Hydrotalcite-like compounds as ionophores for the development of anion potentiometric sensors

A double layered hydroxide anionic clay containing chloride or nitrate as the interlayer anion has been used to prepare ion-selective electrodes (ISE) for potentiometric sensing of the intercalated anionic species. The electrodes exhibited a linear range for the potential response to logarithm of concentration: from 5.0×10−5 to 2.0×10−1 M with an average slope equal to −54.2 mV decade−1 for chloride and from 2.0×10−4 to 1.0 M with an average slope equal to −48.3 mV decade−1 for nitrate. The response time was from 1 to 6 min, depending on the analyte concentration; the stability of the signal was quite satisfactory. The effect of interfering ions has been investigated and the values of the relevant selectivity constants have been determined. The lifetime of the sensors was at least 2 weeks.