Fourier transform infrared spectroscopy with a sample deposition interface as a quantitative detector in...

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Chromatography

Background:

• Solvent-elimination interfaces are vital for coupling liquid chromatography with infrared spectroscopy (LC-IR).
• Quantitative analysis using LC-IR requires optimizing deposition parameters for sensitivity and resolution.

Purpose of the Study:

• To evaluate a commercial solvent-elimination interface for quantitative LC-IR analysis.
• To investigate the impact of eluent flow-rate and substrate speed on deposition quality and chromatographic detail preservation.

Main Methods:

• Utilized a state-of-the-art commercial solvent-elimination interface for LC-IR.
• Investigated eluent flow-rate effects (500 to 25 microl/min) on deposit homogeneity and trace width.
• Assessed chromatographic detail preservation at various substrate moving speeds.
• Evaluated deposition repeatability using size-exclusion chromatography-Fourier transform infrared (SEC-FTIR) of polystyrene standards.

Main Results:

• Low eluent flow-rates (≤50 microl/min) significantly improved trace width (from 2.20 to 1.13 mm) and sensitivity.
• Reduced chromatographic resolution was observed in SEC-FTIR compared to SEC-UV due to inherent band broadening in nebulizer-deposition interfaces.
• Repeatability of deposition showed relative standard deviations (RSD) of 3.2–5.8% for response and 0.21–0.47% for retention time.

Conclusions:

• Optimized eluent flow-rate is critical for high-sensitivity quantitative analysis with LC-IR.
• Nebulizer-deposition interfaces introduce band broadening, impacting resolution in SEC-FTIR.
• The evaluated interface demonstrates good repeatability for quantitative SEC-FTIR applications.