<P> Milli - Q is a trademark created by Millipore Corporation to describe' ultrapure' water of "Type 1", as defined by various authorities (e.g. ISO 3696), as well as their devices for producing such water . The purification processes involve successive steps of filtration and deionization to achieve a purity expediently characterised in terms of resistivity (typically 18.2 MΩ cm at 25 ° C). </P> <P> Milli - Q water purifiers use resin filters and deionization to purify the water . The system monitors the ion concentration by measuring the electrical resistivity of the water . Higher resistivity means fewer charge - carrying ions . Most Milli - Q systems dispense the water through a 0.22 μm membrane filter . </P> <P> Milli - Q purifiers are capable of producing water pure enough to get reproducibility and accuracies within parts per million when using ion mass spectrometers in analytical geochemistry . Other users of this system include molecular biology and atmospheric science . </P>

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