System suitability

Abstract

The preceding list of possible system-suitability tests is by no means exhaustive. If all of these tests were run for every method, there would be no time to run actual samples. It is up to the method developer or analyst to determine which set of tests will provide the most assurance that the method is running as expected. The number of tests and specific results will depend upon the application. The previous nitrofurantoin example listed a typical set of requirements: resolution, retention, precision, and response. A cleverly designed system-suitability test should get the most information out of a minimum number of injections. For example, if you do not need precision data, one injection at the upper limit of the method followed by an extracted blank and an LLOQ sample might be sufficient to generate retention, response, carryover, reagent purity, peak tailing, and pressure measurements. You should set the system-suitability requirements so that they can be met easily if the method is working right but will fail if there is a method problem. Test requirements that are too stringent might not make the method any more reliable, and might only serve to delay the analysis of important samples. The regulatory agencies make one thing clear: system suitability should test the entire chromatographic system, not individual modules. One way of thinking about the system-suitability test is to consider it a minivalidation run just before each set of samples is run. When designed and used properly, system suitability should save you time and money - you will not waste time trying to analyze samples with a method that is not working correctly.