6 - Comparing Ultraviolet-Visible and Near-Infrared Spectrometry

Abstract

Ultraviolet (190–380 nm), visible (380–750 nm), short wave near infrared (750–1100 nm), long-wave near infrared (1100–2500 nm), infrared (4000–400 cm-1), and Raman spectroscopy comprise the bulk of the electronic and vibrational mode measurement techniques. Basic spectroscopic measurements involve the instrumental concepts of bandpass and resolution, signal-to-noise ratio, dynamic range, stray light, wavelength accuracy and precision, and photometric accuracy and precision. This chapter discusses the differences between ultraviolet-visible and near-infrared spectrometry in terms of instrumentation, sampling considerations, and applications. Double-monochromator instruments provide a traditional means for reducing the stray light of an instrument at the point of measurement. Double-monochromator instruments are generally used for applications where high degrees of photometric accuracy and repeatability are required. Varieties of sample presentation methods are also available to the analyst. These include transmission (straight and diffuse), reflectance (specular and diffuse), transflectance (reflectance and transmission), and interactance (a combination of reflectance and transmission).