Autosampler run

It is necessary to study stability in solution in the solvent used to prepare sample solutions for injection in order to establish that the sample solution composition, especially the analyte concentration, does not change in the time elapsed between the preparation of the solution and its analysis by HPLC. This is a problem for only a few types of compound (e.g. penicillins in aqueous solution) when the sample solution is analysed immediately after the preparation of the sample solution to be injected. The determination of stability in solution is more of an issue when sample solutions are prepared and then analysed during the course of a long autosampler run. While the acceptance criteria for stabUity in solution may be expressed in rather bland terms by making a statement such as, e.g. the analyte was sufficiently stable in solution in the solvent used for preparing sample solutions for reliable analysis to be carried out , in practice it has to be shown that within the limits of experimental error, the result of the sample solution analysis by the HPLC method is the same for injections at the time for which stability is being validated as for injections immediately subsequent to the sample solution preparation. While this may be done by a subjective assessment of results with confidence limits, strictly speaking a statistical method known as the Student s t-test should be used. 

Figure 17.8. Data page for browsing all mass spectra of an autosampler run. (Reproduced with permission from Gilson-Micromass.)...

It should be pointed out that there are now flame AA instruments on the market that are achieving higher sample throughput by carrying out element sequential analysis. Most traditional AA instrumentation is operated in sample sequential mode where every sample in an autosampler run is analyzed for one element at a time until all the elements in the multielement run are determined. However, by using the instrument in element sequential mode, all the elements are determined one... 

---