Detection of Multiple Antibiotic Residues in Turkish Pine and Blossom Honeys Using LC-MS/MS Method

Due to the high demand for honey, beekeepers often feed the bees with antibiotics to protect honeybees against illnesses; the determination of veterinary drugs and their residues in bee products especially in honey is gaining importance. In this study, commercially available 15 different brands, a total of 22 honey (14 blossoms and 8 pines) samples obtained from 5 chain supermarkets in the city of Bingöl and Diyarbakır, Turkey were analysed for 29 antibiotic residues. These antibiotics belong to 10 different categories, including tetracyclines, aminoglycosides, macrolides, sulfonamides, fluoroquinolones, benzimidazoles, anthelmintic, amphenicols, quinolines, and oxazolidines. For the qualitative and quantitative determination of the antibiotics, a triple quadrupole liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used. A total of 10 out of 22 honey (8 blossom, 57.14 % and 2 pine, 25 %) samples were found to be positive for antibiotics. Among the tested antibiotics, tetracycline, dihydrostreptomycin, streptomycin, erythromycin, and sulfadimidine were detected in the honey samples. Dihydrostreptomycin and sulfadimidine were detected in 6 samples, erythromycin was determined in 4 samples, streptomycin was found in 2 samples, and lastly, tetracycline was detected only in one sample. The highest and the lowest concentrations of antibiotics detected in the samples were dihydrostreptomycin and erythromycin found at the amount of 992.58 μg/kg and 0.77 μg/kg respectively. The proposed method was validated with a limit of quantification (LOQ) and limit of detection (LOD) ranging between 0.42 and 3.22 μg /kg and 0.13-0.97 μg /kg respectively. Good linearities were also achieved ranging between R2 =0.987 and 0.999.

Streptomycin and dihydrostreptomycin residues in bovine milk from the Brazilian retail market

Pasteurised bovine milk from retail markets in the State of São Paulo, Brazil, was analysed for the presence of streptomycin (STP) and dihydrostreptomycin (DHSTP) residues. An ELISA kit was used for screening and a LC-APCI-MS/MS QToF method for confirmatory analysis. Both methods were intra-laboratory validated and found suitable for screening and confirmatory testing, respectively, for STP and DHSTP residues in pasteurised bovine milk at concentration levels below the maximum residue limit (MRL) established for these substances (200 µg kg(-1) expressed as the sum of the concentrations of STP and DHSTP). No residues of STP and DHSTP at detectable levels were found in the analysed samples (n = 299).

LC-MS of streptomycin following desalting of a nonvolatile mobile phase and pH gradient

Streptomycin (SM) is composed of streptidine, streptose and N-methyl glucosamine sugar moieties. For the determination of SM and its related substances, an ion-pair LC-UV detection method using a Supelcosil LC-ABZ column was developed previously. While analyzing commercial samples, several unknown compounds were detected. Most of these compounds are not yet characterized. In this study, the above LC method was coupled to MS for impurity profiling in a selected commercial sample. However, it could not be directly coupled to MS due to the presence of the nonvolatile salt, buffer and ion-pair reagent in the mobile phase. So, for structural characterization, each peak eluted from the nonvolatile eluent system was collected and transferred to MS after the desalting process. In total, 16 compounds were studied, 15 compounds including 12 unknowns could be identified.

Multi-residue quantitation of aminoglycoside antibiotics in kidney and meat by liquid chromatography with tandem mass spectrometry

Quantitative methods using liquid chromatography coupled with tandem mass spectrometry were developed for seven kinds of aminoglycoside antibiotics in kidney and muscle tissues. Mass spectral acquisition was performed in the positive-ion mode by applying multiple reaction monitoring. Liquid chromatographic separation employed a ZIC-HILIC column (SeQuant) for hydrophilic interaction chromatography. Extraction of the aminoglycosides was performed using liquid extraction with a phosphate buffer containing trichloroacetic acid, followed by a solid-phase clean-up procedure on a weak cation-exchange column with carboxypropyl (CBX) SPE cartridge (Mallinckrodt Baker). The limits of quantification were 25 ng g(-1) for gentamicin, 50 ng g(-1) for spectinomycin, dihydrostreptomycin, kanamycin and apramycin, and 100 ng g(-1) for streptomycin and neomycin. These are well below the maximum residue limits set by the Codex Alimentarius Commission. The recoveries of all compounds from all tissues fortified at the level of quantification limits of 500 and 1000 ng g(-1) were >70%, and the variability (relative standard deviation) was generally <12%.

Characterization of dihydrostreptomycin-related substances by liquid chromatography coupled to ion trap mass spectrometry

Dihydrostreptomycin sulphate (DHS) is a water-soluble, broad-spectrum aminoglycoside antibiotic. For quantitative analysis, the European Pharmacopoeia (Ph. Eur.) prescribes an ion-pairing liquid chromatography/ultraviolet (LC/UV) method using a C18 stationary phase. Several unknown compounds were detected in commercial samples. Hence, for characterization of these unknown peaks in a commercial DHS sample, the Ph. Eur. method was coupled to mass spectrometry (MS). However, since the Ph. Eur. method uses a non-volatile mobile phase, each peak eluted was collected and desalted before introduction into the mass spectrometer. The desalting procedure was applied to remove the non volatile salt, buffer and ion-pairing reagent in the collected fraction. In total, 20 impurities were studied and 14 of them were newly characterized. Five impurities which are already reported in the literature were also traced in this LC/UV method.

Micro-scale analysis of aminoglycoside antibiotics in human plasma by capillary liquid chromatography and nanospray tandem mass spectrometry with column switching

A simple liquid chromatographic method combined with tandem mass spectrometry (LC-MS-MS) is described for the analysis of aminoglycoside antibiotics. Clinically these antibiotics may cause both ototoxicity and nephrotoxicity; therefore, the monitoring of aminoglycoside levels in patient plasma is required for protecting human health. In this study separation of the method is based on ion-pair chromatographic technology on a short capillary reversed-phase C18 column. The method was successfully applied to analyze amikacin in human plasma. In human plasma after deproteinisation with HFBA, an aliquot of 1 microL supernatant was injected into the chromatographic system. Only a small amount of plasma sample, 10 microL, is sufficient for the monitoring of amikacin levels in clinically therapeutic range. The relative standard deviations (RSD) of the method for intra- and inter-day analyses (n=5) are less than 5.8%. Application of this method for the trace analysis of amikacin in human plasma proved simple and workable.

Quantitative determination of dihydrostreptomycin in bovine tissues and milk by liquid chromatography-electrospray ionization-tandem mass spectrometry

Dihydrostreptomycin (DHS) is an aminoglycoside antibiotic used in veterinary medicine in combination with benzylpenicillin for the treatment of bacterial infections in cattle, pigs and sheep. A method to determine its residues in edible tissues of cattle, as well as in milk, was developed and validated. Extraction of DHS from the tissues was performed using a liquid extraction with a 10 mM phosphate buffer containing 2% (w/v) trichloroacetic acid, while milk samples were treated with a 50% (w/v) trichloroacetic acid solution, followed by a solid-phase clean-up procedure on a carboxypropyl (CBA) weak cation exchange column. Ion-pair chromatography, using a mixture of 20 mM pentafluoropropionic acid in water and acetonitrile as the mobile phase, was used to retain DHS and the internal standard streptomycin (STR) on a Nucleosil (5 microm) reversed-phase C18 column. The components were detected and quantified by electrospray ionization (ESI) tandem mass spectrometry. The method could be validated according to EC (European Community) requirements with respect to linearity, trueness and precision, the latter evaluated at the maximum residue limit (MRL) - 1000 ng g(-1) for kidney, 500 ng g(-1) for muscle, liver and fat, and 200 ng g(-1) for milk -, at one-half of the MRL and at one and a half times the MRL. A limit of quantification of 10 ng g(-1) and 1 ng ml(-1) was obtained for all tissues and for milk, respectively, which is far below one-half of the MRL as requested, while the limit of detection was in the low ppb range, varying between 1.9 and 4.2 ng g(-1) for the different tissues tested, and being 0.6 ng ml(-1) for milk. The method was used for the monitoring of DHS residues in incurred tissue and milk samples coming from cattle medicated with DHS in combination with benzylpenicillin by intramuscular injection, in order to evaluate withdrawal times.

Simultaneous determination of streptomycin and oxytetracycline in agricultural antimicrobials by CZE after an experimental design

A capillary zone electrophoresis (CZE) method was developed and validated for the simultaneous determination of both streptomycin (STP) and oxytetracycline (OTC) in bactericidal products to be used in agriculture. Using fused-silica capillaries, the influence of the electrolyte composition, pH and concentration, as well as temperature and applied voltage were investigated using a central composite design to optimize the method. The optimized electrophoretic conditions were as follows: 0.10 M sodium phosphate, pH 2.5, 7.0 kV and 20.0 degrees C. The method was validated for STP and OTC determination in agricultural formulations through the following performance criteria: linearity and linear range, sensitivity, selectivity, intra-day and inter-day precision, detectability, accuracy and ruggedness. This optimized CZE-method for the identification and quantification of STP and OTC is a potential alternative method to the HPLC methods described by the US Pharmacopeia, with the advantage that the same method could be used for the simultaneous determination of these different antibiotics.

On-line concentration of neomycin and screening aminoglycosides in milk by short capillary column and tandem mass spectrometry

An MS-MS method was established for the trace analysis of neomycin and screening aminoglycoside antibiotics (such as amikacin, gentamicin, kanamycin, and tobramycin) in a milk sample. The extraction and purification are based on ion-pair SPE technology on a short fused-silica capillary RP C18 column. The capillary SPE column provided the stationary phase to retain aminoglycoside antibiotics and MS-MS compatible organic acid heptafluorobutyric acid (HFBA) was used as protein precipitation and ion-pair reagent. Aminoglycosides were extracted in this short column and directly eluted to MS-MS without evaporating to dryness and reconstituted with MS-MS compatible solvent after SPE. The LOQ was 0.1 microg/mL and the calibration curve was linear up to 6.4 microg/mL. A small amount of milk product, 10 microL, is sufficient for the analysis and application of this method as the trace analysis of neomycin in the biological matrix proved simple and workable.