Chromatography Forum

Recently in the course of troubleshooting I ran a sample using split ratio 10:1 in an inlet of 180C and starting column temp. of 50C using a methylene chloride solvent for the sample. I also ran splitless injecting 1-uL and splitless injecting 2-uL. The chromatography looked OK to me and the integration was correct - but my main peak area percent changed between all three runs progressively lower from my split ratio run of 97.29%, my splitless 1-uL injection 96.38%, and finally my splitless 2-uL injection was 93.04%! *The integration was correct on all scans.... so what explains what I have found!? NOTE: The product peak elutes ~ 23 minutes of a 32 minute run and is not especially high molecular weight.

Might this discrepancy be due to the combination of additional material in the inlet combined with the lower total flow leading to a slower exit of the sample from the inlet? Some may be lost to the septum purge line if the sample and solvent hang around too long in the inlet. ??