Evaluation of performance and matrix compatibility of mixed mode C18-SCX SPME fibers for compounds with different physicochemical properties

Solid-phase microextraction (SPME) has evolved significantly since its inception, yet challenges remain in developing coatings fully compatible with LC-MS that combine broad polarity coverage with biocompatibility for complex matrices. This study evaluates mixed-mode C₁₈-SCX (strong cation exchange) SPME fibers designed to extract analytes of a wide range of physicochemical properties, addressing limitations in current methodologies. The fibers were tested for extraction efficiency, reproducibility, and matrix compatibility using a group of model compounds with different physicochemical properties, namely, codeine (logP=1.19), carbamazepine (logP=2.45), diazepam (logP=2.82), and propranolol (logP=3.47). Furthermore, the biocompatibility was tested in diverse matrices, such as PBS, blood, plasma, urine, and grape juice.

Results demonstrated exceptional inter-fiber reproducibility (RSD ≤ 15 %, n = 96 fibers) and robust performance in biomatrices, with relative matrix effects primarily governed by analyte binding affinities to matrix macromolecules rather than coating fouling. Absolute matrix effects were negligible (93–111 %), underscoring the fibers’ ability to deliver clean extracts for LC-MS analysis. Fiber reusability was validated over three consecutive extractions (RSD ≤ 10 %), and morphological integrity was preserved post-extraction, even in challenging matrices like whole blood. This work represents the versatility of mixed-mode SPME fibers for high-throughput bioanalysis, offering a significant advancement for in vivo and in vitro targeted and untargeted applications.