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AnalysisofAppleJuices
SamplePreparation
The flavor compoundswereobtainedby liquid-liquidextraction.
Twentymillilitersofmethylenechloridewereadded to16–20oz.
of juice ina500mL separatory funnel andwere then shaken.After
theorganic layer (on thebottom)was removed, theprevious step
was repeated twomore times. The final organicextractwas then
funneled throughabedof sodium sulfateandconcentrated to4mL
inaKuderna-Danishconcentratorwithahotwater bathat 70°C.
Analysis
Theenantiomersof ethyl-2-methylbutyrate, 2-methylbutyrate,
and2-methyl butyric acid for several brands of apple juiceswere
analyzedonbothRt-
β
DEXsm
™
andRt-
β
DEXse
™
columns. Ten
microliters of samplewere introducedviadirect injection.A
1.5mguard columnwas connected to the4mmopen-top
Uniliner
®
sleeve and to thebeta-cyclodextrin column to accom-
modate the large volume injection and toprotect the analytical
min. 6
8
10
12
12
min. 2
4
6
8
10
14
14
16
18
20
column. Some spectral confirmationwas conductedbyGC/mass
spectrometry (MS).
Results
The data revealed thatmost of the tested samples of apple juice
containedalmost enantiomericallypure (S)-ethyl-2-
methylbutyrate and (S)-2-methylbutyrate, as shown inFigure3,
concluding that therewas no flavor adulterationof the juice.
Figure 4 shows the same brand spikedwith racemic ethyl-2-
methylbutyrateand2-methylbutyrate.
Figure5B illustrates the exampleofmatrix interference in some
juices.The2-methylbutyratemay at first appear tobe racemic,
because in this case (R)-2-methylbutyrate coeluteswith
3-methylbutyrateon theRt-
β
DEXse
™
column. InFigure 4, the
3-methylbutyrate is not present inBrand “X”apple juice, but is
inBrand “Y”.
Figure3
Detection of (S)-ethyl-2-methylbutyrate and (S)-2-methylbutyrate inBrand“X”apple juice,
on theRt-
β
DEXsm
™
andRt-
β
DEXse
™
columns respectively, indicates enantiomerically pure flavor.
30m, 0.32mm ID, 0.25µm a) Rt-
β
DEXsm
™
and b) Rt-
β
DEXse
™
columns (cat.#’s 13104 and 13106). 10µL direct injection;
Oven temp.:
40°C (hold 1min.) to 220°C@ 2°C/min.;
Inj. & det. temp.:
220°C;
Carrier gas:
hydrogen@ 80cm/sec.
Figure4
The analysis of Brand“X”apple juice spikedwith both racemates of ethyl-2-methylbutyrate and 2-methylbutyrate
shows how the presence of racemicmixtureswould look.
30m, 0.32mm ID, 0.25µm a) Rt-
β
DEXsm
™
and b) Rt-
β
DEXse
™
columns (cat.#’s 13104 and 13106). 10µL direct injection;
Oven temp.:
40°C (hold 1min.) to 220°C@ 2°C/min.;
Inj. & det. temp.:
220°C;
Carrier gas:
hydrogen@ 80cm/sec.
min.
18
20
12
14
16
14
min.
4
6
8
10
12
10
6
8
2
A) Rt-
β
DEXsm
™
B) Rt-
β
DEXse
™
A) Rt-
β
DEXsm
™
B) Rt-
β
DEXse
™
(S)-EMB
(S)-MB
(S)-EMB
(S)-MB
(S)-EMB
(S)-MB
(R)-MB
(S)-EMB
(S)-MB
(R)-MB
(R)-EMB
(R)-EMB
