Performance monitoring of analytical measurement instrument through control charts

Abstract

The quality management system, based on the good laboratory practices (GLP) principles, implemented in the Analytical Chemistry Division, provides for the maintenance and periodic check of measurement instruments used in the studies. The control charts are tools that visually help, through charts, this equipment's work control and monitoring. There are various models of control charts, being the Shewhart Cycle the most famous model. In this model, average values are used and the results must prove random around the average, not presenting trends. At the laboratory, the checks were made for analytical balances AB 204 S and HR 31 models, both manufactured by Mettler, using standard weight of 10 mg, through weekly checks along one year. The standard weight's uncertainty value corresponds to the expanded uncertainty used, corresponds to 95% trust (coverage factor = 2). After measurements, the X-bar (as they are also known) control charts were prepared, and their access was free to analysts, providing more efficient decision-making.