A novel potentiometric pH electrode based on sulfated natural Fe3O4 and analytical application in food samples

Abstract

A novel solid state potentiometric pH electrode based on sulfated natural Fe3O4 silicone was fabricated. The optimum potentiometric performances such as Nernstian response, response time, selectivity, life-time and reproducibility of pH electrodes were investigated by using a computer-controlled potentiometric device. Moreover, the potentiometric performance of the solid state pH electrodes was studied with different mixtures sulfated natural Fe3O4, silicone and graphite powder. The best potentiometric behavior of proposed pH electrode was obtained with a composition of 20% (w/w) sulfated natural Fe3O4, 40% (w/w) graphite powder and 40% (w/w) silicone. The sub-Nernstian response for pH electrode was exhibited with a slope of 30.8 ± 1.4 mV/pH (r = 0.9963) from pH 2 to pH 12. In addition, the dynamic response time was found as 10 s in acidic medium and further the proposed pH electrode can be used for at least 1 year without any significant slope of the pH–potential curve. The selectivity coefficient of pH electrode was interpreted according to fixed interference method in the presences of Na+, Li+, K+, NH4+, SO42‒, CH3COO‒ and NO3‒ ions. The reproducibility of pH electrode was calculated in pH 4 and pH 6 phosphate buffers and it was found as 0.24 RSD (%) and 0.27 RSD (%) respectively. The proposed pH electrode was used to determine of pH in acid‒bases titration compared with glass pH electrode and is highly stable in corrosive systems including HF solution. Terminally, the pH value was successfully determined in some soft drinks and milk samples by proposed solid state pH electrode at 95% confidence level with satisfactory agreement compared with glass pH electrode.