Is it possible to detect xylitol with Gas Chromatography (GC)?
If it's possible what are the conditions for detection of xylitol with GC? We have a GC with capillary column and FID detector. What is the best method to detect the xylitol by UV Spectrophotometry?
Thank you
Hello Golla
not directly, you have to do a derivatization with HO- Covering reagents, a Silyllation for example. Use a sample of dry matter and dissolve it in Pyridin, add an access of MSTFA, after heating you should get a completely Si- covered sugar that is able to be anaylzed under simple + regular GC Conditions (5-10m Methylsilikon, FID f..e)
The answer is much as Frank mentioned. You derivatise the OH groups with TMS reagent (pyridine:hexamethyldisilazane:trimethylchlorosilane) at room temperature for 30 minutes. We always separate our derivatized monosaccharides on an AT-1 column (30 m, Grace) with a temperature gradient of 140 - 240 degrees at 4 degrees per minute for complex samples, or 8 degrees per minute with fewer components.
What you need to take into account is that your sample may contain more than just xylitol. So you need to run standards as well. And if you expect oligosaccharides or polysaccharide material you may want to do a methanolysis (Methano.HCl 1N) to produce methyl-glycosides, neutralise with AgNO3 and evaporate the methanol. Then re-N-acetylate for GlcNAc, GalNAc, Neu5Ac etc with acetic anhydride and after drying again perform TMS derivatisation and GC analysis.
Not quite true. You can see it directly, but it's not easy. Polar column, high temp injector, Sky liner, split injection (say 5:1) and it will still tail.
Best bet is LC-MSl; way easier.
Mark,
That is assuming that the lab in question has such equipment available.
Golla,
as mentioned before, you have to derivatize your sample. Quite a simple method is acetylation.
Dissolve up to 20 mg of anhydrous xylitol or other alditol in 1 ml of dry pyridine, add the same volume of acetanhydride, close your reaction bottle/5ml vial/ tight and heat the mixture at 90 oC during 30 min. Then evaporate pyridine and acetic acid + excessive acetanhydride at the temperature of 80 oC in a moderate stream of N2. Dissolve xylitol pentaacetate in 1ml of ethylacetate and inject 1 microliter into the CG injector equipped with splitter /in the case of using capillary column/.
You can use hexaacetate of inositol or erythritol tetraacetate as an internal standard. In this cause just add known amounts of inositol or errythritol to your dry xylitol sample prior to acetylation.
Instead of capillary also a glass /or stainless/ column can be used for GLC of alditol acetates. Conditions: 3% SP2330 on Chromaton N-Super, 2.5% of Carbowax 20M on Inerton AW and many other..., Isothermic mode at 220 oC, carrier gas N2, Injector temperature 260 oC and detector temperature 250 oC.
As for the UV determination of xylitol, it is difficult to determine by UV spectroscopy /absorption under 200 nm / unless it is derivatized with convenient agent providing absorbtion in the area of 200 to 400 nm. Benzoylchloride in an anhydrous environment might serve well.
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