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Figure5
Dual-column analysis confirms the enantiomeric purity of (S)-2-methylbutryate.
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.
Figure6
TheRt-
β
DEXsm
™
column confirms enantiomeric purity of (S)-2-methylbutyric acid in
apple juice and cranberry/apple juice.
30m, 0.32mm ID, 0.25µmRt-
β
DEXsm
™
column (cat.# 13104). 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.
25
20
30
35
min.
20
25
30
35
A second column, theRt-
β
DEXsm
™
column, confirms the
presenceof 3-methylbutyrate andnot racemic2-methylbutyrate.
Figure 4A showswhat the presence of both racemateswould
look like fromBrand“X” apple juice on theRt-
β
DEXsm
™
column. Figure5A reveals the enantiomericallypure (S)-2-
methylbutyrateon theRt-
β
DEXsm
™
column.This second
columndoes not have the interferenceof 3-methylbutyrate and,
therefore, is agood confirmational column, especiallywhen
identification confirmationbyGC/MS is not available.
Inspectionof 2-methylbutyric acid in all samples of juice
revealed almost complete enantiomericpurityof (S)-2-
methylbutyric acid. Figure6 illustrates 2-methylbutyric acid in
Brand “Z” apple juice and in cranberry/apple juice.
TheRt-
β
DEXsm
™
andRt-
β
DEXse
™
columns reveal the
enantiomeric ratioof key chiral flavor components in apple juice,
especially in adual-column system. Inspectionof ethyl-2-
methylbutyrate, 2-methylbutyrate, and2-methylbutyricaciddo
not reveal any flavor adulterationof the five brands of juices
analyzed, but the ability todo sohas beendemonstratedwith
chiral capillaryGC.
References
1. Nagy, S., andWade, R., “Methods toDetectAdulteration of
Fruit Juice Beverages,”
Agroscience
, 1995, p. 213.
2. ibid.
3. Rouseff, R.L., and Leahy, M.M., Eds., “Fruit Flavors,
Biogenesis, Characterization, and Authentication,”
ACS Publication
, 1995, pp. 70-77.
4. Mosandl, Schmarr,
J Agr. Food Chemistry,
1991.
5. Werkoff, P., Brennecko, S., Bretscheider,W., Guntert, M.,
Hopp, R., Surburg, H., “ChirospecificAnalysis in Essential Oil,
Fragrance, and Flavor Research,”
Lebensmittel-Untersüchung
und-Forshung
, Springer-Verlag, 1993.
min.
18
20
12
14
16
14
min.
4
6
8
10
12
10
6
8
2
A) Brand“Z”Apple Juice
B) Cranberry/Apple Juice
A) Rt-
β
DEXsm
™
B) Rt-
β
DEXse
™
(S)-MBA
(R)-MBA
(S)-EMB
(S)-2-MB
3-MB
(S)-EMB
(S)-2-MB
3-MB
(S)-MBA
(R)-MBA
