Application Note 20558
GC Analysis of Acylated Sugars
Anila I Khan, Thermo Fisher Scientific, Runcorn, Cheshire, UK
Introduction
Sugars such as glucose and fructose are very difficult to
analyse by GC, as they decompose in the injector port and
“crash” out on the column. The highly polar and
involatile nature of the sugars reduces the efficiency of the
detection of these molecules. To overcome these problems
the sugars can be derivatized to remove the active
hydrogens such as -OH, therefore increasing volatility and
improving detectability. The most commonly used
derivatization method for the analysis of sugars is an
acylation reaction. The Thermo Scientific acylation
reagent MBTFA is used for derivatizing sugars and it is
manufactured to meet the exacting need of sensitive
derivatization reactions. This involves converting the
active hydrogen into trifluroesters via a carboxylic
derivative. The ester in the derivatized sugar improves the
volatility, which makes it easier for analysis by GC/FID
MBTFA, like the majority of derivatization reagents,
produces a by-product. In this case the formation of the
byproduct N-methyltrifluoroacetamide does not interfere
with the analysis as it elutes earlier in the chromatogram.
In order to achieve separation of fructose and glucose
anomers which arise upon derivatization, a mid-polarity
14% cyanophenyl polysiloxane Thermo Scientific TRACE
TR-1701 column was used.
Key Words
Derivatization reagent, acylation, n-methyl-bis(trifluoroacetamine) (MBTFA)
glucose, fructose, sugars, TR-1701
Abstract
Sugars must be derivatized to a volatile form so as to be analyzed by GC.
A commonly used derivatization reagent, N-Methyl-bis (trifluoroacetamide)
(MBTFA) was used for converting sugars to their volatile forms. In order to
achieve separation of TFA sugar derivatives such as fructose and glucose
anomers, a mid-polar 14% cyanopropylphenyl polysiloxane phase GC
column was used.
Experimental Details
Sample Preparation
5 mg each of glucose and fructose were weighed into a
Thermo Scientific Reacti-Vial containing a Reacti-Vial magnetic stirrer.
To the Reacti-Vial, 0.5 mL of MBTFA was added followed by 0.5 mL
of Thermo Scientific silylation grade solvent pyridine. The Reacti-Vials
were then capped and placed in the Thermo Scientific Reacti-Therm
Sample Incubation System and stirred for 1 hour at 65 °C. Once
dissolved the reaction was complete. The final sample was then
transferred to a 2 mL autosampler vial and 1 μL was injected into the
GC/FID.
