Techniques for evaluating control of automated multi-determinant analytical instruments by computer

Abstract

Analytical data collected from calibration standards and other quality control standards using an amino acid analyser (18 ninhydrin products) and a plasma emission spectrometer (20 elements) are logged regularly during analysis periods. Principal components are derived from the data using principal component analysis and those that contain the most variation (usually first three) are plotted on cumulative sum charts (Cusums). Changes in the physico-chemical control of instruments can be clearly demonstrated and out of control events identified. The computer program can be run on any computer with sufficient memory to handle large matrix transformations. The technique is applicable to any instrument measuring several or many variables.