Water determination at low levels (10-20 ppm)

Chromatography Forum: GC Archives: Water determination at low levels (10-20 ppm)
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Benjamin on Tuesday, August 6, 2002 - 12:53 pm:

Friends;

I would like to receive information on systems or techniques applicable to the analysis of low levels of water. The sample matrix is a stream of ACN plus some other non-volatile compounds, some of which react with KF reagents.

We would like the system to have a fast response, perhaps 1-2 min cycle time, or better yet, suitable to on-line measurements. We also need it to be sensitive, with a DL of 1 ppm or less, and easy to calibrate.

Currently we use GC with a TCD detector. The sensitivity obtained is not very good, and the cycle time is in the order of 10 minutes. We have thought about NIR and conductivity, but the information on these techniques is not very encouraging for this case.

Thanks to all in advance.

Benjamin


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Tuesday, August 6, 2002 - 02:35 pm:

I have used a Hayesep R column (4ft 1/8" OD packed in FSOT coated steel with 10m screen on outlet and packing drop of 6 to 9 inches with no screen at the inlet) using Helium at 30cc/min and injector and oven at 120C to measure water with a TCD accurately down to 10 ppm using a 0.2L direct injection volume. You might try to modify this methodology. I was measuring water in methanol, diluting it into Acetonitrile containing an internal standard. Water elutes at about 60 sec. AcN elutes at 5-6 minutes. The water peak is sharp and linear over a large range and never contacts bare metal after injection.


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