Dropping of the mass reference 121m/z and 922 and no improvement even if i increased the isocratic pump flow rate from 2 mlmin to 4 ml/min. I added more Purine and HP0921 to the reference solution but no improvement. I checked the filter and it is OK. I checked if the there was air in the tube but all did not improve the abundance
How are the reference ions being admitted to the source? Are you using UIB or a reference nebulizer.