The near‐infrared (NIR) region (600–1100 nm) offers several advantages in comparison with the conventional ultraviolet/visible (UV/VIS) region for spectroscopic measurements and detection. The lack of commercial instrumentation impeded the development of NIR techniques for years. The advent of inexpensive photodiodes and diode lasers used widely by the telecommunication industry gave the necessary impetus for development of analytical NIR techniques. This article describes the fundamental properties of NIR fluorophores and absorbers and provides a comparison with conventional UV/VIS dyes. The various analytical applications developed in the past decade that have utilized the advantages offered by this region are described with a particular emphasis on bioanalytical uses.

The near-infrared (NIR) region of spectrum provides many advantages over conventional UV--visible region and is particularly useful when background interference is the primary concern. Many NIR fluorophores have high molar absorptivities and fluorescence quantum yields. The use of laser diodes for excitation and photodiodes for detection makes the NIR fluorophores an ideal choice as tracers for various applications. NIR fluorescence immunoassays (NIRFIAs) for disease-related antigens have been developed and optimized in our laboratory during the past few years. NIRFIA can be used in both sandwich and competitive formats. We have successfully adapted the NIRFIA as both a microtiter plate assay and a fiber optic probe. This paper is focussed on the environmental analytical applications of this novel technique. Physical properties of ideal NIR labels and engineering problems of devising remote sensors are discussed. Conventionalimmunoassays have been recognized as a powerful tool in the analysis of minor components in a complex media.The use of laser induced fluorescence in the development of immunoassays has been reviewed (1). The limitations in using conventional lasers as an excitation source are size, high price, and maintenance costs. Recent advances in semiconductor laser technology have made the use of these lasers as an excitation source more

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