My research: Nitrogen carrier and Hydrogen make up

[Bekir]

The dear people of this Forum,

I am currently working on a research for my school and for the company where I am currently doing my internship. Since I have almost never done any chromatography analysis (mostly done spectrometry), I am quite the rookie when it comes to chromatography. But I do posses more of less the knowledge to help myself or understand any scientific paper or research (more or less).

I have to setup a new method on the GC at the company where I am currently doing my internship. The method is the research of rolling oil (I have used Gooogle Translate, the Dutch name for it is: walsolie). It is a mixture of oil and water, which is used as a lubricant at metals and plastic. It can also be used as a cooling product/liquid. And one other thing I have to research, is to look and see whether we can switch from Helium to Nitrogen as a carrier-gas. Because right now, we are using Helium as a carrier-gas and Nitrogen as a Make-up. Right now, as for school and for the company, I have to write a plan of how to handle the situation and tell what I am going to do. So here is where I am stuck.

Since this morning, I am reading my study books again and researching what type of make up gas is good to use at a FID. Unfortunalty I couldn't find the answer for my question. So by asking them here, I hope to learn new things and expand myself in the world of chromatography.

So, I am not asking for people to write down a plan for me, which I wouldn't want anyway, instead, I like to people review my plan and tell me where and what I am doing wrong. So here it is:

Rolling oil does contain the next components (alcohols): C10 (1-decanol, the intern standard), C12 (dodecanol), C14 (tetradecanol) and C16 (hexadecanol). So what I am going to do first, is to check the repeatability of the GC first. It is a GC-Gemini. After that is done, I am going to make standards. At first, I thought my making the standards all together. What I mean by that: Weigh each component one by one and create a calibration line for each component (with C10 still as an intern standard). After this is done succesfull, I plan to do the same, but this time adding them all together and making a 1 single calibration in which the components are in. But, I have a feeling this might not be a good idea, because then the formula I get, might not be representative for all the calculation for all the components (I hope I made myself clear at this part, if not please say it in the comments). And so here is the dilemma; do I do this right away with a Nitrogen carrier gas or should I start off first at Helium as a carrier gas. The company where I am doing my internship, wants this method to be as cheap as possible. So I am thinking (regardless of whether I start analyzing it with Nitrogen or Helium as a carriergas), what should my Make-up gas be? If I want to make it as cheap as possible, I have to go for a cheap make-up gas as well right? So I was thinking about Hydrogen or Helium as a make-up gas with Nitrogen as it's carrier gas. After I have set up the method, I just have to write down an instruction and validate the method, which is easy to do and something I have experience in from my last internship.

I did read something about: if the Hydrogen make-up gas enters the FID from below (along with Nitrogen), it can create a flame which can effect the components in such a way, that I might get unreliable results. Is this true?

I hope the great people here can help me out! Any link, video or comment is welcome! I am looking forward to expand myself in the world of chromatography!

PS: I am sorry for sounding dumb, but I never got the chance to work in the field of chromatography. In advance, I am sorry.

[James_Ball]

Don't be sorry, we all have to start from the beginning

If you are using a capillary column (0.53mm ID or smaller) it may be better to use Hydrogen as the carrier and Nitrogen as the makeup gas for an FID detector.

You will most likely already have Hydrogen and Air as the fuel and oxidizer in the detector so the lower flow of Hydrogen as carrier will not disturb the flame in the detector, as makeup gas the higher flow can cause problems in the detector flame.

Nitrogen or Helium are normally used as makeup gasses. The makeup gas is used because if using a packed column you would have a higher flow through the detector than a capillary column and the detector is designed to have the larger flow coming in. Helium gives the best sensitivity, but Nitrogen will work just a well if you are not doing very low concentration trace analysis, which it seems you will not be doing.(trace would be looking at ppb levels if your analytes). When you are in the ppm to percentage range the Nitrogen makeup would be the best because of expense.

Of course if you are using a larger packed column with a 20ml/minute flow rate of carrier then you only need Nitrogen carrier and no makeup gas.

[Bekir]

Don't be sorry, we all have to start from the beginning

If you are using a capillary column (0.53mm ID or smaller) it may be better to use Hydrogen as the carrier and Nitrogen as the makeup gas for an FID detector.

You will most likely already have Hydrogen and Air as the fuel and oxidizer in the detector so the lower flow of Hydrogen as carrier will not disturb the flame in the detector, as makeup gas the higher flow can cause problems in the detector flame.

Nitrogen or Helium are normally used as makeup gasses. The makeup gas is used because if using a packed column you would have a higher flow through the detector than a capillary column and the detector is designed to have the larger flow coming in. Helium gives the best sensitivity, but Nitrogen will work just a well if you are not doing very low concentration trace analysis, which it seems you will not be doing.(trace would be looking at ppb levels if your analytes). When you are in the ppm to percentage range the Nitrogen makeup would be the best because of expense.

Of course if you are using a larger packed column with a 20ml/minute flow rate of carrier then you only need Nitrogen carrier and no makeup gas.

Hello James,
Thanks for your reply! It did help me out and understand things a lot.
The capillary column we are using is: CP-Wax 52CB 30m 0.25mm 0.25µm - 20°C to 250°C (265°C)
I do remember the specialist telling me not to go above the 250°C, because then it might damage the stationary phase inside the column. You can see in the pictures how the gradient all that other stuff has been done. Since you are suggesting to use Hydrogen (and does make sense to me), I do like to ask you a couple questions:
1) You said:

If you are using a capillary column (0.53mm ID or smaller) it may be better to use Hydrogen as the carrier and Nitrogen as the makeup gas for an FID detector.

---> why is that? I mean, what is the scientific reason behind that? Since my is smaller than 0.53mm, I probably will do what you did suggest to me.
2) Since Hydrogen can explosive and dangerous, I don't really know at what flow I should let it flow. I did post some pictures, you can see the current flows of the GC as Helium as is carrier-gas and Nitrogen as the make-up gas. Can you help me out with this one? Since I do not have any experience in it, I don't really know if I should let the flows the same or not. I assume I should lower a little bit, since the air we are using for oxidizing, does already have Hydrogen. With a high flow or the same as now, the flame of the FID might get too high, right?

I am going to suggest this to the manager, I hope he agrees with it and helps me out. Thanks a lot again!

[James_Ball]

Don't be sorry, we all have to start from the beginning

If you are using a capillary column (0.53mm ID or smaller) it may be better to use Hydrogen as the carrier and Nitrogen as the makeup gas for an FID detector.

You will most likely already have Hydrogen and Air as the fuel and oxidizer in the detector so the lower flow of Hydrogen as carrier will not disturb the flame in the detector, as makeup gas the higher flow can cause problems in the detector flame.

Nitrogen or Helium are normally used as makeup gasses. The makeup gas is used because if using a packed column you would have a higher flow through the detector than a capillary column and the detector is designed to have the larger flow coming in. Helium gives the best sensitivity, but Nitrogen will work just a well if you are not doing very low concentration trace analysis, which it seems you will not be doing.(trace would be looking at ppb levels if your analytes). When you are in the ppm to percentage range the Nitrogen makeup would be the best because of expense.

Of course if you are using a larger packed column with a 20ml/minute flow rate of carrier then you only need Nitrogen carrier and no makeup gas.

Hello James,
Thanks for your reply! It did help me out and understand things a lot.
The capillary column we are using is: CP-Wax 52CB 30m 0.25mm 0.25µm - 20°C to 250°C (265°C)
I do remember the specialist telling me not to go above the 250°C, because then it might damage the stationary phase inside the column. You can see in the pictures how the gradient all that other stuff has been done. Since you are suggesting to use Hydrogen (and does make sense to me), I do like to ask you a couple questions:
1) You said:

If you are using a capillary column (0.53mm ID or smaller) it may be better to use Hydrogen as the carrier and Nitrogen as the makeup gas for an FID detector.

---> why is that? I mean, what is the scientific reason behind that? Since my is smaller than 0.53mm, I probably will do what you did suggest to me.
2) Since Hydrogen can explosive and dangerous, I don't really know at what flow I should let it flow. I did post some pictures, you can see the current flows of the GC as Helium as is carrier-gas and Nitrogen as the make-up gas. Can you help me out with this one? Since I do not have any experience in it, I don't really know if I should let the flows the same or not. I assume I should lower a little bit, since the air we are using for oxidizing, does already have Hydrogen. With a high flow or the same as now, the flame of the FID might get too high, right?

I am going to suggest this to the manager, I hope he agrees with it and helps me out. Thanks a lot again!

I will need to wait until I am at home to view facebook site for photos.

You can use nitrogen for carrier but many believe it is less efficient or more difficult to work with as a carrier for small diameter columns as what you have. Yes, the CP-Wax column will have a lower maximum temperature, because the stationary phase is not stable above about 250C, to operate at higher temperatures you would need a non-polar CP-5 or similar phase, the separation would be different but you would have the ability to work at near 325-350C for the maximum oven temperature, but would only be needed if you have higher boiling point analytes.

The carrier flow in a 0.25ID column will only be 1-2ml/min for He or N2 and maybe 5ml/min for H2, but since that goes through the flame in the detector it will be burned off. The only hydrogen that will be vented into the laboratory will be what comes from the split vent if using a split/splitless injection port. Whether or not that flow will be a problem will depend on the size of the room and the amount of ventilation you have. You can always run some tubing from the split vent port to the outside of the building if needed for safety. Ours just vent into the room since it is a very large room and we have many fume hoods operating constantly.

If you try nitrogen as carrier, you would still want to use nitrogen as makeup gas. I am not sure which manufacturer of GC you have but most have a line for Air, and Hydrogen into the detector for the flame, then a line for carrier and a line for makeup gas(if needed). If you want to use nitrogen carrier for safety reasons, then plumb in the nitrogen to the carrier and makeup connectors, then hydrogen to the fuel connector and air to the oxidizer connector on the GC. Set the hydrogen and air flows as the manual recommends, then set the carrier flow.

A good resource to find the carrier flow you need is here https://www.restek.com/ezgc-mtfc
just put in your information on the right side and it will calculate the values you need for carrier flow or pressure. On the left side you can enter your parameters for Helium and have it convert to what you need for either hydrogen or nitrogen carrier.