Analysis of tetracyclines in honey by high-performance liquid chromatography/tandem mass spectrometry

Accurate determination of four tetracycline residues in chicken meat by isotope dilution-liquid chromatography/tandem mass spectrometry

An analytical method based on isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC‒MS/MS) was developed to accurately determine four representative tetracyclines (tetracycline, chlortetracycline, doxycycline, and oxytetracycline) in chicken meat. Tetracyclines are known to have a great tendency for epimerization and keto-enol tautomerism, which often provoke major challenges in their determination. Since this isomerization was found to be unavoidable during the whole chain of the current analysis, the total content (µg kg^‒1) of individual tetracycline was quantified as a sum of each parent compound and its respective isomeric forms. Using this approach in combination with IDMS analysis, more consistent, accurate, and reproducible measurement results for the four tetracyclines in chicken meat were acquired. LC-MS/MS conditions and sample preparation processes were comprehensively optimized to minimize the chelating effect of tetracyclines and possible co-extracted interferences. Details of the sample preparation scheme, LC‒MS/MS detection, calculation equation, and method validation are described in this article. The method provided very good accuracy (97.7-102.6%) for all analytes across the concentration range of 10-200 µg kg^‒1, with relative standard deviations for intra-day and inter-day precision of less than 4%. The limits of quantification were below 0.2 µg kg^‒1, demonstrating the high sensitivity of the method. Furthermore, the measurement uncertainty was generally below 5.5%. Hence, the established method exhibits high-order metrological quality with superior performance over various existing methodologies. Moreover, this method can provide references for general food testing laboratories close to and far below the established maximum residue limits (100 µg kg^‒1) for animal muscle tissues.

Collaborative compounding of metal-organic frameworks for dispersive solid-phase extraction HPLC-MS/MS determination of tetracyclines in honey

Metal-organic frameworks (MOFs), a sort of dispersive solid-phase extraction (d-SPE) material, has shown considerable prospects in the pretreatment of food, biological and other complex samples. Herein, we developed a method for compounding MOFs for d-SPE and trace determination of tetracyclines (TCs) in honey. When the compounding ratio of MIL-101 (Cr), MIL-100 (Fe) and MIL-53 (Al) was 7:1:2, adsorption-extraction was effective. Followed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the limits of detection were 0.073-0.435 ng/g and the limits of quantitation ranged from 0.239 to 1.449 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline. The method was applied to four kinds of honey samples with recoveries from 88.1% to 126.2%. The compounding of MOFs provides a strategy for purification and multi-target extraction from complex food matrices by d-SPE.

Assessment of Antimicrobial and Pesticide Residues in Food Products Sourced from Peasant Family Farming in Chile

The presence of antimicrobial and pesticide residues in products sourced from peasant family farms selected from eight regions of Chile was determined. A total of 204 samples were analyzed from family farm products, including honey, lettuce, tomato, strawberry, raspberry, lamb meat, and cow's milk. Pesticide residues were found in 43 of 107 samples tested for them, but only 4 samples had concentrations that exceeded the maximum residue limits (MRLs) set by Chilean regulations. As for animal products, 2 of 15 cow's milk samples tested positive for permethrin residues; however, these concentrations did not exceed Chilean MRLs. No pesticide residues were detected in honey samples. As for antimicrobial drugs, 4 of 14 lamb meat samples and 11 of 79 cow's milk samples tested positive for different classes of antimicrobial residues, such as tetracyclines, macrolides, aminoglycosides, and β-lactams. Among these, only three samples exceeded the MRLs for these matrices. Traces of tetracyclines and sulfonamides were detected in 7 of 29 honey samples. These findings show that these chemical contaminants are present in trace concentrations in foodstuffs produced by peasant family farms in Chile; however, most residues did not exceed the regulatory limits. This study is the first assessment of the presence of residues from antimicrobial drugs and pesticides in food products sourced from peasant family farms in Chile. Data about the current state of drug residues in this segment of food products provide a baseline for efforts to close possible gaps in current surveillance schemes.

Development, validation and application to real samples of a liquid chromatography with tandem mass spectrometry method for the determination of tetracyclines in beeswax

Beeswax is a valuable honeybee product, which finds applications in the food and pharmaceutical industries, as well as in cosmetic production. However, some substances used in apiculture, like tetracyclines, can be delivered to hives where they cause contamination of honeybee products such as beeswax. Tetracyclines are commonly used for the treatment of American and European foulbrood diseases, but in the European Union their usage by beekeepers is forbidden. Thus, a sensitive method for the analysis of tetracyclines in beeswax is an important analytical tool. A new liquid chromatography with tandem mass spectrometry method for the analysis of tetracyclines including oxytetracycline, 4-epioxytetracycline, tetracycline, 4-epitetracycline, chlorotetracycline, 4-epichlorotetracycline, and doxycycline in beeswax was developed. The method involved dilution of beeswax in n-hexane after a melting step, liquid-liquid extraction with oxalic acid and clean-up using a weak cation exchange phase. Satisfactory separation was performed on an octadecyl column with 0.1% formic acid and acetonitrile in a total run time of 5 min. The application of this method was evaluated by the analysis of real beeswax samples. The presence of oxytetracycline was confirmed in 5 out of 48 tested beeswax samples, which shows the method can be successfully used to determine the tetracyclines in beeswax.

Design for the transfer of a validated liquid chromatography/tandem mass spectrometry analytical method for the determination of antimicrobial residues in honey from low-resolution to high-resolution mass spectrometry

RATIONALE

This paper investigates the validity of the transfer of a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of veterinary medicinal products in honey and compares it with an LC/linear ion trap/Orbitrap mass spectrometry method. A descriptive statistical approach was used in order to assess whether such a transfer would succeed or fail. This approach is based on the simultaneous evaluation of the trueness and of the intermediate precision for each compound at a 95% interval of confidence of both analytical techniques.

METHODS

Two grams of honey were placed in a centrifuge tube and diluted with 2.5 mL of ultra-pure water and 2.5 mL of acidified methanol with hydrochloric acid at 2 mol.mL^-1 . The extract was purified with 50 mg of primary secondary amine and then analyzed using LC/MS/MS in multiple reaction monitoring (MRM) mode and LC/orbitrap high-resolution mass spectrometry in full scan mode. Both analytical techniques were compared by using the descriptive statistical approach for the determination of antimicrobial residues in honey.

RESULTS

The transfer of the method showed that the Orbitrap system provides the same accurate analytical results compared with the LC/MS/MS method except for 4-epitetracycline, anhydroerythromycin A, erythromycin A enol ether, and dihydrostreptomycin. Furthermore, the LC/LTQ-Orbitrap system is capable of successfully competing with the LC/MS/MS method by additional provision of high mass resolution and mass accuracy even though it shows less sensitivity compared with the LC/MS/MS instrument. CCα levels for most analytes were 1.3 times higher by LC/MS/MS than those observed by LC/LTQ-Orbitrap. The method was assessed in terms of relative bias through analysis of a reference material provided by FAPAS (Food Analysis Performance and Assessment Scheme) and also through the control of several contaminated honey samples from local Lebanese markets. Satisfactory relative bias was below 22% except for tetracycline found in one sample that showed a higher bias at 29%.

CONCLUSIONS

The LC/LTQ-Orbitrap method offers adequate performance in comparison with previously validated method on a LC/MS/MS system resulting in acceptance of the transfer of the method from LC/MS/MS to LC/LTQ-Orbitrap. Copyright © 2017 John Wiley & Sons, Ltd.

Determination of Oxytetracycline and 4-Epi-Oxytetracycline Residues in Feathers and Edible Tissues of Broiler Chickens Using Liquid Chromatography Coupled with Tandem Mass Spectrometry

Antibiotics have been widely used in poultry production for the treatment of bacterial diseases. However, drug residues can remain in products derived from animals after the cessation of the drug therapies. Feathers, in particular, have shown an affinity for antibiotics such as tetracycline, suggesting the persistence of these drugs in nonedible tissue. After the birds are slaughtered, feathers are ground into feather meals, which are used as organic fertilizer or an ingredient in animal diets, thereby entering into the food chain and becoming a potential risk for public health. To evaluate the depletion of oxytetracycline (OTC) and its metabolite 4-epi-oxytetracycline (4-epi-OTC) in the muscles, liver, and feathers, 64 broiler chickens, bred under controlled conditions, were treated orally with a commercial formulation of 10% OTC for 7 days. The analytes were quantified using liquid chromatography-tandem mass spectrometry. OTC and 4-epi-OTC were found in the feathers for 46 days, whereas they were found in the muscle and liver for only 12 and 6 days, respectively. These results prove that the analytes remain in feathers in higher concentrations than they do in edible tissues after treatment with tetracyclines. Thus, feather meals represent a potential source of antimicrobial residue contamination in the food chain.

Residue depletion of oxytetracycline (OTC) and 4-epi-oxytetracycline (4-epi-OTC) in broiler chicken's claws by liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Antibiotics are widely used in poultry production for the treatment of bacterial diseases. However, residues may remain in products and by-products destined for human consumption or animal feeding. The claws of chickens, which are a by-product of the poultry industry, can directly or indirectly enter the food chain as meals destined to feed other productive animals. Thus, it becomes necessary to determine and quantify antimicrobial residues present in this matrix. The objective of the study was to assess the depletion of oxytetracycline (OTC) and its metabolite 4-epi-OTC in broiler chicken's claws. Claws of 32 broilers treated with a therapeutic dosage of 10% OTC during 7 days were analysed. Samples were taken at days 3, 9, 15 and 19 post-treatment. As for the control group, eight broiler chickens were raised under the same conditions. Extraction was carried out through EDTA-McIlvaine buffer, and clean-up employed a SPE C-18 Sep-Pak®. Instrumental analysis was performed through LC-MS/MS. The concentrations of both analytes were determined in claw samples until day 19 post-treatment. Average concentrations were within the LOD (20 μg kg^-1) and LOQ (22 µg kg^-1) for OTC and 84 μg kg^-1 for 4-epi-OTC. Withdrawal times (WDTs) of 39 days for OTC and 54 days for 4-epi-OTC were established in claws based on 95% confidence. These findings demonstrate that claws can be a source of antimicrobial residue entry into the food chain, since the results showed that OTC and its metabolite can be found in chicken's claws for long periods, even exceeding the average lifespan of a broiler chicken.

A direct competitive assay-based aptasensor for sensitive determination of tetracycline residue in honey

Tetracycline (TC) is a common antibacterial agent used for prevention and control of animal diseases. The increasing concern about TC residue in food demands high-performing analytical techniques for food quality assessment. Biosensors represent a promising tool for food safety analysis as they can fulfill some demand that the conventional methods do not attain. In this study, a novel colorimetric aptasensor was developed for sensitive detection of TC in honey. The aptasensor was based on a modified direct competitive enzyme-linked aptamer assay (dc-ELAA) scheme utilizing a 76 mer single-stranded DNA (ssDNA) aptamer selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). The optimized aptasensor showed a good limit of detection (LOD of 0.0978 ng/mL), a wide linear range (0.1-1000 ng/mL) toward TC in honey, with good recoveries (92.09-109.7%) in TC-spiked honey, and was compared with an indirect competitive assay-based aptasensor and validated with a standard ELISA. The biosensor based on dc-ELAA with good limit of detection and simplicity can be applied for high-throughput detection of TC in food.

Development of an indirect competitive assay-based aptasensor for highly sensitive detection of tetracycline residue in honey

Tetracycline (TC) is widely used for prevention and control of animal diseases for its broad spectrum antimicrobial activity and low cost, but its abuse can seriously affect human health and may result in trade loss. Thus there is an imperative need to develop high-performing analytical technique for TC detection. In this study, we developed a biosensor based on an indirect competitive enzyme-linked aptamer assay (ic-ELAA). A 76mer single-stranded DNA (ssDNA) aptamer, selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX), was applied for the recognition and detection of TC in honey. The limit of detection was 9.6×10(-3) ng/mL with a linear working range from 0.01 to 100 ng/mL toward TC in honey, and a mean recovery rate of 93.23% in TC-spiked honey was obtained. This aptasensor can be applied to detect TC residue in food with high sensitivity and simplicity, and it is prospective to develop useful ELAA Kits for TC determination in food.

Beware of Pseudo Matrix-Matched Standard Calibration Curve due to Matrix Effect on Sulfonamide Residue in Honey

Honey was a particular matrix with a variety of composition and origin, which lead to different degree of matrix effect on analytes. As a rule, the matrix-matched calibration curve from blank honey was adopted to quantifying analyte in a batch. This paper investigated matrix effect on sulfonamide in four honey samples by high-performance liquid chromatography hyphenated with mass spectrometry detection. The main goal was to check whether matrix-matched calibration curve obtained from a random blank honey could match the real samples in character within current recommended acceptance criteria. It was found that analyte recovery from true matrix-matched standard calibration curve ranged 87.7-117.3%, whereas recovery from surrogate matrix-matched calibration curves gave a very wide range from 54.3 to 150.2%, far beyond the acceptance criteria. So it was perhaps not feasible to use a surrogated blank sample to prepare matrix-matched calibration curve for quantifying analyte, particularly for largely diverse honey samples in a batch. To reduce error from inter-sample matrix effect, the best solution seemed to use internal standard or standard addition.

Multiclass determination and confirmation of antibiotic residues in honey using LC-MS/MS

A multiclass method has been developed for the determination and confirmation in honey of tetracyclines (chlortetracycline, doxycycline, oxytetracycline, and tetracycline), fluoroquinolones (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, and sarafloxacin), macrolides (tylosin), lincosamides (lincomycin), aminoglycosides (streptomycin), sulfonamides (sulfathiazole), phenicols (chloramphenicol), and fumagillin residues using liquid chromatography tandem mass spectrometry (LC-MS/MS). Erythromycin (a macrolide) and monensin (an ionophore) can be detected and confirmed but not quantitated. Honey samples (approximately 2 g) are dissolved in 10 mL of water and centrifuged. An aliquot of the supernatant is used to determine streptomycin. The remaining supernatant is filtered through a fine-mesh nylon fabric and cleaned up by solid phase extraction. After solvent evaporation and sample reconstitution, 15 antibiotics are assayed by LC-MS/MS using electrospray ionization (ESI) in positive ion mode. Afterward, chloramphenicol is assayed using ESI in negative ion mode. The method has been validated at the low part per billion levels for most of the drugs with accuracies between 65 and 104% and coefficients of variation less than 17%. The evaluation of matrix effects caused by honey of different floral origin is presented.

Quantitative high-throughput analysis of 16 (fluoro)quinolones in honey using automated extraction by turbulent flow chromatography coupled to liquid chromatography-tandem mass spectrometry

A method making use of turbulent flow chromatography automated online extraction with tandem mass spectrometry (MS/MS) was developed for the analysis of 4 quinolones and 12 fluoroquinolones in honey. The manual sample preparation was limited to a simple dilution of the honey test portion in water followed by a filtration. The extract was online purified on a large particle size extraction column where the sample matrix was washed away while the analytes were retained. Subsequently, the analytes were eluted from the extraction column onto an analytical column by means of an organic solvent prior to chromatographic separation and MS detection. Validation was performed at three fortification levels (i.e., 5, 20, and 50 microg/kg) in three different honeys (acacia, multiflower, and forest) using the single-point calibration procedure by means of either a 10 or 25 microg/kg calibrant. Good recovery (85-127%, median 101%) as well as within-day (2-18%, median 6%) and between-day (2-42%, median 9%) precision values was obtained whatever the level of fortification and the analyte surveyed. Due to the complexity of the honey matrix and the large variation of the MS/MS transition reaction signals, which were honey-dependent, the limit of quantification for all compounds was arbitrarily set at the lowest fortification level considered during the validation, e.g., 5 microg/kg. This method has been successfully applied in a minisurvey of 34 honeys, showing ciprofloxacin and norfloxacin as the main (fluoro)quinolone antibiotics administered to treat bacterial diseases of bees. Turbulent flow chromatography coupled to LC-MS/MS showed a strong potential as an alternative method compared to those making use of offline sample preparation, in terms of both increasing the analysis throughput and obtaining higher reproducibility linked to automation to ensure the absence of contaminants in honey samples.

Determination of tetracycline residues in honey by CZE with ultraviolet absorbance detection

We have developed a sensitive CE method to determine eight tetracyclines (TCs) (chlortetracycline, demeclocycline, doxycycline, methacycline, minocycline, oxytetracycline, TC, and rolitetracycline (RTC)) in honey samples. The running buffer was 150 mM sodium borate (pH 9.8) and 2.5% 2-propanol with 15 s hydrodynamic injection at 25 kV. We have also developed an SPE procedure with a C18 cartridge as a clean-up step. Analytes were detected at 360 nm in less than 16 min. LODs ranged in honey from 23.9 microg/kg for TC to 49.3 microg/kg for RTC. Seven samples of Spanish honey of different floral origins were examined. None of them showed contamination with these antibiotics using the proposed method.

[Analysis of tetracyclines in honey and royal jelly by LC/MS/MS]

A simple and accurate method using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) was developed for the determination of tetracyclines (TCs), i.e., oxytetracycline (OTC), chlortetracycline (CTC) and tetracycline (TC), in honey and royal jelly. Mass spectral acquisition was performed in the positive mode. In LC separation, L-column ODS and 0.01% formic acid-acetonitrile were used as the column and mobile phase, respectively. TCs in a honey sample were diluted with water, while TCs in royal jelly were extracted with 2% metaphosphoric acid-methanol (6:4). They were cleaned up with Oasis HLB and Sep Pak C18 cartridges, respectively. The quantification limits of TC, OTC, and CTC were 5, 5, and 10 ng/g, respectively, while those in royal jelly were 25, 25, and 50 ng/g, respectively. The recoveries of TCs from both honey and royal jelly were 75-120%.

Multi-class confirmatory method for analyzing trace levels of tetracyline and quinolone antibiotics in pig tissues by ultra-performance liquid chromatography coupled with tandem mass spectrometry

An ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC/MS/MS) method was developed to screen and confirm multi-class veterinary drug residues in pig tissues including pig kidney, liver and meat. Twenty-one drugs of two different classes including seven tetracyclines and four types of quinolones (quinoline, naphthyridine, pyridopyrimidine and cinoline) were determined simultaneously in a single run. The homogenized sample tissues were extracted with EDTA-McIlvaine buffer solution and further purified using a polymer-based Oasis HLB solid-phase extraction (SPE) cartridge. An ACQUITY UPLC BEH C18 column was used to separate the analytes followed by tandem mass spectrometry using an electrospray ionization source. MS data acquisition was performed in the positive ion multiple reaction monitoring mode, selecting two ion transitions for each target compound. Recovery studies were performed at different fortification levels. The overall average recoveries from pig muscle, kidney, and liver fortified with quinolones and tetracyclines at three levels ranged from 80.2 to 117.8% based on the use of matrix-fortified calibration with the coefficients of variation ranging from 2.1 to 17.8% (n=6). The limits of quantitation (LOQs) of quinolones and tetracyclines in different tissues ranged from 0.03-4.50 microg/kg and 0.16-10.00 microg/kg, respectively. The effects of the extraction solvent, SPE cartridge, elution solvent and sample matrix on the analyte recovery as well as the effects of the mobile phase composition and column temperature on the chromatographic behavior were also studied.

Determination of tetracycline antibiotics in cow's milk by liquid chromatography/tandem mass spectrometry

A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multiresidue method for the simultaneous quantitative determination of oxytetracycline, 4-epi-oxytetracycline, tetracycline, 4-epi-tetracycline, chlortetracycline, 4-epi-chlortetracycline and doxycycline in milk has been developed. An extraction procedure consisting of a liquid extraction of the milk samples with trichloroacetic acid was performed. The extract was centrifuged and the supernatant was filtered. Solid-phase extraction (SPE) with an OASIS HLB SPE column was used to clean up the sample extracts. The samples were analysed by LC/MS/MS. The LC separation was performed on a reversed-phase C18 column using gradient elution with a mobile phase consisting of water and a mixture of methanol/acetonitrile. The tetracycline analytes were detected with a quadrupole mass spectrometer using positive ion electrospray ionisation. The confirmatory method has acceptable detection limits and the different tetracyclines can be detected at a residue concentration between 5 and 20 microg/L. The method is validated according to the European requirements for veterinary drug residues and all determined parameters were found to conform to the criteria. The recovery values ranged from 90.4 to 101.2% with relative standard deviations (RSDs) no larger than 9.7%. The overall or between-day precision of the analytical assay determined as repeatability at several residue concentrations and expressed as RSD ranged from 3.3 to 10%. This analytical assay is a useful tool within the Belgian monitoring programme for confirmation of samples which have been positively screened for residues of tetracyclines in raw farm cow's milk.

Role of zwitterionic structures in the solid-phase extraction based method development for clean up of tetracycline and oxytetracycline from honey

Solid-phase extraction (SPE) based sample clean up of tetracycline (TC) and oxytetracycline (OTC) from honey samples was evaluated using a neutral polymeric sorbent (strata-X), a weak cation exchange polymeric sorbent (strata-X-CW) and a combination of neutral and strong cation exchange sorbents (strata-X plus Strata-Screen-C or strata-X-C). Both TC and OTC are recovered in low yields from the strong cation exchange sorbents strata-X-C and Strata-Screen-C under basic (pH >9) or acidic (pH >or=2) elution conditions. The cleanest extracts along with quantitative recoveries were obtained with strata-X-CW under either acidic or basic elution conditions, as demonstrated by analysis of eluates by both LC/UV and LC/MS-MS. On the other hand, the neutral sorbent (strata-X) was less efficient in eliminating the honey matrix constituents, since it could not retain the tetracyclines with the strong organic wash needed to remove other compounds. The differences in the elution behavior of the strong and weak cation exchange sorbents is rationalized on the basis of divergent deprotonation mechanisms of the tetracyclines, which exist in the zwitterionic structures under the SPE conditions.

Degradation patterns of tetracycline antibiotics in reverse micelles and water

The objective of this study was to determine the chemical stability of tetracycline and oxytetracycline hydro-chlorides in reverse micelles. Their reverse micellar solutions were prepared using cetyltrimethylammonium bromide, water and ethyl formate. The aqueous solutions of the tetracycline antibiotics were also prepared for comparison. The reverse micellar and aqueous solutions were stored at 37 degrees C. Samples were analyzed by high performance liquid chromatography. When evaluation was performed on an aqueous tetracycline HCl solution, its half-life was estimated to be 329 h. Its chemical stability was not improved after being dissolved in the reverse micelles, and a similar half-life of 330 h was observed. However, there were noticeable differences between the two systems in terms of degradation kinetics and degradation byproducts. On the other hand, oxytetracycline HCl was unstable in water so that its half-life was only 34 h. Very interestingly, pronounced improvement in stability was attained with the reverse micellar system: upon dissolving in the reverse micelles, its half-life was increased to 2402 h. There were also marked differences in degradation patterns and mechanisms of oxytetracycline HCl in water and the reverse micelles. Our study indicates that the reverse micellar system has potential applications in solubilizing and stabilizing oxytetracycline HCl, thereby contributing to the development of its dosage forms.

A simple method of isolation of chloramphenicol in honey and its estimation by liquid chromatography coupled to electrospray ionization tandem mass spectrometry

To detect sub-ppb levels of the antibiotic chloramphenicol in honey matrix, a convenient method of extraction and measurement using liquid chromatography with detection by tandem mass spectrometry (LC/MS/MS) was developed. Honey samples fortified with chloramphenicol and isotopically labeled chloramphenicol were extracted using diatomaceous-based supported liquid-liquid extraction cartridges to generate a standard calibration curve. Four MS/MS transitions were used for quantification and four other transitions for confirmation of chloramphenicol. The limit of detection for chloramphenicol was 0.05 ng/g and the lower limit of quantification was 0.1 ng/g. Several commercial honey samples were analyzed for chloramphenicol content using this method.