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What precautions should be kept in our mind, if using chiral...
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+ High pressure liquid chromatography
+ Chiral hplc
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Mark Cascella
What precautions should be kept in our mind, if using chiral...
I agree with Jacek Martinow, it's a matter of experimentation rather than theoretical prediction. With chiralcel columns OD-H, OJ-H, OB-H and Chiralpack AS-H, I can separate many chiral products which come from cyclopropanation, sulfoxidation, epoxidation, hydroxilation, N-H insertion. The mobile phase that I use is Hexane/IPrOH (from 80/20 to 99/1). The products are dissolved in IPrOH for injection.
I agree with Jacek Martinow, it's a matter of experimentation rather than theoretical prediction. With chiralcel columns OD-H, OJ-H, OB-H and Chiralpack AS-H, I can separate many chiral products which come from cyclopropanation, sulfoxidation, epoxidation, hydroxilation, N-H insertion. The mobile phase that I use is Hexane/IPrOH (from 80/20 to 99/1). The products are dissolved in IPrOH for injection.
Chiral columns are expensive. Be sure to look at column specs. Some solvents will ruin the column (eg chlorinated solvents). Make sure you are free of those solvents.
Chiral columns are expensive. Be sure to look at column specs. Some solvents will ruin the column (eg chlorinated solvents). Make sure you are free of those solvents.
Your question is too broad because we do not know what your sample is. As such, can only provide general chiral method development comments. (1) Send your sample to one or more of the column resellers to have them "screen" it against the columns that they sell. If they charge you for this, it is still less expensive then you buying the screening equipment and columns yourself (>$100,000 USD). You might get lucky and they will identify one or more columns and methods for you. (2) Do not just buy a column and try it without some logical reason. Most columns are expensive and you will be wasting money. Search the literature and the web for your compound to see if you can find where someone has done this for you first. (3) Don't use a pre-column or guard column. Instead, invest in some chromatography training and learn how to filter samples, wash down columns after each run and maintain your HPLC system. Learn and understand the flow path of the system before you use it. Knowledge and skills = confident data.
Your question is too broad because we do not know what your sample is. As such, can only provide general chiral method development comments. (1) Send your sample to one or more of the column resellers to have them "screen" it against the columns that they sell. If they charge you for this, it is still less expensive then you buying the screening equipment and columns yourself (>$100,000 USD). You might get lucky and they will identify one or more columns and methods for you. (2) Do not just buy a column and try it without some logical reason. Most columns are expensive and you will be wasting money. Search the literature and the web for your compound to see if you can find where someone has done this for you first. (3) Don't use a pre-column or guard column. Instead, invest in some chromatography training and learn how to filter samples, wash down columns after each run and maintain your HPLC system. Learn and understand the flow path of the system before you use it. Knowledge and skills = confident data.
Just one word from our experience - it is best to dissolve your compound(s) in the solvent mixture used for separation (typically these are isocratic runs). On another note, with ChiralPak series of stationary phases we are able to use eluent solvent mixtures very rich in iPrOH e.g. 75% IPA-25% heptane works very well, if that is necessary due to a higher polarity of the compound(s).
Just one word from our experience - it is best to dissolve your compound(s) in the solvent mixture used for separation (typically these are isocratic runs). On another note, with ChiralPak series of stationary phases we are able to use eluent solvent mixtures very rich in iPrOH e.g. 75% IPA-25% heptane works very well, if that is necessary due to a higher polarity of the compound(s).
The solvent mixture that you specified tells a little bit about the compound you are working with (i.e. not highly polar, probably dissolves in common organic solvents). Ideally you would choose a column with an immobilized chiral substrate that is very robust towards common organic solvents (like Chiralpaks IA for instance). Essentially you can then choose any organic solvent you like (typically mixtures of hexanes/iPrOH or hexanes/DCM). It is always a good place to start with a solvent where your compound is soluble in (let's say DCM) and adding a more apolar solvent gradually (starting with 50:50 DCM/hexanes and working your way up to maybe 5:95), until you achieve a fast, reliable baseline separation. It might also be wise to invest in a small precolumn (or Guard column) to prevent contamination of the expensive chiral column. In that regard, also only use samples that you have run over a classical column or plug or the like (to remove catalysts, bases and so on that would clog the column or destroy it)
The solvent mixture that you specified tells a little bit about the compound you are working with (i.e. not highly polar, probably dissolves in common organic solvents). Ideally you would choose a column with an immobilized chiral substrate that is very robust towards common organic solvents (like Chiralpaks IA for instance). Essentially you can then choose any organic solvent you like (typically mixtures of hexanes/iPrOH or hexanes/DCM). It is always a good place to start with a solvent where your compound is soluble in (let's say DCM) and adding a more apolar solvent gradually (starting with 50:50 DCM/hexanes and working your way up to maybe 5:95), until you achieve a fast, reliable baseline separation. It might also be wise to invest in a small precolumn (or Guard column) to prevent contamination of the expensive chiral column. In that regard, also only use samples that you have run over a classical column or plug or the like (to remove catalysts, bases and so on that would clog the column or destroy it)
Ghazanfar, Transferring TLC Rf values to chiral HPLC usually is not reliably done. There are a few reasons for that, one being that there is a large variety of chiral stationary phases (columns). Some will work in reverse phase mode, but majority will require hydrocarbon-isopropanol mixtures (such as modified oligosugar coated stationary phases, Pirkle phases, or modified oligosugar immobilized stationary phases). In my experience, oligosugar-based columns give best separations, but there well may be cases where the opposite can be true. It is like many other situations in Nature: a good match may depend on so many factors that, due to complexity, it becomes a matter of experimentation rather than theoretical prediction. Another reason for lack of parallel to TLC is that chiral phases are different than regular silica gel phases, they are modified (as mentioned above). Once you have worked with your compound(s) for some time, you may be able to roughly predict which mobile phase composition will be good for this case/column, but that is still never straightforward. In addition, frequently modifiers are used (diethylamine, acetic acid, etc), and these can also influence the behavior of the column. I am attaching for you a review that I think is still very informative (although it is a little older).
Ghazanfar, Transferring TLC Rf values to chiral HPLC usually is not reliably done. There are a few reasons for that, one being that there is a large variety of chiral stationary phases (columns). Some will work in reverse phase mode, but majority will require hydrocarbon-isopropanol mixtures (such as modified oligosugar coated stationary phases, Pirkle phases, or modified oligosugar immobilized stationary phases). In my experience, oligosugar-based columns give best separations, but there well may be cases where the opposite can be true. It is like many other situations in Nature: a good match may depend on so many factors that, due to complexity, it becomes a matter of experimentation rather than theoretical prediction. Another reason for lack of parallel to TLC is that chiral phases are different than regular silica gel phases, they are modified (as mentioned above). Once you have worked with your compound(s) for some time, you may be able to roughly predict which mobile phase composition will be good for this case/column, but that is still never straightforward. In addition, frequently modifiers are used (diethylamine, acetic acid, etc), and these can also influence the behavior of the column. I am attaching for you a review that I think is still very informative (although it is a little older).
I agree with Jacek Martinow, it's a matter of experimentation rather than theoretical prediction. With chiralcel columns OD-H, OJ-H, OB-H and Chiralpack AS-H, I can separate many chiral products which come from cyclopropanation, sulfoxidation, epoxidation, hydroxilation, N-H insertion. The mobile phase that I use is Hexane/IPrOH (from 80/20 to 99/1). The products are dissolved in IPrOH for injection.
I agree with Jacek Martinow, it's a matter of experimentation rather than theoretical prediction. With chiralcel columns OD-H, OJ-H, OB-H and Chiralpack AS-H, I can separate many chiral products which come from cyclopropanation, sulfoxidation, epoxidation, hydroxilation, N-H insertion. The mobile phase that I use is Hexane/IPrOH (from 80/20 to 99/1). The products are dissolved in IPrOH for injection.
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... and I corrected the name, sorry :)
Jacek
... and I corrected the name, sorry :)
Jacek
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Chiral columns are expensive. Be sure to look at column specs. Some solvents will ruin the column (eg chlorinated solvents). Make sure you are free of those solvents.
Chiral columns are expensive. Be sure to look at column specs. Some solvents will ruin the column (eg chlorinated solvents). Make sure you are free of those solvents.
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Your question is too broad because we do not know what your sample is. As such, can only provide general chiral method development comments.
(1) Send your sample to one or more of the column resellers to have them "screen" it against the columns that they sell. If they charge you for this, it is still less expensive then you buying the screening equipment and columns yourself (>$100,000 USD). You might get lucky and they will identify one or more columns and methods for you.
(2) Do not just buy a column and try it without some logical reason. Most columns are expensive and you will be wasting money. Search the literature and the web for your compound to see if you can find where someone has done this for you first.
(3) Don't use a pre-column or guard column. Instead, invest in some chromatography training and learn how to filter samples, wash down columns after each run and maintain your HPLC system. Learn and understand the flow path of the system before you use it. Knowledge and skills = confident data.
Your question is too broad because we do not know what your sample is. As such, can only provide general chiral method development comments.
(1) Send your sample to one or more of the column resellers to have them "screen" it against the columns that they sell. If they charge you for this, it is still less expensive then you buying the screening equipment and columns yourself (>$100,000 USD). You might get lucky and they will identify one or more columns and methods for you.
(2) Do not just buy a column and try it without some logical reason. Most columns are expensive and you will be wasting money. Search the literature and the web for your compound to see if you can find where someone has done this for you first.
(3) Don't use a pre-column or guard column. Instead, invest in some chromatography training and learn how to filter samples, wash down columns after each run and maintain your HPLC system. Learn and understand the flow path of the system before you use it. Knowledge and skills = confident data.
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Just one word from our experience - it is best to dissolve your compound(s) in the solvent mixture used for separation (typically these are isocratic runs).
On another note, with ChiralPak series of stationary phases we are able to use eluent solvent mixtures very rich in iPrOH e.g. 75% IPA-25% heptane works very well, if that is necessary due to a higher polarity of the compound(s).
Just one word from our experience - it is best to dissolve your compound(s) in the solvent mixture used for separation (typically these are isocratic runs).
On another note, with ChiralPak series of stationary phases we are able to use eluent solvent mixtures very rich in iPrOH e.g. 75% IPA-25% heptane works very well, if that is necessary due to a higher polarity of the compound(s).
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Thanks Sir Jacek Martynow
Thanks Sir Jacek Martynow
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Thanks everybody
Thanks everybody
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The solvent mixture that you specified tells a little bit about the compound you are working with (i.e. not highly polar, probably dissolves in common organic solvents). Ideally you would choose a column with an immobilized chiral substrate that is very robust towards common organic solvents (like Chiralpaks IA for instance). Essentially you can then choose any organic solvent you like (typically mixtures of hexanes/iPrOH or hexanes/DCM). It is always a good place to start with a solvent where your compound is soluble in (let's say DCM) and adding a more apolar solvent gradually (starting with 50:50 DCM/hexanes and working your way up to maybe 5:95), until you achieve a fast, reliable baseline separation.
It might also be wise to invest in a small precolumn (or Guard column) to prevent contamination of the expensive chiral column. In that regard, also only use samples that you have run over a classical column or plug or the like (to remove catalysts, bases and so on that would clog the column or destroy it)
The solvent mixture that you specified tells a little bit about the compound you are working with (i.e. not highly polar, probably dissolves in common organic solvents). Ideally you would choose a column with an immobilized chiral substrate that is very robust towards common organic solvents (like Chiralpaks IA for instance). Essentially you can then choose any organic solvent you like (typically mixtures of hexanes/iPrOH or hexanes/DCM). It is always a good place to start with a solvent where your compound is soluble in (let's say DCM) and adding a more apolar solvent gradually (starting with 50:50 DCM/hexanes and working your way up to maybe 5:95), until you achieve a fast, reliable baseline separation.
It might also be wise to invest in a small precolumn (or Guard column) to prevent contamination of the expensive chiral column. In that regard, also only use samples that you have run over a classical column or plug or the like (to remove catalysts, bases and so on that would clog the column or destroy it)
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If you are doing it in RP, use ACN/H20 gradiant system
If you are doing it in RP, use ACN/H20 gradiant system
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Ghazanfar,
Transferring TLC Rf values to chiral HPLC usually is not reliably done. There are a few reasons for that, one being that there is a large variety of chiral stationary phases (columns). Some will work in reverse phase mode, but majority will require hydrocarbon-isopropanol mixtures (such as modified oligosugar coated stationary phases, Pirkle phases, or modified oligosugar immobilized stationary phases). In my experience, oligosugar-based columns give best separations, but there well may be cases where the opposite can be true. It is like many other situations in Nature: a good match may depend on so many factors that, due to complexity, it becomes a matter of experimentation rather than theoretical prediction. Another reason for lack of parallel to TLC is that chiral phases are different than regular silica gel phases, they are modified (as mentioned above). Once you have worked with your compound(s) for some time, you may be able to roughly predict which mobile phase composition will be good for this case/column, but that is still never straightforward. In addition, frequently modifiers are used (diethylamine, acetic acid, etc), and these can also influence the behavior of the column. I am attaching for you a review that I think is still very informative (although it is a little older).
Ghazanfar,
Transferring TLC Rf values to chiral HPLC usually is not reliably done. There are a few reasons for that, one being that there is a large variety of chiral stationary phases (columns). Some will work in reverse phase mode, but majority will require hydrocarbon-isopropanol mixtures (such as modified oligosugar coated stationary phases, Pirkle phases, or modified oligosugar immobilized stationary phases). In my experience, oligosugar-based columns give best separations, but there well may be cases where the opposite can be true. It is like many other situations in Nature: a good match may depend on so many factors that, due to complexity, it becomes a matter of experimentation rather than theoretical prediction. Another reason for lack of parallel to TLC is that chiral phases are different than regular silica gel phases, they are modified (as mentioned above). Once you have worked with your compound(s) for some time, you may be able to roughly predict which mobile phase composition will be good for this case/column, but that is still never straightforward. In addition, frequently modifiers are used (diethylamine, acetic acid, etc), and these can also influence the behavior of the column. I am attaching for you a review that I think is still very informative (although it is a little older).
More
VOTE