Sampling, Sample Preparation, and Sample Selection
Near-infrared (NIR) technology offers a rapid method for the analysis of a wide range of material for a large number of chemical and physicochemical parameters. Both NIR reflectance and transmittance (NIT) have become recognized as rapid, accurate, precise, and pollution-free methods of analysis, and have earned respect among instrumental methods. The main reasons for the rapid climb to fame of NIR technology are (a) its speed while maintaining accuracy, (b) its freedom from chemicals and therefore from pollution, and (c) simple sample preparation. Modern NIR instruments are durable, and are capable of excellent accuracy and precision. They are backed up with comprehensive software and generally reflect a great deal of inspired input from the instrument company engineers. The main sources of error in NIR testing lie with the samples, their selection, preparation, and reference analysis. This chapter is an informal attempt at drawing attention to the chief trouble areas in these aspects of NIR technology. Provided they are efficiently accomplished, excellent analysis can be achieved with several different software systems. If they are not efficiently carried out, consistent and accurate NIR analysis is not possible, no matter how sophisticated the software. More recently, improvements in whole-grain instruments have revolutionized NIT and NIR testing of grains and seeds. This is done mainly to the removal of the need for grinding samples, and the errors thereby induced. Sample preparation, however, (including grinding) is essential to reference analysis, and many ground-sample NIR instruments are still in use.