Hyphenating temperature gradient elution with refractive index detection through temperature-responsive liquid...

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Refractive index detection (RID) offers universal detection in liquid chromatography, enabling standard-independent quantification.
• However, RID's practical application is limited by poor sensitivity and incompatibility with solvent gradients, which cause significant baseline drift.
• Temperature-responsive liquid chromatography (TRLC) modulates retention using temperature changes, offering an alternative to solvent gradients.

Purpose of the Study:

• To demonstrate the feasibility of combining thermal gradient TRLC with RID for improved chromatographic analysis.
• To assess the potential of this combined technique for compound-independent quantification.
• To evaluate the control over baseline drift when using temperature gradients with RID.

Main Methods:

• Implementation of a thermal gradient TRLC system coupled with RID.
• Utilizing temperature gradients to achieve elution profiles similar to solvent gradients in RPLC.
• Analysis of short-chain fatty acids (SCFAs) as model compounds to validate the approach.

Main Results:

• Successfully combined thermal gradient TRLC with RID, observing very minor baseline drift (<5 nRIU min⁻¹).
• Demonstrated that elution profiles comparable to conventional RPLC solvent gradients can be achieved using temperature gradients.
• Obtained overlapping calibration lines for fatty acids from butyric to decanoic acid, indicating compound-independent quantification.

Conclusions:

• The combination of thermal gradient TRLC and RID is a viable technique for universal detection in liquid chromatography.
• This approach effectively overcomes the limitations of traditional RID, particularly regarding gradient compatibility and baseline stability.
• The method shows promise for achieving compound-independent quantification, as evidenced by the analysis of short-chain fatty acids.