Edible oil analysis by FTIR spectroscopy
Fourier-transform infrared (FTIR) spectroscopy offers a new way of approaching edible oil analysis and is well on its way to being developed into a utilitarian quality control tool. This paper provides a brief overview of FTIR spectroscopy, the key elements associated with developing a suitable fats and oils analytical system (sample handling, calibration development, validation, calibration stability and transfer, programming and automation), some methods that have been implemented, and the basic elements of a typical fats and oils FTIR analytical package. It is foreseen that a number of standard AOCS methods will be replaced by this technology, allowing a variety of chemical and physical analyses to be carried out on neat fats and oils in under 2 minutes per sample. © 1996 John Wiley & Sons, Inc.
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ABSTRACT: Introduction The quality or status of a lubricant is directly related to the performance and reliability of machinery and the importance of condition monitoring so as to avoid excessive wear and downtime of equipment and critical components has been recognized (1). The chemical and physical parameters analyzed for are largely based on standardized analytical methods to provide an overall indication of the status of a lubricant. However, key ASTM chemical methods such as the determination of Total Acid Number (TAN), Total Base Number (TBN) and moisture (H 2 O) are troublesome to carry out, being tedious, time consuming and trouble prone even in their automated forms. Today, there is more emphasis on structured condition monitoring to provide trending data so that one can take preventive action on the one hand, but not take unnecessary action on the other. This approach may extend drain intervals and reduce lubricant disposal and maintenance and failure costs. On the other hand, extensive testing is required and data management can become complex. FTIR Spectroscopy In this context, an instrument that has become increasingly prominent in lubricant analysis is the infrared spectrometer, specifically the Fourier transform infrared (FTIR) spectrometer. This analytical instrument effectively provides a spectral snapshot of the base oil and other constituents present. Its power is based on the fact that specific molecular functional groups absorb in unique regions of the mid-infrared spectrum, allowing identification of additives, contaminants and breakdown products. Although IR spectral information is meaningful to a spectroscopist, its meaning is not necessarily apparent to the non-expert. Even with this limitation, IR spectroscopy is still a very powerful tool, simply because it can provide substantial information about oil condition using a single instrument. Indications about the state of oxidation, nitration and sulfation and levels of soot, moisture, glycol and various additives, among others, is available. Extensive IR studies of lubricants and fuels have led to the establishment of standardized protocols to monitor selected condition parameters under the guise of the Joint Oil Analysis Program (JOAP). These protocols, and similar protocols under consideration by the ASTM, provide a comprehensive means of monitoring the condition of lubricants using a single analytical technique.
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ABSTRACT: A primary Fourier transform infrared (FTIR) spectroscopic method for the determination of peroxide value (PV) in edible oils
was developed based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides to produce triphenylphosphine
oxide (TPPO). Accurate quantitation of the TPPO formed in this reaction by measurement of its intense absorption band at 542
cm−1 provides a simple means of determining PV. A calibration was developed with TPPO as the standard; its concentration, expressed
in terms of PV, covered a range of 0–15 PV. The resulting calibration was linear over the analytical range and had a standard
deviation of ±0.05 PV. A standardized analytical protocol was developed, consisting of adding ∼0.2 g of a 33% (w/w) stock
solution of TPP in hexanol to ∼30 g of melted fat or oil, shaking the sample, and scanning it in a 100-µm KCI IR transmission
cell maintained at 80°C. The FTIR spectrometer was programmed in Visual Basic to automate scanning and quantitation, with
the reaction/FTIR analysis taking about 2 min per sample. The method was validated by comparing the analytical results of
the AOCS PV method to those of the automated FTIR procedure by using both oxidized oils and oils spiked with tert-butyl hydroperoxide. The two methods correlated well. The reproducibility of the FTIR method was superior (±0.18) to that
of the standard chemical method (±0.89 PV). The FTIR method is a significant improvement over the standard AOCS method in
terms of analytical time and effort and avoids solvent and reagent disposal problems. Based on its simple stoichiometry, rapid
and complete reaction, and the singular band that characterizes the end product, the TPP/TPPO reaction coupled with a programmable
FTIR spectrometer provides a rapid and efficient means of determining PV that is especially suited for routine quality control
applications in the fats and oils industry.
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