Analytical Sciences

Novel Potentiometric Sensor for Monitoring Beryllium Based on Naphto-9-crown-3

Mohammad Reza GANJALI,*  Azadeh DAFTARI,* Majid FAAL-RASTEGAR,* and Abolghasem MOGHIMI**

*Departments of Chemistry, Tehran University, Tehran, Iran
**Departments of Chemistry, Imam Hossein University, Tehran, Iran

A novel poly(vinyl chloride) (PVC) membrane electrode based on naphto-9-crown-3 was prepared and tested for the selective detection of beryllium ions. A suitable lipophilicity of the carrier and appropriate coordination ability were found to be essential for designing an electrode with good response characteristics. A PVC membrane with 9% naphtho-9-crown-3 carrier, 58% o-NPOE plasticizer, 3% tetraphenylborate anionic excluder and 30% poly(vinyl chloride) satisfied these requirements. The proposed sensor displayed a linear response to beryllium over a wide concentration range of 1.0 x 10^-1 - 8.0 x 10^-6 M with a Nernstian slope of 29.5 mV per decade. The electrode showed very short response time (<15 s) and could be used in the pH range 3.5 - 9.0. The selectivity coefficient for alkali, alkaline earth, transition and heavy metal ions was smaller than 4.0 x 10^-4. The sensor was successfully used as an indicator electrode in the potentiometric titration of Be²⁺ with EDTA. The proposed Be(II) sensor was also used for the determination of Be2⁺ ions in binary mixtures.

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