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!!