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Posted: Thu Jul 07, 2005 7:50 pm
by DR
Water sources have been house supplied RO water polished with a multi cartridge system (Millipore, US Filter type units - some w/ a TOC lamp, some without).
Posted: Sat Jul 23, 2005 3:53 am
by Uwe Neue
Sorry for responding somewhat late, but my memory is not the best any more.
Millipore used to sell a "Norganic" cartridge filled with activated carbon for cleaning up water. This project happened nearly 20 years ago, and I am not sure if they still make such a thing.
Posted: Mon Jul 25, 2005 2:48 pm
by HW Mueller
That in turn reminds me of an article by Millipore + Waters people which just appeared in LC GC Europe, vol 18, #7, 410 (2005). They mention precleaning with reverse osmosis + electrodeionization, then comes their 4 part cartridge giving "ultrapure H2O", 2ppb TOC (total organic C). It really seems to me that shooting this through a filter, etc., isn´t going to do it any good.
Uwe, maybe you know Jim Krol, ..... would be neat if you could find out whether they tried such further "purification".
Posted: Mon Jul 25, 2005 5:23 pm
by John G
We have been dealing with this issue in our lab for a few years now. We have seen these "ghost peaks" on several gradient methods, while other methods using the same water source are fine. We used the 3M empore XDB-XC disks to clean up the water before preparing moble phase and found that they pretty much eliminated all the ghost peaks. We actually recieved at defiency from the FDA stating that ghost peaks in the blank are not acceptable. Our problem stems from high organic concentration in the tap water. Our water system's capacity to remove organic contaimination is exhasted long before the ion exchange capacity. Our system are older, >10 years and do not have TOC monitoring or UV TOC removal. Water from an adjacent lab with brand new water systems produced ghost peak free chromtograms, with even lower baselines then the empore pre-treated water, same system, moble phase prep and lot #s. As far as I know there is no TOC specification from the USP on HLPC grade water, which is the root of the problem. Garbage in garbage out.
I have seen this problem with bottled water as well. It seems to depend on your local water source, lake versus well, and how good your water system is at removing organics. Most of the new polishers allow you to change the organic cartridge independantly of the ion exchange which is a great cost advantage, but TOC monitoring is a must if you want to control the issue
John