Calcium(II)-selective potentiometric sensor based on α-furildioxime as neutral carrier

A highly selective poly(vinyl chloride)-based membrane sensor using α-furildioxime (I) as neutral carrier have been prepared and explored as Ca2+-selective electrode. Effect of various plasticizers, viz. dibutylphthalate (DBP), dioctylsebacate (DOS), acetophenone (AP), benzyl acetate (BA), tributylphosphate (TBP) and o-nitrophenyloctyl ether (o-NPOE) with anion excluder sodium tetraphenylborate (NaTPB) and KTpClPB were studied. Best performance was exhibited by the membrane having composition as I:PVC:DBP:KTpClPB as 4:32:62:2 (wt%). This membrane worked well over a wide concentration range 2.56 × 10−7–1.0 × 10−1 M of Ca2+ with a Nernstian slope of 29.5 ± 0.5 mV/decade of Ca2+ activity. The response time of the sensor is 10 s and the membrane can be used over a period 3 months with good reproducibility. The proposed electrode works well in a wide pH range 3.5–9.0 and can be used in a non-aqueous solution containing up to 20% (v/v). The sensor has also been used as an indicator electrode in the potentiometric titration of calcium(II) ions against ethylenediaminetetraacetic acid (EDTA). The sensor has been used for the analysis of Ca2+ ions in soil drainage water samples.