RestekCorporation • (800)356-1688 • (814) 353-1300 •
food& flavor
30m, 0.25mm ID, 0.25µm Famewax
™
(cat.# 12497).
Oven temp.:
200°C to 250°C@ 8°C/min.
(hold 3min.)
Carrier gas:
hydrogen
Linear velocity:
31cm/sec.
1. C14:0
2. C16:0
3. C16:1n7
4. C17:0
5. C18:0
6. C18:1n9
7. C18:2n6
8. C18:3n3
9. C20:0
10. C20:1n9
11. C22:0
30m, 0.25mm ID, 0.25µm Famewax
™
(cat.# 12497).
1.0µL split injection of #14 FAME Standard (cat.# 35035).
Oven temp.:
200°C to 250°C@ 8°C/min.
(hold 3min.)
Inj./det. temp.:
250°C
Det. sensitivity:
8 x 10
-11
AFS
Carrier gas:
hydrogen
Linear velocity:
31.4cm/sec. @ 200°C
Split ratio:
45:1
1
2
3 4
5 6
7
8
9
10
11
min.
2
4
6
8
Predicted
Actual
Figure1
CocoaButter FAMEReference Standard
software, theFAMEswere analyzedusing anoptimized
temperature program chosenby the software. Table I shows the
percent error between the predicted and the actual retention
times. The program’s average prediction errorwas only0.2%,
with amaximum error less than1%!
ModelingSaturatedandUnsaturatedFAMEs inCocoa
Butter
AOACMethod963.22, entitled “Methyl Esters of FattyAcid in
Oils andFats,” describes theGC analysis of FAMEs ranging
from 8 to 24 hydrocarbons in chain length. Although themethod
describesGC using packed columns, capillary columns coated
withCarbowax
®
PEG20M can easily exceed the required
specifications. Theminimum separation requirements are: 1) a
resolutionvalue (R) of at least 1.25betweenmethyl stearate
(C18:0) andmethyl oleate (C18:1n9); and 2) baseline resolution
ofmethyl linolenate (C18:3n3),methyl arachidate (C20:0), and
methyl gadoleate (C20:1).Methyl stearate should elute 15
minutes after the solvent peak, and the analytical column should
have at least 2000 theoretical plates.
GCoperating conditionswere entered into the computer program
toobtain the optimum analysis of a reference standardof cocoa
butter FAMEs. Then, a verybroad range of temperature condi-
tions including the initial temperature, the program rate, and the
final temperaturewere entered into the software. Basedupon
these selection criteria, over 1000possible temperature programs
were evaluatedby the software inonly a fewminutes. The
solutionswere automatically ranked according to the best
separations and fastest analysis times. In this instance, the default
resolution factorwas set at 1.5 to provide baseline resolution.
Although this value is typical, itmaybe increasedor decreased
tomeet the unique needs of a specific analysis.
The software predicted that all of the cocoa butter FAMEs could
be separated adequately in less than10minutes on a 30m,
0.25mm ID, 0.25µmFamewax
™
column (cat.#12497). Using
this optimized capillarymethod, total analysis is completed in
less time thanmethyl stearate elutes under the originalAOAC
recommended conditions! This capillary column provides
approximately2700plates-per-meter, which exceeds the
efficiency requirement specified inAOACMethod963.22. The
new analytical conditions not only provide baseline resolution of
the required components, but of all components (R>1.5), thereby
easily exceeding themethod’s resolution requirement. Figure 1
shows the predicted chromatogramprovidedby the software and
the actual analysis of the cocoa butter FAMEs standard reference
mixture. The actual chromatogram shows excellent correlation to
the chromatogrampredictedby the software.
ReducingAnalysisTime ofMenhadenOil PUFAs
GC analysis ofmenhadenoil is described inAOACMethod
991.39, entitled “FattyAcids inEncapsulatedFishOils andFish
OilMethyl andEthyl Esters,” and inAOCSOfficialMethodCe
1b-89, entitled “FattyAcidComposition byGLC.”These
methods illustrate chromatograms of polyunsaturated fatty acids
(PUFAs) onCarbowax
®
-20M capillary columns. Any column
providing the same elutionpatternof FAMEs andbaseline
