ANALYTICAL PROBLEM OF ION SUPPRESSION

The presence of ion suppression, or other deleterious effects, can be evaluated via several experimental protocols. One involves comparison of (1) the instrument response for standards (including any internal standards) injected directly in mobile phase and (2) the same amount of compound spiked into preextracted samples. The data for the standard in mobile phase provide a relative 100% response value. The data for the same amount of compound spiked into preextracted samples show the effect of sample matrix on MS response (ion suppression). 

Another potential source of ion suppression is the effect that chromatographic ion-pairing agents may have on signal intensity. For example, trifluoroacetic acid (TFA) has been used in HPLC-UV analyses because it improves peak shape and retention times. Unfortunately, for MS analyses TFA alsb causes signal suppression and must be considered if this acid is used in the mobile phase. Being a component of the 

Ion suppression is not limited to just HPLC-MS or ESI interfaces. For MALDI analysis, arginine-containing peptides have been reported to dominate the peptide pattern for protein digests,the extent of which depends on the matrix used. The presence of ionic detergents, such as Triton X-100 and Tween 20, has also been shown to cause signal suppression in MALDI experiments, which can be countered by modifications to the matrix.  

Annesley TM. Ion Suppression in mass spectrometry. Clin Chem 2003 49 1041-4. 

Arnott D, Shabanowitz J, Hunt DW. Mass spectrometry of proteins and peptides. Sensitive and accurate mass measurement and sequence analysis. Clin Chem 1993 39 2005-10. 

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