Think Small Revisited: Handheld Spectroscopy

Feb 01, 2007


John P. Coates
In the October issue of Spectroscopy, John Coates (1) described a miniaturized spectral sensing concept based upon a spectral engine. In that column, the idea of a miniaturized platform for spectral measurements was developed. It discussed how miniaturization can enable analysts to bring the measurement system to the sample, rather than vice versa. The focus was on development of in-line and on-line measurement systems for continuous monitoring. The topics covered were beyond the traditional process analytical applications and included unconventional thinking on in-line water measurements for environmental monitoring and public safety applications, applications in the wine and brewing industries, and medical and life science applications. They involved the fabrication of low-cost components as either a true spectrometer or spectral sensor on a chip. In volume, like all chip-based technologies, the cost of such devices can drop to a point where spectral measurements can be entertained in consumer applications and consumer-based products.


Emil W. Ciurczak is chief technical officer at Cadrai Technology Group (Bel Air, MD). He can be reached via e-mail at: emil@ciurczak.com
In this column, the theme is expanded to include handheld measurements using a palm-sized device. This device provides the full spectral capability discussed in the earlier article, but with a slant toward making common analytical measurements at a personal level. It is a truly portable system functioning as a spectrometer and can be used either open ended or as a dedicated analyzer. As an analyzer, it can make use of "canned" standard methods that are available as Internet downloads or it can run user-developed methods. A method is defined as a recipe for measurement of a specific chemistry or a material property from a natural or induced chromophore (role of a reagent) and from the resultant spectral data followed by the necessary data conditioning and calculations. Another key element of any spectral analysis is how the sample is handled and optically interfaced to the system. The device in this column brings everything together in a single unit, where a complete analysis can be performed by a single-handed operation.

This column provides readers with an insight into how it is best to consider the development of instrumentation on a platform basis. By definition, platforms (such as the infamous IBM PC) are flexible, easy to customize, and can be applied to multiple applications — some previously not considered for spectroscopic analysis. The platform discussed leads into an affordable palm-sized measurement system. The hope is that readers will be encouraged to think beyond the traditional limits of spectroscopy; also, another byproduct of this thinking is to introduce a concept that will open doors into the educational system and into the home or consumer market.

By education and training, this author is an analytical chemist with a background in analytical methods development and use of instrumentation. Early involvements with computers (back in the mid-1960s) led to the expansion of applications by the processing of spectral data for material characterization and automated methods of analysis. Since the mid-1970s, the focus has expanded further to include the development and design of instrumentation and sensors. Drawing on all these experiences and skill requirements, the author has fulfilled some of his ambitions to develop a miniaturized spectral measurement system that is automated, easy to use, and readily customizable to meet the needs of a broad range of chemical, physical, and life science–based measurements.

The thought processes involved are reviewed here. The first consideration is the sample. For years, discussions have been going back and forth about what should come first, the instrument or the sample. Traditionally, the instrument is designed first and the sample handling is fitted in somewhere, either in a sample compartment or an extension of a sample compartment: some interface that is generated by "light pipes" or optical fibers. In all cases, the sample optical interface might be a compromise relative to light-coupling efficiency and convenience of use. In the current system under consideration, the sample and its method of introduction and optical interfacing were examined first, and the instrument was designed to interface with the sampling device.