Fluorinated tripodal receptors for potentiometric chloride detection in biological fluids

Abstract

Fluorinated tripodal compounds were recently reported to be efficient transmembrane transporters for a series of inorganic anions. In particular, this class of receptors has been shown to be suitable for the effective complexation of chloride, nitrate, bicarbonate and sulfate anions via hydrogen bonding. The potentiometric properties of urea and thiourea-based fluorinated tripodal receptors are explored here for the first time, in light of the need for reliable sensors for chloride monitoring in undiluted biological fluids. The ion selective electrode (ISE) membranes with tren-based tris-urea bis(CF) tripodal compound (ionophore I) were found to exhibit the best selectivity for chloride over major lipophilic anions such as salicylate ( [Formula: see text] ) and thiocyanate ( [Formula: see text] ). Ionophore I-based ISEs were successfully applied for chloride determination in undiluted human serum as well as artificial serum sample, the slope of the linear calibration at the relevant background of interfering ions being close to Nernstian (49.8±1.7mV). The results of potentiometric measurements were confirmed by argentometric titration. Moreover, the ionophore I-based ISE membrane was shown to exhibit a very good long-term stability of potentiometric performance over the period of 10 weeks. Nuclear magnetic resonance (NMR) titrations, potentiometric sandwich membrane experiments and density functional theory (DFT) computational studies were performed to determine the binding constants and suggest 1:1 complexation stoichiometry for the ionophore I with chloride as well as salicylate.

New Insights into the Anion Transport Selectivity and Mechanism of Tren‐based Tris‐(thio)ureas

“…The chloride bindingp roperties of these compounds has been previously reported, [16] however developmentsi nb inding isotherm fitting methodology now allows more complex equilibria to be analysed. [17] The compounds were found to bind chloride with stepwise higher stoichiometry, [18] and the curve-fitting analysiso ft he binding isotherms for compounds 1-10 gave abetter fit to the 1:2receptor:anion bindingm odel than the 1:1m odel. The associationc onstants (K a )o btained (Table 1) show thiourea compounds 6-10 bind chloride with ah igher affinity compared to the analogousu rea compounds 1-5.This has been observedp reviously,and is presumably due to the more acidic nature of the thiourea hydrogen bond donor.…”

Tripodal Squaramide Derivative as a Neutral Chloride Ionophore for Whole Blood and Sweat Chloride Measurement

“…Compound 3 based membrane had linear response toward chloride ion from 10 −5 to 10 −1 M with slope of 55 mV/decade. The sensor exhibited fast response time and superior selectivity to previous reported chloride ionophores .…”

“…Due to the lack of selective chloride ionophores for samples that contain salicylate or thiocyanate as in the case of blood or serum samples no suitable ISEs available for chloride measurement [34]. Although it had been reported that the ion selective membranes with tren-based tris-urea bis(CF 3 ) tripodal compound exhibited the selectivity for chloride over salicylate and thiocyanate, the interfering anions are still preferred at the same concentration level with logK Cl À , Sal À (pot) = + 1.0 [34]. In this work the tripodal squaramide derivatives with different phenyl substitutes 1-3 were incorporated into plasticized PVC membranes with TDMACl as ion exchangers.…”

Ion‐exchange Microemulsions for Eliminating Dilute Interferences in Potentiometric Determinations

“…This is because the interfering ion is effectively removed from the membrane surface by diffusion into the membrane bulk. The effect is most useful with membranes that contain a high ion‐exchanger salt concentration and that exhibit a relatively high ion mobility . For relatively short contact times a reduced level of interference is observed, seemingly in defiance of the ion‐exchange equilibrium.…”