Webinar Highlights: How to Obtain the Best Water Quality for Your Laboratory Experiments

Do you think water contaminants are impacting your experiments? Obtaining sufficiently pure water is crucial for accurate and reproducible results. Numerous contaminants, such as bacteria and ions, can have a significant effect on your analyses and consequently produce unreliable results.

In a recent SelectScience webinar, Dr. Estelle Riche, of Milli-Q® Lab Water Solutions, discussed the potential impacts of water contaminants and the importance of obtaining pure water for your experiments, as well as explaining how to adapt your water purity to suit your needs.

Missed the webinar? Don't worry, you can now watch the webinar on demand here>>

At the end of the webinar, Riche answers live questions from our listeners, and the highlights of this Q&A session can be read below:

Q: When I want to analyze clean water, must I use a purer kind of water to do it, for example ultra-purification water or similar?

ER: It is better to use the cleanest water possible. The purer the water you want to analyze, the purer the water you should be using to prepare your blanks and dilutions. Otherwise the water used for dilution is not as clean as the water you are analyzing and you won’t know where impurities are coming from.

Q: How long do you recommend storing water for HPLC?

ER: It will depend on how sensitive your analyses are. I don’t usually recommend storing ultrapure water; it is best to change it every day or every two days if you can. If kept for longer, you will have to ensure that you protect it from the lab air by putting filter tops on and try not to keep it more than a week. In the summer, there are risks of bacteria developing so try not to keep it that long and try not to store water in front of the window, as algae and other organisms may develop.

Q: Does ultrapure water need to be replaced every day for UPLC analysis?

ER: It is even more necessary to change the water daily for UPLC than HPLC. In UPLC, the particles in the columns are much smaller, therefore any kind of bacteria or particle that is present will have more impact on results. Change the eluent every day if you can, otherwise protect it from the air.

Q: How often do I need to change the cartridges of my water system?

ER: The good thing is that modern water purification systems tell you when to change the cartridges, or it will say so in a manual. My advice would be to do it when the system tells you. I think of it like changing the oil in your car, you don’t want to wait until you have problems and your cartridges are saturated, you want to ensure water quality is always optimal.

Q: I tried to measure the pH of my lab water but I obtained strange results that weren’t pH 7, do you know why?

ER: It depends what kind of water it was - if it was ultrapure water it should be 7. The issue is that if you used ultrapure water, you don’t have enough ions in the water for your pH meter to function properly, as the electrodes need ions for the current to go through. It will be the same with pH paper. The other issue is that if you want to measure the pH of ultrapure water, as the water is in contact with air, it will start to dissolve carbon dioxide, shifting the pH to the acidic side due to the formation of carbonates and carbonic acid. Some people add KCl when measuring the pH of ultrapure water, as that adds ions but does not impact the pH, but this is difficult to do without affecting the results. I would also recommend using specialized pH electrodes because regular electrodes will have difficulty with this as well. But if you're using ultrapure water and the resistivity is 18.2 MOhm.cm, you don’t need to measure the pH as that means the pH is already 7 and there are no ions in your water. If there were any ions that could impact the pH, the resistivity would not be 18.2 MOhm.cm.

Q: Sometimes during PCR, even with ultrapure water, we get bacterial 16S amplification. How do I avoid this problem?

ER: That means there are some bacteria or their by-products present and you may want to check the maintenance of your system to make sure your final filter has been changed in time. We would recommend using ultra-filtration to be certain no bacteria by-products can go through and to use freshly purified water, and not water that has been stored.

Q: Could you explain how water softening works?

ER: The purpose of water softening is to remove calcium and magnesium ions, which form scale, by ion exchange, replacing them with sodium. This is beneficial as you don’t have scale forming anymore, however water will not be that much purer as it still contains a lot of ions.

Find out more on this topic from Dr. Riche by watching the full webinar on demand>>

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