Carbohydrates tend to be high-melting solids.
They can be made much more volatile by converting their
#"ROH" stackrelcolor(blue)("CH"_3"I" color(white)(mm))(→) "ROCH"_3#
or trimethylsilyl ethers
#"ROH" stackrelcolor(blue)(("CH"_3)_3"SiCl" color(white)(mm))(→) "ROSi"("CH"_3)_3#
The ethers are volatile enough to be separated by gas chromatography.
They are injected into a moving gas stream that carries them through a column of a stationary liquid or solid.
As the components move the through the column with the carrier gas, they are separated by their relative vapour pressures and affinities for the stationary phase.
The compounds that elute from the GC column are often sent to a mass spectrometer for detection and identification.