Chapter 5 - Miniaturized near-infrared spectroscopy in current analytical chemistry: from natural products to forensics

Abstract

Near-infrared (NIR) spectroscopy is a powerful tool for qualitative and quantitative analysis in a variety of applications. As a rapid and high-throughput analytical method, with minimal requirements for sample preparation and applicability to wide range of sample types, NIR spectroscopy offers significant practical advantages compared to the conventional methods of analysis. In the past decade, the continuous progress in technology has led to dynamic development of portable, miniaturized NIR spectrometers and enabled a new spectrum of applications of this technique in science and industry. Novel miniaturized spectrometers further enhance the potential of this technique by enabling spectral analysis directly on-site. In a number of cases, this enables using NIR spectroscopy in previously unattainable roles. The advantages of miniaturized NIR spectroscopy are particularly exposed in several fields, where rapid and nondestructive on-site analysis is essential. In this context, natural products and resources, as well as agro-food items, feature chemical diversity that can vary depending on the geographical origin, cultivation and/or storage conditions, or harvest time. Portable NIR sensors are of keen interest in a number of industrial applications as well as environmental monitoring. The miniaturization is required to implement a number of distinct engineering solutions into these sensors. These devices differ by the key elements used for their construction, e.g., wavelength selectors and detector configurations. Different design philosophies make the performance and applicability of various miniaturized NIR spectrometers specific, governed by the operating spectral region, resolution, and sensitivity. Their resulting analytical worthiness is often inferior in absolute terms to the benchtop laboratory instrumentation. Therefore, the attention of research laboratories is given to feasibility studies and evaluation of the applicability of various miniaturized NIR sensors to different analytical problems. This chapter discusses miniaturized NIR spectroscopy with focus given on application potential. The design principles and characteristics of portable instruments are discussed; current state and future application potential is critically assessed in a variety of analytical scenarios.