Ghost Peaks Appearing Randomly

While running a long sequence, I started seeing ghost peaks appear randomly in blanks and sometimes in unrelated samples.

At first, I thought it was carryover, but after thorough needle washes and even changing vials, the issue persisted. I eventually traced it back to mobile phase contamination. I had reused an old acetonitrile bottle and later realized it had absorbed impurities from the environment.

Switching to freshly opened solvent bottles solved the issue. Now I always label solvent bottles with opening dates and discard them regularly.