Peak disappears in some samples, than comes back to normal

Hello everybody!

We have the issue that in our run (ca. 100 - 200 samples, 7 min each) for like 20 samples there is no signal, just the technical background noise. Not even the peak that is in the Blank appears. An the it sowly comes back over 2 samples.

There is no error massage in the log book, and the run continues like normal, all QCs ar fine. Does anyone have had this problem before? Or knows what could cause this?

HPLC: 1260 Infinity II Flexible Pumpe, G7104C

QQQ: Triplequadrupole 6470 with an ESI Ion source (G6470B)

Thank you in advance!

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