Chromatography Forum

Hi guys, I am a new user for GCMS. I would like to test methanol in my liquid sample. May I know that is DB-5 column suitable to separate it out? What is the operating parameters? Between, how do i prepare the calibration standard?

Can someone reply me as soon as possible? I am highly appreciated for your guidelines and advices

Thank you

Methanol will not be retained hardly at all on a DB-5 type column. And peak shape will be OK, but not great. If your "liquid" is low boiling or water, tough. What's your "liquid" and about what levels of methanol is expected?

Most often, a polar column such as a PEG type is used for stuff like methanol.

Hi Consumer Product Guy, thank you for your precious comment

My solvent will be either DMF or THF. Actually I unable to predict the level of methanol produced and I just predict methanol will be my product. In this case, what is your suggestion in standard calibration preparation? What range should I start?

Between, do you know that any company like Merck will provide methanol stock solution?

Anyway, do you have standard method or procedures to share with me?

Supelco, Restek and many others will prepare std solutions for you. Just do a simple search with Google for a whole litany of companies.

You can even make your own solutions ! It isn't rocket science.

Your analytical conditions can vary depending upon the contaminants in the solvents.

Try isothermal at 60C with a 100:1 split to start and then begin a oven ramp up to 200C.

Good luck,

Rod

Hi Rod, finally I saw you drop me a message. Previously, I read a lot of your messages left in this forum

Indeed, I surf net to find out GC methanol standard but the links did not direct me to the product.

Actually can you share some links with me here?

Else, I am interested to know that the preparation of GC standard solution by ourself. Can you share the detailed procedures with me? I have > 99.9% GC grade of methanol. If I would like to prepare 20 ppm methanol standard, what is the volume should I mix?

Thanks you for your opinions

You can do ppm by weight or ppv by volume.

Determine the density of your solvent from the bottle or from a reference.

Pour out 1 kg of solvent into container.

Add 1 mg (per each ppm unit desired) of methanol to the container of solvent. As you ask for 20 ppm that would be 20 mg or about 25 microliters of methanol. (See density of methanol and determine the volume needed for 20 mg.)

Mix thoroughly in a sealed container and I would sample the solution into smaller sealed containers which are filled FULL, ie no or minimal headspace volume so you don't lose methanol prior to opening the container.

Search the web for companies that prepare standard solutions. Don't focus on methanol.

Supelco will prepare stds for you, but there are others. (I used to work for Supelco in R+D).

good luck,

Rod

http://accustandard.com/

is another commercial company besides Supelco.

Std aren't cheap.

Really, make your own.

best wishes,

Rod

Rod, thanks for your sharing. I knew what is my next step. Thank you

siewpei,

I do not envy you in this analysis. Methanol is 32, oxygen is 32. Your MS is always pulling in a little bit of oxygen which is why most people start scanning at 35 or 45 or some such. If you are looking for very low levels, this will be a very challenging problem. If you have access to an FID that is what I would recommend, and even that may be a challenge due to sensitivity issues. I am not trying to be a curmudgeon here, I just wish to point out the challenge.

Best regards,

AICMM

Hi guys, I am a new user for GCMS. I would like to test methanol in my liquid sample. May I know that is DB-5 column suitable to separate it out? What is the operating parameters? Between, how do i prepare the calibration standard?

Can someone reply me as soon as possible? I am highly appreciated for your guidelines and advices

Thank you

Please let us know what columns you have in your column/s inventory.
you may need more polar column than DB5 for methanol.

Please let us know what columns you have in your column/s inventory.
you may need more polar column than DB5 for methanol.

See first reply in this thread.

hi guys thanks for your comments.

As consumer product mention, a polar column PEG will be suitable to separate methanol product out and I also gather some information from this website http://www.sisweb.com/art/pdf/ms-maint.pdf

AICMM, may I know that what method will you suggest to detect methanol product in my sample? Kindly give your advices here.

Thank you

Mass Spec is not the best choice for measuring methanol due to its low molecular weight.

But if that is all you have, and cannot afford a simple FID, or argon or helium ionization detector, then if you get false positives and high values over the actual, are you concerned?

One has to deal with the situation within you exist.

But even a TCD might be a better choice for a detector.

PEG columns give a nice peak shape and a useable retention for methanol.

Thicker film is better than thin film, as long as it doesn't bleed too much into your MS.

Good luck,

Rod

siewpei,

I would probably recommend an FID in this case if you have access to one. Sensitivity is not the greatest since you have a C1 compound with an attached oxygen but it may be enough for what you want to do. I would suspect this would be easier than MS.

If your levels are low enough you might also consider using a Low-Ox type column from Agilent or Varian (wait, Agilent....) since these will give you pretty unique retention capabilities. Otherwise I would move to a wax as Rod notes above.

Best regards,

AICMM