Chromatography Forum

Does anyone have a good method protocol for doing BHA BHT in edible oils via GC. I am having trouble getting decent recovery especially of BHT. I am dissolving in Pet ether and extracting with acetonitrile but need to do at least 3 extraction to get full recovery of BHT using up a lot of solvent and I don't have a turbovap here to blow it down.

See Quantitative determination of BHT in soap products by capillary gas chromatography, » Journal of the American Oil Chemists Society
» Volume 59, Issue 12 , pp 579-582

Works for BHA too, and in fatty acids, fats and oil as well. You won't have the fragrance interferences they had with finished bar soaps.

Thanks for the reference but I decided to just dilute the oil .1g to 100ml with ethanol and even at 50:1 I have enough sensitivty for either Scan or SIM but I decided on SIM (why not the S/N is great).

One of the issues that just came up is I am able to resolve 2-BHA from 3-BHA. My samples contain ~5% 2-BHA but my refernce standards are all 3-BHA. I quant off the 165 m/z ion which is the base ion for both 2 and 3-BHA but I am concerned the response factors are a bit different so I am hesitant to just add the 2-BHA area to the 3-BHA.

Looks like I am almost there. My samples are based in soybean oil the antioxidant is ~20%BHA and 20%BHT and the finished product about 1% BHA and 1% BHT. I started the validation. I am diluting the antioxidant 20000 fold in 96% ethanol (from the liquor store) with di-BHA ITSD and the finished product 1000 fold and doing it in SIM mode with a single quant ion 50:1 split with calibration points at 1, 5, 10, and 25ppm. I am just adding the 2-BHA to the 3-BHA area count.

My recoveries in artificial samples (BHA and BHT dissolved in soybean oil) are 95-105% and the precision is ~2%RSD

There still seems to be a bias about 5-7% low compared to the parent company lab and supplier's COA which use HPLC-DAD.