Chromatography Forum

Dear colleagues,

our environmental laboratory planning to buy gas chromatograph for air impact analysis. Seems our choice is seconf hand HP5890 Series II with FID (perhaps, later with MSD too) and thermal desorption (seems, td-3 from sisweb.com). I think it will be enought for start and meet first time expirience.

But I newbie in this area and can't understand difference between HP5890 Series II with EPC (electronic pressure control - besides default option for Series II Plus) and without this option. I suppose that it should be more progressive option but difference in price is wide as well...

thanks a lot!

with best rgrds,
-vadym

I strongly recommend getting an EPC on the inlet. It makes life much easier in the long run with regard to making changes and it allows you to use constant flow methods.

If you only intend to ever run a single method on the instrument then the lack of EPC probably won't be too much of an issue.

Rich

I strongly recommend getting an EPC on the inlet. It makes life much easier in the long run with regard to making changes and it allows you to use constant flow methods.

If you only intend to ever run a single method on the instrument then the lack of EPC probably won't be too much of an issue.

Rich

Agree with Rich; if you're going to change inlet pressures, split ratios, want to run constant flow v. constant pressure, then EPC is your ticket. For a QC instrument which will be set up for maybe a single assay, non-EPC would be OK. Bear in mind that 5890 is out of factory support, but that doesn't mean not to do it; 5890 is excellent GC, we still run several here.

EPC impacts operation of the instrument both from a user perspective and from a chromatography perspective, both strongly positive.

As was well discussed, it simply makes operation easier by having direct control in the method of the instrument. So long as you save the method, there is never a question regarding head pressure, splitless time, etc. Without EPC, if an analyst fails to record the GC conditions in a log book, with manual control, it's pretty easy for them to be lost over time.

Regarding the actual chromatography, the best way to understand what it's doing for you is to think about setting the optimal flow for any particular column. Your separation, is controlled by the column flow (depending upon column and carrier there is a published "best" flow rate). However, gas viscosity increases with temperature. So with a manual system, the question is then, at what temperature do you set the flow? One way or another, some part of the chromatogram is compromised.

With EPC, you can set the flow to the ideal, and the electronics maintains the flow (with a constant flow mode) through-out the run by increasing the pressure as the temperature is raised. This will give you generally much better overall separation.

Greg

Don't forget...the 5890 series2 is not supported since 2 years by Agilent