Analysis of oligosaccharides using a liquid chromatography system and a chromatographic column in which the LC system and column's internal metal surface has been modified with a layer of inert material

1 . A method of separating and analyzing a sample comprising one or more non-modified oligosaccharides with degree of polymerization 6 or higher, the method comprising:

i. providing a hydrophilic interaction liquid chromatography (HILIC) column, wherein at least one component of the HILIC column comprises a fluid-contacting alkylsilyl coating on metal surfaces;

ii. injecting the sample onto the HILIC column;

iii. flowing the sample through the HILIC column; and

iv. separating and analyzing the sample, wherein carry-over of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher is decreased at least 10× compared to an uncoated HILIC column.

2 . The method of claim 1 , wherein the analyzing comprises analyzing the separated sample and a blank sample injected after the separated sample with a detector to determine the amount of carry-over.

3 . The method of claim 1 , wherein carry-over of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher is decreased at least 15× compared to an uncoated HILIC column.

4 . The method of claim 1 , wherein carry-over of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher is decreased 20× compared to an uncoated HILIC column.

5 . The method of claim 1 , wherein the fluid-contacting alkylsilyl coating comprises a vapor deposited product of bis(trichlorosilyl)ethane or bis(trimethoxysilyl)ethane.

6 . The method of claim 1 , further comprising connecting the HILIC column to a liquid chromatography system, wherein internal surfaces of the liquid chromatography system are coated with the fluid-contacting alkylsilyl coating.

7 . The method of claim 1 , wherein the one or more non-modified oligosaccharides with degree of polymerization 6 or higher is selected from the group consisting of galactooligosaccharides (GOS), fructooligosaccharide, and combination thereof.

8 . The method of claim 1 , wherein the sample comprises dextran.

9 . The method of claim 1 , wherein total weight concentration of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher in the sample is from about 0.0005% to about 5% of the sample.

10 . The method of claim 1 , wherein total weight concentration of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher in the sample is from about 0.003% to about 1% of the sample.

11 . The method of claim 1 , wherein the analyzing comprises analyzing the separated sample with a UV detector, a fluorescence detector, a mass spectrometer, or a mass spectrometer coupled with a UV detector and/or a fluorescence detector.

12 . A method of separating and analyzing one or more non-modified oligosaccharides with degree of polymerization 6 or higher from a sample, the method comprising:

i. adding a fluorescent labeling reagent to the sample to label at least one of the one or more non-modified oligosaccharides with degree of polymerization 6 or higher to form a fluorescent labeled sample;

ii. injecting the fluorescent labeled sample onto a hydrophilic interaction liquid chromatography (HILIC) column, wherein at least one component of the HILIC column comprises a fluid-contacting alkylsilyl coating on a metal surface;

iii. flowing the injected sample through the HILIC column;

iv. separating the injected sample into components, wherein at least one of the components comprises a fluorescent labeled non-modified oligosaccharide with degree of polymerization 6 or higher; and

v. analyzing the at least one of the components with a UV detector and/or a fluorescence detector.

13 . The method of claim 12 , before injecting, further comprising:

a. adding an internal standard in a known amount to the sample;

b. diluting the fluorescent labeled sample with acetonitrile/water solvent mixture to form a diluted sample for injection; and

wherein analyzing the at least one of the components comprises quantification of the at least one of the components using a detected peak area of the internal standard.

14 . The method of claim 13 , wherein the internal standard comprises laminaritriose.

15 . The method of claim 13 , comprising adding an enzyme selected from the group of consisting of amyloglucosidase, β-galactosidase and combination thereof to the sample prior to adding the internal standard.

16 . The method of claim 12 , wherein the fluid-contacting alkylsilyl coating comprises a vapor deposited product of bis(trichlorosilyl)ethane or bis(trimethoxysilyl)ethane.

17 . The method of claim 12 , wherein the one or more non-modified oligosaccharides with degree of polymerization 6 or higher is selected from the group consisting of galactooligosaccharides (GOS), fructooligosaccharide and combination thereof.

18 . The method of claim 12 , wherein the UV detector or the fluorescence detector is coupled to a mass spectrometer.

19 . The method of claim 12 , wherein the fluorescent labeling reagent is 2-aminobenzamide or 6-amino-N-[2-(diethylamino) ethyl]-2-quinolinecarboxamide.

20 . The method of claim 12 , wherein the sample is a nutritional bar, nutritional liquid, or nutritional powder.