astm d5501 vs internal standardization for analyzing ethanol

[Amalena]

I would like to know if anyone here has tried using the astm d5501 method and method using an internal standard in analyzing ethanol purity?

which one is better?

thanks!

[Consumer Products Guy]

We've assayed alcohol gel products here for years, ethanol content 60 to 70% (v/v)

We used a modification of the AOAC procedure using n-propyl alcohol as internal standard on a PEG-type column for years. But for the last few years we've used ACN as internal standard and a DB-624 type column, we essentially follow USP 611 as written; we validated this on the finished products.

[AICMM]

Amalena,

Have a customer doing 5501 every day during the season. Works quite well. Do not use an IS.

Not sure why you would need an IS in this application, CPG help me out here? With gel product you would probably have either HS or extraction and that would make sense but with 5501 you are shooting the neat.

Best regards,

AICMM

[Consumer Products Guy]

I suggested USP because that is applicable to the assay of ethanol, and poster asked about nalyzing ethanol purity. If poster wants % ethanol, this USP 611 will work as is. If poster wants to look for other stuff, then USP 611 is not a drop-in.

I'm not familiar with the ASTM method listed.

We dissolve our samples in water (about 2% ethanol content) then a portion is taken and internal standard solution added, just like ASTM. We don't have to filter. We have validated this on our products.

[AICMM]

Amalena,

CPG is dissolving his sample and under these circumstances using an internal standard can help you quantify your ethanol. If you are running neat ethanol, then and internal standard isn't really necessary (and not called for in D5501.)

Best regards,

AICMM

[Amalena]

Thank you all for your inputs.

Im new to this type of method (and in GC analysis for that matter). In the 5501 method, the listed
typical relative response factor are in mass, but i am having a hard time duplicating (or getting even close to it) the mass relative response factors of the suggested 3 components (ethanol, methanol and n-heptane).
Is it ok to use volume response factor directly by preparing the standard solution by volume and not do it in mass terms that needs calculating it in volume terms using the typical densities (because ill be needing the %vol)?
And with that premise, how shall i check the volume response factors i got?

And another thing, i also need to measure methanol, if ever its present in the sample. And the limits in methanol is too low vs the minimum in ethanol. Is it ok that in a set of standard solution both the lowest and highest concentration of the solution will be used in calculation or shall i prepare a different batch for methanol?

Thanks in advance for all your help. I am sorry if my question is too noob.

[Amalena]

Thank you all for your inputs.

Im new to this type of method (and in GC analysis for that matter). In the 5501 method, the listed
typical relative response factor are in mass, but i am having a hard time duplicating (or getting even close to it) the mass relative response factors of the suggested 3 components (ethanol, methanol and n-heptane).
Is it ok to use volume response factor directly by preparing the standard solution by volume and not do it in mass terms that needs calculating it in volume terms using the typical densities (because ill be needing the %vol)?
And with that premise, how shall i check the volume response factors i got?

And another thing, i also need to measure methanol, if ever its present in the sample. And the limits in methanol is too low vs the minimum in ethanol. Is it ok that in a set of standard solution both the lowest and highest concentration of the solution will be used in calculation or shall i prepare a different batch for methanol?

Thanks in advance for all your help. I am sorry if my question is too noob.

just updating this query...

and another question: since the method is for denatured ethanol, how can i use this if an unknown only shows ethanol peak and doesnt have any of the expected denaturant? i think the relative resp factor calculation would not be applicable, if so, what would be the calibration method to employ on this?

thank you very much and hope to hear from you guys...

[CharapitsaS]

Thank you all for your inputs.

Im new to this type of method (and in GC analysis for that matter). In the 5501 method, the listed
typical relative response factor are in mass, but i am having a hard time duplicating (or getting even close to it) the mass relative response factors of the suggested 3 components (ethanol, methanol and n-heptane).
Is it ok to use volume response factor directly by preparing the standard solution by volume and not do it in mass terms that needs calculating it in volume terms using the typical densities (because ill be needing the %vol)?
And with that premise, how shall i check the volume response factors i got?

And another thing, i also need to measure methanol, if ever its present in the sample. And the limits in methanol is too low vs the minimum in ethanol. Is it ok that in a set of standard solution both the lowest and highest concentration of the solution will be used in calculation or shall i prepare a different batch for methanol?

Thanks in advance for all your help. I am sorry if my question is too noob.

just updating this query...

and another question: since the method is for denatured ethanol, how can i use this if an unknown only shows ethanol peak and doesnt have any of the expected denaturant? i think the relative resp factor calculation would not be applicable, if so, what would be the calibration method to employ on this?

thank you very much and hope to hear from you guys...

Hi,
we propose to use ethanol as internal standard for determination of volatile compounds in spirit products by gas chromatography. Brief descripbtion see here http://www.inp.bsu.by/labs/lar/eis.html .

Regards,
Siarhei