How to achieve silylation faster

[bhimavarpu]

Hi All,

I am using acetonitrile as solvent and TMCS as silylating agent for surface modification of an acid (silicic acid). 10% of TMCS is being used to achieve silylation. But it takes more than 48 hrs and still the silylation is still not complete. Is there any better silylating reagent to TMCS? or any catalyst that enhance the reaction.

Thanks in advance

[Consumer Products Guy]

I used trimethylsilylation a lot for GC and GCMS of hydroxy groups. Typically I used DMF or pyridine as solvents, and added BSTFA as the silylation agent to the autosampler vial. Silylation was practically instantaneous.

When I had to silylate an amine, I used pyridine, BSTFA, and heated in a sealed autosampler vial 10 minutes.

[bhimavarpu]

Thanks, CPG. I will try with BSTFA

[MSCHemist]

I used trimethylsilylation a lot for GC and GCMS of hydroxy groups. Typically I used DMF or pyridine as solvents, and added BSTFA as the silylation agent to the autosampler vial. Silylation was practically instantaneous.

When I had to silylate an amine, I used pyridine, BSTFA, and heated in a sealed autosampler vial 10 minutes.

Sorry to resurrect this old thread.

I am working on a general large chain and nonvolatile, and hydroxy acids method using BSTFA or BSTFA+TMCS.

I have done silylation in the past using pyridine dried with NaOH. I saw some issues with calibration linearity when operating from 10-1000ppm that improved when I reduced it from 1-100ppm instead. I have been reviewing the literature and found one that recommends using DMF https://www.lmaleidykla.lt/ojs/index.ph ... /4100/2989

and reviewing the literature and Daniel Knapp's book of Analytical Derivatization Reactions I see there is conflict in the literature about whether pyridine helps or actually inhibits the reaction. There is also conflict as to whether a base is necessary (which pyridine is) like triethylamine or not in other solvents.

Did you see major differences between DMF and Pyridine?

[Consumer Products Guy]

I have done silylation in the past using pyridine dried with NaOH.

We did that back in 1975-1976, before I started using BSTFA containing TMCS

Did you see major differences between DMF and Pyridine?

Yes, used pyridine when derivatizing amines. Otherwise we used DMF, as less odor.

[MSCHemist]

Thanks I tried the paper method 50ul of BSTFA in 950ul pyridine (instead of DMF) containing the sample at room temp. It worked well for alkyl carboxylic acids, my internal standard glutaric succinic and fumaric and it failed my hydroxy acids malic, citric, and tartaric but did to lactic. I think I need heat for those.

when I did it in the past I did 125ul of BSTFA/TMCS + 250ul pyridine I was hoping to cut down the BSTFA usage. It worked but I had issue with calibration lineariety from 10-1000ppm but better linearity from 1-100ppm.

[Consumer Products Guy]

I derivatized alpha hydroxy acids without issues.

[MSCHemist]

I derivatized alpha hydroxy acids without issues.

I think my BSTFA might be old or something but I am seeing the same thing as last time.

I like to run my calibration from 10-1000ppm (10 50 250 1000) So I took 1ml, evaporated, and redissolved in either 300ul pyridine or acetonitrile which both work well and add 100ul BSTFA+TMCS and heat at 70degC for 1 hour. I am using glutaric acid as an ITSD. As my calibration level increases I am seeing the BSTFA peak rapidly shrinking and my calibration curving to a plateau. 100ul of BSTFA should be plenty so that it isn't anywhere close to being a limiting reagent?

I'll try it again when I get some fresh BSTFA.

[MSCHemist]

I derivatized alpha hydroxy acids without issues.

It could be I need to purchase silanized ALS vials. I have been using regular cheapo 1.5ml's for the reaction.