EXPERT SYSTEM FOR REPEATABILITY TESTING OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHODS

Abstract A repeatability test is performed as part of the validation of the precision of a high-performance liquid chromatographic method. The purpose of the test is to establish the random errors of the method wit respect to various method features. It is usual to test the repeatability of the sample preparation and the injection procedure by a number of repetitions. The number of repetitions depends on the application of the method. For instance, a quality control method is expected to analyse up to and over 50 samples in a single run. The repeatability test of the injection process therefore needs to reflect this number, in order to identify fully potential errors. These errors could be due to the instrument error or to drifting factors such as temperature. The expert system described provides the necessary expertise to identify the required tests and interpret the results. It also contains a diagnosis module which can identify sources of unacceptable errors. The diagnosis module is linked to a reoptimization process which can modify the method to improve the resolution between a critical pair of peaks. This expert system was built as part of the ESCA project, which is a 3-year project investigating the application of expert systems to analytical chemistry. A repeatability test requires both heuristic and algorithmic knowledge and therefore provides a good challenge for expert system technology. The system is implemented in a multiple windows software environment and uses workstation hardware. This software has been evaluated in practical laboratory environments and some of the results and conclusions are described. The major advantage of an expert system implementation appears to be that it can give advice when problems occur. It also ensures that the statistics are used and interpreted correctly. This is not possible using conventional algorithmic software.