Water sample preserved with HCL

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

14 posts Page 1 of 1
Hello,

The water sample that i got are preserved with HCL. I am using GC-FID with DB-Wax column. The water sample contains glycol and is preserved of ph=2. If i inject the water i might damage the column or inlet parts. What can i do. Neutrilizing with the base is not a good idea either. Dilution is not a good idea either because the glycol is at very low concentrations. Do you guys have any suggestions on what to do?
Why can you not neutralize the reaction? Would neutralizing it cause damage to your sample? You could dilute that sample, do an extraction, and then dry it down to the volume that you need. It would take extra time, though.
ACLLogan wrote:
Why can you not neutralize the reaction? Would neutralizing it cause damage to your sample? You could dilute that sample, do an extraction, and then dry it down to the volume that you need. It would take extra time, though.


Difficult to extract glycol from water with a solvent, thus most of the time glycol samples are injected directly onto column.

HCl should be ok, it is not as destructive to the column as sulfuric or nitric acid is. You may want to run a few meters of uncoated guard column/retention gap in front of the analytical column if you are worried about the aqueous HCl being injected directly onto the main column.
The past is there to guide us into the future, not to dwell in.
Injecting water into your GC isn't too worrisome if you're set up correctly. Ionic liquid stationary phases have been reported as robust for water analysis:
I'd give your Supelco rep a call and inquire about your application. If nothing else, they can demo it in their apps lab and give you an idea of whether it's a good way forward. Glycol in water at pH 2 should be a reasonable request. Let us know what you find out!
Have you considered derivatizing glycols. I use phenylboronic acid for glycols and 3-mcpd. It derivatizes fine in water and the derivatives have a stronger signal on MS and FID, extract very easily in hexane, and give very nice chromatography on standard nonpolar columns such as db1, db5 etc.

Phenylboronic acid derivatizes 1,2 and 1,3 diols. The protocol is pretty much 1ml of PBA in 95% acetone to 5 ml aqueous sample, 90degC for 30 minutes, add salt and hexanes, inject.
James_Ball wrote:
ACLLogan wrote:
Why can you not neutralize the reaction? Would neutralizing it cause damage to your sample? You could dilute that sample, do an extraction, and then dry it down to the volume that you need. It would take extra time, though.


Difficult to extract glycol from water with a solvent, thus most of the time glycol samples are injected directly onto column.

HCl should be ok, it is not as destructive to the column as sulfuric or nitric acid is. You may want to run a few meters of uncoated guard column/retention gap in front of the analytical column if you are worried about the aqueous HCl being injected directly onto the main column.


Well i did already inject 40 samples. The propylene glycol peak started melting. The column is gone. I baked it. But still nothing. I even trimmed the column, but nothing. I changed the whole column and the peaks were good again. So HCL is not good for the column
MSCHemist wrote:
Have you considered derivatizing glycols. I use phenylboronic acid for glycols and 3-mcpd. It derivatizes fine in water and the derivatives have a stronger signal on MS and FID, extract very easily in hexane, and give very nice chromatography on standard nonpolar columns such as db1, db5 etc.

Phenylboronic acid derivatizes 1,2 and 1,3 diols. The protocol is pretty much 1ml of PBA in 95% acetone to 5 ml aqueous sample, 90degC for 30 minutes, add salt and hexanes, inject.


Interesting i will look into this further. Thank you
sohaib1 wrote:
James_Ball wrote:
ACLLogan wrote:
Why can you not neutralize the reaction? Would neutralizing it cause damage to your sample? You could dilute that sample, do an extraction, and then dry it down to the volume that you need. It would take extra time, though.


Difficult to extract glycol from water with a solvent, thus most of the time glycol samples are injected directly onto column.

HCl should be ok, it is not as destructive to the column as sulfuric or nitric acid is. You may want to run a few meters of uncoated guard column/retention gap in front of the analytical column if you are worried about the aqueous HCl being injected directly onto the main column.


Well i did already inject 40 samples. The propylene glycol peak started melting. The column is gone. I baked it. But still nothing. I even trimmed the column, but nothing. I changed the whole column and the peaks were good again. So HCL is not good for the column


Maybe something like this will work

http://www.restek.com/catalog/view/1433
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
sohaib1 wrote:
James_Ball wrote:

Difficult to extract glycol from water with a solvent, thus most of the time glycol samples are injected directly onto column.

HCl should be ok, it is not as destructive to the column as sulfuric or nitric acid is. You may want to run a few meters of uncoated guard column/retention gap in front of the analytical column if you are worried about the aqueous HCl being injected directly onto the main column.


Well i did already inject 40 samples. The propylene glycol peak started melting. The column is gone. I baked it. But still nothing. I even trimmed the column, but nothing. I changed the whole column and the peaks were good again. So HCL is not good for the column


Maybe something like this will work

http://www.restek.com/catalog/view/1433


OH OK thank you very much
MSCHemist wrote:
Have you considered derivatizing glycols. Phenylboronic acid derivatizes 1,2 and 1,3 diols. The protocol is pretty much 1ml of PBA in 95% acetone to 5 ml aqueous sample, 90degC for 30 minutes, add salt and hexanes, inject.


How much salt (NaCL?) and hexane?

Perkin Elmer has a clinical application like that, but they put the PBA in dimethoxypropane and heat on a headspace sampler, apparently an instantaneous conversion. I never tried because I didn't have the HS setup.
I just dump a bunch of salt in to saturate it and extract it. I mainly test for 3-monochloropropane diol as the company I work for makes acid hydrolyzed vegetable protein. I extract with 2ml hexane and inject 2ul splitless. I've used the same method with a higher split ratio for propylene glycol, 1,3 propane diol and use ethylene gylcol as an ITSD.

https://www.ncbi.nlm.nih.gov/pubmed/20450199
Thanks- definitely going to try that.
late reply but we have ruined a 624 column and a few guard columns injecting 1-2 ul of water that was acidified with most likely HCL..clients accidently used preserved HCL water sampling jars and our chemist did not check the pH...now we check the pH of every sample...pH of those samples was 1-2....certain compounds will drop out completely and/or exhibit poor peak shape like cyclohexanol (our IS) or Phenol but not so much Methanol or some other compounds...the one time it ran overnight and both the guard and column were destroyed...we try to stay@pH 4sh and above...
eg@aaclab wrote:
late reply but we have ruined a 624 column and a few guard columns injecting 1-2 ul of water that was acidified with most likely HCL..clients accidently used preserved HCL water sampling jars and our chemist did not check the pH...now we check the pH of every sample...pH of those samples was 1-2....certain compounds will drop out completely and/or exhibit poor peak shape like cyclohexanol (our IS) or Phenol but not so much Methanol or some other compounds...the one time it ran overnight and both the guard and column were destroyed...we try to stay@pH 4sh and above...


Good to know. Each phase will have a different tolerance to acid, and that isn't something commonly listed in the properties for these columns.
The past is there to guide us into the future, not to dwell in.
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