The silanol concentration of quartz was determined by mixing 50 mg ground silica sample with 500 mg KBr followed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and chemometric data analysis. Reference samples were prepared by blending ground quartz of different silanol content. Good correlation was achieved between 10 and 240 ppm Si–OH by mass. The chemometric model's quality is characterized by a correlation coefficient of 0.965 (cross-validation) using five latent variables (factors) and a root mean square error of calibration (RMSEC) of 7 ppm. Chemometric data is compared to results from univariate data analysis. The biggest impact on the reproducibility is due to sample preparation (grinding and blending), which is dependant on the operator involved.
Markus M. Haider, Ingrid Hartinger, Karin Göschl, and Andreas Demmelmair, "Quantitative Determination of Silanol in Quartz Applying Diffuse Reflectance Infrared Fourier Transform and Chemometrics," Appl. Spectrosc. 58, 679-682 (2004)