Portable Spectroscopy and Spectrometry, Applications

Richard A. Crocombe, Pauline E. Leary, Brooke W. Kammrath, Richard A. Crocombe, Pauline E. Leary, Brooke W. Kammrath

• Publisher: Wiley
• Year: 2021
• ISBN:
  9781119636434
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Spectroscopy & Spectrum Analysis

The most comprehensive resource available on the many applications of portable spectrometers, including material not found in any other published work

Portable Spectroscopy and Spectrometry: Volume Two is an authoritative and up-to-date compendium of the diverse applications for portable spectrometers across numerous disciplines. Whereas Volume One focuses on the specific technologies of the portable spectrometers themselves, Volume Two explores the use of portable instruments in wide range of fields, including pharmaceutical development, clinical research, food analysis, forensic science, geology, astrobiology, cultural heritage and archaeology.

Volume Two features contributions by a multidisciplinary team of experts with hands-on experience using portable instruments in their respective areas of expertise. Organized both by instrumentation type and by scientific or technical discipline, 21 detailed chapters cover various applications of portable ion mobility spectrometry (IMS), infrared and near-infrared (NIR) spectroscopy, Raman and x-ray fluorescence (XRF) spectroscopy, smartphone spectroscopy, and many others. Filling a significant gap in literature on the subject, the second volume of Portable Spectroscopy and Spectrometry:

• Features a significant amount of content published for the first time, or not available in existing literature
• Brings together work by authors with assorted backgrounds and fields of study
• Discusses the central role of applications in portable instrument development
• Covers the algorithms, calibrations, and libraries that are of critical importance to successful applications of portable instruments
• Includes chapters on portable spectroscopy applications in areas such as the military, agriculture and feed, hazardous materials (HazMat), art conservation, and environmental science

Portable Spectroscopy and Spectrometry: Volume Two is an indispensable resource for developers of portable instruments in universities, research institutes, instrument companies, civilian and government purchasers, trainers, operators of portable instruments, and educators and students in portable spectroscopy courses.

1
The Role of Applications in Portable Spectroscopy

Richard A. Crocombe¹, Pauline E. Leary², and Brooke W. Kammrath^{3, 4}

¹Crocombe Spectroscopic Consulting, Winchester, MA, USA

²Federal Resources, Stevensville, MD, USA

³Department of Forensic Science, Henry C. Lee College of Criminal Justice and Forensic Sciences, University of New Haven, West Haven, CT, USA

⁴Henry C. Lee Institute of Forensic Science, West Haven, CT, USA

1.1 Introduction

As described in Volume 1 of this book, we regard a portable spectrometer as an analytical instrument that generates clear answers for its operator when it is carried to the sample, i.e. a spectrometer to the sample, rather than a sample to the spectrometer. The operators of these instruments are rarely scientists – although that is advantageous for several applications – but instead may be hazardous‐material technicians, armed‐services personnel, or even scrap‐metal dealers. In many instances, level‐A personnel protective equipment (PPE) must be worn during the analysis.

Operators rely on the instrument to obtain accurate and actionable information. In some cases, the result might be a sample identification; in others, it may be a pass/fail visual or audible alarm (green light/red light). In order to achieve this, the portable instrument has to process the spectrum or spectra to generate the result, without any intervention by the operator. Therefore, for identification, a combination of spectral libraries or databases is required, in conjunction with a suitable matching algorithm. For quantitation, a validated calibration is required, and again a suitable algorithm must have been used to generate that calibration. Consequently, considerations such as PPE, databases, calibrations, and algorithms are all essential components of the instrument (Figure 1.1).

1.2 The Evolution of Applications

The initial investigations and proof of concept of a new application for a portable spectrometer may be carried out using existing laboratory instruments, including determination of the spectral range, signal‐to‐noise ratio (SNR), and spectral resolution required. In general, though, it is best to develop the final application on the new product itself, because it will have an identical resolution, spectral range, etc., to the commercial product. Development of potential applications for a portable spectrometer typically begins as a response to an unmet market need. For instance, over many years, vendors of portable X‐ray fluorescence (XRF) instruments were asked at trade shows whether their products could distinguish grades of stainless steel, especially “H” and “L” grades, differentiated based upon levels of carbon. H grades have between 0.04 and 0.1% carbon, while L grades have less than 0.03% carbon. The ability to distinguish these in the field is important because L grades, while more expensive, provide better corrosion resistance after in‐situ welding where annealing is not possible. Handheld XRF is not sensitive to carbon, so the enquiries spurred investigations and subsequent development of portable optical emission (OES) instruments, and, more recently, portable laser‐induced breakdown spectroscopy (LIBS) systems.

Figure 1.1 A successful portable spectroscopy platform must extend beyond the spectrometer (engine) performance, and also include consideration of operational requirements, environmental conditions, and application infrastructure. The algorithm, database, and calibration required to process one or more spectra into results are key components.

In the government, safety, and security sectors, development may be spurred by real‐world events that create new requirements. For example, the events of 9/11 and subsequent anthrax attacks in 2001 drove the requirement that response teams must be able to rapidly and reliably detect and identify white powders at the scene. As a result, many agencies issued solicitations looking for solutions that would help them achieve this goal. The development of portable infrared (IR) and Raman spectrometers thrived as a result since those methods worked well for this application.

A good example of an application‐driven platform is the MX908 by 908Devices, which possesses different “modes” of operation, such as “drug‐hunter,” “CWA‐hunter,” and “explosives‐hunter.” When operating in these different modes, the system uses the same hardware and software interface, but allows the user to, with the click of a button, select the analysis settings (i.e. search algorithm, sampling time, etc.) that will give them the best result for the type of sample being analyzed. These different configurations of the same base platform allow the end user to optimize the instrument at the time of analysis. The advantage is that the operator can carry one piece of optimized equipment for a number of different types of samples. XRF instruments are similar in that the same instrument can include calibrations for alloys, precious metals, consumer goods, etc. Selecting one of these calibrations sets will optimize the data collection parameters (including the tube voltage and current, x‐ray filters and measurement time), and the algorithm used to generate the results.

In many cases, once a “platform” has been established for one application, it becomes apparent that it can be employed elsewhere. This is illustrated in Figure 1.2, where customers make requests because of marketplace exposure and experience. Subsequently, new application innovations take place, most likely involving the development of new or amended databases, algorithms, and calibrations, with the prospective customer possibly supplying or giving access to the samples of interest. This cycle has been most evident for portable XRF and Raman instruments and is illustrated in Figures 1.3 and 1.4.

Figure 1.2 The typical cycle of product and application developments.

Figure 1.3 The evolution of portable XRF spectroscopy applications. The first handheld XRF was developed for the detection of lead in paint and then applied to metal alloys. Applications in metal alloys spread to the whole of the metals “food chain.” Heavy metals remain an application area for consumer product safety, precious metal mining and recycling, and several other fields, as shown.

Figure 1.4 The evolution of portable Raman spectroscopy applications. This starts with hazardous materials and moves into military applications. A separate thread takes the applications into general material identification, leading to chemical and pharmaceutical manufacturing. Street drugs emerged as a major application a few years ago, with the proliferation of synth...