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Milli-Q water filtration station installed in an analytical laboratory

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.[1] 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).

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.

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.[2] Other users of this system include molecular biology[3] and atmospheric science.[4]


  1. ^ Millipore – "Lab Water Tutorial, Water Contaminants and Water Monitoring"., accessed 2011-08-15
  2. ^ Yokoyama, Tetsuya; Makishima, Akio; Nakamura, Eizo (May 1999). "Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion". Chemical Geology. 157 (3–4): 175–187. doi:10.1016/S0009-2541(98)00206-X.
  3. ^ Muyzer, G.; de Waal, E C; Uitterlinden, A G (March 1993). "Profiling of complex microbial populations by denaturing gradient gel electrophoresis analysis of polymerase chain reaction-amplified genes coding for 16S rRNA". Applied and Environmental Microbiology. 59 (3): 695–700. PMC 202176. PMID 7683183.
  4. ^ Iverfeldt, Åke (April 1991). "Occurrence and turnover of atmospheric mercury over the nordic countries". Water, Air, & Soil Pollution. 56 (1): 251–265. doi:10.1007/BF00342275. ISSN 0049-6979.

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