HPLC separation of tetracycline analogues: comparison study of laser-based polarimetric detection with UV detection.

A sensitive and specific high-performance liquid chromatography (HPLC) method based upon laser-based polarimetric detection is developed for the determination of six tetracycline analogues. By interfacing the laser-based polarimeter online with an HPLC system, the specific rotation of each analogue is obtained as compounds elute from the separation system. The six structurally similar tetracycline analogues exhibit significant differences in specific rotations. The experiments suggest that specific rotation can be useful in identifying closely related tetracycline analogues. Linear relationships are found to be in the range of 0.342-0.0043 mg for the tetracycline analogues. Five of the six analogues exhibit excellent linearity (R(2) value >/= 0.99). The polarimetric results are compared with UV detection. The HPLC-laser-based polarimetric detection instrument is able to quantitate the studied tetracycline analogues with high precision, accuracy, and sensitivity, which make it useful for the development of a standard method for the determination of tetracyclines in biological specimens. The performance of the HPLC-polarimetric system for the analysis of tetracyclines in a biological matrix is evaluated. The selectivity of polarimetric detection provides a distinct advantage in the analysis of tetracycline analogues in milk. The HPLC-polarimetric system provides a rapid and sensitive technique that involves minimal sample cleanup and pretreatment for the analysis of tetracyclines in milk.