Certified Reference Materials for Calibration of Conductivity Meter at The Measuring of Electrolytic Conductivity in Water: Preparation and Its Measurement

The electrolytic conductivity is a very important parameter in water because the amount of electrolytic conductivity can describe the quality of water. To get the accurate result of measurement, the conductivity meter must be calibrated using certified reference materials (CRM) which has traceability property to SI. Based on this, the availability of CRM for measuring electrolytic conductivity is an inevitable requirement for testing laboratories. At present in Indonesia, most CRM are obtained from foreign producers with fairly expensive import prices and limited self-life due to the shipping time. In an effort to provide standard solution reference material for conductivity meter calibration in Indonesia, a research for preparation of CRM has been carried out. The CRM, made from standard solutions of 0.1 M KCl solution, is traceable to the primary reference material CRM-1603 from Danish Fundamental Metrologi, DFM (conductivity = 9.996 mS/cm with uncertainty is 0.13%) and is intended to calibrate conductivity meter in measurements of water conductivity between 1 to 20 mS/cm. The measurement of the CRM conductivity value was carried out by the secondary method, namely the Jones cell method using Cell C. The conductivity values of the secondary reference material KCl 0.1 M was 12.880 mS/cm at 25 degrees C with uncertainty value at 0.50%. From the stability test at room temperature (20-27 degrees C), the reference materials stored in plastic bottles were stable for 9 months, demonstrating the reference material for testing conductivity has been successfully made in Indonesia and can replace imported reference materials.