Argentation in Countercurrent Distribution to Separate Isologues and Geometric Isomers of Fatty Acid Esters.

Scholfield, C. R.; Jones, E. P.; Butterfield, R. O.; Dutton, H. J.

doi:10.1021/ac60204a013

Cited by 59 publications

(20 citation statements)

References 16 publications

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“…The deviation from 100% trans values for Fractions B and D is believed due to lower absorptivities (based on peak height alone) for dienoic esters containing one trans double bond. Similar low absorptivities have been observed by others (14). The width of the absorption band, however, is visibly A comparison of capillary gas-liquid chromatography and oxidative cleavage data for both monoenoates and dienoates is given in Tables I1 and 111.…”

Section: Results a N D Discussionsupporting

confidence: 81%

Analysis of Methyl Actadecenoate and Octadecadienoate Isomers by Combined Liquid-Solid and Capillary Gas-Liquid Chromatography.

Kuemmel¹,

Chapman²

1966

Anal. Chem.

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Section: Results a N D Discussionsupporting

confidence: 81%

Analysis of Methyl Actadecenoate and Octadecadienoate Isomers by Combined Liquid-Solid and Capillary Gas-Liquid Chromatography.

Kuemmel¹,

Chapman²

1966

Anal. Chem.

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“…Consequently, an underestimation of the trans content in samples high in PUFA must be expected. For trans isomers of 18:2n-6 the response relative to elaidic acid has been reported to be about 85% (6,7,10). When the height of the trans peak at 967 cm −1 was measured with the baseline drawn according to Cd 14-95, the GC-IR spectra gave a response of 92% for the trans DB in all-trans-18:2n-6.…”

Section: The Figures Inmentioning

confidence: 99%

A rapid method for the analysis of hydrogenated fats by GC with IR detection

Mjøs¹,

Pettersen²

2003

J Americ Oil Chem Soc

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A rapid method for analysis of trans and cis FA in hydrogenated fats has been developed. The method is based on a single analysis by GC with IR detection. Multivariate partial least squares regression is applied on the IR spectra to predict the number of cis and trans double bonds. For each chain length the method provides information about the amount of the saturated FA, the amount of trans monoenes, the amount of cis monoenes, the amount of PUFA, and the average number of cis and trans double bonds in PUFA. The method has been validated by summing the values to a total trans value and total unsaturation. These sum values were compared with total trans unsaturation, as determined by AOCS method Cd 14-95, and iodine value, as determined by AOCS Cd 1d-92. Paper no. J10488 in JAOCS 80, 839-846 (September 2003).KEY WORDS: Gas chromatography, hydrogenated fats, hydrogenation, infrared spectroscopy, partial least squares regression, trans fatty acids.Trans double bonds (DB) in oils and fats can be quantified by IR spectroscopy by measuring the absorption at approximately 967 cm −1 (1,2). This principle is used in several standard procedures (3-5). Methyl elaidate (trans 18:1n-9) or glyceryl trielaidate is usually applied as external standard in these methods. Several reports have shown that the absorption at 967 cm −1 from trans DB in geometric isomers of linoleic acid (18:2n-6) (6-8), linolenic acid (18:3n-3) (9), and trans FA found in hydrogenated fats (8,10) is weaker than the absorption from the trans DB in elaidic acid (trans 18:1n-9). Underestimation of the amount of trans DB may therefore occur in some samples.The IR spectra also contain information about the chain length and the number of cis DB. The most important signals for the determination of FA structure have been summarized by Guillén and Cabo (11). The number of cis DB in a FA can be calculated from the signals at 3020 and 2920 cm −1 (12). Iodine value (IV) also can be calculated from the ratio between the signals at 3030 and 2857 cm −1 (13). Van de Voort et al. (14) obtained good correlation between IR spectra and IV using whole spectra as input in partial least squares (PLS) regression.Trans FA also are analyzed by GC using long polar capillary columns. The GC methods provide more detailed molecular information than IR analysis and have lower detection limits. The major drawback of the GC methods is overlap between the chromatographic zones of cis and trans FA. This overlap may lead to severe errors in quantification, especially when complex samples such as hydrogenated fats are analyzed.Attempts have been made to combine the two techniques using GC with IR detection, often in combination with FID or MS detectors. Using a lightpipe GC-IR interface, Wahl et al. (15) were able to identify 31 unsaturated reference FA including both cis and trans isomers, and reported the detection limit for single isomers to be about 25 ng. GC-MS combined with GC-IR equipped with a direct deposition interface has been used to identify individual isomers in hydrogen...

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“…The data of Table V resulted from an attempt to correlate the number of double bonds in the CI8 fatty methyl esters with a shift in p-value due to the presence of silver nitrate. The system of hexanego% aqueous methanol containing 0.2M AgNOa, which has been studied' extensively by countercurrent distribution (9), gave p-values that were too high; hexane95% aqueous methanol containing 0.1M AgN08 was therefore used. [The previous workers (9) used 40-ml.…”

Section: As Shown Inmentioning

confidence: 99%

“…The system of hexanego% aqueous methanol containing 0.2M AgNOa, which has been studied' extensively by countercurrent distribution (9), gave p-values that were too high; hexane95% aqueous methanol containing 0.1M AgN08 was therefore used. [The previous workers (9) used 40-ml. lower and 10-ml.…”

Section: As Shown Inmentioning

confidence: 99%

“…A p i $ k 2 n e t r y and gas-liquid chromatography (GLC) has been achieved, using pressure reduction systems (6,9) for the direct coupling of the two instruments and fast-scanning techniques for recording mass spectra. Combined instruments of this type offer several important advantages: e:g., mass spectral data can be obtained with extremely minute quantities of a volatile organic compound, and grossly impure samples may be used provided the desired compound is eluted as a single component from the GLC column.…”

Section: Combination Of Massmentioning

confidence: 99%

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