The differences in matrix effects between supercritical fluid chromatography and reversed phase liquid chromatography coupled to ESI/MS analyzing blood plasma

• Introduction The increasing popularity of supercritical fluid chromatography (SFC) in combination with electrospray ionization mass spectrometry (ESI/MS) within several fields calls for a deeper knowledge regarding this combination of techniques. The ESI source is known for its sensitivity regarding matrix effects, often a factor controlled during method development and validation using LC. The different chemistry and chromatographic selectivity of LC and SFC give potentially different impact on the ionization process in ESI; however, this an area still not well studied.   Aim: To investigate how the matrix effects in ESI/MS differ for human plasma samples between SFC and reversed-phase LC, using generic screening conditions for both techniques, and a set of typical low molecular weight drug substances.Methods Pooled human plasma (500 µl) was precipitated using ice-cold acetonitrile (1000 µl). After mixing and centrifuging, 1200 µl of the supernatant were removed and evaporated at 40 ̊C. When dry, the samples were dissolved in 500µl water+0.1% FA (for LC) or acetonitrile:water 75:25 (for SFC). The samples were analyzed using SFC (Acquity UPC2, Waters®) and LC (Acquity UPLC, Waters®) and general screening conditions, using 10 min gradients. The same MS-system, a Q-ToF (Synapt G2-S, Waters®) acquiring in full scan mode, was used for detection with both separation techniques. The matrix effect was mainly evaluated using the Matrix Effect Profile, achieved from post-column compound infusions and injections of pretreated sample matrix and neat standards. From these data the average ME% was calculated for each data-point in the chromatogram, and through the full-scan mode using ToF, the compounds co-eluting with areas of suppression could be tentatively identified, suspected of creating the suppression.  Results and discussion The Matrix Effect Profile-evaluation of the experiments, combining qualitative and quantitative information with the added ability to use HRMS-data to identify interfering compounds from the same experiments were most useful for our aim. Phospholipids, creatinine, polyethylene glycol and cluster formations are examples of important interferences co-eluting with areas of ion suppression, but with different impact depending on chromatographic technique. The results also showed several areas of enhancement using LC, an effect not seen using SFC. 

Ämnesord

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

Nyckelord

Analytical Pharmaceutical Chemistry

Analytisk farmaceutisk kemi

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