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By Anonymous on Tuesday, November 18, 2003 - 06:57 am:
I wonder if someone has an idea how to transfer Triclosan solved in Ethylacetate to Acetonitrile or an Acetonitrile-Water-Mixture?
SPE, LLE or anything?
Thank you very much!!!
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By Consumer Products Guy on Tuesday, November 18, 2003 - 07:01 am:
We've worked with triclosan for decades. If you would like some help, please start from the beginning: what is the sample matrix in which you're trying to determine triclosan, and the approximate level expected.
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By Anonymous on Tuesday, November 18, 2003 - 11:42 pm:
Hello Consumer Products Guy,
thank you for offering me support.
The problem is, that we don´t do a lot hplc in my lab. The column we use is a silica based C18 Phase. The mobile Phase is ACN/Water/TFA.
We usually use this setup to determine Triclosan in ACN/Water.
Our new task is to prove that the amount of Triclosan in an ethylacetate sample is below a not yet specified level. Since there should be no Triclosan in the Ethylacetate at all the measurement should be as sensitive as possible.
We don´t want to change the column or the ingredients of the mobile Phase.
Any suggestions or do you think it´s pointless?
Thanks a lot!
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By Consumer Products Guy on Wednesday, November 19, 2003 - 06:41 am:
We also do trace triclosan here occasionally. Start out using the same mobile phase and column as you do now (no need to re-invent the wheel). I'd absolutely inject the ethyl acetate solution DIRECTLY; the only issue here is that the amount injected must be small (maybe 5 ul on a 2.1 mm i.d. column, or 10 ul on a 4.6 mm i.d. column) so you don't overwhelm the mobile phase with the 100% organic (ethyl acetate). We inject from strong solvents all the time, the trick is to keep the injection amount low so the chromatography is better. You definitely should easily be able to determine triclosan levels below 5 ppm in the ethyl acetate, we can readily.
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By Anonymous on Wednesday, November 19, 2003 - 07:45 am:
Why don't you evaporate the ethyl acetate under a stream of air and reconstitute in ACN followed by a dash of water to suit your mobile phase? That way you'd solve the problem of ethyl acetate removal and you'd get great sensitivity because you've concentrated the triclosan and you can inject as much as you want.
John
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By Consumer Products Guy on Wednesday, November 19, 2003 - 08:31 am:
Personally, I never never add steps to any procedure if they're not necessary, that's why I recommended trying "as is" first. Steps left out of a procedure are never performed improperly.
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By Anonymous on Wednesday, November 19, 2003 - 08:47 am:
I would agree with that sentiment Mr Consumer. I just thought that if trace levels were being analysed you could guess that a concentartion step would be needed.
Another thought I had was why not try GC. We used to do derivatised triclosan using ECD detection and you could see ng/ml levels.
Cheers
John
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By Consumer Products Guy on Wednesday, November 19, 2003 - 12:02 pm:
We have also done triclosan GC, also after derivatization. I would investigate HPLC first.
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By MG on Wednesday, November 19, 2003 - 12:54 pm:
Consumer Products Guy:
I commonly inject strong solvents as well (MeOH, ACN) with small volumes as you do. But isn't EtOAc water immiscible? Is it really OK to inject immiscible solvents? Or does it become miscible in the ternary mixture with even small percentages of acetonitrile?
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By Anonymous on Thursday, November 20, 2003 - 01:47 am:
The Mobile Phase I use is ACN/Water 90/10 and I can add a lot of ethylacetate before the phases unmix.
So I think it´s not a problem to inject the pure ethylacetate.
The idea to use GC came to my mind as well but I don´t have a suitable column. So I´m going to follow the hplc approach as cosumer guy suggested.
Thank a lot for your support!
-------------------------------------------------------------------------------------------------------
By Hopfully helpful on Saturday, June 26, 2004 - 06:54 am:
Since ethylacetate is immiscible with water it may not be soluble in your eluent. If that is the case, injecting it onto an exteremely oleophylic octyldecyl HPLC column does not sound to me like such a good idea. The triclosan will pass through the column, seperating from all other components. The most hydrophylic component will elute first, the most hydrophobic last. However the ethylacteate may just stay on the column. As more samples are injected, more of the column will become coated and retention times will decrease. Eventually you may lose all capacity. If you are going to inject on an "as is" basis, and I agree with Consumer Guy to not change the analytical method, you might want to add a column clean up after all samples have been run. I suggest rinsing your column sequentially with a series of solvents going from water to an organic solvent in which ethylacetate is highly soluble. This will have to be done in steps employing solvents that mix readily with each other. For example water to methanol to acetonitrile. If required you could go from methanol to propanol to hexane, Etc. Reverse these steps to leave your column in proper eluent for storage when not in use. Column care is very important and can be a big cost savings to HPLC analytical procedures. If you must change the method, do not want to take the time to exchange solvents in the sample manually through sample preparation steps and do not want to manually rinse columns, try a gradient program which can rinse your columns between injections and return it to a stable starting condition with your eluent of choice.
I wonder if someone has an idea how to transfer Triclosan solved in Ethylacetate to Acetonitrile or an Acetonitrile-Water-Mixture?
SPE, LLE or anything?
Thank you very much!!!
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Tuesday, November 18, 2003 - 07:01 am:
We've worked with triclosan for decades. If you would like some help, please start from the beginning: what is the sample matrix in which you're trying to determine triclosan, and the approximate level expected.
-------------------------------------------------------------------------------------------------------
By Anonymous on Tuesday, November 18, 2003 - 11:42 pm:
Hello Consumer Products Guy,
thank you for offering me support.
The problem is, that we don´t do a lot hplc in my lab. The column we use is a silica based C18 Phase. The mobile Phase is ACN/Water/TFA.
We usually use this setup to determine Triclosan in ACN/Water.
Our new task is to prove that the amount of Triclosan in an ethylacetate sample is below a not yet specified level. Since there should be no Triclosan in the Ethylacetate at all the measurement should be as sensitive as possible.
We don´t want to change the column or the ingredients of the mobile Phase.
Any suggestions or do you think it´s pointless?
Thanks a lot!
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Wednesday, November 19, 2003 - 06:41 am:
We also do trace triclosan here occasionally. Start out using the same mobile phase and column as you do now (no need to re-invent the wheel). I'd absolutely inject the ethyl acetate solution DIRECTLY; the only issue here is that the amount injected must be small (maybe 5 ul on a 2.1 mm i.d. column, or 10 ul on a 4.6 mm i.d. column) so you don't overwhelm the mobile phase with the 100% organic (ethyl acetate). We inject from strong solvents all the time, the trick is to keep the injection amount low so the chromatography is better. You definitely should easily be able to determine triclosan levels below 5 ppm in the ethyl acetate, we can readily.
-------------------------------------------------------------------------------------------------------
By Anonymous on Wednesday, November 19, 2003 - 07:45 am:
Why don't you evaporate the ethyl acetate under a stream of air and reconstitute in ACN followed by a dash of water to suit your mobile phase? That way you'd solve the problem of ethyl acetate removal and you'd get great sensitivity because you've concentrated the triclosan and you can inject as much as you want.
John
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Wednesday, November 19, 2003 - 08:31 am:
Personally, I never never add steps to any procedure if they're not necessary, that's why I recommended trying "as is" first. Steps left out of a procedure are never performed improperly.
-------------------------------------------------------------------------------------------------------
By Anonymous on Wednesday, November 19, 2003 - 08:47 am:
I would agree with that sentiment Mr Consumer. I just thought that if trace levels were being analysed you could guess that a concentartion step would be needed.
Another thought I had was why not try GC. We used to do derivatised triclosan using ECD detection and you could see ng/ml levels.
Cheers
John
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Wednesday, November 19, 2003 - 12:02 pm:
We have also done triclosan GC, also after derivatization. I would investigate HPLC first.
-------------------------------------------------------------------------------------------------------
By MG on Wednesday, November 19, 2003 - 12:54 pm:
Consumer Products Guy:
I commonly inject strong solvents as well (MeOH, ACN) with small volumes as you do. But isn't EtOAc water immiscible? Is it really OK to inject immiscible solvents? Or does it become miscible in the ternary mixture with even small percentages of acetonitrile?
-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, November 20, 2003 - 01:47 am:
The Mobile Phase I use is ACN/Water 90/10 and I can add a lot of ethylacetate before the phases unmix.
So I think it´s not a problem to inject the pure ethylacetate.
The idea to use GC came to my mind as well but I don´t have a suitable column. So I´m going to follow the hplc approach as cosumer guy suggested.
Thank a lot for your support!
-------------------------------------------------------------------------------------------------------
By Hopfully helpful on Saturday, June 26, 2004 - 06:54 am:
Since ethylacetate is immiscible with water it may not be soluble in your eluent. If that is the case, injecting it onto an exteremely oleophylic octyldecyl HPLC column does not sound to me like such a good idea. The triclosan will pass through the column, seperating from all other components. The most hydrophylic component will elute first, the most hydrophobic last. However the ethylacteate may just stay on the column. As more samples are injected, more of the column will become coated and retention times will decrease. Eventually you may lose all capacity. If you are going to inject on an "as is" basis, and I agree with Consumer Guy to not change the analytical method, you might want to add a column clean up after all samples have been run. I suggest rinsing your column sequentially with a series of solvents going from water to an organic solvent in which ethylacetate is highly soluble. This will have to be done in steps employing solvents that mix readily with each other. For example water to methanol to acetonitrile. If required you could go from methanol to propanol to hexane, Etc. Reverse these steps to leave your column in proper eluent for storage when not in use. Column care is very important and can be a big cost savings to HPLC analytical procedures. If you must change the method, do not want to take the time to exchange solvents in the sample manually through sample preparation steps and do not want to manually rinse columns, try a gradient program which can rinse your columns between injections and return it to a stable starting condition with your eluent of choice.
