Multi-wavelength transmission spectroscopy revisited for micron and submicron particle characterization.

Multi-wavelength transmission (MWT) ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, a technique underappreciated for particle characterization, is systematically explored using a set of NIST traceable standards over the nominal size range of 20 to 20,000 nm. Experimental results demonstrate that the particle size distributions obtained from MWT spectral data are in excellent agreement with the values reported by the manufacturer. In addition, it is shown that quantitative information on the particle concentration can be obtained--which is not currently accessible from commercially available light scattering instrumentation. The results validate that MWT UV-Vis-NIR spectroscopy has a considerable dynamic range for particle size measurements and offers significant advantages over other particle characterization techniques. Among these are the simplicity of the instrumentation and the measurements and the wealth of quantitative information contained in the MWT spectra. Most importantly, with standardized measurement protocols and standardized spectrometer configurations, MWT measurements can be used to provide the user and the manufacturer of particles with traceable data (i.e., the spectra and the quantitative analysis) for quality assurance.