Quantitative analysis of oxytetracycline and its impurities by LC-MS-MS

Molecularly imprinted polymers-isolated AuNP-enhanced CdTe QD fluorescence sensor for selective and sensitive oxytetracycline detection in real water samples

A molecularly imprinted polymers (MIPs)-isolated AuNP-enhanced fluorescence sensor, AuNP@MIPs-CdTe QDs, was developed for highly sensitive and selective detection of oxytetracycline (OTC) in aqueous medium. The developed sensor combined the advantages of strong fluorescence signal of metal-enhanced fluorescence (MEF), high selectivity of MIPs, and stability of CdTe QDs. The MIPs shell with specific recognition served as an isolation layer to adjust the distance between AuNP and CdTe QDs to optimize the MEF system. The sensor demonstrated the detection limit as low as 5.22 nM (2.40 μg/L) for a concentration range of 0.1-3.0 μM OTC and good recovery rates of 96.0-103.0% in real water samples. In addition, high specificity recognition for OTC over its analogs was achieved with an imprinting factor of 6.10. Molecular dynamics (MD) simulation was utilized to simulate the polymerization process of MIPs and revealed H-bond formation as the mainly binding sites of APTES and OTC, and finite-difference time-domain (FDTD) analysis was employed to obtain the distribution of electromagnetic field (EM) for AuNP@MIPs-CdTe QDs. The experimental results combined with theoretical analyses not only provided a novel MIP-isolated MEF sensor with excellent detection performance for OTC but also established a theoretical basis for the development of a new generation of sensors.

Application of Nontarget Analysis and High-Resolution Mass Spectrometry for the Identification of Thermal Transformation Products of Oxytetracycline in Pacific White Shrimp

ABSTRACT

Oxytetracycline (OTC) is an antibiotic authorized for use in aquaculture; it is often detected in seafood products, especially shrimp. Previous studies investigating the fate of OTC in shrimp tissues after cooking were limited to quantification of parent compound residues and did not describe any potential transformation products formed. Hence, the main objective of this study was to apply a nontarget analysis workflow to study the fate of OTC in shrimp muscle. Furthermore, "water" and "spiked" models were evaluated for their suitability to track the transformation of OTC in incurred muscle and to determine whether the matrix plays a role in the transformation pathway. First, four different extraction methods were compared for the determination of OTC in muscle. Second, raw and cooked samples were then extracted using a suitable method (acidified water-methanol-acetonitrile, with cleanup of samples achieved using freezing) and were analyzed by high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. OTC levels were reduced by 75 and 87% in muscle and water, respectively. Identification of thermal transformation products was limited to formula generation, but results showed that different compounds were identified in spiked and incurred muscle.

HIGHLIGHTS

Evaluation of Antibiotic Dissemination into the Environment and Untreated Animals, by Analysis of Oxytetracycline in Poultry Droppings and Litter

Simple Summary

Oxytetracycline (OTC) is an antibiotic used mainly in feed and drinking water. OTC is poorly absorbed in the gastrointestinal tract of poultry; making droppings a potential route of dissemination of this antibiotic. The aim of this study was to evaluate the dissemination of oxytetracycline excreted from treated birds to the environment and other untreated animals (sentinels), through the analysis of their droppings and litter by HPLC-MS/MS following the end of treatment. In treated bird droppings, the average concentration of OTC+4-epi-OTC ranged from 347.63 to 2244.66 µg kg⁻¹. OTC+4-epi-OTC in litter reached concentrations of 22,741.68 µg kg⁻¹. Traces of OTC+4-epi-OTC were detected in the droppings and litter from sentinels. Therefore, OTC+4-epi-OTC can persist in the litter of treated animals at high concentrations and can be transferred to untreated birds that share the same environment. This exposure has the potential to increase the likelihood of selection of resistant bacteria in the environment.

Abstract

Oxytetracycline (OTC) is widely used in broiler chickens. During and after treatment a fraction of OTC is excreted in its original form and as its epimer, 4-epi-OTC in droppings. To address the transfer of OTC into the environment, we evaluated the dissemination of OTC and 4-epi-OTC from treated birds to the environment and sentinels, through the simultaneous analysis of broiler droppings and litter. Male broiler chickens were bred in controlled conditions. One group was treated by orogastric tube with 80 mg kg⁻¹ of OTC and two groups received no treatment (sentinels). OTC+4-epi-OTC were analyzed and detected by a HPLC-MS/MS post the end of treatment. The highest concentrations of OTC+4-epi-OTC were detected in the droppings of treated birds 14-days following the end of treatment (2244.66 µg kg⁻¹), and one day following the end of treatment in the litter (22,741.68 µg kg⁻¹). Traces of OTC+4-epi-OTC were detected in the sentinels’ droppings and litter (<12.2 µg kg⁻¹). OTC+4-epi-OTC can be transferred from treated birds to the environment and to other untreated birds. The presence and persistence of OTC+4-epi-OTC in litter could contribute to the selection of resistant bacteria in the environment, increasing the potential hazard to public and animal health.

Aptamer-Based Fluorescent Switch for Sensitive Detection of Oxytetracycline

Oxytetracycline (OTC) is one of the most used antibiotics in veterinary medicine. There is a large concern about developing antibiotic resistance in humans as a result of the consumption of products contaminated with OTC, so a fast detection technique for an on-field screening test is highly in demand. Here we introduce a novel aptasensor for fast detection of OTC, based on a triple helix molecular switch (THMS) complex formation. The limit of detection (LOD) of this sensor was 1.67 and 6.44 nM in phosphate buffer and milk samples, respectively. Moreover, the sensor showed a high selectivity towards OTC.

Relationship between antibiotic residues and occurrence of resistant bacteria in Nile tilapia (Oreochromisniloticus) cultured in cage-farm

The aim of this study was to investigate the relationship between antibiotic residues found in the muscle of cage-farm-raised Nile tilapia (Oreochromisniloticus), the occurrence of resistant bacteria, and the sanitary practices adopted by farmers in Ilha Solteira reservoir, Brazil. Nine fish (three small fish, 40-200 g; three medium-sized fish, 200-500 g; and three large fish, 500-800 g) were collected from four cage farms every three months from April 2013 to January 2014. Ten antibiotic residues were determined using liquid chromatography-mass spectrometry, and bacteria were isolated and tested for antibiotic resistance to determine the multiple antibiotic resistance (MAR) index. Only three antibiotics (oxytetracycline, tetracycline, and florfenicol) were detected in the muscle of Nile tilapia, and their residues were the highest in small fish; however, the MAR index was higher in large fish. In addition, a direct positive relationship between the MAR index and the concentration of antibiotic residues in Nile tilapia was found. Overall, the adoption of prophylactic management practices improved the sanitary status of cage farms, reducing bacterial infections and hampering the development of antibiotic-resistant bacteria.

A Critical Review of Properties and Analytical Methods for the Determination of Oxytetracyline in Biological and Pharmaceutical Matrices

Antibiotics have an unquestionable importance in the treatment of many infections. Oxytetracycline is an antibiotic belonging to the class of tetracyclines, available for use in human and veterinary medicine. Development of analytical methods that prove the quality and efficacy of these drugs is fundamentally important to the pharmaceutical industry. In this context, the research presents an overview of the analytical profile of oxytetracycline, describing its chemical and pharmacological properties, and analytical methods for quantification of this drug in biological samples and pharmaceutical products. Oxytetracycline can be analyzed in these matrices by many types of methodologies. However, high-performance liquid chromatography is the most widely used, being recommended by official compendia. This kind of study can be useful to support the development of new efficient and sustainable analytical methods that may be utilized in the quality control routine of oxytetracycline in pharmaceutical products and pharmacokinetic monitoring in biological samples.

Study of spatial and temporal distribution of antimicrobial in water and sediments from caging fish farms by on-line SPE-LC-MS/MS

An on-line solid phase extraction liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method for the determination of 12 antimicrobials in sediment and surface water was developed and validated. Furthermore, the spatial and temporal antimicrobials distributions in the sediment and in the water of four fish farms located in the hydroelectric dam of Ilha Solteira Reservoir in Brazil were investigated over four seasons in three sampling sites: at the fish cages, 100 and 1,000 m downstream far from the cages. The method was performed using an Agilent Zorbax 80 SB-C8 column (9.4 × 15 mm, 5 µm) as the loading column, and the Agilent Zorbax Eclipse Plus C18 column (3.0 × 100 mm, 3.5 µm) as a separation column within a run time of 13 min. The limits of quantification were less than 9 ng·L(-1) for the antibiotics in water and 16 µg·kg(-1) in sediment; the recovery ranged from 80 to 119%, with a variation coefficient less than 11%, and the repeatability was lower than 15%. Oxytetracycline was found in the water in all sample seasons. However, florfenicol was identified in April and October 2013 and January 2014, and tetracycline was present in July 2013. Regarding the sediment, oxytetracycline and tetracycline were found in all sampling periods, but chlortetracycline was only identified in January 2014. The spatial distribution of antimicrobials showed that the main pollution source came from the fish farms. This study demonstrated that the proposed method is reliable for the monitoring of antimicrobials in water and sediments and it showed contamination in both matrices from Ilha Solteira Reservoir.

Comparison of oxytetracycline degradation behavior in pig manure with different antibiotic addition methods

Using manure collected from swine fed with diet containing antibiotics and antibiotic-free swine manure spiked with antibiotics are the two common methods of studying the degradation behavior of veterinary antibiotic in manure in the environment. However, few studies had been conducted to co-compare these two different antibiotic addition methods. This study used oxytetracycline (OTC) as a model antibiotic to study antibiotic degradation behavior in manure under the above two OTC addition methods. In addition, the role of microorganisms present in the manure on degradation behavior was also examined. The results showed that degradation half-life of OTC in manure from swine fed OTC (9.04 days) was significantly shorter than that of the manure directly treated with OTC (9.65 days). Concentration of 4-epi-OTC in manure from swine fed OTC peaked earlier than that in manure spiked with OTC, and the degradation rates of 4-epi-OTC and α-apo-OTC in the manure from swine fed OTC were faster, but the peak concentrations were lower, than those in manure spiked with OTC. Bacterial diversity and relative abundance of Bacillus cereus data demonstrated that sterilization of the manure before experiment significantly decreased OTC degradation rate in both of the addition methods. Results of the present study demonstrated that the presence of the metabolites (especially 4-epi-OTC) and microorganisms had significant influence on OTC degradation.

Upconversion luminescence resonance energy transfer-based aptasensor for the sensitive detection of oxytetracycline

In this work, a biosensor based on luminescence resonance energy transfer (LRET) from NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) to SYBR Green I has been developed. The aptamers are covalently linked to UCNPs and hybridized with their complementary strands. The subsequent addition of SYBR Green allows SYBR Green I to insert into the formed double-stranded DNA (dsDNA) duplex and brings the energy donor and acceptor into close proximity, leading to the fluorescence of UCNPs transferred to SYBR Green I. When excited at 980 nm, the UCNPs emit luminescence at 477 nm, and this energy is transferred to SYBR Green I, which emits luminescence at 530 nm. In the presence of oxytetracycline (OTC), the aptamers prefer to bind to its corresponding analyte and dehybridize with the complementary DNA. This dehybridization leads to the liberation of SYBR Green I, which distances SYBR Green I from the UCNPs and recovers the UCNPs' luminescence. Under optimal conditions, a linear calibration is obtained between the ratio of I530 to I477 nm (I530/I477) and the OTC concentration, which ranges from 0.1 to 10 ng/ml with a limit of detection (LOD) of 0.054 ng/ml.

Comparison between Source-induced Dissociation and Collision-induced Dissociation of Ampicillin, Chloramphenicol, Ciprofloxacin, and Oxytetracycline via Mass Spectrometry

Mass spectrometry (MS) is a very powerful instrument that can be used to analyze a wide range of materials such as proteins, peptides, DNA, drugs, and polymers. The process typically involves either chemical or electron (impact) ionization of the analyte. The resulting charged species or fragment is subsequently identified by the detector. Usually, single mass uses source-induced dissociation (SID), whereas mass/mass uses collision-induced dissociation (CID) to analyze the chemical fragmentations Each technique has its own advantages and disadvantages. While CID is most effective for the analysis of pure substances, multiple- step MS is a powerful technique to get structural data. Analysis of veterinary drugs ampicillin, chloramphenicol, ciprofloxacin, and oxytetracycline serves to highlight the slight differences between SID and CID. For example, minor differences were observed between ciprofloxacin and oxytetracycline via SID or CID. However, distinct fragmentation patterns were observed for ampicllin depending on the analysis method. Both SID and CID showed similar fragmentation spectra but different signal intensities for chloramphenicol. There are several factors that can influence the fragmentation spectra, such as the collision energy, major precursor ion, electrospray mode (positive or negative), and sample homogeneity. Therefore, one must select a fragmentation method on an empirical and case-by-case basis.

Simultaneous determination of tetracyclines and their degradation products in environmental waters by liquid chromatography-electrospray tandem mass spectrometry

A sensitive method was developed for the trace determination of six tetracyclines and ten of their degradation products in influent, effluent, and river waters using liquid chromatography-electrospray tandem mass spectrometry detection, combined with Oasis hydrophilic-lipophilic balance (HLB) cartridge extraction and Oasis mixed-mode strong anion exchange (MAX) cartridge cleanup. Tetracyclines and their products were separated by liquid chromatography in 9.5min, and the instrument detection limits were generally between 0.03 and 0.1microg/L except for minocycline (0.5microg/L). The chromatograms were improved through the MAX cleanup and no apparent matrix effect was found. The recoveries of all the target compounds except for 4-epianhydrochlortetracycline and anhydrochlortetracycline (34-52%) were 75-120% for influent, 61-103% for effluent, and 64-113% for river waters. The method detection limits (MDLs) of the analytes varied in the range of 0.8-17.5ng/L in all studied matrices. The method was applied for the determination of tetracyclines and their products in a sewage treatment plant (STP) and surface waters in Beijing, China. Oxytetracycline (3.8-72.5ng/L), tetracycline (1.9-16.5ng/L), and five products including 4-epitetracycline, 4-epioxytetracycline, isochlortetracycline, anhydrotetracycline, and 4-epianhydrochlortetracycline (5.7-25.3ng/L) were detected in wastewater, while only oxytetracycline and tetracycline (2.2 and 2.1ng/L) were detected in surface water samples.

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.

C18 columns for the simultaneous determination of oxytetracycline and its related substances by reversed-phase high performance liquid chromatography and UV detection

Simultaneous determination of oxytetracycline, 4-epioxytetracycline, alpha-apooxytetracycline, tetracycline and beta-apooxytetracycline on C(18) columns has been accomplished using a high performance liquid chromatographic method with UV detection. Separation was achieved on a Hypersil BDS RP-C(18) column (250 mm x 4.6 mm) and on a Waters C(18) Symmetry column (150 mm x 3.9mm), 5 microm particle size each. These columns were equilibrated with mobile phases consisted of methanol-acetonitrile-0.1M phosphate buffer pH 8.0 (12.5:12.5:75, v/v/v) and (15:15:70, v/v/v), respectively. The flow rate was 1.0 ml/min and the total elution time was 15 and 5 min, respectively. Both methods were applied to oxytetracycline raw material, human and veterinary formulations, where the excipients did not interfere. External standard calibration curves were linear for 4-epioxytetracycline, oxytetracycline, alpha-apooxytetracycline, tetracycline and beta-apooxytetracycline in the concentration range of 0.27-200 microM, 0.05-200 microM, 0.03-200 microM, 0.35-200 microM and 0.20-200 microM on column A and 0.08-200 microM, 0.15-200 microM, 0.09-200 microM, 0.25-200 microM and 0.47-200 microM on column B, respectively. Day-to-day relative standard deviation of the determination for every component was less than 3%. Concerning the first column, limits of detection and quantification of the above compounds were in the concentration ranges of 10-106 nM and 30-352 nM, respectively, whereas on the second column these ranges became 27-144 nM and 81-475 nM, respectively. Recovery of the separated compounds was 95-105%.

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.

Optimization of the separation conditions of tetracyclines on a preselected reversed-phase column with embedded urea group

The use of a C12 stationary phase with embedded polar group has been investigated for the separation of seven tetracyclines. The influence of pH, organic modifier, buffer, and temperature on the peak shape and analyte separation was discussed. It appears that all the chromatographic conditions had a great effect on both the resolution and peak shape whereas the elution order was not affected. The baseline separation with symmetrical peaks of the seven tetracyclines can be obtained with a mobile phase containing either 5 mM phosphate buffer pH 2.5/ACN (84:16 v/v) or 5 mM perchlorate buffer pH 2.5/ACN (75:25 v/v) at a temperature not exceeding 20 degrees C. This study reveals that the retention mechanism is ion-pairing.

HPLC-DAD and LC-ESI-MS analysis of doxycycline and related impurities in doxipan mix, a medicated premix for incorporation in medicated feedstuff

HPLC-DAD and LC-ESI-MS methods have been developed for the analysis of doxycycline (DOX), including the identification of the related impurities metacycline (MTC) and 6-epidoxycycline (EDOX) and its determination in a medicated premix. The chromatographic separations have been performed on Luna C18 stationary phase and on Synergi (4 microm) Polar-RP 80A, using both acidic (pH 2.5) and basic (pH 8.0) mobile phases. The Synergi Polar-RP column, in combination with a mobile phase of oxalic acid (0.02 M; pH 2.5)-acetonitrile 82:18 (v/v), allowed the complete separation of MTC, EDOX and DOX. The same separation was also obtained using Luna C18 stationary phase with a pH 8 mobile phase. Application of a LC-ESI-MS system and MS/MS analysis, using both positive and negative polarity, allowed the peak identity to be confirmed. A method based on Luna C18 column and UV detection at 346 nm was validated for the determination of DOX in a medicated premix for incorporation in medicated feedstuff.

A comparison of performance of various analytical columns in pharmaceutical analysis: conventional C18 and high throughput C18 Zorbax columns

New improved types of analytical columns Zorbax Eclipse XDB-C18 (75 mm x 4.6 mm i.d., 3.5 microm) and Zorbax Eclipse XDB-C18 (50 mm x 4.6 mm i.d., 1.8 microm) have been tested for determination of estradiol (active substance), methylparaben, propylparaben (preservatives) and estrone (degradation product) and compared with the conventional C18 columns (250 mm x 3.0 mm i.d., 5.0 microm). The Zorbax columns differ with their particle size, column length and ODS (octadecylsilica) type as well. Higher flow-rates (up to about 2.5 ml min(-1)) could be applied regardless to back-pressure. The analysis - previously done at 40 degrees C - could be performed even at ambient temperature. Analytical run was shortened to 3.5 min (from 12 min used for the conventional C18 column) with the same or better retention characteristics. System suitability data for all Zorbax columns show the advantages of these columns for the practical use in routine quality control of pharmaceuticals, particularly from the point of view of speed of analysis and solvent consumption.

Complexities in tetracycline analysis—chemistry, matrix extraction, cleanup, and liquid chromatography

The extraction and cleanup of commonly used tetracyclines (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) from sample matrix, and their subsequent determination via liquid chromatography can be problematic. Many manuscripts report on various challenges encountered when developing a method for tetracycline antibiotics determination. These complexities often result in less than perfect recoveries or chromatograms and are based on the underlying chemistry associated with tetracyclines. This review compiles, compares, and discusses the results and observations found in published methods, while focusing on chemical principles in order to increase the practicing chemist's understanding of TCs to aid him/her in developing useful analyses.