TY - JOUR
T1 - A new Fourier transform infrared method for the determination of moisture in edible oils
AU - Al-Alawi, Ahmed
AU - Van De Voort, Frederick R.
AU - Sedman, Jacqueline
PY - 2005/10
Y1 - 2005/10
N2 - A rapid, practical, and accurate Fourier transform infrared (FT-IR) method for the determination of moisture content in edible oils has been developed based on the extraction of water from oil samples into dry acetonitrile. A calibration curve covering a moisture content range of 0-2000 ppm was developed by recording the mid-infrared (MIR) spectra of moisture standards, prepared by gravimetric addition of water to acetonitrile that had been dried over molecular sieves, in a 500 μm ZnSe transmission flow cell and ratioing these spectra against that of the dry acetonitrile. Water was measured in the resulting differential spectra using either the OH stretching (3629 cm-1) or bending (1631 cm-1) bands to produce linear standard curves having standard deviations (SDs) of approximately ±20 ppm. For moisture analysis in oils, the oil sample was mixed with dry acetonitrile in a 1:1 w/v ratio, and after centrifugation to separate the phases, the spectrum of the upper acetonitrile layer was collected and ratioed against the spectrum of the dry acetonitrile used for extraction. The method was validated by standard addition experiments with samples of various oil types, as well as with oil samples deliberately contaminated with alcohols, hydroperoxides, and free fatty acids to investigate possible interferences from minor constituents that may be present in oils and are potentially extractable into acetonitrile. The results of these experiments confirmed that the moisture content of edible oils can be assessed with high accuracy (on the order of ±10 ppm) by this method, thus providing an alternative to the conventional, but problematic, Karl Fischer method and facilitating the routine analysis of edible oils for moisture content.
AB - A rapid, practical, and accurate Fourier transform infrared (FT-IR) method for the determination of moisture content in edible oils has been developed based on the extraction of water from oil samples into dry acetonitrile. A calibration curve covering a moisture content range of 0-2000 ppm was developed by recording the mid-infrared (MIR) spectra of moisture standards, prepared by gravimetric addition of water to acetonitrile that had been dried over molecular sieves, in a 500 μm ZnSe transmission flow cell and ratioing these spectra against that of the dry acetonitrile. Water was measured in the resulting differential spectra using either the OH stretching (3629 cm-1) or bending (1631 cm-1) bands to produce linear standard curves having standard deviations (SDs) of approximately ±20 ppm. For moisture analysis in oils, the oil sample was mixed with dry acetonitrile in a 1:1 w/v ratio, and after centrifugation to separate the phases, the spectrum of the upper acetonitrile layer was collected and ratioed against the spectrum of the dry acetonitrile used for extraction. The method was validated by standard addition experiments with samples of various oil types, as well as with oil samples deliberately contaminated with alcohols, hydroperoxides, and free fatty acids to investigate possible interferences from minor constituents that may be present in oils and are potentially extractable into acetonitrile. The results of these experiments confirmed that the moisture content of edible oils can be assessed with high accuracy (on the order of ±10 ppm) by this method, thus providing an alternative to the conventional, but problematic, Karl Fischer method and facilitating the routine analysis of edible oils for moisture content.
KW - Acetonitrile
KW - Edible oils
KW - FT-IR spectroscopy
KW - Fourier transform infrared spectroscopy
KW - Moisture content
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U2 - 10.1366/000370205774430846
DO - 10.1366/000370205774430846
M3 - Article
C2 - 16274543
AN - SCOPUS:27644531841
SN - 0003-7028
VL - 59
SP - 1295
EP - 1299
JO - Applied Spectroscopy
JF - Applied Spectroscopy
IS - 10
ER -