For past few days, I've experienced high BEC for certain elements (eg. Na, Mg, K, Ca, Fe), can't obtain a good calibration. I've cleaned the cones, lens, torch and spray chamber. I checked nebulizer for any blockages and replaced the tubing, but yet still the problem still occur. Tune report is fine, but there's a difference in the mass graph.
Above image is before the problem occur and below is the current situation.
Any suggestions on what to do next, is there something that I am missing?
Appreciate for any help.