Free testosterone is a crucial measure of hormonal health and a diagnostic tool. Unlike total testosterone levels, free testosterone reflects the biologically active form of testosterone. Analysis of free testosterone is generally performed by equilibrium dialysis. This method of analysis is time-consuming, taking up to several hours to perform. A newer method using a plate, referred to as rapid equilibrium dialysis, still takes 2 hours to perform prior to a separate extraction like liquid-liquid or solid-phase extraction (LLE or SPE).

In this poster, a patented size exclusion chromatography (SEC) tip with 1500 Da molecular weight cutoff resin is used to separate protein-bound testosterone from free testosterone.

Traditional gel-filtration within a pipette tip column is used to isolate large molecules (greater than the cut-off) from small molecules and buffers. SEC Tips from DPX Technologies incorporate traditional SEC resins within a pipette tip for high throughput, easy-to-use, buffer exchange and desalting methods. Recent research and development has led to the utilization of SEC Tips for small molecule isolation from larger molecules (proteins, lipids, etc) for LC-MS/MS analysis in clinical and forensic applications.² 

The SEC Tip method takes less than 30 minutes to perform for up to 96 samples at one time. Following the SEC separation, a μXTR Tip method is used to concentrate the sample and remove ion suppression and interferences without solvent evaporation.

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