Sampling Techniques for Infrared Analysis in the Environmental and Forensic Laboratories *
In the environmental and forensic laboratories, typically the most difficult and crucial factor in solving a problem is determining the appropriate analytical technique. Secondarily, the sampling method used in the analytical technique of choice can help answer the question or preclude any definitive results. Sampling techniques must not only consider the matrix in which the sample resides, but also the phase in which the sample exists. In general, infrared analytical sampling can be divided into four main areas: transmission, reflectance, microspectroscopy, and chromatographic effluents. Infrared reflectance spectroscopy covers a very broad area of applications. These techniques include internal reflectance, diffuse reflectance, and specular reflectance and can be used in a number of different configurations for most liquid and solid samples. Identification of foreign materials in biological samples has been greatly assisted by the development of infrared microscopy.