The differences in matrix effect between supercritical fluid chromatography and reversed phase liquid chromatography coupled to ESI/MS

Highlights: • Matrix effects were compared using screening methods with SFC/ESI-MS and RPLC/ESI-MS. • Blood plasma, horse urine and influent/effluent wastewater were investigated. • Through the use of post-column infusions, matrix effect profiles were generated. • Quantitative and qualitative information was compared, interferences tentatively identified. • Ion suppressions were generally more common for SFC, and enhancements for LC. - Abstract: For many sample matrices, matrix effects are a troublesome phenomenon using the electrospray ionization source. The increasing use of supercritical fluid chromatography with CO₂ in combination with the electrospray ionization source for MS detection is therefore raising questions: is the matrix effect behaving differently using SFC in comparison with reversed phase LC? This was investigated using urine, plasma, influent- and effluent-wastewater as sample matrices. The matrix effect was evaluated using the post-extraction addition method and through post-column infusions. Matrix effect profiles generated from the post-column infusions in combination with time of flight-MS detection provided the most valuable information for the study. The combination of both qualitative and semi-quantitative information with the ability to use HRMS-data for identifying interfering compounds from the same experiment was very useful, and has to the authors' knowledge not been used this way before. The results showed that both LC and SFC are affected by matrix effects, however differently depending on sample matrix. Generally, both suppressions and enhancements were seen, with a higher amount of enhancements for LC, where 65% of all compounds and all sample matrices were enhanced, compared to only 7% for SFC. Several interferences were tentatively identified, with phospholipids, creatinine, and metal ion clusters as examples of important interferences, with different impact depending on chromatographic technique. SFC needs a different strategy for limiting matrix interferences, owing to its almost reverse retention order compared to RPLC.