LC/MS/MS Quadrapole Sensitivity Issues

[bisnettrj2]

Thank you for finishing out the thread, oftentimes these issues are left unresolved in this forum. Were you given any advice on preventing contamination of the quads? Like, electrospray needle position, or increased gas flows? On my 4000 QTrap, the service engineer tells me to run at the highest curtain gas flow rate I can without diminishing my sensitivity, and to run the needle at the highest position away from the orifice I can without sacrificing sensitivity, to keep the system as clean as possible.

[BHolmes]

No problem, I like to be able to finish what I started - because chances are there is someone out there with a similar problem!

Your service rep's advice is basically the same as what mine told me - try to reduce sample load into the quads. With our system we have a diverter valve which I have been trying to program within the method to switch flow from detector to waste (and vice versa) when I know nothing is coming off column. Every little bit that I can do to reduce load on detector is what I was told to strive for.

Overall this is frustrating, these instrument manufacturers design and build these state of the art SUPER sensitive instruments BUT... they can't handle a large sample load (matrix and/or analytes), so we analysts have to dilute and dilute and dilute our samples in order to minimize instrument downtime for maintenance. As it stands right now, I am going to have to vent the instrument monthly to clean the Ion Block of my Xevo TQ-S MS/MS, that procedure takes an entire day to complete and bring system back to normal.

Although i have to admit, perhaps we are just pushing these instruments to the extreme limits of their normal range by taking shortcuts in sample prep, high sample throughput, reducing analysis time, etc...