Determination of Calcium Ion in Environmental Samples Using a Potentiometric Sensor as a Detector in Flow Injection Analysis Method

In this study, Ca2+-selective potentiometric PVC-membrane electrode was developed with the commercially purchased ionophore substance to be used to determine calcium concentration in water samples. The potentiometric performance characteristics of the electrode were determined and their suitability for environmental analysis was investigated The measurements taken with the Ca2+-selective electrode indicated an average potential change of 23,5 mV per decade against the main ion concentrations. The electrode showed linear behavior against the main ion solution in the concentration range between 1×10-1-1×10-5 mol L-1, and it was found to be highly selective against the main ion besides the alkali and alkaline earth metal ions. Micro dead volume flow cells were prepared in the laboratory and the calcium determination was made in environmental water samples by using the home-made electrode as a detector in the flow injection analysis (FIA) system. In the flow-injection analysis system (FIA), 5×10-5 M CaSO4 ve MgSO4; 1×10-6 M NaCl, KNO3, LiNO3 ve NH4Cl solution mixture was used as the mobile phase. In this system, the flow-rate was set to 1,0 mL min-1 and injection volume 20 μL. In addition, calcium determination in water samples was performed by standard addition method and all measurements were compared with potentiometric results. The results show that the Ca2+-selective micro-potentiometric PVC-membrane electrode can effectively be used for routine determination of calcium ion in water in environmental samples