The purging with inert gas prevents the oxidation of the sample in the tube. As Lewis pointed out that sealing can be safely done if the tube is already fused with a ground joint through a constricted opening. We have done similar exercise long ago for air and moisture sensitive organometallic compounds and the spectra were recorded in Germany as we did not have the necessary facilities at that time.
The purging with inert gas prevents the oxidation of the sample in the tube. As Lewis pointed out that sealing can be safely done if the tube is already fused with a ground joint through a constricted opening. We have done similar exercise long ago for air and moisture sensitive organometallic compounds and the spectra were recorded in Germany as we did not have the necessary facilities at that time.
Around 1970, it was essential to remove molten oxygen when measuring NOE with the Varian HA-100. For that purpose, I thought about how to degas and seal the sample tube, and made the equipment. This cannot be conveyed by text alone. However, with the FT machine, NOE measurement is possible by putting a capillary in the sample tube and bubbling nitrogen gas. Experimentally, if you want to know my method, please tell me the address where you can attach the figure, look for the slide at that time and attach a copy.
Around 1970, it was essential to remove molten oxygen when measuring NOE with the Varian HA-100. For that purpose, I thought about how to degas and seal the sample tube, and made the equipment. This cannot be conveyed by text alone. However, with the FT machine, NOE measurement is possible by putting a capillary in the sample tube and bubbling nitrogen gas. Experimentally, if you want to know my method, please tell me the address where you can attach the figure, look for the slide at that time and attach a copy.
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes: Flame sealing a sample in a glass tube under vacuum https://www.youtube.com/watch?v=icZ62A1_dCo Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration. Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes: Flame sealing a sample in a glass tube under vacuum https://www.youtube.com/watch?v=icZ62A1_dCo Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration. Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
To seal NMR tubes under vacuum, you need to freeze the solution with liquid nitrogen, otherwise it will evaporate. The operation is rather tricky because of the connection between the tube and the pump. As soon as you melt the glass, the hot glass is "sucked in" ; you may have to practice on old/broken tubes. Another problem I encountered with volatile solvents (CH2Cl2) and reactive gases (BF3) is the decomposition of the vapors on hot glass surfaces during sealing. You could see some fumes and colors on the internal glass surface that make an efficient sealing difficult or ineffective. This is a good reason to cool the liquid, but under an inert gas, to avoid humidity condensation and have a "blanket" of inert gas above the liquid. Argon is good (heavier that air) to purge the tubes, but more expensive that nitrogen.
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To seal NMR tubes under vacuum, you need to freeze the solution with liquid nitrogen, otherwise it will evaporate. The operation is rather tricky because of the connection between the tube and the pump. As soon as you melt the glass, the hot glass is "sucked in" ; you may have to practice on old/broken tubes. Another problem I encountered with volatile solvents (CH2Cl2) and reactive gases (BF3) is the decomposition of the vapors on hot glass surfaces during sealing. You could see some fumes and colors on the internal glass surface that make an efficient sealing difficult or ineffective. This is a good reason to cool the liquid, but under an inert gas, to avoid humidity condensation and have a "blanket" of inert gas above the liquid. Argon is good (heavier that air) to purge the tubes, but more expensive that nitrogen.
Serum cap for the NMR tubes is another alternative . Remove the air inside the tube in a Glove box and cover it with the serum cap. Of course, the entire operation can be done with Schlenk line as Prof.Edelman has suggested.
Serum cap for the NMR tubes is another alternative . Remove the air inside the tube in a Glove box and cover it with the serum cap. Of course, the entire operation can be done with Schlenk line as Prof.Edelman has suggested.
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes: Flame sealing a sample in a glass tube under vacuum https://www.youtube.com/watch?v=icZ62A1_dCo Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration. Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes: Flame sealing a sample in a glass tube under vacuum https://www.youtube.com/watch?v=icZ62A1_dCo Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration. Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
I doubt that serum caps in usual materials (rubber...) could be better than normal plastic caps fitting tightly NMR tubes. Rubber(s) absorb a lot of organic solvents and are more sensitive to corrosive compouds.
I doubt that serum caps in usual materials (rubber...) could be better than normal plastic caps fitting tightly NMR tubes. Rubber(s) absorb a lot of organic solvents and are more sensitive to corrosive compouds.
The purging with inert gas prevents the oxidation of the sample in the tube. As Lewis pointed out that sealing can be safely done if the tube is already fused with a ground joint through a constricted opening. We have done similar exercise long ago for air and moisture sensitive organometallic compounds and the spectra were recorded in Germany as we did not have the necessary facilities at that time.
The purging with inert gas prevents the oxidation of the sample in the tube. As Lewis pointed out that sealing can be safely done if the tube is already fused with a ground joint through a constricted opening. We have done similar exercise long ago for air and moisture sensitive organometallic compounds and the spectra were recorded in Germany as we did not have the necessary facilities at that time.
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Around 1970, it was essential to remove molten oxygen when measuring NOE with the Varian HA-100. For that purpose, I thought about how to degas and seal the sample tube, and made the equipment. This cannot be conveyed by text alone. However, with the FT machine, NOE measurement is possible by putting a capillary in the sample tube and bubbling nitrogen gas. Experimentally, if you want to know my method, please tell me the address where you can attach the figure, look for the slide at that time and attach a copy.
Around 1970, it was essential to remove molten oxygen when measuring NOE with the Varian HA-100. For that purpose, I thought about how to degas and seal the sample tube, and made the equipment. This cannot be conveyed by text alone. However, with the FT machine, NOE measurement is possible by putting a capillary in the sample tube and bubbling nitrogen gas. Experimentally, if you want to know my method, please tell me the address where you can attach the figure, look for the slide at that time and attach a copy.
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VOTE
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes:
Flame sealing a sample in a glass tube under vacuum
https://www.youtube.com/watch?v=icZ62A1_dCo
Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration.
Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes:
Flame sealing a sample in a glass tube under vacuum
https://www.youtube.com/watch?v=icZ62A1_dCo
Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration.
Good luck with your work and best wishes, Frank Edelmann
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Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
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Thank you all for your answers and the valuable information you brought in. It really is helpful.
Thank you all for your answers and the valuable information you brought in. It really is helpful.
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To seal NMR tubes under vacuum, you need to freeze the solution with liquid nitrogen, otherwise it will evaporate. The operation is rather tricky because of the connection between the tube and the pump. As soon as you melt the glass, the hot glass is "sucked in" ; you may have to practice on old/broken tubes. Another problem I encountered with volatile solvents (CH2Cl2) and reactive gases (BF3) is the decomposition of the vapors on hot glass surfaces during sealing. You could see some fumes and colors on the internal glass surface that make an efficient sealing difficult or ineffective. This is a good reason to cool the liquid, but under an inert gas, to avoid humidity condensation and have a "blanket" of inert gas above the liquid. Argon is good (heavier that air) to purge the tubes, but more expensive that nitrogen.
To seal NMR tubes under vacuum, you need to freeze the solution with liquid nitrogen, otherwise it will evaporate. The operation is rather tricky because of the connection between the tube and the pump. As soon as you melt the glass, the hot glass is "sucked in" ; you may have to practice on old/broken tubes. Another problem I encountered with volatile solvents (CH2Cl2) and reactive gases (BF3) is the decomposition of the vapors on hot glass surfaces during sealing. You could see some fumes and colors on the internal glass surface that make an efficient sealing difficult or ineffective. This is a good reason to cool the liquid, but under an inert gas, to avoid humidity condensation and have a "blanket" of inert gas above the liquid. Argon is good (heavier that air) to purge the tubes, but more expensive that nitrogen.
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VOTE
Serum cap for the NMR tubes is another alternative . Remove the air inside the tube in a Glove box and cover it with the serum cap. Of course, the entire operation can be done with Schlenk line as Prof.Edelman has suggested.
Serum cap for the NMR tubes is another alternative . Remove the air inside the tube in a Glove box and cover it with the serum cap. Of course, the entire operation can be done with Schlenk line as Prof.Edelman has suggested.
More
VOTE
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes:
Flame sealing a sample in a glass tube under vacuum
https://www.youtube.com/watch?v=icZ62A1_dCo
Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration.
Good luck with your work and best wishes, Frank Edelmann
Dear Salem Baroudi many thanks for asking this interesting technical question. Flame-sealing of NMR tubes was quite common in the 1980's and 1990's when chemists wanted to measure highly air-sensitive organometallic compounds. A potentially helpful YouTube tutorial video is available, although it does not particularly deal with NMR tubes:
Flame sealing a sample in a glass tube under vacuum
https://www.youtube.com/watch?v=icZ62A1_dCo
Nowadays we use only screw-cap NMR tubes which can be filled with the sample inside a dry-box or using a Schlenk line. Such NMR tubes are available form various commercial vendors. They are a bit expensive, but using them saves you a lot of time and potential frustration.
Good luck with your work and best wishes, Frank Edelmann
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VOTE
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
Dear Salem Baroudi I fully agree with Jean-François Gal in that serum caps or normal plastic caps are most likely not suitable for your purposes. If your samples are highly volatile but not really air-sensitive, I would suggest to use NMR tubes with a stable screw cap. If the samples are also air-sensitive, J Young NMR tubes with an inlet for vacuum / inert gas (as suggested by Lewis Copsey) are certainly the best choice.
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Thank you once again for those precious details!
Thank you once again for those precious details!
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I doubt that serum caps in usual materials (rubber...) could be better than normal plastic caps fitting tightly NMR tubes. Rubber(s) absorb a lot of organic solvents and are more sensitive to corrosive compouds.
I doubt that serum caps in usual materials (rubber...) could be better than normal plastic caps fitting tightly NMR tubes. Rubber(s) absorb a lot of organic solvents and are more sensitive to corrosive compouds.
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You can also try Tetrachloroethane-d2 if you want to heat without sealing.
You can also try Tetrachloroethane-d2 if you want to heat without sealing.
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