Evaluation of turbidity measuring instruments using statistical process control

Abstract

The quality management system (QMS) and environmental management system (EMS) are currently being widely developed in laboratories, and have contributed to significant improvements in measurement management processes and client opinion. The purpose of this work is to establish appropriate methodologies for assessing the turbidity measurement that guarantee the quality of the results concerning precision and accuracy and also to test the service performance of the Water Analysis Laboratory of the Engineering Department (LAADEG) of Federal University of Lavras (UFLA). The research assessed two bench turbidimeters "A and B" through a statistical process capability study, analyzing the potential capability indexes (Cp) and performance capability (Cpk). We identified special causes also present in the control through non predetermined random patterns. After the studies, it was found that turbidimeter "B" should be used for all turbidity measurements in LAADEG, since its precision was higher than turbidimeter "A".