% water by GC

[mccarrik24]

Can anyone push me in the right direction for a gc analysis of a product that is 40 - 60 % water (balance organomet/halide)?

[Okkie]

just depends on what you would like to analyse.
Water can be directly injected into a hot injector. Be aware of 1 µl liquid will be >1000 µl vapour so use less than 0.5 µl

If you need to analyse (semi)- apolair components, dissolved in the water, make an extraction with diethyl ether or dichloromethane.

[chromatographer1]

Okkie is quite right. Your cryptic question is difficult to answer.

If you wish to measure water content then a better solution would be to use a packed column instead of capillary, a 4mm ID instead of 2mm ID, and a medium polarity porous polymer column such as Porapak R, an injector and column temperature of 120°C minimum, and a TCD or pHID detector in your GC.

A Chaney adapter would be recommended for your syringe and a slow injection technique to minimize the effects of the flash vaporization of the water sample.

If you want to measure something else please let us know.

Give the Forum a little more information and they will be able to give you a better answer.

Good luck.

Rod

[mccarrik24]

I apologize, I did not mean to be cryptic.
I would like to analyze the amount of water in a product that is 40 - 60 % water.
I am open as far as column type, and was looking to use TCD.
I have Porapak Q in the lab, would that work?

Thanks.

[chromatographer1]

Yes and no.

If the column is contaminated from sample injections it may not give the most accurate results, especially at low levels.

But if you wish to measure in the 50% range it should work as long as the tailing is not too pronounced. Temperature will help this and don't use too high a carrier flow rate.

The R or N polymer packing is a better choice for water analysis due to the more symmetrical peak water gives eluting from these porous polymer supports.

Remember to inject slowly. I have had excellent reproducibility using packed columns. You may need to dilute your sample or to use an internal standard for best results. I often use acetonitrile to dilute water bearing solvents in measuring water content.

Good luck.

Rod

[wsayers]

You might have an easier time using a non-gc method. If you can dilute your sample in dry methanol, Karl Fisher titration gives reproducible results. There are a number of fairly inexpensive KF titrators available.