Can anyone explain the differences between Milli-Q and DD water in terms of purity, conductivity, ions, Chemical differences etc. And what makes these differences ?
Distilled water is made by continuous (as opposed to fractional) distillation of a water source. Many times it is distilled a second and even a third time. The problem with it is that since it is continuous distillation, some contaminants will come across with the water.
Milli-Q water is made by passing the source water through mixed bed ion exchange and organics (activated charcoal) cartridges. The source does not have to be distilled or deionized (reverse osmosis) but it will help extending the cartridge life. Finally the water is passed through a filter (0.22 um) which should pull out any intact organisms. Sometimes there is a UV lamp attached, as well.
The purity of the water is monitored by measuring the conductivity. The higher resistance, the fewer ions in the water. A value greater than 18.2 MΩ cm-1 (@ 25 °C) is desirable for Milli-Q. Double Distilled Water has a value between 15 and 18 MΩ cm-1 (@ 25 °C).
Distilled water is made by continuous (as opposed to fractional) distillation of a water source. Many times it is distilled a second and even a third time. The problem with it is that since it is continuous distillation, some contaminants will come across with the water.
Milli-Q water is made by passing the source water through mixed bed ion exchange and organics (activated charcoal) cartridges. The source does not have to be distilled or deionized (reverse osmosis) but it will help extending the cartridge life. Finally the water is passed through a filter (0.22 um) which should pull out any intact organisms. Sometimes there is a UV lamp attached, as well.
The purity of the water is monitored by measuring the conductivity. The higher resistance, the fewer ions in the water. A value greater than 18.2 MΩ cm-1 (@ 25 °C) is desirable for Milli-Q. Double Distilled Water has a value between 15 and 18 MΩ cm-1 (@ 25 °C).
Thank you Sir.
Can you please elaborate on the " Since it is continuous distillation, some contaminants will come across with the water". What are the chances to get the contamination when we are collecting the condensed water directly into a clean container?
For double distilled water you should consider that as soon as you use either contaminated or inappropriate vessels, you will get contaminations. So as soon as you use a plastic container, you will have some kinds of plasticisers in your water. We then use only glas ware that was rinsed at least 3 times with tripple distilled water.
Milli-Q water is produced by reversed osmosis that normally can even remove bigger ions.
Distilled water is purified via distillation i.e boiling and then condensation of the water. So, a double distilled water has gone through the process of distillation twice. While mQ water has been deionised/demineralised and gone through filter to remove all life forms or treated with UV-irradiation. Overall, distilled water is usually less purer than mQ water and can not be used instead of mQ water, however mQ water can be used instead of distilled water.
These three terms are shorthand for deionized water (diH2O), distilled water (dH2O), and double-distilled water (ddH2O). They are the most common types of purified water that are used in laboratories. Although similar, there are slight differences in preparation and usage between them.
diH2O water, as the name suggests, has had the charged molecules (ions) in the solution removed by filtration through a bed of ion exchange resins. These small plastic beads with a positive or negative charge, attract the undesirable molecules and replace them with either a H+ ion or an OH- ion, which combine to form pure water. The process does not remove anything without a charge, including viruses and bacteria. diH2O, due to the lack of ions, has very low electrical conductivity. The process is relatively inexpensive, as there is minimal hands-on time, the plastic beads can be ‘recharged’ multiple times with strong acids and bases, and the tanks require infrequent cleaning.
dH2O is produced by heating water to boiling and gathering the resulting water vapor in a clean container. Any contaminants and undesirable molecules are left behind in the original container as precipitated solids. The boiling process sterilizes the water, meaning viruses and bacteria are killed during the procedure. It is the oldest method of purification and is still in common usage. However, some dissolved impurities can have a lower boiling temperature than water and may be gathered in the secondary container along with the purified water vapor. The distillation process requires more hands-on time and cleaning of the solid contaminants out of the distillation chamber after every procedure, which can be challenging or even hazardous depending on the initial cleanliness of the water.
ddH2O is traditionally considered the ‘most pure’ type of laboratory-grade water. This is simply the secondary distillation of the water vapor of a prior distillation procedure. This process is the most time-consuming out of the three and does not necessarily avoid the risks of potential impurities being carried along with the vapor.
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