Strange problems for LC/MS. API 3000, any idea?

[lu_optimum]

Hello everyone,

We have a API 3000. We are trying to verify the status using POS PPG standard. We then had strange problem. We did Qq scan on the POS PPG standard. There should be 8 MCA signal peaks at M/Z of 59, 175, 616, 907, 1255, 1545, 2009, 2242. However, we only got three: 59, 176, 616. When change the Q1 resolution setting from unit to low, we got 59, 176, 618, 907 and barely seen peak at 1255 (very small). When comparing the spectra with previous one, we basically only have 3 good ones (59,176,618 m/z), worse one at m/z 907 and the other 4 are just blank. It is not the off calibration problem. Clearly with m/z increase, the intensity (cps) decreased significantly (more like after m/z 600, the sensitivity decrease significantly that not signal show up. According to the maintenance procedure, we cleaned up the orifice plate and all others beyond the point of the rods. After cleaning, still no improvement.

Any one has idea on what happened? Thanks in advance.


Ze

[PeterS]

The signal you get at 59, 606 is that comparable to earlier tests or is it worse (the count of 10MCA samples)?
Did you try a full scan to see if the mass calibration is OK?

PeterS

[maartendekoning]

Can you send a screenshot of your analyst window?

[lu_optimum]

Hi,

I don't know how to upload image into the forum. So sorry for the late reply. The problem has been solved. Really appreciate the help from both of you.


Ze