Which one is better, DB-WAX or DB-624 for alcohol analysis?

[Anthony_Ng]

Hi all,

Have you used these 2 columns (or similar) for alcohol analysis? We are going to use n-propanol as internal standard and analyse ethanol content in food and wine samples.

We will prepare the standard solution by water (and also sample preparation). If I inject 1ul of it, will water kill the column easily? Some people say water will hydrolyse the PEG column and cause bleeding. Is it true?

Any better suggetions are welcome. Thanks a lot!

[Forse]

Water expands a lot when it turns to gas in the liner, so make sure your liner can handle the volume of the water vapor.

I don't know anything about the columns, sorry, but maybe you can use this.

http://chromatographyonline.findanalyti ... rticle.pdf

[kdamme]

I've analysed these compounds in water and soil (environmental) and used WAX52-CB column from Varian. A few times we also injected orange juice-samples with few problems.

I agree with Forse on the liner: we started that analysis with a 1 µL injection and later made it 0.5 µL because the watervolume was too large for the liner.

[chromatographer1]

Try to avoid having water condense onto the column surface AS A LIQUID.

The real issue is breaking the chemical bonds holding the phase onto the fused silica. Water as VAPOR is not as damaging as it is as a liquid.

best wishes,

Rod

[aldehyde]

Water expands a lot when it turns to gas in the liner, so make sure your liner can handle the volume of the water vapor.

I don't know anything about the columns, sorry, but maybe you can use this.

http://chromatographyonline.findanalyti ... rticle.pdf

That is a great article and his conclusions definitely mesh with my experience. Headspace and GC water based samples are "OK" as long as you are careful when optimizing the amount you are injecting and your inlet temperatures. Excess vapor flashing into the lines will have two consequences: sample will contaminate your split vent line and "top insert weldment" (the top of the inlet including the septa and the gas lines that go to the EPC). You may also damage the EPC and cause early failure or inconsistent flows.

[JTM]

If this is going to be a long term testing solution for you, you need to look at something other than the conventional system like a Tekmar Purge and Trap or an extraction method.

The vent line filters are only the size of a small pencil... they do not last long under heavy use.

The DB-WAX seems to be the industry standard, but as having done limited alcohol testing on the DB-624, I know that it works.

[Anthony_Ng]

Thanks all for the advice.

Hence, probably I will try this: Use a DB-WAX (or equivalent column), injection 0.5ul sample (and water as extraction solvent).

By the way, just wonder this situation:

If I set the inlet temp high enough, e.g. 250oC, all water (and ethanol) should be gas phase in the inlet. Then, the oven temp start from 40oC and ramp up slowly. Will the gas phase water vapor condense back at the column head? (i.e. from 250oC back to 40oC). So, the column head will damage after a prolong analysis?

[Consumer Products Guy]

Hi all,

Have you used these 2 columns (or similar) for alcohol analysis? We are going to use n-propanol as internal standard and analyse ethanol content in food and wine samples.
We will prepare the standard solution by water (and also sample preparation). If I inject 1ul of it, will water kill the column easily? Some people say water will hydrolyse the PEG column and cause bleeding. Is it true?
Any better suggetions are welcome. Thanks a lot!

We actually use both DB-wax type and DB-624 capillaries for ethanol assays in hand sanitizer products. The 624 capillary is same as specified in USP-611, which is the procedure we use, and yes, our QA still made us validate it anyway, as they said USP was for ethanol solutions, and our products have some other ingredients. That USP 611 (and us) detail acetonitrile as internal standard (although we did also do with n-propyl alcohol, which worked fine under same USP-specified conditions. This is a wide-bore capillary and utilizes a 0.5ul split injection.

We formerly used the wax-type column, also 0.53mm wide-bore capillary, and that assay utilizes n-propyl alcohol, the logical internal standard. But my company agreed that it would be better to move to USP, which we did. That also used 0.5ul split injection. We used a 5ul syringe for both.

[Larry Ellison]

I have used the Rtx-WAX column for aqueous alcohol analysis and strongly recommend it. I had similar GC parameters as the ones you have listed except that I injected 1uL. I would recommend rinsing the auto sampler syringe with a solvent if you are not going to us it again for a while. If the syringe sits unused for a period of time it will “seizeâ€

[Consumer Products Guy]

1 ul of water as solvent expands a lot in the injection port, typically will expand to larger than the split liner volume. I'd recommend 0.5 ul instead. We rinse our syringes with water as part of the autosampler program.

[Lucap]

DB-WAX is better for resolution of iso-propanol and ethanol, when IP is in ppm range. But food and wine you must analyse only by head-space!

[chemist23]

Hi all,

Have you used these 2 columns (or similar) for alcohol analysis? We are going to use n-propanol as internal standard and analyse ethanol content in food and wine samples.
We will prepare the standard solution by water (and also sample preparation). If I inject 1ul of it, will water kill the column easily? Some people say water will hydrolyse the PEG column and cause bleeding. Is it true?
Any better suggetions are welcome. Thanks a lot!

We actually use both DB-wax type and DB-624 capillaries for ethanol assays in hand sanitizer products. The 624 capillary is same as specified in USP-611, which is the procedure we use, and yes, our QA still made us validate it anyway, as they said USP was for ethanol solutions, and our products have some other ingredients. That USP 611 (and us) detail acetonitrile as internal standard (although we did also do with n-propyl alcohol, which worked fine under same USP-specified conditions. This is a wide-bore capillary and utilizes a 0.5ul split injection.

We formerly used the wax-type column, also 0.53mm wide-bore capillary, and that assay utilizes n-propyl alcohol, the logical internal standard. But my company agreed that it would be better to move to USP, which we did. That also used 0.5ul split injection. We used a 5ul syringe for both.

Were you able to tests for multiple alcohols on the 624? I am trying to create a method that assay a few alcohols along ethyl acetate and acetalaldehyde. I am curious to know your experience with this.

[larkl]

You will have problems if you inject 1 uL of water. You can get the agilent gas volume calculator here https://www.agilent.com/en/support/gas- ... alculators. That much water is going to overload the inlet. Could you use something else polar for a solvent, like one of the butanols or THF?

[Consumer Products Guy]

Were you able to tests for multiple alcohols on the 624? I am trying to create a method that assay a few alcohols along ethyl acetate and acetalaldehyde. I am curious to know your experience with this.

We were only interested in ethyl alcohol, for our hand sanitizer products.

We never investigated much for other alcohols, but n-propyl alcohol and methanol were resolved, and I believe IPA.

[MSCHemist]

It's been a while since I checked but from what I remember the wax columns usually do not resolve ethanol from isopropanol and the MSD is no help either same major ions the molecular for isopropanol is nearly nonexistant. I use headspace sampling for ethanol with acetonitrile as my ITSD.