The kind of statistics that you need is not specific to ion chromatography, or even to chemistry, it is just basic statistics. You need to compare the mean retention time of sets of injections under whatever different conditions you are experimenting on. You estimate the mean and the standard deviation from the raw data. A t test is probably what you need, but I am not sure that I understand what it is that you are trying to do - if there are no significant differences in the retention times of four compounds then you do not have a separation, and the method does not work.
Yes, there are calculations that you should do. You can do them with Excel.
Keep in mind that you can get large differences in retention time, but still not have statistical significance, if large variations in retention time are due to a poor method or sloppy operator technique. Two equally poor methods might not have a significant difference in retention if their retentions are not repeatable, but two good method with repeatable retentions might have a significant difference.
Peter