2015 Volume 64 Issue 1 Pages 25-34
A liquid chromatography/tandem mass spectrometric (LC-MS/MS) procedure for the determination of four tetracycline antibiotics [chlortetracycline (CTC), tetracycline (TC), oxytetracycline (OTC) and doxycycline (DC)] and iso-chlortetracycline (iso-CTC) of CTC metabolite in water samples has been developed. The target analytes in a water sample were solid-phase extracted by the use of a hydrophilic-lipophilic balance cartridge, which were then determined by LC-MS/MS. The combination of the addition of disodium ethylenediaminetetraacetate (EDTA-2Na) as a metal chelation agent to the water sample and elution by back-flushing with methanol/water with 0.1% formic acid (1 : 1, v/v) from the cartridge resulted in quantitative recoveries by solid-phase extraction. The mean recoveries in water samples ranged from 80 to 106% (c.v. 1.9 – 9.0%), and the method detection limits were between 2.8 and 6.2 ng L−1. It was found that this method enables the reliable determination of tetracycline antibiotics and iso-CTC of CTC metabolite residues in water samples at the ng L−1 level. Furthermore, to confirm the derivation of iso-CTC from CTC in an aquatic environment, recovery tests of CTC added to water samples were conducted using this determination method. The results showed that some of the CTC in aquatic environment are converted into iso-CTC, which is affected by a water matrix less than CTC, indicating that iso-CTC is likely to remain in the aquatic environment.
