Many Millipore Milli-Q systems dispense the water through a 0.22 μm membrane filter, so check your system specs.
thanks all for the answers. but what about TOC and conductivity limits of the milli Q water you used for HPLC.
Yes you can use it. I have used it quite often and it posed no problems. Filtration is advisable if you face any problems.
We also use Millipore MilliQ water dispensed through 0.22 micron filter with 18.2 MΩ.cm conductivity. But I wonder if the values for conductivity are arbitrary or should we pay much attention to these?
You should not need to filter MilliQ water for HPLC or LCMS applications.
However you might consider to check that the resine cartdridge of your MilliQ water dispenser gets changed on a regular basis.
As a colleague has mentioned earlier, you might also want to degas your LC solvent mixture, either by filtering process or by sonication.
thanks all. what about TOC,I read that there is a limit for TOC in water for HPLC e.g. 5-10 ppb, anyone have already experience in this issue.
Specs say that the TOC limit of your feed water should be below 2000ppb then there won't be a problem to get below 5ppb TOC in your purified water. We have been using MilliQ for HPLC since I can remember - without any problems. But it depends on the application filter used. I suggest the "LC PAK polisher" application pack.
Millipore Milliq system is claim to dispense water of 18.2 MOhm-cm conductivity. However it should always be use a fresh because it may be get contaminated on storing under laboratory conditions. Though further filtration is not required; degassing is advisable through sonication for HPLC or LCMS applications. Also to maintain quality of water regular monitoring of MilliQ water dispenser is and cleaning of filter cartridge and replacement if defective is essential.
In most cases 18.0 MOhm is good enough. Even with water of 15 MOhm a HPLC system will correctly work, but 0.22 or 0.45 micron filtration of both the mobile phase and the injected samples is mandatory. TOC is usually not important in Milli-Q processed water for HPLC.
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