Ghost peaks in MS chromatogram

[ghie malig]

Hello everyone!

My company just purchased a new Shimadzu LC-MS detector (that have undergone PQ and OQ). We are new users of the instrument but were given the pressure of coming up with a method for felodipine in plasma. We are experiencing inconsistent ghost peaks eluting at the retention time of our active and the IS. We used StrataX 30 mg SPE cartridge for our sample preparation.

What we have tried so far in order to trace the contaminants that seem to appear as ghost peaks were:

1. Purge the sampler with pure Acetonitrile for 25 minutes before injection.

2. Injected the reagent blank (have undergone SPE process) --- ghost peaks appeared

3. Injected processed blank plasma (have undergone SPE)--- ghost peaks appeared

4. Injected mobile phase --- no ghost peaks

5. Injected MP in doubly washed vial -- no ghost peaks

6. Injected MP in any vial --- no ghost peaks

7. Injected NaOH 50 uL (1M) in 1 mL water (pretreatment solution of SPE cartridge) --- no ghost peaks

It seemed that the contaminants came from the processed blank plasma and the reagent blank. However, we did a second injection of the blank plasma and reagent blank and no ghost peaks appeared. We thought that we can already proceed with our method but from time to time, ghost peaks still appear during the run.

More info about the method:

Sample Prep: Strata X, 30 mg cartridge

M.P. : ACN-0.5% Formic acid , 80:20

Column: 150 x 2mm, Shimpack C18 column, 40 degrees

Analyte: Nifedipine

IS: Nimodipine

Where do the ghost peaks come from? We haven't tried examining the SPE cartridge though, but based on the result of the pretreatment solution and those that have not undergone SPE, no ghost peaks appeared in the chrom. Could it be that the contaminants came from the cartridge?

Any feedback would be appreciated. thanks


ghie malig

[HW Mueller]

The "ghost" peaks give the same MS as your Analyte, IS? Maybe your ghosts are carryover and you just need to clean up your act. If it´s intermittannt, as you seem to say, it could well be the result of some carelessness in any case.