Micro GC 990 Data Analysis

Our micro GC 990 is Natural Gas Analyzer B and B extended version with 3 channels (PoraPLOT U, 6-meter CP Sil 5 CB, CP-Molsieve 5A). We are having trouble with data processing.  We have 2 calibration gases from Agilent (Natural Gas mixture and Universal Gas mixture). I assume that there is a chance to calibrate with only one point using these 2. 

  1. How to perform a multi-point calibration? If it is needed to buy some gases with different percentages, what is to be suggested?


  1. What method is used If air content or high oxygen contained components should be analysed with Universal Gas Mixture and Natural Gas Analyzer Mixture? I have been told that only 5 % percentage of oxygen has been allowed to measure. Above that value the GC can't calculate the oxygen concentration. What is the way of calculation by myself?


  1. How to calculate the concentrations with one point calibration on 3 channels. I have already tried to sum the area % of 3 channels components and calculate the concentration for each component on calibration standard result. But it seems to me it failed due to the response factor. Please share the experience with calculating example if there is anything. 
  • Q1:  Multi-point calibration is very common, and we have what refer to as "levels" in the software.  As far as calibration standards, it is sample specific.  I suggest a high and low standard similar to your expected sample, and maybe a mid level standard.  

    Q2:  I am not sure what you mean here.  We don't have a 5% limit for O2.  

    Q3:  Again, I am not sure what you mean.  My suggestion is make sure you are not analyzing each channel individually.  

  • Thank you for the answers. I have only one external standard which currently cant calculate the concentration of O2 of air. So even with that one I can make multi-point calibration? I did only one point calibration and with the one some components cant be detected due to I guess percentage of components. 

  • Do you have all components in your standard?  Also, do you see peaks for the compounds not detected?  

  • Hi, 

    Really dont see a reason for multipoint calibration if you have NGA and RGA mixture 

    Do you have NGA/RGA addon ?

    For example, in 990 manual you can find method of determination, there is many different methods for your combination  , run you standard mixture. assigne  name as in certificate and then use NGA/RGA addon ,basically it is custom calculation to calculate value of all gases in mix and the same actions for you sample.

    It works with OL2 , dont have experience with EZCrhrome , but as i know for EZChrome exist additional calculation SW from vendor, Diablo if i remember it right 

    Here is application for you system

    Q3: you dont need to sum area from 3 channels , choose 1 )

  • Thank you for the reply. I already did single-point calibration on mixture seperately and I didn't think it was possible to make multi-calibration. The problem is the universal gas mixture has more components than NGA's such as Oxygen. I have some enquiries

    1. As I mentioned, I have calibration methods for single-point calibration of 2 mixtures. These have good results which I want to use in further analyzes. Unfortunetaly, once I set on continious flow for GC, the standard I was performing on, was used up. Could I mix 2 calibration datas to create multi-point calibration for now? 

    2. I want to calculate the concentration of air. But only one mixture contains that with concentration 0,0512% which is far than air's. How to determine that?

    3. I haven't tried Diablo yet. On excel file, I tried to create multi-calibration table and plot graphic by using 2 single-point calibration datas. External standards should always intersect 0 point? By intersecting 0 for some components I could have 3 points and I plot the graphic. 

  • I created single-point calibration on 2 mixtures seperately. I have good chromatogram which has everything on both. But on the other one, some components like oxygen, acetylene were absent so I couldn't make multi-calibration table. How to mix the datas of 2 single-point calibrations. I messed up at first and didn't use level 1, level 2..

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