hplc water quality

[Victoria]

Hi: I am Victoria and I recently joint to this forum. It´s great!! I would like to ask about HPLC water. We are buying hplc water until now, but we decide to produce our own water at the laboratory. My question is: which is the best method to do it? I heard about cartridge equipments and that it could carry some contamination problems with resins used in it.
Can you give me some advice about this topic?
Thanks

[DR]

A good water system can reliably (if maintained) produce better water than you can buy and for less money (assuming you use enough of it).

US Filter, Barnstead and Millipore (among others) all make good lab water polishing units that rely on a series of reverse osmosis membranes, deionizing resin beds, carbon, "mop" and/or membrane filters, usually coupled with a UV lamp to photometrically oxidize any stray organic polymer molecules shed from a contact surface. These systems tend to come in a variety of configurations depending on your lab's specific needs and what you will be using as source water for the polishing unit. For example - if you already have a decent house DI setup, you may just need a polishing unit w/ resin, TOC and final membrane filtration. If you go to Millipore and want to use tapwater, they'll install an Elix purification unit between the tap and the polishing unit... best thing is to put a list of wants together, email all of the water purifier reps in your area and let them submit quotes. If you can stomach it, have tehm come in and give presentations during which each and every one of them will probably run their competition into the ground in an effort to convince you that theirs is the best value.

Get up front service contract quotes for these systems as well (if there is even a remote possibility that you will want them to service/validate the unit(s)).

[Bruce Hamilton]

The actual maintenance and operational costs of laboratory water purification units are significant, around US$ 2000pa here if you follow recommended change intervals. As DR notes, you need to identify your total actual water needs, and then decide how to achieve them.

There will be a usage point where the cost of purchasing bottled HPLC water is greater than the capital and ongoing costs of a purification unit. I've been told that a local laboratory with two analytical HPLCs found bottled water was the most cost effective option.

Also, there are units specifically designed for different HPLC requirements, eg an HPLC in a regulated lab will have much greater operational costs than a research unit where point-of-use quality monitoring isn't required and there's no requirement to scavenge out trace levels of organic material.

Service and support are important, so find out what models/brands nearly labs have, and their perceptions about both the unit and the supplier and support.

Please keep having fun,

[lmh]

... a side-line: the major problem I've found with bottled water in low-usage labs is that after opening, things start to grow in the bottle, particularly if it's left somewhere in the light. People aren't used to things growing in Winchesters, and they tend not to think about tipping half a bottle of water down the sink. I've seen green inlet filters because of this.... one of the biggest benefits of having your own RO water supply is that you will probably get into the habit of changing aqueous solvents daily, or every few days, rather than letting them hang around for weeks.

[Victoria]

Hi!
Thanks for your advice! I am far from everything, so I have to look for a robust equipment, and buy a good provision of consumables. I am working with agrochemical formulates, but in a future perhaps I have to analize them in soil and water. I will concentrate on formulates and see this matter first.
Once again, thanks all of you.

Regards,
Victoria

[analyte]

We use Millipore Milli-Q A10 Synthesis water purification system (no ads). It gives high quality 0.22 micron-filtered water of which TOC level is about 5 ppb and resistivity over 15 MOhmcm. I think that generally water with a TOC lower than 20 gives adequate results. (An important point to mention, UV-lamp of Milli Q system has to be changed after every 365 days.)

[DR]

We use Millipore Milli-Q A10 Synthesis water purification system (no ads). It gives high quality 0.22 micron-filtered water of which TOC level is about 5 ppb and resistivity over 15 MOhmcm. I think that generally water with a TOC lower than 20 gives adequate results. (An important point to mention, UV-lamp of Milli Q system has to be changed after every 365 days.)

Actually, there are 2 UV lamps in A10 units - the one that is changed annually (that lowers TOC) and another, smaller one that plays a role in determining the TOC level in the product water. Millipore tends to change this on an "as needed" basis. Also, they generally want to swap cartridges and do a cleaning every 6 months.

Whether a TOC level of 20 is adequate is a function of the type of chromatography you are doing and the wavelength monitored (for UV detectors). If you have a peak eluting near the end of a gradient and your detector is at or below 210nm, you may well find 20ppm TOC to be unacceptable and have need of further pretreatment for your water. Under other conditions and higher wavelengths, 20 is probably fine.

[analyte]

Yes, you are right and I agree with you.
Generally for 254 nm, 20 ppb of TOC in HPLC water is adequate, but under 210 nm, 5 ppb of TOC becomes essential.
And about Milli-Q A10, as you mentioned, after about a year we started using it, a warning appeared on the lcd screen of the unit, that says "Exchange A10 UV lamp"; and later we learned that it is a standard warning message that appears per 365 days. And after about 6 month,s our TOC level have raised to 11 ppb, but it did not create so much problematic results in the assays.
There is a good study about "TOC" fact, which was published in LC/GC. The article was entitled as "The Misunderstood Laboratory Solvent: Reagent Water for HPLC", (link: http://chromatographyonline.findanalyti ... ail/143793). This article answers many questions on HPLC grade water.