We found that pyridine-2-carbaldehyde-2-(4-methyl-1,3-benzothiazol-2-yl) hydrazone (PCMHT) can be used as a suitable neutral ionophore for preparing an Er(III) membrane sensor with high selectivity. The optimum composition was found to be PCMHT-PVC-KTpClPB-BA with the ratios of 6.0:30.0:5.0:59.0, respectively. The Nernstian response was of 21.8 ± 0.5 mV decade-1 of Er(III) activity, the linear range of the sensor was found to be relatively wide (from 1.0x10-5 to 1.0 x10-2 mol L-1). Its applicability pH range of 2.5-12.0 seems to make it suitable for analytical applications. The lower detection limit (LDL) of the sensor was 5.0 x10-6 mol L-1. The excellent Er(III)-selectivity of the proposed sensor with regard to most common metal ions, and especially, lanthanide ions is another advantage. It was successfully used as an indicator electrode for titration of 25 mL of a 1.0 x 10-4 mol L-1 Er(III) ions with a 1.0 x 10-2 mol L-1 EDTA. The proposed sensor was used for direct monitoring of Er(III) in binary mixtures and indirect determination of fluoride ions in two mouth wash preparations.
Er(III); ion selective electrode; PVC; pyridine-2-carbaldehyde-2-(4-methyl-1,3-benzothiazol-2-yl)hydrazone
