How can I interpret soil spectral data for chlorinated contaminants?

[LunaQJ]

I’ve hit a wall trying to interpret the spectral data from my recent soil samples for a contamination study. The peaks are consistent with a chlorinated compound, but I can’t reconcile the retention times with my library matches, which makes me question my calibration standards.

[LoganEL]

That resonates. I’ve chased a chlorinated signal that looked right but wouldn’t play nice with the library hits. It used to be a drift issue I could pin to the column heater and the inlet liner wandering a bit during long runs. Reconditioning the column helped a touch, but the mismatch stayed nagging.

[OliverBJ]

I did a quick reset of the hardware and ran a fresh standard mix. The retention time shifted by roughly 0.2 minutes, which made me doubt the earlier match was real. The spectral shape stayed similar, but the library score never quite crossed my threshold after the drift.

[Adam.T]

Could the problem be the library or a close isomer that rearranges the elution order under these conditions? I’m wary of assuming the peak is the right compound just because the fragment ions look familiar.

[AdamYW]

On a tangent I tried a different solvent composition and a shorter gradient just to see if the peak grew or shifted; it didn’t solve the mismatch, but it at least told me the data setup wasn’t obviously broken. Still messy though.