Fluorinated covalent organic frameworks as a stationary phase for separation of fluoroquinolones by capillary electrochromatography

A fluorinated covalent organic framework composed of 2,3,5,6-tetrafluoroterephthaldehyde (TFA) and 1,3,5-tri(4-aminophenyl)benzene (TAPB) is proposed for electrochromatographic separation. TFA-TAPB is for the first time regarded as the stationary phase of capillary electrochromatography. The TFA-TAPB-coated capillary columns exhibited satisfactory separation (resolution values > 1.5) and good reproducibility towards fluoroquinolones. The intraday relative standard deviations (RSDs) of retention time and peak areas were 0.54-0.68% and 1.69-2.82%, respectively. The interday RSDs of retention time and peak areas were less than 1.79% and 2.30%, respectively. The column-to-column RSDs of retention time and peak areas were 0.22-0.73% and 0.74-1.86%, respectively. And, the inter-batch RSDs of retention time and peak areas were less than 0.39% and 1.67%, respectively. Moreover, the possible separation mechanism was discussed, and it was found that the n-n stacking effect, hydrophobic interaction, hydrogen bonding, and fluorous interactions were the main factors. Overall, these results demonstrated that TFA-TAPB has high prospect for CEC separation.