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Retention time shift for one analyte

Question asked by megaflorch on Jul 16, 2019
Latest reply on Jul 30, 2019 by ryoboyle




This question is related to my previous question about method development. The method I devised seems to work well, in that a calibration standard run after my curve is set up yields results that I expected. There is virtually no interferences from the new solvent chosen other than having to monitor solvent levels on the GC/FID because of hot weather and evaporation. When I run samples, which are prepared the same way that my calibration standards are prepared, there is a distinct retention time shift with only one of the compounds in the group of analytes. 1,2 trans dichloroethylene shows the retention time shift when it is run as a component of the sample. In calibration standards the retention time is 1.746 min and when it is part of a sample, the retention time is 1.726 min. The other component analytes all retain their retention times that match the calibration standards with no variation. I dont understand why first there is a shift and second, the other analytes in the sample show no retention time shift. I would appreciate any helpful insights or suggestions for resolving this. Also, I am rather a novice when manipulating integration parameters, and that makes me think that that has something to do with my dilemma. Thanks!!