Calibration of Agilent 7890 GC-FID

Discussions about GC and other "gas phase" separation techniques.

12 posts Page 1 of 1
Hello all,

I've put together a lab and purchased an Agilent 7890 GC with double FID. I'm new to ChemStation and i'm struggling setting up a calibration table. The main purpose of this purchase is purity test of essential oils.
I'm using a Agilent HP-5 (19091J-215) column, H2 as carrier gas from a Paker ChromGas H2 generator. The method is RTLocked to n-Pentadecane at 70.000 min, I'm getting results trough the RTSearch as described here: https://www.agilent.com/en-us/support/s ... flavorsrtl
The Flavour database is actually working very well, it names 70% of the peaks, the problem is that i get only the names of the peaks and no results in %, ppm, or any other units.

I'm wondering if any of you GC specialists in this world could be able to give me a hand trough a TeamViewer session, i'm paying for the service.
Hi ,

Worth looking at :

http://www.chromforum.org/viewtopic.php ... hemstation

Its for HPLC but should help for quantification and % /ppm
The main purpose of this purchase is purity test of essential oils.


Out of interest, what exactly are your analytical conditions and which flavour essential oils are you checking?

i get only the names of the peaks and no results in %, ppm, or any other units.

Do you have a reference standard?


The method is RTLocked to n-Pentadecane at 70.000 min,

Am I correct in assuming that pentadecane standard is eluting at 70 minutes?
If so, that seems to be rather late for this HP-5 phase.

Leffingwell have some useful purchasable databases for flavours and essential oils with retention indices that I have used successfully. (I have no affiliation to them)

http://www.leffingwell.com/baciseso.htm
Regards

Ralph
GOM wrote:
Out of interest, what exactly are your analytical conditions and which flavour essential oils are you checking?

The method is RTLocked to n-Pentadecane at 70.000 min,


Am I correct in assuming that pentadecane standard is eluting at 70 minutes?
If so, that seems to be rather late for this HP-5 phase.

Leffingwell have some useful purchasable databases for flavours and essential oils with retention indices that I have used successfully. (I have no affiliation to them)

http://www.leffingwell.com/baciseso.htm


Dear Ralph,

Thank you for the link!

The conditions are as following:
GC Agilent 7890A
Oven
Ramp ’C/min ’C Hold min
Initial 50 0.00
Ramp 1 2 280 0.00
Runtime 115 min

Inlet Split/Splitless
Temp 250 ’C
Mode Split
Carrier H2
Split Ratio 100:1
Injection volume: 0,2uL pure essential oil

Column HP- 5 part # 19091J-215
Mode Constant pressure
Pressure 38.1 kPa (adjusted to RTLock)
Outlet Pressure Ambient

Detector FID
Temp 300 ’C
Hydrogen 40 mL/min
Air 450 mL/min
Makeup Nitrogen 45 mL/min

The only difference is that Agilent use He as carrier gas so the pressure is tweaked a bit. I would personally start the method at 70'C because there are no constituents in essential oils eluting earlier, i would ramp 1'C/min to 100'C and then around 5'C/min to 280 then 10'C/min to 320'C.

I am checking around 60 different essential oils and a few are simple like for example Wintergreen has Methyl salicylate 99,5% and 6 other constituents in the remaning 0,5%. Then we have many more complex essential oils like Frankincense, Rose, Sandalwood, for example Spearmint (Mentha spicata oil) contains about 70 different natural constituents.

There are a lot of companies that are selling fake, old oxidized essential oils, other are adulterated crap. Aromatherapy is growing and people buy and use essential oils that are dangerous for their health every day but there are no autorities checking these companies. I know because i bought a bad essential oil a few years ago that turned my life up side - down. What i've learned from this is that are a lot of bandits everywhere selling everything to earn money without a conscience or a thought for another human being.
You might think now that essential oils are bad... well No, not all of them.

I'm setting this lab up myself, with my own money working for no profit, the only thing i want is to keep the customers safe because no one else seems to care (at least no one in EU).
Thank you

I understand your concerns. I have worked with analysing the same essential oils as is and adulterated

You will need a standard essential oil to compare

May I suggest diluting your oil with ethanol to reduce the viscosity for injection

Certainly, The ESO 2000 database may well help with the essential oils that you have suggested.

The only problem with this database is that it is not compatible with Windows 10 and requires setting up a virtual XP machine - I have a copy that I purchased some years ago but am having some problems re-installing and setting it up on my new Windows 10 64 bit laptop after previous laptops dying :-(

ESO 2000 (update 2006) - The Complete Database of Essential Oils

More than 4,125 Quantitative Analyses of Essential Oils including Latin names and references;

Chemical identities and CAS numbers of more than 4,200 natural compounds;

Retention indices on various GC-columns (DB-1, DB-5, CBWX 20M, SPCWX 10, OV-101, SE-54) of about 2500 compounds.
Regards

Ralph
Thank you for the fast answer!!

I know that undiluted oils cause problems but i like to see the "fine small peaks" and after every run of oil i use to run analythical acetone, methanol or ethanol to flush the system.

My ChemStation is installed on a W7 32 bit machine. Have other pc's that i could install the software, the only wish i have is to make this work somehow.

I have 4 essential oils bought from USA and i have received the GC/MS analysis for them, hopefully i can start this way. There are those complicated ones, 2 types of Frankincense (Boswellia serrata and carterii), Ginger and Citronella.

Is ESO compatible with ChemStation or is a stand alone software?
I have different types of DB-1, DB-5, BPX-5, DB-wax and HP-5

My mail is ant78se(a)gmail.com same ant78se on skype.

Kind regards and many thanks!!
/Alvin
Hi Alvin

Yes, it is a stand alone database and gives retention indices for those phases

I have 4 essential oils bought from USA and i have received the GC/MS analysis for them, hopefully i can start this way. There are those complicated ones, 2 types of Frankincense (Boswellia serrata and carterii), Ginger and Citronella.

The ESO database would cover these essential oils. You can download a free demo

I have emailed you privately in case there are any minor points that I can help you with but, as have said in the email, I would prefer to keep the general discussion on the forum so that others may contribute and we can all learn
Regards

Ralph
Ralph, thanks a lot for your time and effort to help me!

I have chromatograms from different labs in the world for almost all the essential oils and then there are compounds that overlap depending the oil composition (alpha-pinene is in every essential oil). My problem is still the calibration table and peak identification after all.
Bought this GC secound hand almost new but the company couldn't help with the instalation. Manuals followed only for maintenance and no info for ChemStation which i find really unlogical (compared with older Varian software that is more end user friendly). Have been in touch with Agilent by phone they couldn't answer any question regarding calibration, peak identification or even the RTLdatabase that they had created. They gave me three options: buy an MS, change to their latest software or order a service. All three options have horrible price tags so i had to pass.

Anyway i have just prepared a mixture of Ethanol + Acetone 1-5-10-25ppm in Methanol and the same for Wintergreen oil.

Stupid question: Do i need to use the calibration mixture in every analysis from now on? Does this 4-point calibration table going to make any difference in the results?

By the way i have checked this ESO database for a few weeks ago, registered in order to get the demo but i never heared received anything. Same thing today after you mentioned it, i have registered again and didn't got any download link or mail from them.
Hi Alvin,

My name is Alfonso Madrigal and I am with a service company, we have set up a similar lab for in-house testing for one of our clients. If you are still interested we can provide training via teamviewer for you. Please feel free to email me with any questions.

Thank you,

Alfonso Madrigal
E: amadrigal@aasystems.com
Although this is an older thread resurrected by Alfonso it reminds me to update an earlier comment

Just for record in case anyone else is interested and for future reference for anyone searching the forum, I would now add to my earlier comment in this thread about the analysis of essential oils by GC using the expensive paid for ESO 2000 database.

My son discovered that exactly the same essential oil database ( with 1000s of GC analyses and RIs ) is available for free after registration at

https://essentialoils.org/plans
Regards

Ralph
Sadly my 7890 is getting packed and soon ready for shipping to USA.

Ralph, i will need some help resurrecting my old Varian 3800 in a few days...

/Alvin
Dear Alvin,

the relative amount of each individual component of the essential oil can be calculated as the percentage in accordance to the following formula

Concentration (i) [m/m, %] = RRF(i)*Response(i)/(Summ(RRF(j)*Response(j))*100 [%] (1)

As a response, the peak area Area (i) can be selected.
In the first (initial) approximation, we can assume that all Relative Response Factors (RRF) are equal to one. In this case, the equation is simplified to the following form

Concentration (i) [m/m, %] = Area(i)/(Summ(Area(j))*100 [%] (2)

Easy, cheap and no calibrations.

Best regards,
Siarhei
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