A Differential Thermal Lens Spectrometry Method for Trace Detection

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Optical Techniques

Background:

• Thermal lens spectroscopy (TLS) is a sensitive technique for quantifying light-absorbing substances.
• Existing TLS methods can be further optimized for enhanced sensitivity and lower detection limits.

Purpose of the Study:

• To implement and validate a transient thermal lens spectroscopy (TLS) configuration with enhanced sensitivity.
• To reduce the detection limit of TLS by approximately 50% using a novel differential measurement approach.

Main Methods:

• Utilized a transient TLS setup with coaxial focused pump and collimated probe beams.
• Incorporated a Fabry-Perot optical resonator for multi-passing of the probe beam.
• Developed a differential measurement by comparing far-field center spot signal with a spatially filtered (eclipsed) signal.

Main Results:

• The differential measurement strategy significantly reduced the detection limit compared to standard TLS measurements.
• Measurements on Deyman's organic dye (Strawberry 2143 v.7) in ethanol demonstrated the effectiveness of the technique.
• The differential signal showed a marked improvement in sensitivity for determining dye concentration.

Conclusions:

• The implemented differential measurement in transient TLS effectively lowers the detection limit by approximately half.
• This enhanced TLS method offers improved sensitivity for analyzing light-absorbing species.
• The technique shows promise for precise concentration determination in various analytical applications.