Chromatography Forum

Hi,

I want to make a method for determination by GC-MS. There is methods for GC-FID but i want to analysis alcohols with GC-MS

I am trying to analysis Methanol, Ethanol and isopropyl alcohol.

I am using DB-VRX Column.

My solvent is water.

Oven program is 40 °C (5 min)
7 °C increase 100 °C

When i try this method i want to find alcohols. But methanol peak comes so close with solvent peak. I can not seperate them.

Question 1: Is water harmful for column or anything else ?
Question 2: Which solvent can i use except water ?

ucanmoruk wrote:
Hi,

I want to make a method for determination by GC-MS. There is methods for GC-FID but i want to analysis alcohols with GC-MS

I am trying to analysis Methanol, Ethanol and isopropyl alcohol.

I am using DB-VRX Column.

My solvent is water.

Oven program is 40 °C (5 min)
7 °C increase 100 °C

When i try this method i want to find alcohols. But methanol peak comes so close with solvent peak. I can not seperate them.

Question 1: Is water harmful for column or anything else ?
Question 2: Which solvent can i use except water ?

Hello


What is your Column flow? and what is the matrix?

The column can suffer but not much. You can use n-hexanol like solvent.

Regards

Henry

Henrylozano wrote:

Hello


What is your Column flow? and what is the matrix?

The column can suffer but not much. You can use n-hexanol like solvent.

Regards

Henry

Column flow 1.0

Matrix is cosmetic products.

Regards

ucanmoruk wrote:
Matrix is cosmetic products.

I'm surprised you're not sticking with FC-FID for this. Especially if the product is an OTC drug product with alcohol as active.

Consumer Products Guy wrote:

ucanmoruk wrote:
Matrix is cosmetic products.

I'm surprised you're not sticking with FC-FID for this. Especially if the product is an OTC drug product with alcohol as active.

In fact the product is alcohol-free cosmetic products. So we want to detect alcohols at lower limits

DB-VRX is a non-polar column.
Using a polar column may help getting the methanol away from the solvent peak.

What method are you using for sample introduction ? Direct injection ? headspace? Purge and trap ?

I too think you'll have a difficult time beating the FID for these small molecules. Getting a good separation is the most difficult thing for this problem.

Alcohols typically don't give a strong molecular ion in the mass spectrometer. Many times, they come off looking like hydrocarbons. Their main fragments are common to almost every other molecule in existence.

The folks at Restek made a nice blog post a while back that summarizes when you should not use MS as a detector. Your problem is one of those.

https://blog.restek.com/?p=6662

You will have a tough time beating the FID for this. If it were me, I'd spend more time getting a good sampling technique (e.g., SPME) to get better detection limits for the alcohol free cosmetics.

-zwitterion+ wrote:
What method are you using for sample introduction ? Direct injection ? headspace? Purge and trap ?

I am using direct injection. I have no headspace.

Andy F wrote:
DB-VRX is a non-polar column.
Using a polar column may help getting the methanol away from the solvent peak.

Thx. I'm looking for a new column.

rb6banjo wrote:
I too think you'll have a difficult time beating the FID for these small molecules. Getting a good separation is the most difficult thing for this problem.

Alcohols typically don't give a strong molecular ion in the mass spectrometer. Many times, they come off looking like hydrocarbons. Their main fragments are common to almost every other molecule in existence.

The folks at Restek made a nice blog post a while back that summarizes when you should not use MS as a detector. Your problem is one of those.

https://blog.restek.com/?p=6662

You will have a tough time beating the FID for this. If it were me, I'd spend more time getting a good sampling technique (e.g., SPME) to get better detection limits for the alcohol free cosmetics.

Thx for your answer and guidance. When i read the Resteks blog, i understood the subject better. Because of methanols low m / z, it seems not to analysis by MS dedector.

If you really want to do alcohol by MS you may want to look at the column from Restek the StabilWax-MS. The wax phase is better for polar analytes like alcohols and the MS phase is low bleed for MS use. You also may want to try split injections to keep as much water from the analyzer as possible.

Which MS are you using? Some handle water better than others.

The DB-ALC1 or DB-ALC2 column for blood alcohols may also be a good choice, as they separate methanol, acetaldehyde, ethanol, acetone, and isopropanol well with short run times.

https://www.agilent.com/en/products/gas ... /alc1-acl2

My experience was been with headspace/FID methods, from blood, so I'm less familiar with a direct injection which may have more water; however this reference mentions both a CP-WAX 52 column with direct injection of human plasma, as well as headspace methods with the DB-ALC1 and ALC2 columns with chromatograms which might mix-and-match with your requirements.

https://www.agilent.com/cs/library/appl ... cology.pdf

ucanmoruk wrote:

Consumer Products Guy wrote:

ucanmoruk wrote:
Matrix is cosmetic products.

I'm surprised you're not sticking with FC-FID for this. Especially if the product is an OTC drug product with alcohol as active.

In fact the product is alcohol-free cosmetic products. So we want to detect alcohols at lower limits

Our hand sanitizer products were over 60% ethanol, but in our validation studies boss made us go down to extremely low levels, even those would be so many orders of magnitude less than our target levels. He was "afraid" of ever having to answer a question should an auditor ask.

Consumer Products Guy wrote:

ucanmoruk wrote:

Consumer Products Guy wrote:

I'm surprised you're not sticking with FC-FID for this. Especially if the product is an OTC drug product with alcohol as active.

In fact the product is alcohol-free cosmetic products. So we want to detect alcohols at lower limits

Our hand sanitizer products were over 60% ethanol, but in our validation studies boss made us go down to extremely low levels, even those would be so many orders of magnitude less than our target levels. He was "afraid" of ever having to answer a question should an auditor ask.

Were you able to also test sanitizing wipes? I am curious to know how you prepared sample and the method you used.

chemist23 wrote:

Consumer Products Guy wrote:

ucanmoruk wrote:

In fact the product is alcohol-free cosmetic products. So we want to detect alcohols at lower limits

Our hand sanitizer products were over 60% ethanol, but in our validation studies boss made us go down to extremely low levels, even those would be so many orders of magnitude less than our target levels. He was "afraid" of ever having to answer a question should an auditor ask.

Were you able to also test sanitizing wipes? I am curious to know how you prepared sample and the method you used.

Our wipes did not contain alcohol.

I'm not sure "why" you want to assay for trace alcohol (maybe for a cleaning validation?), but if I was going to assay a wipe or swab, I see two sampling techniques other than headspace: squeezing the liquid out of a wipe or swab and diluting that with water, and then the squeezed liquid would be the sample. Or throw the swab or wipe into a container and extract with water.

Consumer Products Guy wrote:

chemist23 wrote:

Consumer Products Guy wrote:

Our hand sanitizer products were over 60% ethanol, but in our validation studies boss made us go down to extremely low levels, even those would be so many orders of magnitude less than our target levels. He was "afraid" of ever having to answer a question should an auditor ask.

Were you able to also test sanitizing wipes? I am curious to know how you prepared sample and the method you used.

Our wipes did not contain alcohol.

I'm not sure "why" you want to assay for trace alcohol (maybe for a cleaning validation?), but if I was going to assay a wipe or swab, I see two sampling techniques other than headspace: squeezing the liquid out of a wipe or swab and diluting that with water, and then the squeezed liquid would be the sample. Or throw the swab or wipe into a container and extract with water.

I am mainly trying to determine if the alcohol content in the wipe matches to the label claim. I will try each of the techniques you mentioned. I wasn't sure if headspace was possible since water would be the diluent and has a high expansion coefficient, unless I only vial the wipe.