LC-MS Analysis of Serum for a Wide Analyte Range

This article from Issue 10 of the Analytix Reporter, produced by Merck, presents a study that analyzed calf serum for a mixture of twenty compounds including pharmaceuticals with LogP values ranging from -0.89 to 4.65 and demonstrated the broad utility of the new hydrophilic lipophilic balanced (HLB) SPE phase― Supel™ Swift HLB.

Introduction
The preparation of biological samples can have a large impact on the reproducibility and accuracy of their analytical results. But, solid phase extraction (SPE) provides an opportunity to reduce matrix effects such as ion suppression and aid in the reliability of consistent results. Hydrophilic-Lipophilic Balanced (HLB) cartridges contain a sorbent offering good wettability for hydrophilic compounds, in addition to providing reverse phase retention. These properties allow HLB cartridges to effectively handle a broad range of compounds with varying properties. In this study, a mixture of twenty example compounds with LogP values ranging from -0.89 to 4.65 were analyzed from spiked calf serum using a Supel™ Swift HLB SPE cartridge for cleanup and LC-MS determination.

Results & Discussion
The recoveries of the 20 analytes following their SPE cleanup from both the 3-Step and 5-Step methods of the Supel™ Swift HLB SPE cartridges are presented. Overall, the 5-Step method showed better recovery (100.7 ±6.8%) compared to the 3-Step process (85.1 ±4.2%), partly because of the two earliest eluting compounds (amiloride and nizatidine, both below 70% recovery in 3-Step method). Under the 5-Step process, all twenty analytes had recoveries between 80% and 120%. For 16 of the 20 analytes, the 3-Step process achieved recoveries in the 80% to 120% range.

Conclusion
Through the use of twenty analytes with various LogP values, the Supel™ Swift HLB SPE cartridges
demonstrated excellent recoveries (100% of analytes in the range of 80-120% with the 5-step method) and minimal effects on analyte ionization for 80% of the analytes, indicating a good matrix removal. The advantages of the Supel™ Swift HLB SPE cartridges were further demonstrated on their comparison to a commercially available HLB cartridge under the same set of conditions.

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*The life science business of Merck operates as MilliporeSigma in the U.S. and Canada.