Simultaneous determination of 23-antibiotics in mariculture water using solid-phase extraction and high performance liquid chromatography-tandem mass spectrometry

A method for the determination of 23 antibiotics from 6 categories in water was developed by using solid-phase extraction and high performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS/MS). Water samples were enriched and cleaned-up by solid-phase extraction cartridges. The MS detection parameters of the analyzed antibiotics, the pH values of loading buffers and the volumes of the eluents were optimized by comparing the sample recoveries under different conditions. All antibiotics were separated by gradient elution with the mobile phases of 0.1% (v/v) formic acid and 1 g/L ammonium formate in water and aceto-nitrile-methanol (1:1, v/v) mixture. The eluate was then analyzed by HPLC-MS/MS in both positive and negative electrospray ionization conditions with multiple reaction monitoring (MRM) mode. The method detection limits (MDLs) were in the range of 0.1-2.9 ng/L and the recoveries of 23 antibiotics in water ranged from 47.3% to 132.6%. The developed method was applied to the analysis of 5 water samples from mariculture ponds located in Dongying City, Shandong Province. The results showed that the antibiotics could be detected in all water samples. The trimethoprim showed the highest detection rate, and the florfenicol had the highest mass concentration which reached 261. 0 ng/L. The results showed that the developed method is efficient, sensitive and reliable, which is suitable for the detection of antibiotics in seawater samples.