Abstract

Near-infrared (NIR) spectroscopy normally requires gram quantities of sample. This is not a serious constraint because the technique is generally used where large amounts of the material under investigation are available. However, during the development of NIR methods of analysis it is desirable to obtain reference spectra of pure compounds. If these are available in only small quantities then the large sample requirement of the normal sample cup causes frustration. Special sample cups for small samples have been developed, but the expense of obtaining them can only be justified if they are going to be used regularly—a condition which would not be met in the average NIR laboratory. While in the past our own work had occasionally been constrained by our inability to obtain spectra from small samples, we had not been hampered sufficiently to cause us to obtain a special cell. However, during work on the development of a method of analysis for the glucosinolate content of rapeseed, we became interested in obtaining spectra of pure glucosinolates, which were available to us in quantities ranging from 50 to 300 mg. This note reports a very simple method which enabled satisfactory spectra to be obtained from 100-mg sized samples without any special apparatus.

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A Simple Digital Near Infrared Spectrometer

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