144
M. Talebi et al.
the determination by food manufacturers of the levels of each type of fatty acid, as
each has different known or suspected health effects [42, 43, 46, 77, 82].
The SLB-IL111 column with a length of 100 m or 200 m is usually used for
detailed analysis of fatty acids in food samples [42, 43, 58, 59]. The exceptionally
polar characteristic of a SLB-IL111 column allows separation of key cis/trans FAME
isomers that are hard to resolve on other columns. It also provides a complementary
elution profile of FAMEs typically separated on the biscyanopropyl siloxane columns
[42]. Excellent performance of the SLB-IL111 was shown in separation of cis/trans
conjugated linoleic acid (CLA) isomers, where c9, t11-CLA, and t7, c9-CLA, the
most abundant CLA isomers in ruminant fats, were completely resolved from each
other [42]. Octadecenoic acid (C18:1) is the foremost constituent of dietary fats
and oils with distributions of 26 cis and trans isomers having various double bond
positions in the range of 4–16. Oleic acid (C18:1 cis9 ), the most naturally abundant isomer, is quantifiable with the SLB-IL111 column separation and not with
any other commercial column due to coelution with other C18:1 isomers [83]. The
major trans C18:1 fatty acid in ruminant-derived foods, especially milk fat, is trans
vaccenic acid (tVA, t11-C18:1). Studies have shown that t11-C18:1 is beneficial for
the human body, and it is a precursor for conjugated linoleic acids (CLA). Trans-10
is another notable trans C18:1 isomer, which unlike trans-11 is not known to provide any useful health benefits in humans [84–87]. While using the official AOCS
method results in coelution of trans 9–11 C18:1 isomers, most of the trans FAME
geometrical isomers including t10-C18:1 and t11-C18:1 can be separated using the
SLB-IL111 column [43, 46]. The SLB-IL111 is also proficient at separating odd and
branched-chain fatty acids (OBCFAs) from other milk FAs eluting in the same chromatographic region [88]. These FAs are the chief lipids in bacterial membranes and
are considered as biomarkers of ruminant fat intake [89]. By definition, the branching on the iso-methyl-branched fatty acids is positioned on the penultimate carbon,
while the methyl substituent in anteiso-branched fatty acids is located on the antepenultimate carbon atom. The elution behavior of iso fatty acids on the SLB-IL111
is very similar to the conventional polymer stationary phases. The iso FA with n
C-atoms elutes at a carbon number (CN) of (n–1 + 0.5). Accordingly, iso-C13:0
elutes between C12:0 and C13:0 fatty acids (or CN = 12.5). On the other hand, the
aiso, a FA containing n C-atoms, retains slightly longer than the iso isomer, at CN
of (n–1 + 0.7). Furthermore, unlike cis and trans FA isomers, the relative retention
times are not affected for iso and aiso isomers by changing the isothermal program
on ionic liquid columns [88].
The 200 m SLB-IL111 column was further used for determination of total, trans,
saturated, and cis unsaturated fats in 32 representative fast food samples [46]. The
content of trans fat ranged from 0.1 to 3.1 g per serving, as determined according to
American Oil Chemists’ Society (AOCS) official method Ce 1j-07. The improved
separation of trans C18:1 positional isomers and enhanced resolution of trans C18:2
and C18:3 FAME isomers are two major advantages of the SLB-IL111 column,
relative to the biscyanopropyl siloxane stationary phases.
The fatty acid composition in marine oils and products is very complex with
a wide variety of chain length and unsaturation [47]. The SLB-IL111 column has
M. Talebi et al.
the determination by food manufacturers of the levels of each type of fatty acid, as
each has different known or suspected health effects [42, 43, 46, 77, 82].
The SLB-IL111 column with a length of 100 m or 200 m is usually used for
detailed analysis of fatty acids in food samples [42, 43, 58, 59]. The exceptionally
polar characteristic of a SLB-IL111 column allows separation of key cis/trans FAME
isomers that are hard to resolve on other columns. It also provides a complementary
elution profile of FAMEs typically separated on the biscyanopropyl siloxane columns
[42]. Excellent performance of the SLB-IL111 was shown in separation of cis/trans
conjugated linoleic acid (CLA) isomers, where c9, t11-CLA, and t7, c9-CLA, the
most abundant CLA isomers in ruminant fats, were completely resolved from each
other [42]. Octadecenoic acid (C18:1) is the foremost constituent of dietary fats
and oils with distributions of 26 cis and trans isomers having various double bond
positions in the range of 4–16. Oleic acid (C18:1 cis9 ), the most naturally abundant isomer, is quantifiable with the SLB-IL111 column separation and not with
any other commercial column due to coelution with other C18:1 isomers [83]. The
major trans C18:1 fatty acid in ruminant-derived foods, especially milk fat, is trans
vaccenic acid (tVA, t11-C18:1). Studies have shown that t11-C18:1 is beneficial for
the human body, and it is a precursor for conjugated linoleic acids (CLA). Trans-10
is another notable trans C18:1 isomer, which unlike trans-11 is not known to provide any useful health benefits in humans [84–87]. While using the official AOCS
method results in coelution of trans 9–11 C18:1 isomers, most of the trans FAME
geometrical isomers including t10-C18:1 and t11-C18:1 can be separated using the
SLB-IL111 column [43, 46]. The SLB-IL111 is also proficient at separating odd and
branched-chain fatty acids (OBCFAs) from other milk FAs eluting in the same chromatographic region [88]. These FAs are the chief lipids in bacterial membranes and
are considered as biomarkers of ruminant fat intake [89]. By definition, the branching on the iso-methyl-branched fatty acids is positioned on the penultimate carbon,
while the methyl substituent in anteiso-branched fatty acids is located on the antepenultimate carbon atom. The elution behavior of iso fatty acids on the SLB-IL111
is very similar to the conventional polymer stationary phases. The iso FA with n
C-atoms elutes at a carbon number (CN) of (n–1 + 0.5). Accordingly, iso-C13:0
elutes between C12:0 and C13:0 fatty acids (or CN = 12.5). On the other hand, the
aiso, a FA containing n C-atoms, retains slightly longer than the iso isomer, at CN
of (n–1 + 0.7). Furthermore, unlike cis and trans FA isomers, the relative retention
times are not affected for iso and aiso isomers by changing the isothermal program
on ionic liquid columns [88].
The 200 m SLB-IL111 column was further used for determination of total, trans,
saturated, and cis unsaturated fats in 32 representative fast food samples [46]. The
content of trans fat ranged from 0.1 to 3.1 g per serving, as determined according to
American Oil Chemists’ Society (AOCS) official method Ce 1j-07. The improved
separation of trans C18:1 positional isomers and enhanced resolution of trans C18:2
and C18:3 FAME isomers are two major advantages of the SLB-IL111 column,
relative to the biscyanopropyl siloxane stationary phases.
The fatty acid composition in marine oils and products is very complex with
a wide variety of chain length and unsaturation [47]. The SLB-IL111 column has