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Comments
To
inject a blank: Inject a volume of mobile phase in the same way that you
inject sample. This mobile phase should have exactly the same composition
as that pumped at the time of injection. If your sample is dissolved in
a solvent different from this, then it is instructive to make an additional
blank injection using the sample solvent. This will show if the artifacts
are caused by the difference in solvents.
Spurious peaks are more likely when operating at high detector sensitivity and can be a difficult problem to troubleshoot. In some cases they are not real substances, but artificial signals from the detector. In other cases they are real substances, but they come from outside of the injector, either by being unintentionally loaded with the blank, or by being desorbed from the column due to the injection of the blank. In rare cases they are substances which have contaminated the internal parts of the injector.
Use only genuine Rheodyne replacement parts.
Artifact Peaks
Artifacts are peaks that appear unexpectedly. The problems are separated into three groups: carryover peaks, spurious peaks, and distorted peaks:
- Carryover peaks are those produced because of cross contamination from a previous injection (see Fig. 12). When a blank is injected a miniature chromatogram appears.
- Spurious peaks are those that are unrelated to the previously injected sample (see Fig. 13). When a blank is injected these "ghost" peaks appear as peaks with retention times that are different from sample components.
- Distorted peaks are those that look unfamiliar. A blank injection looks OK, but when the sample is injected some of the peaks are fronting, tailing, or split (double). (See Fig. 14.)
It’s best that you read all parts of “Artifact Peaks,” including the comments, before taking action. You may also want to consider the problem is caused by a component other than the injector (see Appendices C and D).
Fig. 12. Peaks in blank are CARRYOVER from previous sample.
Fig. 13. SPURIOUS peaks in blank are unrelated to sample.
Fig. 14. Blank injection is OK, but peaks in sample are DISTORTED.
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