Quantitative mid-infrared diffuse reflection of occupational wood dust exposures

Area of Science:

• Analytical Chemistry
• Occupational Health
• Spectroscopy

Background:

• Occupational exposure to airborne wood dust is linked to health issues, including nasal carcinoma.
• Current methods like gravimetric analysis for wood dust exposure are non-specific.
• There is a need for more accurate and specific methods to assess wood dust exposure in occupational settings.

Purpose of the Study:

• To adapt a mid-infrared (mid-IR) diffuse reflection (DR) method for direct, specific determination of wood dust mass on filters.
• To evaluate the suitability of different mathematical functions (Kubelka-Munk and log(1/R)) for quantitative analysis of wood dust spectra.
• To recommend optimal filter types for improved on-filter wood dust analysis.

Main Methods:

• A mid-IR diffuse reflection method was modified with a translational stage for on-filter spectral collection.
• Diffuse reflection spectra were collected from filters containing red oak and yellow pine dust.
• Lignin-specific absorption bands (~1595 and 1510 cm⁻¹) were monitored for quantitative analysis using Kubelka-Munk and log(1/R) functions.

Main Results:

• The Kubelka-Munk function showed nonlinear dependence for wood dust masses below 10 mg, indicating it's not ideal for thin samples.
• The pseudo-absorption function log(1/R) demonstrated a closer-to-linear dependence and is proposed as a preferred method for thin wood dust samples.
• Silver metal membrane filters are suggested as a superior alternative to glass fiber filters for direct on-filter wood dust analysis.

Conclusions:

• Mid-infrared diffuse reflection spectroscopy, particularly using the log(1/R) function, provides a specific and potentially more accurate method for quantifying wood dust mass on filters.
• The findings suggest this method can improve the assessment of occupational wood dust exposure compared to non-specific gravimetric techniques.
• The use of silver membrane filters enhances the direct on-filter analysis of wood dust.