Acrylamide

[Lapitskaya]

Hi everyone!
Now im working on determination of acrylamide in food by GC (ECD). But i have some problems.
Firstly its calibration curve.
I have 6 standard solutions.
Preparation of these solutions: I addKBr, hydrobromic acid ( to pH 1-3), bromine water in water solution of AA
Then bromination during 1 hour in refrig. After i need neutralize the bromine with 1M sodium thiosulfate.
Then I add sodium sulfate and stir, then extraction the aqueous solution twice with 10 ml of ethyl acetate 10 min each extraction.Add triethylamine. Dry organic phase with Na2SO4. Evap to dryness. Add to it 2 ml of ethylacetate and GC.
Problem: calibration curve is not stable. Why?
And another question: i must use salt (Na2SO4) before extraction with ethylacetate?
Thx a lot!

[MSCHemist]

I took a try at acrylamide a while back GC/MS. Though you may be locked into bromination with the ECD the xanthydrol method looked promising. I was having trouble though with sample cleanup on that method. The standard and internal standard looked beautiful when I tried it on sample I got a lawn of junk and no analytes even when spiked. If I really had a pressing need I'm sure I could make it work.

[Steve Reimer]

I've only done that analysis on drinking water and it was 20 years ago. So this is from vague memories.
The salt is added to assist the extraction with ethyl acetate. When you say the standards aren't stable do you mean that they degrade with time? i.e. debrominating?

[James_Ball]

The salt is to push the analyte into the organic phase more efficiently.

I have never used GC for acrylamide, we use HPLC/UV which works great and requires no sample prep for water samples other than filtering.

[Rndirk]

The salt is to push the analyte into the organic phase more efficiently.

I have never used GC for acrylamide, we use HPLC/UV which works great and requires no sample prep for water samples other than filtering.

What levels of acrylamide can you reach in water samples? We use LCMS, but the matrix is often food (fries and stuff) at ppb levels. I'd be worried about interferences in food extracts with short wavelength detection.

[MSCHemist]

If you are using methacrylamide as your ITSD I read that can be problematic with the bromination method. I forgot the reason I think it was the reaction was less efficient due to the tertiary position.

[James_Ball]

The salt is to push the analyte into the organic phase more efficiently.

I have never used GC for acrylamide, we use HPLC/UV which works great and requires no sample prep for water samples other than filtering.

What levels of acrylamide can you reach in water samples? We use LCMS, but the matrix is often food (fries and stuff) at ppb levels. I'd be worried about interferences in food extracts with short wavelength detection.

It has been a while since I ran these but we were using EPA 8316, which lists 10ppb as the detection limit. I am sure with a narrow bore column we were getting lower than that. I want to say it was 1ppb in waste water.

In food you would need to calculate the dilution factor from the extraction process.

I think there were some articles using HPLC/UV involving Acrylamide in french fries or potato chips, if you can find that it may give a good extraction method to use.

[Lapitskaya]

When you say the standards aren't stable do you mean that they degrade with time? i.e. debrominating?
No, it means that area peak is not the same
For example iinlet into column solution of AA with concentration 800 micro g/ml and I expect to get area peak 35000, but sometimes I get only 8000. Why?

[Steve Reimer]

Does the area go down and not back up? Or is it unpredictable?
If it is unpredictable, check out your inlet conditions. You may be "too close to the edge" and small differences in injections are causing loss of analyte.
If you reinject the same standard vial do you get a similar result?

[Lapitskaya]

Often it goes down. And its unpredictable. I dont inject by myself coz i have autosampler. And i tried reinject by autosampler but it was the same result!
And also i 've noticed that a peak has on its line small peaks. What does it mean i dont know
But i think that there is two reasons
The first reason: acrylamide react with stationary phase on capillary column
The second reason: reagents (ethyl acetate or hexane are not too clean...)