Paper addresses methods for quantitative biodiesel measurements

By Erin Voegele | May 03, 2011

Wilks Enterprise Inc. recently published a white paper that demonstrates how lower resolution infrared spectroscopy can provide higher performance for quantitative biodiesel measurements.

According to the company, resolution is often used as the yardstick of instrument performance in infrared spectroscopy, especially when measurements are energy limited as they are in mid-infrared. “While resolution is important to qualitatively examine specific components and attributes of a sample, quantitative analysis does not always benefit from higher resolutions,” said Wilks Enterprise in a press release. “In fact…a lower resolution instrument will actually perform better for quantitative measurements where absorbance peaks are well defined and not overlapping.” According to Wilks Enterprise, this can be demonstrated with the analysis of biodiesel in diesel.

To complete its study, Wilks Enterprise used a Nicolet FT-IR spectrometer, Model 5-PC—which is capable of analysis as multiple resolutions—to analyze samples of biodiesel blended fuel. According to the white paper, samples were collected at 4 cm-1 and 16 cm-1 using a 10 bounce Attenuated Total Reflection sample stage.

When looking at the resulting spectra alone, the white paper notes that it appears as if the higher resolution spectra would give the best results in a quantitative analysis. However, further evaluation shows the opposite to be true. Wilks Enterprise determined that the lower resolution calibration performed better in most cases. According to results of the study, the company found that higher resolution can actually be detrimental due to the fact that the noise level typically grows as resolution increases.

“Since lower resolution infrared instruments can be made with few or no moving parts, they can be ruggedized and made portable,” said Wilks Enterprise in the white paper. “This allows for a portable instrument having performance similar to that of a lab-based instrument and is ideally suited for dedicated or simple on-site quantitative analysis. The InfraSpec Variable Filter Array-IR Spectrometer, manufactured by WIlks Enterprise Inc., is a typical example of an instrument that provides very good signal to noise in a compact low resolution design capable of accurate, on-site quantitative analysis.”

A full copy of the white paper can be downloaded from the company’s website.


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