Could BSTFA be a contamination source for GC-MS?

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

12 posts Page 1 of 1
Hi All,

I am working on GC-MS analysis of chlorophenols with BSTFA derivatization. Recently I found the sensitivities of the chlorophenols are lower and one of them even missing. This could be due to contamination in my system (GC column DB1701). I cleaned the EI souce, replaced liner, septum, gold plate, and guard column, but this could not resolve the issue.

Someone has just suggested that the BSTFA might be the contamination source, but I have no idea about it. I am add an excess of the BSTFA (100 uL) for the derivatization as I am working on food matrix.

Does anyone here have any idea about the BSTFA thing? Thanks.
Hi,
BSTFA will cause the source to become dirty a lot faster than non derivatised compounds. Usually, I put between 5-8 solvent injections after the final BSTFA sample and 1-2 in between the BSTFA samples. After a long sequence I would also recommend changing the septum and liner. Can you reduce the amount of BSTFA used; I usually only use 50uL for drugs of abuse and that is enough to prevent making the source needing cleaned too often; once or twice a month at most.
I made a nice living using BSTFA/TMCS for GC and GCMS assays for alcohol- and phenolic-type analytes, including several publications, and did not have such issues. So I'm thinking more of a GC issue than detector issue.

I'd suggest trying a new column, or at least snipping off 0.5 meter from the the head of the existing column, and maybe a good cleaning of the inlet. What kind of guard column are you using (we didn't use such for GC/GCMS).

Chloroxylenol was one analyte we could assay this way, but we also used HPLC for phenolic stuff.
@pumpedupchemist: Thanks for the suggestion. I have not tested to reduce the BSTFA amount, as I am working with beef matrix and want to have enough BSTFA to derivatize chlorophenol samples. But it is good to give a shot.

@Consumer Products Guy: Thanks for your response. I replaced the analytical column and am running my sample again to see if the contamination is from the column.
The guard column we are using is just a Deactivated Fused Silica column from Agilent. We usually replace it quite often as we are injecting a lot of drity samples.
@Consumer Products Guy: after replacing the analytical column, the missing chlorophenol shows up again, confirming the contamination in the column.

But do you think 100uL of BSTFA (with 1% TMCS) is too much and could cause contamination? I am working with beef sample and adding excess BSTFA just want to derivatize all the chlorophenol samples.

Thanks
@Consumer Products Guy: just to add more info - I am working on a DB1701 column.
Simon001 wrote:
@Consumer Products Guy: after replacing the analytical column, the missing chlorophenol shows up again, confirming the contamination in the column.


That's a good learning. Many managers don't think of columns as consumables. We had success with reverse flushing bonded capillary columns with solvents (see Restek for more information and a device for this) and sometimes with breaking off the head (inlet end) of the column.


Simon001 wrote:
But do you think 100uL of BSTFA (with 1% TMCS) is too much and could cause contamination? I am working with beef sample and adding excess BSTFA just want to derivatize all the chlorophenol samples.


We would extract consumer products containing up to 80% water 0.25 grams in 10ml dimethylformamide. Then we would filter if necessary and mix 250 µl of that with 125 µl of the BSTFA/TMCS, shake, then inject into GC or GCMS.
@Consumer Products Guy: Thanks for the response.

I am working on a few tetrachlorophenols and a pentachlorophenol in meat matrix. It seems that the matrix DOES NOT affect the tetrachlorophenols, but DOES selectively affect the pentachlorophenol.
Consumer Products Guy wrote:
Simon001 wrote:
We had success with reverse flushing bonded capillary columns with solvents (see Restek for more information and a device for this)


Do you mean the reverse flushing the GC column with solvent? I have not heard of it before.
Simon001 wrote:
Consumer Products Guy wrote:
Simon001 wrote:
We had success with reverse flushing bonded capillary columns with solvents (see Restek for more information and a device for this)


Do you mean the reverse flushing the GC column with solvent? I have not heard of it before.


Just because YOU haven't heard of this (or anything else) DOES NOT mean that such does not exist !!! https://www.restek.com/catalog/view/488
Consumer Products Guy wrote:

Just because YOU haven't heard of this (or anything else) DOS NOT mean that such does not exist !!! https://www.restek.com/catalog/view/488


I agree with your comments ^_^! I only worked with reverse flushing the LC columns.

Many thanks for your suggestion!!!
I wanted to chime in and say I have had success with reverse solvent flushing columns too. It can be laborious but does work. My boss thought I was nuts. I use this when a 0.5m trim fails to return performance (contaminants have traveled far into the column).

I have also injected a lot of samples dissolved in MSTFA (quite similar to BSTFA) without issue. Issues arise when prep is not so clean. Either spend time on prep, or on instrument consumables & cleaning. Often the prep time investment is better in my experience, but time is money in some labs, so the right call depends on your situation.
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