Chromatography Forum

Hi I have been trying to calibrate my HP6890GC with FID detector to detect BHT (Butylated Hydroxy Toluene) in a water matrix. I have standards of 3 to 60 ppm, with myristic acid (I had it in the fridge) as IS. The BHT and IS were dissoled in methanol in intermediate standards.

Inlet Conditions : Splitless, Temp 250°C, Purge Time 1.00, purge Flow 50.0, saver Flow 20.0, Saver Time 5.00 - Drilled Uniliner Direct injection (hole at top)
Injection 1µl manual
Column ZB- Wax Plus (30m x 0.32 mm ID x 0.25µm thickness)
Oven 80 (2mins) to 160°C @ 10°C/min, hold for 2.00min, then 50°C/min to 250 for 2 minutes
FID Detector 250°C (H2 30, Air 300, Make Up N2 30.0)
Carrier Gas Nitrogen @ 3.0ml/min

I can see the IS no problem but have not seen the BHT peak.

Any suggestions??

Are you sure your two compounds are separated ?

I've assayed trace BHT directly but used split injection and a non-polar capillary, and BHT is quite non-polar.

Most times, our finished products were fragranced, so for those we derivatized the BHT before injecting.

For a water matrix, I might even consider extracting the BHT to concentrate it, or just trying HPLC.

Thanks for the quick responses.

I'm pretty confident the BHT and myristic acid are not co-eluting, as the peak is the same size with the 60ppm and 3 ppm BHT std.

I do have a SGE BP1 (100% Dimethyl Polysiloxane) column sat around doing nothing in the cupboard. How will it cope with the water matrix? I might just try it anyhow....I'll stick with the splitless injection to start with a go back to split if it doesn't work.

I have been asking for a HPLC for a while as I could then do a sweep for a host of antioxidants with 1 method that we should be checking for. Getting them to invest is never easy though....

At first glance I'd say you are over loading your liner. It's counter intuitive for water injections, but you should lower the injection temp to 110-120, change to a straight 4mm liner, and inject no more than 0.5 ul.