Chromatography Forum

Hi! Help me, please!
I have GC Agilent 7890.
How to get a Report of Amounts of gases in absolute units, not in Weight or Volume persents?

The report does not come from the 7890 GC. It comes from the data system connected to your GC. If you are doing gas analysis and you want the report in absolute units, you should ask for an 'External Standard' report. However, this will also depend on what units your calibration gas is reported in. What ever units you are using in your calibration table, these will be the units of your standard report.

Gasman

jamaica1953,

Assuming Chemstation, Look at View, Data analysis, Calibration, Calibration settings... and you can define the units you want to report.

Also, look at Report, specify report, Calculate (drop down menu) and you can tell it you want percent report, ESTD report, etc...

Best regards,

AICMM

AICMM,

You are half correct in your reply. When you define the units that you want in your report, please note that this is only a label for the column amount. There is no calculation behind it. I just set my units to 'oranges', and sure enough the label at the top of the column reads 'amount (oranges)'.

Gasman

jamaica1953,

So, if your standard came in the door with units of "oranges" then you can report in oranges. However, if your standard came in with units such as ug/mL or mole percent, then these are the steps to get your report labeled with ug/mL or mole percent.

Best regards,

AICMM

The problem is that we can't get the specifity of units from Agilent's program (Chemunder_10)

jamaica1953

Before we can help you, more information is needed.

1. What data system are you using

2. What units is the calibration gas in.

3. What units do you want your report in.

4. What gases are in your calibration mixture.

4. Which gases do you want reported.

Gasman

1. What data system are you using
- Chemunder_10, report form ESTD-Detail

2. What units is the calibration gas in.
- This is the main question for me.
When I order report in the form ESTD-Detail, I get calibration graphics for each of gases. There ordinate, “Area” is in uV*s, and absciss “Amount” is in undefined units, probably in vi/v2 %. I think so vi is the partial volume of gas i, and v2 is the total volume of gas probe. I am right?

3. What units do you want your report in.
- In mL or mg

4. What gases are in your calibration mixture.
- hydrogen, oxygen, nitrogen, CO, CO2 and about 20 species of light carbohydrates (C<6)

4. Which gases do you want reported.
- similarly

The data system Chemunder_10 does not mean much to me. If I Google it, nothing comes up except your posting on this Forum. Who is the manufacturer of this software?

When I asked for the units of the calibration gas, I am refering to the gas tank with your calibration gas in it. You should first check the units stated on the gas cylinder. These will not be in ml or mg. If you need your report to give the number of mg of hydrogen, for example, you will first have to calculate how many mg of hydrogen you inject into your GC when you use the calibration gas. For this, you will need to know the size of the gas sample loop in your GC, assuming that you are using a gas sampling valve to inject your sample. The number of mg would be the number that you enter into your calibration table for hydrogen. You will need to calculate the amounts for each compound in the calibration gas mixture. Your ESTD report will then have the amounts for the gases in mg for your unknown samples.

Gasman

Hi!
Thanks to all, I more or less understood.