Novel ISE modified with synthesized magnetite nanoparticles for sulfates determination

• Due the fact sulfates have significant impact to environment, developing a simple and inexpensive sensor for their determination is desirable. On the other hand, potentiometric ion-selective electrodes (ISEs) are the sensors known with their feasibility and can be manufactured easily and can be used for on field investigations. ISEs have application food industry, agriculture, environmental analysis and drug analysis as they offer numerous advantages: high selectivity and sensitivity, low limit of detection, small size, easy handling, portability and low cost. • According previously mentioned, we developed a solid-state ISE for the potentiometric determination of sulfate ions. The membranes are based on a mixture of barium sulfate, silver sulfide, polymer and metal oxide nanoparticles (NPs). The mass ratio of BaSO 4 , Ag 2 S and polytetrafluoroethylene (PTFE) in the membranes was 1 : 1 : 2, with an addition of 0.25-1,0% Fe 3 O 4 , 0.5% α-Fe 2 O 3 , and 0.25% Al 2 O 3 and 0.25% ZnO nanoparticles in mixture. The membrane containing magnetite NPs showed a positive effect on the linear response range for sulfate anions. In particular, the membrane containing 0.6% magnetite NPs showed a linear potential change with a slope of 27.7 mV dec −1 , which is very close to the theoretical Nernst's value (29.6 mV dec −1 ), with a regression coefficient of 0.9970 in the concentration range between 4.88 ∙ 10 −5 mol L −1 and 1.00 ⸱ 10 −2 mol L −1 with LOD 4.34 ∙ 10 −5 mol L −1 . Finally, the membranes showed no response to barium ions even at high concentrations (≥ 1.00 ∙ 10 −3 mol L −1 ). These results confirm that our newly developed potentiometric sensor has a high membrane selectivity for the determination of sulfate ions and, most importantly, that it is a fast, reliable and cost-effective tool. Potentiometric ISEs are one of the fastest developing sensors in electrochemistry due to their wide range of applications. They are used in the food industry, agriculture, environmental and drug analysis as they offer numerous advantages: high selectivity and sensitivity, low LOD, small size, easy handling, portability and low cost. We have therefore developed a solid-state ISE for the potentiometric determination of sulfate ions. The membranes are based on a mixture of barium sulfate, silver sulfide, polymer and metal oxide nanoparticles. The mass ratio of BaSO 4 , Ag 2 S and PTFE in the membranes was 1 : 1 : 2, with the addition of various metal oxide NPs, such as Fe 3 O 4 , α-Fe 2 O 3 , Al 2 O 3 or ZnO, to the membrane composition. The membrane containing magnetite NPs showed a positive effect on the linear response range for sulfate anions. In particular, the membrane containing 0.6% magnetite NPs showed a linear potential change with a slope of 28.5 mV dec −1 , which is very close to the theoretical Nernstian value (29.6 mV dec −1 ), with a regression coefficient of 0.9978 in the concentration range between 4.88 ∙ 10 −5 mol L −1 and 1.00 ⸱ 10 −2 mol L −1 with LOD 4.40 ∙ 10 −5 mol L −1 . Finally, none of the membranes showed response to barium ions even at high concentrations (≥ 1.00 ∙ 10 −3 mol L −1 ). These results confirm that our newly developed potentiometric sensor has a high membrane selectivity for the determination of sulfate ions and, most importantly, that it is a fast, reliable and cost-effective tool.