A New Zn2+-Selective Potentiometric Sensor
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Chem. Anal. (Warsaw), 51, 889 (2006) Keywords: Poly(vinyl chloride) (PVC); Nernstian slope; Zinc selective sensor; Dithizone A New Zn 2+ -Selective Potentiometric Sensor Based on Dithizone PVC Membrane by V.K. Gupta*, A.K. Jain and G. Maheshwari Department of Chemistry, Indian Institute of Techn ology, Roorkee, Roorkee-247 667 (India) Zn 2+ - selective sensor has been fabricated using poly(vinyl chloride) (PVC) matrix mem- branes containing a neutral carrier dithizone ( I) as an ionophore. The sensor exhibited the best performance for the following membrane composition: ( I) : PVCsodium tetraphenyl borate1-chloronapthalene (5 : 150 : 2: 150). This membrane worked well ov er a wide con- centration range of Zn 2+ , i.e. 5.1 × 10 6 1.0 × 10 1 mol L 1 and the corresponding calibration plots exhibited a Nernstian slope of 29.7 ± 0.1 mV per decade of Zn 2+ activity. The response time of the sensor was shorter than 8 s and the membrane could be used over a period of 6 months with good reproducibility. The proposed sensor could be operated over a wide pH range (3.16.5) and demonstrated good selectivity towards the analyte in the presence of several mono-, di- and trivalent cations. It could be also used in partially non-aqueous media containing up to 20% (v/v) of methanol, ethanol, or acetone and its Nerstian slope in the working concentration range remained almost unchanged. The proposed sensor has been used for determination of Zn 2+ in human hair samples by direct potentiometry. Sensor Zn 2+ -selektywny przygotowano u¿ywaj¹c membran na bazie matrycy z poli(chlorku winylu) (PCW) zawieraj¹cej obojêtny nonik ditizon (I) jako jonofor. Najlepsze w³a- ciwoci wykazywa³a membrana o sk³adzie (I): PCW: tetrafenyloboran sodu: 1-chloronaftalen w stosunku 5 : 150 : 2 : 150. Membrana ta pracowa³a poprawnie w zakresie stê¿eñ Zn 2+ szerszym ni¿ 5.1 × 10 6 1.0 × 10 1 mol L 1 z Nernstowskim nachyleniem 29.7 ± 0.1 mV/ dekada. Czas odpowiedzi sensora jest mniejszy ni¿ 8 s i membrana mo¿e pracowaæ przez okres d³u¿szy ni¿ 6 miesiêcy z dobr¹ odtwarzalnoci¹. Zaproponowany sensor dzia³a pop- rawnie w szerokim zakresie pH (3.16.5) i wykazuje dobr¹ dyskryminacjê wobec wielu jedno-, dwu- i trójwartociowych kationów. Sensor mo¿e byæ stosowany w czêciowo nie- * Corresponding author. E-mail: vinodfcy@iitr .ernet.in; Fax: +91-1332285043
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