Novel separation mode of HPLC based on phase-separation multiphase flow

Area of Science:

• Analytical Chemistry
• Chromatography
• Separation Science

Background:

• High-performance liquid chromatography (HPLC) is a cornerstone of chemical analysis.
• Developing novel separation modes is crucial for improving analytical efficiency and resolving complex mixtures.
• Understanding eluent behavior under different temperature conditions is key to optimizing chromatographic separations.

Purpose of the Study:

• To introduce and investigate a novel HPLC separation mode based on phase-separation multiphase flow.
• To evaluate the effect of temperature and eluent composition on the separation of model analytes.
• To explore the potential of this new mode for achieving effective chromatographic separations.

Main Methods:

• Utilized a standard HPLC system equipped with an octadecyl-silica (ODS) packed column.
• Employed water/acetonitrile/ethyl acetate ternary mixed solutions at varying compositions (1:8:1, 1:3:1, 16:3:1 v/v/v) as eluents.
• Conducted experiments at two distinct temperatures: 20 °C (homogeneous flow) and 5 °C (heterogeneous flow).

Main Results:

• Separation of 1-Naphthol (NA) and 2,6-naphthalenedisulfonic acid (NDS) was achieved under specific conditions.
• At 20 °C, separation occurred only with eluent 16:3:1 (NDS then NA).
• At 5 °C, separations were observed with eluents 1:3:1 (NA then NDS) and 16:3:1 (NDS then NA), with the latter showing enhanced effectiveness compared to 20 °C.

Conclusions:

• Phase-separation multiphase flow represents a novel and effective mode for HPLC.
• Temperature plays a critical role in controlling the eluent's flow behavior (homogeneous vs. heterogeneous) and thus the separation outcome.
• The observed separation behavior and elution order are directly linked to the phase-separation multiphase flow phenomenon.