Single-Path Supercontinuum Near- to Mid-Infrared Correlation Spectroscopy of Aqueous Samples.

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Combining near-infrared (NIR) and mid-infrared (MIR) spectroscopy offers enhanced analytical capabilities, particularly for methods like two-dimensional correlation spectroscopy.
• Performing simultaneous NIR and MIR spectroscopy on aqueous samples is challenging due to variations in molar absorption coefficients and material transparency.
• Integrating spectral data from separate instruments or sample presentations can introduce artifacts, compromising predictive model accuracy.

Purpose of the Study:

• To develop a unified spectroscopic approach for analyzing aqueous samples across both NIR and MIR regions.
• To overcome the inherent difficulties in combining NIR and MIR spectroscopy for aqueous solutions using a single instrument.
• To achieve consistent instrument response for robust correlation spectroscopy.

Main Methods:

• Utilized a single supercontinuum (SC) laser source (1000–4000 nm) as the light source.
• Employed an attenuated total reflection (ATR) crystal and a transmission cuvette within a single-path configuration.
• Demonstrated near-infrared-mid-infrared (NIR-MIR) correlation spectroscopy.

Main Results:

• Achieved a more consistent instrument response for combined NIR and MIR measurements.
• Successfully applied NIR-MIR correlation spectroscopy to a set of 22 aqueous samples.
• Analyzed varying concentrations of ethanol, sucrose, and L-proline in aqueous solutions.

Conclusions:

• The developed single-path configuration with a supercontinuum laser effectively integrates NIR and MIR spectroscopy for aqueous samples.
• This approach mitigates spectral variations, enabling more reliable correlation spectroscopy and predictive modeling.
• The method demonstrates potential for robust analysis of complex aqueous mixtures.