Use of an Improved Version of C₈+SCX Mixed Mode Solid Phase Extraction Material for Clean Extraction and Recovery of Basic and Zwitterionic Compounds from Biological Fluids

Abstract

Mixed mode bonded silica, containing both reversed phase and cationic exchange compositions, is one of the most versatile solid phase extraction (SPE) products in the market due to generic extraction methods and some successful applications for cleaner extraction of basic compounds from biological fluids. However, the present study shows that many zwitterions compounds and polar basic compounds cannot be effectively extracted and recovered from the current C₈+SCX mixed mode products. The inability is due to too low an ion exchange capacity. In order to solve the problem, the SCX functional coverage is optimized to develop an improved version of C₈+SCX mixed mode material. Three generic extraction protocols have been categorized. The first one is used to completely recover basic and zwitterions compounds with some hydrophobicity, and this protocol offers the cleanest background. The second one is used to recover polar basic and zwitterions compounds, and/or the third one is used to systematically fractionate basic and zwitterions compounds from neutral and acidic compounds for further analysis. The considerable advance greatly improves the performance of cationic mixed mode SPE products and the corresponding data reproducibility.

Keywords:

• C₈+SCX mixed mode
• Solid phase extraction (SPE)
• Systematic toxicology analysis
• Illegal drug

Acknowledgments

This work was funded in part by the National Science Foundation of China (30470277), Gansu National Science Foundation (ZS031‐A25‐039‐D), and Gansu Key Technologies R&D Program (ZGS052‐A41‐0006‐03). The content of the work reflects the personal view of the author and not necessarily the view of the organization.