Submitted to: Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2007
Publication Date: 3/1/2008
Citation: Obeidat, S., Bai, B., Rayson, G.D., Anderson, D.M., Puscheck, A.D., Landau, S.Y., Glasser, T. 2008. A multi-source portable light emitting diode spectrofluorometer. Applied Spectroscopy. 62:327-332. Interpretive Summary: Determining the botanical composition of the standing crop together with animal diets is fundamental to free-ranging animal management. Most methods currently used to document botanical composition require instrumentation not built with field portability in mind. As a result there is often a substantial temporal separation between gathering the samples, analyzing the data and interpreting the results before being able to implement practical management decisions. This research outlines the development of a lightweight (~1.5 kg) luminescence spectrofluorometer powered from a laptop computer that uses seven broad-band light emitting diodes (LED’s) to excite samples. Tests using chemical standards as well as buffered saline extracts from several plants and a feed supplement were evaluated. The results suggest data from the portable instrument, when analyzed using multi-way principal component analysis (MPCA), allowed accurate discrimination among the samples evaluated.
Technical Abstract: A portable luminescence spectrofluorometer weighing only 1.5 kg that uses multiple light emitting diodes (LEDs) as excitation sources was developed and evaluated. Excitation using a sequence of seven individual broad-band LED emission sources enabled the generation of excitation-emission spectra using a light weight (<1.5 kg) spectrometer. Limits of detection for rhodamine 6G, rhodamine B and fluorescein were 2.9, 3.2, and 11.0 nM, respectively. Generation of excitation-emission matrices (EEMs) enabled the analysis of samples containing mixtures of rhodamine B and fluorescein. Buffered saline plant and animal feed extracts were also analyzed using this instrument. These samples included the woody plants Pistacia lentiscus (Evergreen pistache or Mastic) and Philyria latifolia, and the herbaceous species Medicago sativa (alfalfa), Trifolium spp. (clover), and a feed concentrate. Application of multi-way principal component analysis (MPCA) to the resulting three-dimensional data sets enabled discernment among these various diet constituents.