BTEX and Phthalates

[wilky44]

I currently have an Agilent 6890 GC (FID only), and am looking to develop a quick "screening" method for the above analytes in water. (They would be confirmed by GCMS at an external lab)

Concentrations could vary from low ppm to % levels

However, a lot of methods I have came across, particularly for BTEX, are either headspace or purge and trap. I only have a liquid autosampler and am reluctant to inject water into my system. Does anybody have know of any methods, perhaps liquid/liquid extraction or SPE that may be suitable?

Mark

[AICMM]

Wilky44,

Headspace screening for BTEX is easy and can certainly be done by hand by GC-FID. Detection limits won't be great but if just for screening maybe that is not such a bad deal. 15 mL water in 20 mL vial and inject 0.5 mL of the headspace for example. You won't put much water on the instrument since you are taking the headspace (just the amount that partitions...)

For the phthalates, perhaps a methylene chloride extraction, take off the bottom layer and inject using your autosampler. Again, detection limits not that great unless you blow down the methylene chloride (even then, 10's of ppm at best....)

Problem I see is that one column will not really work for both of these all that well. BTEX is relatively light, phthalates are relatively heavy. Can you swap columns?

Best regards.

[wilky44]

Hi AICMM

thanks for the reply . Swapping the column would not be a problem, nor are the detection limits.

With regards to standards for the headspace analysis, what would be the best way to approach this for the BTEX method, with the insolubility of them in water. Make them up in a solvent perhaps?

[pueblito]

Volatiles such as Trihalomethanes and BTEX are stable in methanol.
Stock solutions:
In a tared volumetric flask (with grond glass stopper) with methanol, weigth a mass of pure compounds, and mix by inverting three times only.

more information about Volatiles at:

http://www.epa.gov/sw-846/pdfs/8260b.pdf

a detailed procedure at:

http://www.mass.gov/dep/cleanup/laws/vph0504.pdf

[kdamme]

What about a pentane extraction. Using a Varian CP-Sil 8 column it's possible to find BTEX + phtalates together in one injection.
We have done this analysis for years this way (GC-MS).

Because of detection limits we changed the extraction to methylene chloride and now do P&T for the BTEX. As detection limits are not that important to you, a pentane extraction should be possible.