204 years of near infrared technology: 1800-2003

Near infrared spectroscopy has come of age. Today, it takes its place along side other major analytical technologies. Though it has inherent problems, its advantages make it an appealing tool for solving all sorts of analytical problems, for all sorts of samples, found in numerous fields, including food, agriculture, chemical, pharmaceuticals, textiles, polymers, cosmetics and medical-just to mention a few. Healthy, strong and still growing, NIR spectroscopy is a source of thrills and chills for many, whether from new measurement technology, chemometrics or from understanding and being able to express "old" ideas in fresher, clearer ways.' Modern NIR instruments integrate numerous technologies for determining absorbances at specific wavelengths: Monochromator, Fourier Transform, Filters [including, narrow-band interference filters, tilting filters, Acousto Optical Tunable Filters (AOTF) and Liquid Crystal Tunable Filters (LCTF)], Hadamard, Diode Emitters and Diode Arrays. Software for developing calibrations, utilising some types of classical and/or modern multivariate methods, is available with every commercial instrument. In addition, software vendors, independent of manufacturers, have designed and are marketing advanced chemometric packages for carrying out a variety of multivariate tasks, including mathematical spectral pretreatment, calibration and prediction, plus the implementation of process control statistics. The plethora of instruments and software has provided a sound basis for developing all sorts of applications throughout numerous fields. As a result, there are today more than 25,000 citations in the NIR literature and, since 1960, Medline alone has logged 2341 citations with NIR implications for the medical community, all tributes to the strength and viability of this fascinating spectroscopy. This review is a look at the big picture of NIR spectroscopy. It covers the field of NIR from the beginning to present day-204 years (1800-2003)-in six sections: Introduction, Reviews, Books, Instrumentation, Applications and Conclusions: Past, Present and Future.