Application of 1-ethyl-3-(2,5-dihydro-4-(3,5-dimethyl-1 H-pyrazol-4-yl)-5-oxo-1 H-pyrazol-3-yl)thiourea as sensing material for construction of Tm 3+-PVC membrane sensor

Abstract

A thulium(III) membrane sensor was made using 2% sodium tetraphenyl borate (NaTPB), 65% dibutylphthalate (DBP), 30% poly(vinyl chloride) (PVC) and 3% 1-ethyl-3-(2,5-dihydro-4-(3,5-dimethyl-1 H-pyrazol-4-yl)-5-oxo-1 H-pyrazol-3-yl)thiourea (ET) as an ionophore. Conductometric study shows selectivity of the Et toward Tm 3+ ions. Nernstian response of 19.6 ± 0.4 mV per decade of thulium concentration was observed, and the electrode worked well in concentration range of 1.0 × 10 − 6 to 1.0 × 10 − 2 mol L − 1 with a lower detection limit (LDL) of 7.2 × 10 − 7 mol L − 1 , in a pH range of 4.3–10.4. The selectivity of the sensor over alkaline, alkaline earth, transition and heavy metal ions was also found to be in a satisfactory range. To check the analytical applicability of the proposed Tm 3+ sensor, it was successfully used as an indicator electrode in analysis of thulium in certified reference materials.