Carbonate sensors based on 4-hexyltrifluoroacetophenone (Hex-TFA) and its 3-nitro- and 3-bromo-derivatives (NO₂-TFA and Br-TFA) were studied. The acceptor substituents in phenyl ring of Hex-TFA increase Lewis acidity of fluoroketone group and provide better carbonate selectivity of ionophore against lipophilic anions. The sensors containing hexyl trifluoroacetylbenzoate (HE) were used as reference. Variation of membrane composition and plastisizer were performed to optimize the selectivity. Potentiometric properties of carbonate sensors such as sensitivity, selectivity, detection limit (DL) and pH-dependence of sensor response were studied. The sensors based on NO ₂-TFA demonstrated significantly better selectivity than the sensors based on unmodified Hex-TFA, the effect was up to three orders of magnitude for salicylate and nitrate, more than four orders for thiocyanate. However, NO ₂-TFA sensors exhibited higher pH-dependence of sensor response and higher detection limits. The sensors based on Br-TFA showed the properties similar to that of HE-based sensors. These results allow recommending trifluoroacetophenone derivatives with acceptor substituents in phenyl ring as promising ionophores for carbonate sensors.