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By Anonymous on Monday, June 21, 2004 - 02:58 am:
Can someone explain me how can i prepare C18 water to use it in HPLC? Currently i'm using double distilled water which i pass it through 0.45 μm Nitrocellulose filters in order to remove the dust and particullates. Thank you in advance and sorry for my poor English.
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By bill tindall on Tuesday, June 22, 2004 - 12:09 pm:
It may be that you mean 18 megaohm water, megaohm refering to the conductivity of the water. Conductivity is a measure of dissolved ionic impurities in the water.
In liquid chromatography, trace ionic impurities are often not significant. In liquid chromatography trace amounts of organic impurities are more harmful. I do not think that 18 megohm water is necessary for liquid chromatography.
The water that you are preparing should be adequate for most chromotography. If you see evidence of organic contamination of your water, add some potassium permanganate and sodium hydroxide to the first distillation to oxidize organic impurities. I do not recall the exact amounts of permanganate and hydroxide to use but about 0.01 molar in each should be about right.
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By Anonymous on Tuesday, June 22, 2004 - 02:12 pm:
Thank you for your reply. When i say C18 water i mean Double distilled water passed through C18 disks before use it. I have heard somewhere for this type of water but i did't remeber how to prepare it exactly. I want to ask how many litters of water i can pass each time from the filter and with which solvent i must wash the filter and storage it for the next time. Thanks
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By DR on Wednesday, June 23, 2004 - 05:56 am:
I use C18 disks (47mm Empore extraction disks) for treatment of water that is to be used for A-phase prep if and only if it's for a gradient method that is prone to system peaks (usually because of low wavelength, poor feedwater etc).
I'll feed the disk 1L of water, then flush it with a little MeOH, rinse, repeat. It is very time consuming, so I only do it if I have a serious problem with system peaks and a guard column between the A pump outlet and mixing chamber doesn't work (or if only low pressure mixing systems are available).
Can someone explain me how can i prepare C18 water to use it in HPLC? Currently i'm using double distilled water which i pass it through 0.45 μm Nitrocellulose filters in order to remove the dust and particullates. Thank you in advance and sorry for my poor English.
-------------------------------------------------------------------------------------------------------
By bill tindall on Tuesday, June 22, 2004 - 12:09 pm:
It may be that you mean 18 megaohm water, megaohm refering to the conductivity of the water. Conductivity is a measure of dissolved ionic impurities in the water.
In liquid chromatography, trace ionic impurities are often not significant. In liquid chromatography trace amounts of organic impurities are more harmful. I do not think that 18 megohm water is necessary for liquid chromatography.
The water that you are preparing should be adequate for most chromotography. If you see evidence of organic contamination of your water, add some potassium permanganate and sodium hydroxide to the first distillation to oxidize organic impurities. I do not recall the exact amounts of permanganate and hydroxide to use but about 0.01 molar in each should be about right.
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By Anonymous on Tuesday, June 22, 2004 - 02:12 pm:
Thank you for your reply. When i say C18 water i mean Double distilled water passed through C18 disks before use it. I have heard somewhere for this type of water but i did't remeber how to prepare it exactly. I want to ask how many litters of water i can pass each time from the filter and with which solvent i must wash the filter and storage it for the next time. Thanks
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By DR on Wednesday, June 23, 2004 - 05:56 am:
I use C18 disks (47mm Empore extraction disks) for treatment of water that is to be used for A-phase prep if and only if it's for a gradient method that is prone to system peaks (usually because of low wavelength, poor feedwater etc).
I'll feed the disk 1L of water, then flush it with a little MeOH, rinse, repeat. It is very time consuming, so I only do it if I have a serious problem with system peaks and a guard column between the A pump outlet and mixing chamber doesn't work (or if only low pressure mixing systems are available).
