Applications of Portable Near‐infrared Spectrometers

Abstract

The near‐infrared (NIR) region covers the transition from the visible spectral range to the mid‐infrared (IR) region, spanning the wavelength range 750–2500 nm (13 300 to 4000 cm −1 ). Light in the NIR region was discovered in 1800 by Herschel. However, the earliest applications of near‐infrared spectroscopy (NIRS) were only reported in the 1950s. The use of portable NIR spectrometers is relatively recent (1990s) owing to obvious technological constraints, but since its onset, the applications were immediately expanded to a vast array of fields. The staggering development of hardware and components of these past decades, combined with a miniaturizing trend of highly performant constituents and accessories, has enabled the development of state‐of‐the‐art portable NIR equipment. Among the different components of portable NIR instruments, wavelength selectors and detectors are the most important in the instrument performance and key factors when selecting the appropriate instrument for a specific purpose. This technology is now used in monitoring processes and quality control studies, among others, at the forefront of such innovative fields and industries such as agriculture and food products, art conservation and cultural heritage studies, pharmaceutical industry, and clinical applications to name just a few.