Ion-Pairing Agents in the HPLC System

Lyseigic acid diethyl amide Lysergic add methyl propyl amide MW 323.43 MW32a43 

Interference with the ionization of an analyte by a disturbing component is widely called ion suppression , even if the signal gets enhanced rather than suppressed. Most prone to this effect is of course electrospray, but APCI and APPI may occasionally also be affected. This interference of eluting compounds is a complex issue and is extensively discussed in Section 3.3.4. 

Those users of LC/MS with some experience in mass spectrometry tend to polish the ion source and ion optics before introducing an important series of samples. Of course, maximum signal intensities in API LC/MS ionization techniques will be achieved when all residues are completely eliminated from the ion source surfaces. The electrical fields that are necessary to form and/or transport the ionic analytes before they reach the mass analyzer are influenced by the degree of contamination with non-volatile sample constituents. On the other hand, experienced LC/MS users know that the long-term stability of an LC/MS system will be increased if the spray chamber is intentionally slightly contaminated. This is of particular importance when one wishes or has to quantify by means of external calibration. With the most commonly used ion sources it is sufficient to inject the sample matrix 10-20 times in order to achieve an almost constant analyte response after an initial exponential drop. 

---