid chromatography

Abstract The chromatographic behaviour of the sulphoxide, sulphone and 2-aminosulphone metabolites of albendazole has been investigated as a function of the pH and the type and concentration of the pairing ions added to the mobile phase. Experiments were carried out using both tetrabutylammonium cations and octanesulphonate anions as pairing agents. The results showed that improvements of peak shape and marked differences in selectivity with alterations in elution order can be achieved by changing the ionisation state of the solutes and the type and the concentration of the pairing ion in the mobile phase. Although it was clear that at pH 2.3 the tetrabutylammonium cations exerted the conventional effect of a competing base whereas the octanesulphonate anions the conventional effect of a pairing agent, the lack of quantitative correlation and the exceptions at pH 7.4 indicated that the retention mechanisms may be more complex.