Microfabricated refractive index gradient based detector for reversed-phase liquid chromatography with mobile phase...

Area of Science:

• Analytical Chemistry
• Chromatography
• Detector Technology

Background:

• Traditional refractive index (RI) detectors struggle with mobile phase gradient elution in liquid chromatography (LC) due to baseline drift.
• Accurate detection during gradient elution is crucial for sensitive and reproducible chromatographic separations.

Purpose of the Study:

• To develop and demonstrate a sensitive, highly reproducible microfabricated refractive index gradient (micro-RIG) detector for gradient elution LC.
• To enable robust baseline correction procedures for gradient LC separations.

Main Methods:

• Utilized a microfabricated borosilicate glass chip with a collimated diode laser beam to probe a refractive index gradient (RIG).
• Implemented a baseline correction method involving subtraction of mobile phase gradient blanks.
• Performed reversed-phase high-performance liquid chromatography (RP-HPLC) separations of proteins and polymers under varying gradient conditions.

Main Results:

• The micro-RIG detector maintained on-scale signals throughout mobile phase gradients, allowing for effective baseline correction.
• Achieved reproducible, flat baselines after blank subtraction, leading to high signal-to-noise ratios for analytes.
• Demonstrated consistent limits of detection (LODs), with a 3-sigma deflection angle LOD of 16 microrad, corresponding to 7 ppm for cytochrome c.

Conclusions:

• The chip-based micro-RIG detector is a viable solution for sensitive and reproducible gradient elution LC.
• The detector design is compatible with both traditional and miniaturized LC systems.
• Despite minor sensitivity variations due to viscosity effects, the micro-RIG detector offers reliable performance for complex separations.