A new strategy to eliminate sample mixing during in-tube solid phase microextraction

Area of Science:

• Analytical Chemistry
• Chromatography
• Sample Preparation

Background:

• In-tube solid phase microextraction (SPME) can suffer from sample mixing with the mobile phase.
• This mixing can entrain sample, impacting analyte recovery and data quality, especially for compounds with low sorbent affinity or interfering matrix components.

Purpose of the Study:

• To quantify the sample mixing effect in in-tube SPME.
• To develop and validate a novel method to eliminate sample mixing during in-tube SPME.
• To demonstrate the method's effectiveness for diverse analytes.

Main Methods:

• Quantified sample mixing by analyzing ranitidine and polycyclic aromatic hydrocarbons (PAHs).
• Developed a new approach using a switching valve between the metering pump and capillary.
• Optimized capillary flush conditions, draw/eject speed, and extraction time for ranitidine.
• Validated the method for ranitidine, PAHs, and beta-blockers.

Main Results:

• Calculated sample volume equivalents of mixing: 37 μL for ranitidine and 20 μL for PAHs.
• The novel switching valve method eliminated apparent sample mixing for all tested analytes.
• Achieved highly linear calibration curves for ranitidine, PAHs, and beta-blockers, indicating resolved data quality issues.

Conclusions:

• The developed switching valve approach effectively resolves sample mixing issues in in-tube SPME.
• This method improves data quality and reliability for various analyte classes.
• Optimized conditions and the switching valve strategy provide a robust solution for in-tube SPME method development.