Oxytetracycline confirmation

For confirmatory assay, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is becoming more frequently used in the analysis of OTC owing to its high sensitivity and ability. Electrospray ionization (ESI) [55-57] and atmospheric pressure chemical ionization (APCI) [41] methods combined with tandem mass spectrometry are favored because of their higher sensitivity and better reproducibility. Hamscher et al. [58] developed a method for the determination of persistent TC residues in soil fertilized with manure by HPLC tandem mass spectrometry, MS-MS, and confirmation by MS-MS-MS. Zhu et al. [59] developed an LC-tandem mass spectrometry for the analysis of common tetracyclines in water. The detection limit for oxytetracycline was 0.21 pg/L. Lykkeberg et al. [60] used LC-MS/MS for determination of oxytetracycline and its impurities EOTC, TC, ETC, ADOTC, oc-AOTC, and /i-AOTC. 

Results showed a total of 2.8% of the samples (n 2972) to be inhibitor positive by the Delvotest SP test further examination identified 1.7% as -lactam antibiotics, and 1.1 % as sulfonamides and dapsone. The percentage of chloramphenicol suspicious samples determined by the Charm II test was amazingly high however, tests for confirmation were not available and contamination of the samples by residues of the chloramphenicol-based preservative azidiol could not be excluded with certainty. Low concentrations of streptomycins were also detected in 5.7% of the samples (n 1221), but the MRL was not exceeded. Macrolide and tetracycline residues were not found in significant levels. Model trials with commercially applied yoghurt cultures confirmed how important the compliance to MRLs can be to dairy industry compared to antibiotic-free milk, a pH of 5.0 was reached with a delay of 15 min in the case of contamination with cloxacillin 30 min in the case of penicillin, spiramycin, and tylosin and 45 min in the case of oxytetracycline contamination. 

Quantification and confirmation of tetracycline, oxytetracycline, and chlortetracycline residues in milk (84) as well as chloramphenicol residues in calf muscle (85) have been also carried out using LC-PB-NCI-MS. Use of an SIM mode allowed a detection limit of about 100 ppb for the tetracyclines and 2 ppb for chloramphenicol residues. 

MC Carson, MA Ngoh, SW Hadley. Confirmation of multiple tetracycline residues in milk and oxytetracycline in shrimp by liquid chromatography-particle beam mass spectrometry. J Chromatogr B 712 113-128, 1998. 

Residues of oxytetracycline, tetracycline, and chlortetracyline in bovine milk were determined and confirmed after centrifugation of the milk, filtration over a 25 kDa cut-off filter, and SPE on a C,8 cartridge. Methanol-oxalic acid-acetonitrile was used as mobile phase. Four ions for each tetracycline from the negative-ion mass spectra were used for confirmation at 100 ng/ml level [97]. Carson et al. [98] reported the determination of tetracycline residues in milk and oxytetracycline residues in shrimp. Off-line metal-chelate affinity chromatography on Cu " -loaded chelating Sepharose in combination with SPE on polymeric ENVI-ChromP material was used for sample pretieatment. LC is performed using a PLRP-s polymeric material and 5 mmol/1 oxahc acid in the mobile phase. The method is vahdated with samples spiked at 30 ng/ml in milk and 100 ng/g in shrimps. 

P.J. Kijak, M.G. Leadbetter, M.H. Thomas, E.A. Thomson, Confirmation of oxytetracycline, tetracycline and chlortetracycline residues in milk by particle-beam liquid chromatography-mass spectrometry, Biol. Mass Spectrom., 20 (1991) 789. 

Similar results were found in 16 other patients taking various combinations of phenytoin, carbamazepine, primidone or phenobarbital. The serum doxycycline levels of almost all of them fell below 0.5 micrograms/mL during the 12 to 24 hour period following their last dose of doxycycline 100 mg. Tetracycline, methacycline, oxytetracycline, demeclocycline and chlortetracycline levels were not significantly affected by these antiepilepties. Other studies confirm this interaction between some barbiturates (amobarbital, pentobarbital, phenobarbital) and doxycycline. ... 

Fawcett and Pepys (1976) reported the case of a patient who developed immediate bronchospasm and an urticarial reaction after ingestion of a commercial combination of three tetracyclines no reactions could be elicited by oral challenge with the different tetracyclines, tartrazine, or the blue coating of the drug, whereas a provocation test with the commercial preparation was positive. Other clinical patterns, such as fixed drug eruptions (Kandil 1969 Delaney 1970 Csonka et al. 1971 Brown 1974 Shimizu and Shimao 1977 Pasricha and Shukla 1979), vascular purpura (Schoenfeld 1964) and a picture similar to systemic lupus erythematosus (SLE) (Sulkowski and Haserick 1964) have also been described. Contact dermatitis seems to be a very rare complication it was, however, observed after contact with oxytetracycline (Dohn 1962 Bojs and Moller 1974) and minocycline. In the latter case subsequent oral therapy with the same drug was followed by a systemic reaction and the sensitivity was confirmed by epicutaneous tests (Shelley and Heaton 1973). 

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