Diffraction-based label-free photothermal detector for separation analyses in a nanocapillary.

Area of Science:

• Analytical Chemistry
• Separation Science
• Nanotechnology

Background:

• Miniaturization in liquid chromatography is crucial for single-cell proteomics and metabolomics.
• Micro/nanoscale open tubular (OT) capillaries offer efficient separation for ultra-small sample volumes.
• Highly sensitive, label-free on-column detection remains a challenge for nanocapillaries.

Purpose of the Study:

• To develop a sensitive, label-free detection method for nanocapillary liquid chromatography.
• To enable concentration determination of unlabeled samples in nanocapillaries.
• To demonstrate the utility of the detector in micro/nanoscale separation analyses.

Main Methods:

• Development of a photothermal detector utilizing optical diffraction phenomena.
• Application of the detector to a single nanocapillary with a 460 nm inner diameter.
• Performance of normal-phase chromatography on a 12 cm nanocapillary.

Main Results:

• Achieved a limit of detection of 0.12 µM, corresponding to 16 molecules in 0.23 fL.
• Demonstrated femtoliter sample injection and efficient separation of dye molecules.
• Successfully performed label-free detection of unlabeled sample solutions.

Conclusions:

• The developed photothermal detector provides highly sensitive, label-free detection for nanocapillaries.
• This technology is a universal tool for chemical and biological analyses using micro/nanoscale capillaries.
• The method significantly advances capabilities in single-cell and ultra-small volume analyses.