Baseline interference - electrical interferences?

What is your run threshold?  This type of baseline change will show up when the background is quite low and the threshold is close to the total background. The TIC appears to jump higher when all that is really happening is a few background ions now are higher than the threshold. Try lowering the threshold by 50% and see if that changes it. The Y axis scale you are showing is very zoomed in.  The first peak at 0.75 minutes or so is probably caused by the flow/pressure upset from the HS valve.

One other thing - please add a 0.3 or 0.4 minute Solvent Delay. Some older versions of MassHunter Acquisition need some seconds of delay from the run start to the actual start of acquiring data to avoid issues that are very hard to diagnose. It's easiest to tell operators to add a bit of time.

Hello Paul, Thank you for your reply.

I am running a SIM method and with your input about the solvent delay I was able to have a good baseline and perform the analysis.

However, the equipment was not running samples or blanks during the weekend and now I am having the same problem (I am still using the method with solvent delay). I already baked out the column in order to try eliminate possible compounds that could be retained and be the cause of this issue, but I was not successful. Can you please help me? This is only a blank injection.

Thank you so much for the kind attention. 

This is in SIM. What are your SIM parameters?   The scale here is only 3,750 counts from 0.25 to 4 x 10^3...very small.

Please do a blank run in SCAN mode, 30 to 350, threshold 100... and share that.  There could be a mess coming out that you are not looking at in SIM that is suppressing the ionization in the source or doing something else strange.

Hello paul,

This is the result from the scan: 

My SIM parameters are:

That is as much as 400,000 counts (0.4 x 10^6) of background...that is unacceptably high and should be resolved.  What are some spectra across the run?  Choose some spots along the chromatogram, top of peaks and on the mostly flats, and get the spectrum there.  If there are the same/similar ions in them, do an extracted ion chromatogram to see if those ions are in the entire run and their responses.  Eliminating that stuff and getting the baseline down to some low thousands will help your SIM run.

Extracting your SIM ions from this run will probably show about the same SIM as you shared above.

What are your SIM ions?   Eventually you may need to slightly reduce the 100ms dwell times per ion to get the cycle time a bit faster. What you've shown lead to ~two cycles per second and that acquisition speed may not be fast enough to give good chromatographic peak shape for decent integration. You need at least eight to ten data points on a peak for it to be integrated properly.

That is as much as 400,000 counts (0.4 x 10^6) of background...that is unacceptably high and should be resolved.  What are some spectra across the run?  Choose some spots along the chromatogram, top of peaks and on the mostly flats, and get the spectrum there.  If there are the same/similar ions in them, do an extracted ion chromatogram to see if those ions are in the entire run and their responses.  Eliminating that stuff and getting the baseline down to some low thousands will help your SIM run.

Extracting your SIM ions from this run will probably show about the same SIM as you shared above.

What are your SIM ions?   Eventually you may need to slightly reduce the 100ms dwell times per ion to get the cycle time a bit faster. What you've shown lead to ~two cycles per second and that acquisition speed may not be fast enough to give good chromatographic peak shape for decent integration. You need at least eight to ten data points on a peak for it to be integrated properly.