Oxytetracycline residues in giant freshwater prawn (Macrobrachium rosenbergii)

The distribution of oxytetracycline (OTC) in male and female Macrobrachium rosenbergii was examined after the prawns had been given medicated feed containing OTC at levels of 2.5 and 5.0 g/kg of feed for 1 week and nonmedicated feed thereafter. OTC levels in the heads of both male and female prawns were consistently higher than in the muscles. Batches of both male and female prawns treated with higher dosages had significantly higher OTC residues in both head and muscle tissues than the batches treated with lower dosages. During treatment, peak concentrations in the head and muscle from each group were reached within 4-6 days. After drug treatment ceased, 13 days for the head and 10 days for the muscle were required to reduce OTC residues to safe levels in all batches of both sexes and dosages. In practice, to account for variations in water temperature, drug dosage, duration of therapy, and other environmental conditions, a withdrawal period of 21 days is recommended.

Analysis of oxytetracycline, tetracycline, and chlortetracycline in water using solid-phase extraction and liquid chromatography-tandem mass spectrometry

A method using liquid chromatography-tandem mass spectrometry has been developed for determination of trace levels of tetracycline antibiotics in ground water and confined animal feeding operation waste water. Oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) were extracted from water samples using both polymeric and C18 extraction cartridges. The addition of a buffer containing potassium phosphate and citric acid improved tetracycline recoveries in lagoon water. Method detection limits determined in reagent water fortified with 1 microg l(-1) OTC, TC, and CTC were 0.21, 0.20, and 0.28 microg l(-1). Method detection limits in lagoon water samples fortified at 20 microg l(-1) for OTC, TC, and CTC were 3.6, 3.1, and 3.8 microg l(-1). Variability in recovery from laboratory fortified blanks ranged from 86 to 110% during routine analysis.

[Detection of residual antibiotics in honey with capillary electrophoresis]

Five antibiotics compounds, tetracycline (TC), oxytetracycline (OTC), doxycycline (DOC), chlortetracycline (CTC) and chloramphenicol (CP), were successfully separated and determined by high performance capillary electrophoresis(HPCE). Effects of buffer pH, various organic additives and temperature on electrophoretic separation of antibiotics were investigated. Satisfactory separation of these five antibiotics was achieved in the buffer of pH 3.2, 0.02 mol/L Na2HPO4-0.01 mol/L citric acid with addition of 4% (V/V) N-methylmorpholine and 12% (V/V) acetonitrile within 20 minutes. The calibration graphs were linear by plotting the peak area against the sample concentration over the range of 150 micrograms/L to 750 micrograms/L and the correlation coefficients were greater than 0.9917. The detection limits were 10 micrograms/L for CP, 20 micrograms/L for TC, OTC and DOC and 40 micrograms/L for CP (signal to noise ratio > 5). HPCE method was successfully applied to the analysis of trace antibiotics in honey.

Microbiological and chemical detection of incurred penicillin G, oxytetracycline, enrofloxacin and ciprofloxacin residues in bovine and porcine tissues

Incurred penicillin G, oxytetracycline, enrofloxacin and ciprofloxacin residues in bovine and porcine muscle and kidney samples were analysed by microbiological and chemical methods, the former using Bacillus subtilis BGA as a test organism on agar media of pH 6, pH 7.2 and pH 8 and the latter using liquid chromatography. Least squares fits between the logarithms of the chemically obtained concentrations of the antimicrobials and the widths of the inhibition zones were used to estimate the inhibition zone widths corresponding to the maximum residue limit concentrations. In vitro sensitivities were determined with standard antimicrobial solutions. The results indicate that if B. subtilis BGA is used as a test organism, muscle tissue cannot be used as test material for screening oxytetracycline, enrofloxacin and ciprofloxacin residues on the plates used in this study, while penicillin G can be screened from muscle tissue. Because of the numerous factors causing or increasing variation in the analysis, the inhibition zone caused by a given antibiotic concentration cannot be predicted precisely. Therefore, a positive agar diffusion test needs to be confirmed chemically. If a kidney sample gives a positive agar diffusion test result, the antimicrobial concentration in a muscle sample from the same carcass should be checked chemically.

Metabolites of oxytetracycline, tetracycline, and chlortetracycline and their distribution in egg white, egg yolk, and hen plasma

4-epioxytetracycline and N-demethyloxytetracycline, as metabolites of oxytetracycline (OTC), 4-epitetracycline and N-demethyltetracycline, as metabolites of tetracycline (TC), and 4-epichlortetracycline, isochlortetracycline (ICTC), 4-epi-ICTC, and N-demethyl-ICTC, as metabolites of chlortetracycline (CTC), were detected in egg yolk and plasma obtained from feeding studies with either OTC, TC, or CTC. In egg white, only OTC, TC with its 4-epimer, and ICTC with its 4-epimer were detected in substantial concentrations. The ratios of epimerization and N-demethylation in the eggs did not change during the medication period. The samples were analyzed by an automated HPLC system (ASTED) with UV, fluorescence, or MS-MS detection.

Identification and determination of oxytetracycline, tiamulin, lincomycin, and spectinomycin in veterinary preparations by thin-layer chromatography/densitometry

A thin-layer chromatographic/densitometric method was developed for the identification and quantitation of oxytetracycline, tiamulin, lincomycin, and spectinomycin in veterinary preparations. Silica gel-coated thin layer chromatography plates and 2 mobile phases were used to separate these constituents. The appropriate compositions of the suitable mobile phases were established: 10% citric acid solution-n-hexane-ethanol (80 + 1 + 1, v/v) and n-butanol-ethanol-chloroform-25% ammonia (4 + 5 + 2 + 5, v/v). Along with Rf values and spot colors, direct UV and visual densitometric measurements were used for identification. Similar measuring ranges were used for quantitative analysis to obtain repeatable and reliable results for the preparations examined. The results of the quantitative analysis are characterized by a small confidence interval and are close to the declared contents of active constituents: oxytetracycline 30.01 +/- 0.38 g at lambda = 350 nm and 30.24 +/- 0.86 g at lambda = 430 nm; tiamulin, 10.19 +/- 0.86 g at lambda = 450 nm; lincomycin, 2.27 +/- 0.08 g at lambda = 278 nm; and spectinomycin, 2.18 +/- 0.07 g at lambda = 421 nm. The recoveries for all antibiotics ranged from 100.01 to 102.54%.

Preliminary assays to elucidate the structure of oxytetracycline's degradation products in sediments. Determination of natural tetracyclines by high-performance liquid chromatography-fast atom bombardment mass spectrometry

A very specific high-performance liquid chromatography-mass spectrometric method for the determination of natural tetracyclines was developed in order to characterise the degradation products of oxytetracycline in sediments. First, extraction used a clean up step with a Bond Elut Certify LRC cartridge. A 3 microm Spherisorb ODS1 column was then used with a methanol, acetonitrile and oxalic acid mobile phase gradient. Chromatographic resolution in these conditions was 3.31 between oxytetracycline and tetracycline. Two liquid chromatography-mass spectrometry methodologies based on a particle beam and a frit fast atom bombardment interface were developed. In the first approach, ionisation was performed in the negative chemical mode using methane as reacting gas. In the other case, glycerol-thioglycerol mixture was used as matrix to ensure good sensitivity. MS-MS experiment was performed to determinate oxytetracycline fragmentation pattern in the perspective of degradation product study.

A rapid high performance liquid chromatographic (HPLC) assay for the determination of oxytetracycline in commercial pharmaceuticals

In the present study, a simple, sensitive and rapid reversed-phase high performance liquid chromatographic (HPLC) method with ultraviolet detection for the analysis of oxytetracycline (OTC) is developed and applied to the determination of the antibiotic in commercial pharmaceutical preparations (powder, capsules, vaginal tablets and ointment). The isocratic elution is performed with methanol-0.01 M oxalic acid, pH 3.0 (30:70, v/v) at a flow rate of 0.95 ml min, using a Silasorb C8 analytical column, 250 x 4 mm, 10 microm. Codeine is used as internal standard. Absorbance is monitored at 250 nm where both analyte of interest and internal standard have significant absorption. Total analysis time was approximately 7 min. Data with respect to precision and accuracy and limits of detection are reported and discussed. The described method can be readily utilised for analysis of pharmaceutical products and pharmacokinetic studies as well.

Food safety implication: certain antibiotics may rapidly contaminate egg albumen during the process of its formation

1. Egg white formation occurs in 3 phases: synthesis and storage of albumen proteins prior to ovulation, secretion of proteins during passage of the ovum down the reproductive tract (preplumping) and addition of water (plumping phase). 2. This study was to determine if oxytetracycline would transfer into egg albumen during the latter 2 phases of albumen formation. 3. In 2 experiments 48 hens were injected with either 400 mg/kg oxytetracycline or physiological saline. Hens were dosed at 0.5 h (preplumping phase) or 5.5 h (plumping phase) after oviposition. 4. Five hours following injections, hens were euthanised and albumen was collected from the reproductive tract. 5. Oxytetracycline transferred into albumen during both phases of albumen formation. Concentrations (ppm) were greater in the preplump vs plump phase (3.2 vs 1.8 in experiment 1; or 2.8 vs 1.6 in experiment 2. However, when differences in albumen weights were accounted for, total microg transfer did not differ between the 2 phases. 6. Drugs may transfer into egg whites during the latter phases of formation prior to oviposition. Therefore, poultry producers or veterinary practitioners dosing laying hens must consider that egg whites contained in the 1st egg laid after dosing may contain drug residues.

Sorption and mobility of metronidazole, olaquindox, oxytetracycline and tylosin in soil

Laboratory studies were conducted to characterise four different antibiotic compounds with regard to sorption and mobility in various soil types. Distribution coefficients (Kd values) determined by a batch equilibrium method varied between 0.5 and 0.7 for metronidazole, 0.7 and 1.7 for olaquindox and 8 and 128 for tylosin. Tylosin sorption seems to correlate positively with the soil clay content. No other significant interactions between soil characteristics and sorption were observed. Oxytetracycline was particularly strongly sorbed in all soils investigated, with Kd values between 417 in sand soil and 1026 in sandy loam, and no significant desorption was observed. Soil column leaching experiments indicated large differences in the mobility of the four antibiotic substances, corresponding to their respective sorption capabilities. For the weakly adsorbed substances metronidazole and olaquindox the total amounts added were recovered in the leachate of both sandy loam and sand soils. For the strongly adsorbed oxytetracyline and tylosin nothing was detected in the leachate of any of the soil types, indicating a much lower mobility. Results from defractionation and extraction of the columns (30 cm length) showed that 60-80% of the tylosin added had been leached to a depth of 5 cm in the sandy loam soil and 25 cm in the sand soil.

The dissolution kinetics of sulfamethoxazol, trimethoprim and oxytetracycline hydrochloride from multicomponent solid dispersion capsules ("Sulfoxytrim")

Release profiles and dissolution kinetics of active substance, viz. sulfamethoxazol (SMO), trimethoprim (TMP), and oxytetracycline hydrochloride (OTC) from capsulated multicomponent dispersions was studied in a flow-cell apparatus at 37 degrees C by using a dissolution medium of 0.1 mol/l HCl. The results revealed that the relative dissolution efficiency (DE) and dissolution profiles of one active ingredient were affected by the presence of the two others. Vitamin C added caused the decreased the dissolution rate constants (K) and DE--values of all the active substances studied.

Spiramycin, oxytetracycline and sulphamonomethoxine contents of eggs and egg-forming tissues of laying hens

Spiramycin (SP), oxytetracycline (OTC) or sulphamonomethoxine (SMM) was fed to laying hens at a dietary level of 400 p.p.m. for 7 successive days. After 7 days of medicated feed, the concentrations of SP, OTC and SMM were determined in the blood, liver, ovary, oviducts (magnum and isthmus plus shell gland) and eggs (albumen and yolk) by high-performance liquid chromatography. Of the three drugs, OTC showed the lowest content in the above tissues and eggs, while the reverse was true for SMM. Low concentrations of SP were measured in the blood, whereas contents in the liver and the oviducts were relatively much higher.

[Detection of residual antibiotics in honey by capillary high performance liquid chromatography]

The quantitative analysis of the three antibiotics-tetracycline(TC), oxytetracycline(OTC) and chlortetracyclinum(CTC) was carried out with a self-packed Hypersil C18 150 mm x 0.5 mm i.d. column. As little as 0.5 nanogram of antibiotics can be well detected, the capillary high performance liquid chromatographic method is 100 times more sensitive than that with ordinary HPLC method. The coefficients of linear correlation of mass concentration from 0.5 nanogram to 20 nanogram were rOTC = 0.99695, rTC = 0.99778 and rOTC = 0.98836. It showed that capillary HPLC is a good method used for sensitive analysis of antibiotics in honey.

Determination of oxytetracycline in bovine kidney and medicated milk replacer by liquid chromatography

Improvements and optimization of AOAC INTERNATIONAL Official Method 995.09 for the detection of oxytetracycline in bovine kidney at the new U.S. tolerance of 12 ppm are reported. Recoveries from kidney fortified at 4 concentrations over the range of 3-40 ppm averaged 84-98%. Results from the kidney of a calf fed medicated milk replacer containing oxytetracycline are also reported. Additionally, adaptation of this method to the detection of oxytetracycline in medicated milk replacer is discussed.

Antibiotic residues in milk samples obtained from cows after treatment for papillomatous digital dermatitis

OBJECTIVE

To determine whether there would be detectable antibiotic residues in milk obtained from dairy cattle with papillomatous digital dermatitis (PDD) after topical treatment with oxytetracycline.

DESIGN

Randomized controlled clinical trial.

ANIMALS

28 lactating Holstein cows with PDD.

PROCEDURE

Cows were assigned to 2 treatment groups. Treatment 1 (n = 16) consisted of spraying of PDD lesions with 15 ml of a solution containing 100 mg of oxytetracycline/ml; lesions were sprayed twice daily for 7 days, using a garden sprayer. Treatment 2 (n = 12) consisted of a one-time application of a bandage that consisted of cotton soaked with 20 ml of a solution containing 100 mg of oxytetracycline/ml. Milk samples were obtained before and after treatment and assayed for tetracycline content by use of high-performance liquid chromatography and a commercially available tetracycline screening test.

RESULTS

None of the cows in either treatment group had violative residues of oxytetracycline in milk samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Producers treating lactating cows that have PDD, via topical application of oxytetracycline solution at the concentrations reported in this study, have a low risk of causing violative antibiotic residues in milk.

A bridging study for oxytetracycline in the edible fillet of rainbow trout: analysis by a liquid chromatographic method and the official microbial inhibition assay

Oxytetracycline (OTC) is a drug approved by the U.S. Food and Drug Administration (FDA) to control certain diseases in salmonids and catfish. OTC is also a likely control agent for diseases of other fish species and for other diseases of salmonids and catfish not currently on the label. One requirement for FDA to extend and expand the approval of this antibacterial agent to other fish species is residue depletion studies. The current regulatory method for OTC in fish tissue, based on microbial inhibition, lacks sensitivity and specificity. To conduct residue depletion studies for OTC in fish with a liquid chromatographic method, a bridging study was required to determine its relationship with the official microbial inhibition assay. Triplicate samples of rainbow trout fillet tissue fortified with OTC at 0.3, 0.6, 1.2, 2.4, 4.8, and 9.6 ppm and fillet tissue with incurred OTC at approximately 0.75, 1.5, and 3.75 ppm were analyzed by high-performance liquid chromatography (HPLC) and the microbial inhibition assay. The results indicated that the 2 methods are essentially identical in the tested range, with mean coefficients of variation of 1.05% for the HPLC method and 3.94% for the microbial inhibition assay.

Validation study for the determination of tetracycline residues in animal tissues

An interlaboratory study of the liquid chromatographic (LC) determination of tetracyclines--oxytetracycline (OTC), tetracycline (TTC), and chlortetracycline (CTC)--in animal tissues was conducted. Isolation was performed with oxalic buffer followed by dechelation and deproteination with oxalic acid-acetonitrile. The extract was cleaned with a styrene-divinylbenzene cartridge. LC analysis was performed with a PLRP-S column and 0.01 M oxalic acid-acetonitrile (75 + 25, v/v) as mobile phase. Participants analyzed 2 control and 10 fortified porcine muscle and kidney samples. Additionally, porcine muscle samples containing incurred residues of tetracyclines were analyzed. Mean recoveries of fortified residues from porcine tissue ranged from 76.00 to 86.89%. Repeatabilities varied from 2.05% for OTC to 3.61% for TTC for muscle samples and from 6.75% for CTC to 8.74% for OTC for kidney samples. Reproducibilities ranged from 2.05 to 4.30% for muscle samples and from 15.77 to 18.81% for kidney samples.

Monitoring of oxytetracycline in ovine milk by high-performance liquid chromatography

A method for 'in vivo' determination of the oxytetracyclin residues in ovine milk at low levels is described. Two groups of Sardinian breed sheep were treated with a dose of oxytetracycline by intramammary infusion and intramuscular administration, respectively. Oxytetracycline residues in extracts obtained from a preliminary cleanup procedure, were detected by an isocratic high-performance liquid chromatography (HPLC) method. Linear calibration plots were obtained over a large concentration range of 1 mg ml(-1)-10 ng ml(-1), with correlation coefficients higher than 0.996. Recoveries between 85.8 and 98.9% were obtained. Limit of detection (LOD) and limit of determination (LOQ) were 5.2 and 17.5 ng ml(-1), respectively. This method would be useful for routine monitoring of oxytetracycline residues in ovine dairy milk.

Rapid and simple determination of oxytetracycline in chicken products

A rapid and simple method for determining residual oxytetracycline (OTC) in chicken products (muscle, liver, and eggs) by high-performance liquid chromatography (HPLC) was developed. Samples were prepared by homogenization with acetonitrile-n-hexane (5 + 4, v/v) followed by centrifugation to minimize fat and protein contents. OTC in the acetonitrile layer was free from interfering compounds when examined by HPLC using a LiChrospher 100 RP-8 end-capped column, a mobile phase of acetonitrile-acetic acid-0.01 M disodium EDTA (28 + 2 + 70, v/v/v), and a photodiode array detector. Average recoveries from samples spiked with OTC (0.1, 0.2, and 1.0 ppm) were > 88%, with coefficients of variation between 2.3 and 5.1%. The limit of detection was 0.05 ppm.

Capillary electrophoresis of some tetracycline antibiotics coupled with reductive fast cyclic voltammetric detection

The separation and quantitative performance parameters for tetracycline, chlortetracycline and oxytetracycline antibiotics were investigated by capillary zone electrophoresis coupled with fast cyclic voltammetric detection. Optimization of pH and complexation with a boric acid-sodium tetraborate buffer provided good resolution of all compounds. Detection by electrochemical reduction using fast on-line cyclic voltammetric detection with a Hg-film-microm electrode gave detection limits (2 x peak-to-peak baseline noise) of 7 x 10(-7) mol/l for tetracycline and chlortetracycline, and 1.5 x 10(-6) mol/l for oxytetracycline. The influence of electrode material, potential range and scan rate was examined and discussed. Optimal electrochemical detection was obtained at a Hg-film electrode with a waveform that consisted of an initial constant potential of -0.6 V for 200 ms followed by a cyclic voltammetry (CV) scan at 300 V/s from - 0.6 V to a vertex potential of 1.7 V. The analytical signal was obtained by plotting the integrated values of the CV current from each applied waveform as a function of time. The calibration plot (peak areas) for each separated peak was found to be linear over three-orders of magnitude.

Rapid liquid chromatographic determination of oxytetracycline in milk

A simple method for the determination of residual oxytetracycline (OTC) in milk by high-performance liquid chromatography (HPLC) was developed. The sample preparation could be made without complex extraction and clean-up procedures. A LiChrospher 100 RP-8 end-capped column and a mobile phase of acetonitrile-acetic acid-water (28:4:68, v/v/v) with a photo-diode array detector was used. The average recoveries from spiked OTC (0.1, 0.5 and 1.0 microgram/ml) were in excess of 89.8% with coefficients of variation between 0.6 and 4.1%. The limit of detection was 0.05 microgram/ml. The total time required for the analysis of one sample was below 10 min.

Oxytetracycline transfer into chicken egg yolk or albumen

This study was conducted to determine whether the approved doses of oxytetracycline (OTC) for breeder hens and meat-type poultry would produce drug residue transfer into egg components when fed to laying hens. Twenty hens were assigned to equal groups (n = 10) and fed either 50 or 200 g/ton OTC for 5 d. Oxytetracycline concentrations in egg components were determined daily during a 2-d pretreatment control period, the 5-d dosing period, and following drug withdrawal. The stability and drug content of the medicated feed were determined the day dosing was started and the day of withdrawal. Residues of OTC were not detectable during the predosing, dosing, or withdrawal period in egg yolks. Oxytetracycline residues were detectable, however, in egg albumen during the 5th d of treatment and the 1st d of medicated feed withdrawal. These concentrations were close to the limit of the assay's sensitivity (117 ppb). These data indicate that illegal or unintentional dosing of laying hens with feed medicated at the doses allowed for breeder hens or meat-type poultry should not produce consistently detectable levels of residues of OTC in eggs.

Determination of oxytetracycline, tetracycline, and chlortetracycline in milk by liquid chromatography with postcolumn derivatization and fluorescence detection

A multiresidue method for isolation and liquid chromatographic determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in milk is presented. The sensitivity of the method is adequate to meet the needs of regulatory agencies. The European Community established 100 micrograms/kg as the maximum residue limit (MRL) in milk for TC, CTC, and OTC. Recoveries exceeded 80% for all tetracyclines at all levels, with good precision. Correlation coefficients of standards curves for individual tetracyclines isolated from fortified samples ranged from 0.991 for CTC to 0.998 for OTC. Other antibiotics that might interfere with analysis did not interfere with elution times of OTC, TC, and CTC. The procedure is rapid, precise, and quantitative and requires minimal preparation and minimal use of organic solvents. It can be applied to routine surveillance programs. We can prepare 10 samples for analysis in about 1.45 h.

Tetracycline, oxytetracycline and chlortetracycline determination by flow injection potentiometry

This paper describes tetracycline (TCH), oxytetracycline (OTCH) and chlortetracycline (CTCH) determination by flow injection potentiometry. In the flow system proposed TC samples are inserted in a carrier solution and converged with a Cu(II) solution of known concentration; the Cu(II) decrease due to its complexation with tetracyclines (TC) was monitored. The detector used was a homogeneous crystalline CuS/Ag2S double membrane tubular electrode with increased sensitivity. The present system allows tetracyclines determinations within a 48.1-4.8 x 10(3) ppm for TCH, 49.1-4.9 x 10(3) ppm for OTCH and 51.5-5.1 x 10(3) ppm for CTCH and a precision better than 0.4% for the three TC species. This procedure accomplishes 150-200 samples h(-1) with a Cu(II) consumption of about 13 microg determination(-1).

Results of a European interlaboratory study for the determination of oxytetracycline in pig muscle by HPLC

An interlaboratory study was organised in 1996 in order to determine laboratory testing performance for measuring oxytetracycline (OTC) and 4-epioxytetracycline (4-epiOTC) residues in pig muscle. The organisation was designed according to the 'International Harmonised Protocol for Proficiency Testing of (Chemical) Analytical Laboratories' produced by the Association of Official Analytical Chemists (AOAC International) and the International Union of Pure and Applied Chemistry (IUPAC). Fourteen National Reference Laboratories (NRLs) out of the 15 asked to participate agreed to analyse the samples. These laboratories were from 13 different European Union (EU) Member States and each participant was allowed to use the extraction method of their own choice but had to use liquid chromatography as the analytical technique. Most of the methods used were based on UV detection (simple wavelength or diode-array detection) but some involved fluorimetric detection. The production of incurred samples was prepared on-site. The OTC and 4-epiOTC concentrations present in the samples were determined by taking the mean of the results (excluding outliers) and the deviation of each result from the assigned value was measured. The performance of the laboratories was evaluated by calculating the 'z-scores'. The results were globally satisfactory and showed that all 14 laboratories were capable of determining OTC and 4-epiOTC in pig muscle with satisfactory accuracy. Only two laboratories obtained a questionable result in terms of repeatability.