Tetracycline metal chelate affinity chromatography

Elimination of coextracted materials and concentration of tetracyclines have also been accomplished using mixed-phase extraction membranes with both re-versed-phase and cation-exchange properties (294,295), or solid-phase extraction columns packed with cation-exchange materials such as CM-Sephadex C-25 (301), aromatic sulfonic acid (310), and carboxylic acid (283, 300). For the same purpose, metal chelate affinity chromatography has also been employed. In this technique, the tetracyclines are specifically absorbed on the column sorbent by chelation with copper ions bound to small chelating Sepharose fast flow column (278-281, 294-296). 

In a different approach, Cooper et al. (305) developed an online metal chelate affinity chromatography-liquid chromatographic method for the determination of oxytetracycline, tetracycline, demeclocycline, and chlortetracycline residues in animal tissues and egg. According to this method, a 2 g blended egg or thinly sliced tissue is homogenized with citrate buffer pH 5 (pH 4, for chicken... 

MC Carson, W Breslyn. Simultaneous determination of multiple tetracycline residues in milk by metal chelate affinity chromatography—collaborative study. J AOAC Int 79 29-42, 1996. 

S Croubels, KEI Vanoosthuyze, CH VanPeteghem. Use of metal chelate affinity chromatography and membrane-based ion-exchange as cleanup procedure for trace residue analysis of tetracyclines in animal tissues and egg. J Chromatogr B 690 173-179, 1997. 

G Stubbings, JA Tarbin, G Shearer. Online metal chelate affinity chromatography cleanup for the high-performance liquid chromatographic determination of tetracycline antibiotics in animal tissues. J Chromatogr B 679 137-145, 1996. 

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. 

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. 

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