Chromatography Forum

Any body familiar with EO residual analysis by HP 6890. I run 100 ppm, 50 ppm, 10, 5, and 1ppm standard to calibrate the GC. My problem is 100 ppm spits out EO and ECH values but nothing comes in 50 ppm and so on.

Standard prep is 200ul EO + 500ul ECH + 9ml HPLC water = 100 ppm

Look like I need to set integration paramenter but what....any body know about htis.....

Thanks.

I'm not sure of your compounds, and am assuming EO is ethylene oxide, and ECH ethylene chlorohydrin. Is that what you meant?

Are you seeing peaks for the lower levels of these compounds and just can't integrate them, or are you not seeing peaks at all (or seeing peaks much smaller than expected)?

You give absolutely no information on your GC conditions (inlet, column and detector) which makes addressing your question very difficult. One thing that comes to mind is activity - a very old problem less frequently encountered these days. If some component in your system is active, then you analytes may be adsorbed onto this with the result that only the higher level injections give rise to peaks. The best fix is to get rid of the activity. The traditional work-around was to "saturate the active sites" with your compounds before you begin the analysis, proper.

Give us more information and perhaps we can provide better assistance.

The water is probably suppressing the EO ( assuming it's ethylene oxide).

However I can't make sense of your 100 ppm standard - 200 ul EO ( presumably gaseous ) with 9 mls of water ( presumably liquid ), comes to approx. 20 ppm v/v in the gaseous form - but how are you mixing and injecting that?.

Bruce Hamilton

Is this a packed or capillary column system. These compounds chromatograph well on the right column, but preparation of these volatile standards is always difficult.

If you need help with integration, that is another issue. Check with the Help screens or the ChemStation manual for some hints on using the integrator. The options will change with the version of software that you are using.