Fiber-Optic Infrared Reflection Absorption Spectroscopy for Trace Analysis on Surfaces of Varying Roughness: Sodium Dodecyl Sulfate on Stainless Steel

Abstract

The effect of surface roughness on the analytical performance of a fiber-optic grazing-angle infrared reflection absorption spectroscopy (IRRAS) system has been investigated. The instrument was used to develop calibrations to quantify trace surface loadings for sodium dodecyl sulfate (SDS) on 316 stainless steel with three different surface finishes. Partial least squares (PLS) calibrations were developed for both individual finishes and combinations of finishes. For SDS on individual surface finishes, the root mean square (rms) error of cross-validation (RMSECV) varied between 0.08 and 0.12 μg cm⁻² with values of R² between 0.89 and 0.96. A combined model for SDS on all surfaces gave an RMSECV of 0.18 μg cm⁻² with an R² of 0.85.