Chlortetracycline ultrafiltration

Alternative sample extraction techniques include an approach that combines the deproteinizing efficiency of dichloromethane with the ion-pairing ability of phenylbutazone for isolating tetracyclines from eggs (308). Another approach that was employed for extracting oxytetracycline from milk (285) or swine tissues (309), and tetracycline, oxytetracycline, and chlortetracycline from milk (284), was based on ultrafiltration. With ultrafiltration, however, not all low molecular-mass proteins are retained in the cut-off filters while interfering substances pass through the filter. 

Ultrafiltration (278, 279) and immunoaffinity chromatography (282) have also been described for removal of matrix components from milk extracts, while online trace enrichment has been reported for isolation/purification of tetracycline, oxytetracycline, demeclocycline, and chlortetracycline residues from animal tissues and egg constituents (305). The latter technique involves trapping of the analytes onto a metal chelate affinity preconcentration column (Anagel-TSK Chelate-5PW), rinsing of coextracted materials to waste, and finally flushing of the concentrated analytes onto the analytical column. 

With the differential pulse polarography [245], the antibiotics can be determined at low concentration, if necessary, at the ppm or even sub-ppm level. Tetracycline hydrochloride is determined in aqueous acetate buffer pH 4 (detection limit 0.1 ppm), but for the analysis of chlortetracycline hydrochloride, oxytetracycline hydrochloride and free tetracycline, a non-aqueous medium must be used. Streptomycin sulphate is analysed in alkaline solution, trace quantities of zinc being masked by Na2EDTA, and the detection limit is 1 ppm. A determination in blood serum or urine is also possible but the peak potentials are shifted here to more negative values. The polarographic determination is preceded by ultrafiltration. Penicillin G potassium and ampicillin must be first functionalised by nitrosation. The authors also recommend an analysis of mixtures which is however demonstrated only with chloramphenicol and tetracycline, at 2.4 and 4.2 ppm, respectively. 

Goto et al. " described a simple, rapid, and simultaneous analysis method for oxytetracycline, tetracycline, chlortetracycline, penicillin G, ampicillin, and nafcillin in meat using electrospray ionization tandem mass spectrometry. The samples were homogenized with water followed by a centrifugal ultrafiltration after addition of internal standards (demeclocycline, penicillin G-ds, ampicillin-fi 5, and... 

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