Comparison of Liquid–Liquid Extraction, Microextraction and Ultrafiltration for Measuring Free Concentrations of Testosterone and Phenytoin

Abstract

Aim: The purpose of the study was to find methods suitable for measuring the free concentrations of testosterone and phenytoin. Materials & methods: Sample solutions of the compounds in buffer and human albumin were processed using liquid–liquid extraction, microextraction and ultrafiltration and analyzed by LC–MS/MS. Results: Liquid–liquid extraction with dibutyl phthalate provided complete extraction from buffer solutions and partial extraction from albumin samples. Spintip C18 devices provided exhaustive extraction from buffer and albumin samples. Spintip C8 devices offered complete extraction from buffer and approximately 50% recovery from albumin samples. Centrifree ultrafiltration devices showed high recovery of free concentrations from all the samples, while Amicon and Nanosep devices provided partial recovery. Conclusion: Spintip C8 and Centrifree devices proved useful for measuring free concentrations.

Keywords:

• albumin
• free concentration
• liquid–liquid extraction
• phenytoin
• plasma protein binding
• solid-phase microextraction
• testosterone
• ultrafiltration

Financial & competing interests disclosure

The authors acknowledge funding from the US National Institutes of Health (1R15GM126510). The article will be deposited on the NIHMS system/PMC. The authors’ work was independent of the funders. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.