Automated quantitative analysis of isolated (nonconjugated) trans isomers using fourier transform infrared spectroscopy incorporating improvements in the procedure

Sleeter, Ronald T.; Matlock, Mark G.

doi:10.1007/bf02653294

Cited by 7 publications

(13 citation statements)

References 3 publications

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“…In recent years, as a result of the development of FTIR instrumentation and computerized data analysis techniques, various modifications to the AOCS method for the IR determination of trans content have been investigated. Several of these (11,14,15) measure the trans content from the IR spectrum of neat oil (or melted fat) or methyl esters recorded in a short-pathlength (~0.1 mm) transmission cell or by the attenuated total reflectance (ATR) sampling technique, thereby eliminating the use of CS 2 . Because of the inconvenience of injecting samples into short-pathlength cells and the drawbacks of the ATR sampling method, particularly the difficulty of cleaning the ATR crystal and the extreme sensitivity of ATR/FTIR measurements to changes in the alignment of the crystal and temperature fluctuations, the McGill IR Group developed a trans method based on the use of a heated flow-through transmission cell sample-handling accessory, designed specifically for the analysis of neat fats and oils (8).…”

Section: Resultsmentioning

confidence: 99%

Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

Sedman

Voort

Ismail

et al. 1998

J Americ Oil Chem Soc

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A Fourier transform infrared (FTIR) edible oil analysis package designed to simultaneously analyze for trans content, cis content, iodine value (IV), and saponification number (SN) of neat fats and oils by using calibrations based on pure triglycerides and derived by application of partial-least-squares (PLS) regression was assessed and validated. More than 100 hydrogenated rapeseed and soybean samples were analyzed by using the edible oil analysis package as well as the newly proposed modification of the AOCS IR trans method with trielaidin in a trans-free oil as a basis for calibration. In addition, ~1/3 of the samples were subsequently reanalyzed by gas chromatography (GC) for IV and trans content. The PLS approach predicted somewhat higher trans values than the modified AOCS IR method, which was traced to a combination of the inclusion of trilinolelaidin in the calibration set and the effects of baseline fluctuations. Eliminating trilinolelaidin from the triglyceride standards and the use of second-derivative spectra to remove baseline fluctuations produced excellent concurrence between the PLS and modified AOCS IR methods (mean difference of 0.61% trans). Excellent internal consistency was obtained between the IV and cis and trans data provided by the edible oil analysis package, and the relationship was close to that theoretically expected [IV = 0.86 (cis + trans)]. The IV data calculated for the GC-analyzed samples matched the PLS IV predictions within 1 IV unit. The trans results obtained by both IR methods were linearly related to the GC data; however, as is commonly observed, the GC values were significantly lower than the IR values, the GC and IR data being related by a slope factor of 0.88, with an SD of ~0.80. The concurrence between the trans data obtained by the two FTIR methods, and between the FTIR and GC-IV data, as well as the internal consistency of the IV, cis and trans FTIR predictions, provides strong experimental evidence that the edible oil analytical package measures all three variables accurately. JAOCS 75, 33-39 (1998).

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Section: Resultsmentioning

confidence: 99%

Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

Sedman

Voort

Ismail

et al. 1998

J Americ Oil Chem Soc

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“…The standard curves derived from the spectra, shown in Figures 2A and 2B, are presented in Figures 3A and 3B, respectively. These plots are reasonably linear, although we and others (15) have noted that there is significant curvature beyond 50% trans and that accurate analysis beyond this value requires a quadratic fit. The equations obtained by simple linear regression over the range of 0-50% trans are presented in Equations 1 and 2, respectively.…”

Section: Methodsmentioning

confidence: 73%

“…For shortpathlength transmission cells, the introduction of viscous oil samples into conventional IR cells can be difficult and awkward, and solvent rinses can be problematic in an industrial setting. In most of the previous work (15)(16)(17) on trans analysis of neat oil samples, the critical issue of temperature con- trol has not been addressed, and the sample accessories used were not designed to operate at elevated temperatures and thus were not suitable for the routine analysis of solid fats. Even properly designed heated ATR cells tend to be problematic.…”

Section: Discussionmentioning

confidence: 98%

“…Much effort has gone into overcoming these problems, and several authors have worked on means of eliminating CS 2 (15)(16)(17) by measuring the trans content from the IR spectrum of neat oils (or melted fats) or their methyl esters with attenuated total reflectance (ATR) sampling techniques or shortpathlength (~0.1 mm) transmission cells. Although both approaches are workable, each has limitations.…”

Section: Discussionmentioning

confidence: 99%

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Upgrading the AOCS infrared trans method for analysis of neat fats and oils by fourier transform infrared spectroscopy

Sedman

Voort

Ismail

1997

J Americ Oil Chem Soc

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An automated protocol for the direct, rapid determination of isolated trans content of neat fats and oils by Fourier transform infrared (FTIR) spectroscopy was devised, based on a simple modification of the standard AOCS trans method, eliminating the use of CS 2 and methylation of low trans samples. Through the use of a commercially available, heated transmission flow cell, designed specifically for the analysis of neat fats and oils, a calibration (0-50%) was devised with trielaidin spiked into a certified, trans-free soybean oil. The single-beam spectra of the calibration standards were ratioed against the single-beam spectrum of the base oil, eliminating the spectral interference caused by underlying triglyceride absorptions, facilitating direct peak height measurements as per the AOCS IR trans method. The spectrometer was preprogrammed in Visual Basic to carry out all spectral manipulations, measurements, and calculations to produce trans results directly as well as to provide the operator with a simple interface to work from. The derived calibration was incorporated into the software package, obviating the need for further calibration because the program includes an automatic recalibration/standardization routine that automatically compensates for differences in optical characteristics between instruments, instrument drift over time, and cell wear. The modified AOCS FTIR analytical package was evaluated with Smalley check samples for repeatability, reproducibility, and accuracy, producing SD of ± 0.07, 0.13, and 0.70 trans, respectively, the FTIR predictions being linearly related to the Smalley means (r = 0.999; SD = ± 0.46), and well within one SD of the Smalley sample means. Calibration transfer was assessed by implementing the calibration on a second instrument and reanalyzing the Smalley check samples in cells of two different pathlengths (25-and 50-µm). There were no statistically significant differences between the FTIR trans predictions obtained for the Smalley samples from the two instruments and two cells, indicating that the software was able to adjust the calibrations to compensate for differences in instrument response and cell pathlength. The FTIR isolated trans analysis protocol developed by the McGill IR Group has the benefit of being based on the principles of an AOCS-approved method, matches its accuracy, and allows the analysis to be performed on both neat fats and oils, producing trans predictions in less than 2 min per sample. It is suggested that this integrated approach to trans analysis, which requires a minimum level of sample manipulation and operator skill, be considered as a modification of the proposed Recommended Practice CD14b-95. JAOCS 74, 907-913 (1997).Edible fats and oils vary in their triglyceride makeup, relative degree and forms of unsaturation (cis and trans), weight-average molecular weight, and overall fatty acid composition/distribution, and these complex determinants define the physicochemical properties of the lipid system. For stability and functionality reasons,...

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“…In those protocols the application of dispersive IR instruments is specified. The Fourier Transform IR (FTIR) technique has been introduced successfully for the determination of isolated TFA isomers in dietary fats (Lanser and Emken, 1988;Sleeter and Matlock, 1989). This type of instrumentation offers several advantages over conventional IR spectrometers (Giinzler and Beck, 1983): (a) improved S/N ratio due to the averaging of multiple scans, (b) high accuracy of the wavelength calibration due to a reference He-Ne laser, (c) improved light through-put and speed of analysis due to the Michelson interferometer principle and (e) spectra manipulation by means of computers due to the digital format of the spectroscopic data.…”

Section: Introductionmentioning

confidence: 99%

Determination of Low Level Trans Unsaturation in Fats by Fourier Transform Infrared Spectroscopy

Ulberth¹,

Haider²

1992

Journal of Food Science

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Fourier Transform infrared spectroscopy (FTIR) was an excellent tool for rapid determination of trans unsaturation in edible fats. Methyl esters were determined as a neat solution, thereby avoiding cumbersome weighing operations and handling of CS2. The method was calibrated by gravimetrically prepared mixtures of methyl elaidat in methyl esters of a trans fatty acid (TFA) free soy oil. In contrast to TFA concentrations > lo%, which could be determined easily by the classic baseline technique, low TFA values were only quantifiable (with high accuracy) after a computer-assisted spectral subtraction procedure.

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Automated quantitative analysis of isolated (nonconjugated) trans isomers using fourier transform infrared spectroscopy incorporating improvements in the procedure

Cited by 7 publications

References 3 publications

Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

Upgrading the AOCS infrared trans method for analysis of neat fats and oils by fourier transform infrared spectroscopy

Determination of Low Level Trans Unsaturation in Fats by Fourier Transform Infrared Spectroscopy

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