Assigned value determination by expert laboratory consensus on heavy metals proficiency testing of environmental laboratory 2018

Abstract

Abstract Determination of assigned values is an important stage in proficiency testing schemes in accordance with SNI / ISO 17043: 2010. Assigned value is a reference for determining the laboratory performance status in proficiency test participants. One alternative in determining Assigned value is through expert laboratory consensus. This method has an advantage over the reference value method, namely when there is no certificate reference material (CRM) that matches the proficiency test commodity or the corresponding CRM value is not in place. This study was aimed at determining the assigned value of laboratory proficiency testing of heavy metal parameters by employing the expert laboratory consensus method. In this study, the expert laboratory tested were 20 laboratories included the one in the environmental metrology road map. The laboratories have been accredited according to ISO / IEC 17025. Statistical calculations through Algorithm A, and iteration technique were implemented in this procedure. This will make it easier to determine the assigned value because it does not need to be through the reference value calibration of the CRM value. It was found out that the assigned value in mg/L for each metal, i.e Zn, Fe, Mn and Cd were 0.08; 0.4; 0.3 and 0.06 respectively. It was also shown that the assigned value derived from this expert laboratory consensus were not significantly different from the target value, except for Zn metal that differed from the target by 0.01 mg/L. However, it is important to keep reviewing the competence of the expert laboratory on a regular basis to ensure the validity of the values produced.