What Is Ultrapure Water?

by Kate Onissiphorou

Ultrapure water, or UPW, is a high-grade water that’s free from impurities like microbes, minerals, and dissolved gases. It only contains H2O molecules and has a purity level of, or very near, 100%.

Water must undergo a stringent process for it to become ultrapure and free of any dissolved or suspended organic and inorganic compounds. Ultrapure or highly purified water (HPW) is a term used to show that water has undergone treatment to achieve the highest level of purity. 

UPW is primarily used in the semiconductor and pharmaceutical industries for analytical and manufacturing applications. 

The production of ultrapure water

Ultrapure water is typically produced through the three-stage process summarised below. It requires different levels of purification based on standardised specifications.

  1. Pre-treatment stage
    In this stage of a water purification chain, potable water is purified by removing ions through an electrodeionization (EDI) system./li>
  2. Primary stage for further purification
    The water then passes through a combined system of reverse osmosis and ultraviolet (UV) light exposure. During reverse osmosis, water passes through a semipermeable membrane that removes large molecules and particles. Meanwhile, the UV treatment involves two wavelengths of UV light, which can kill bacteria and other microbes.
  3. Polishing stage
    After the second stage of purification, the deionised water is stored in an inert polythene tank. This protects it from contaminants and prevents biofilm from forming. The deionised water then passes through a UV lamp and a polishing cartridge, which removes trace amounts of ions and organic materials. While there’s no perfect system that can guarantee the absolute removal of contaminants, this process makes UPW virtually devoid of contaminants in terms of parts per trillion. In some processing plants, nanotechnology is also used to make UPW.

An ultrapure water system

You can either buy ultrapure water from an online supplier or purchase your own compact ultrapure water system for your laboratory. ReAgent's 25l packsize of ultrapure water

However, you’d need to invest considerably more money if you intend to supply ultrapure water for industrial use. If you do choose this option, the multi-staged system can be designed to suit your specifications and target output.

What is the conductivity of ultrapure water?

By definition, ultrapure water contains only H2O molecules and hydrogen and hydroxyl (H+ and OH) ions in equilibrium. It has a conductivity of 0.055 microsiemens per centimetre (μS/cm) at a temperature of 25oC. 3D illustration of a water molecule

This makes ultrapure water almost like an insulator compared to copper, which has a conductivity of 58.14 x 106 siemens per metre.

UPW has a resistivity of 18.2 mega ohm. This, combined with the lack of minerals, makes it dangerous to consume. If you were to drink a glass of UPW, it would strip important electrolytes from your cells. This could prove fatal as your cells and neural activities are dependent on the right balance of electrolytes to function properly.

Is ultrapure water the same as distilled?

Ultrapure water is not the same as distilled water. The distillation process involves boiling water into vapour form and then condensing it back into water in a separate container. While this kills bacteria and removes some of the impurities, the water that’s produced is not ultrapure. The distillation process

In the illustration above, salt or any substance that’s been dissolved in the water is removed by evaporating the water from the florence flask. The vapour then passes through the condenser tube, which consists of an interior and exterior tube.

The vapour enters the typically coiled interior tube while a water coolant passes continuously through the exterior tube. This allows the vapour to cool down and condense in the receiving Erlenmeyer flask. A similar but large-scale process is used in petroleum refining.

Both ultrapure water and distilled water have roles in analytical chemistry and clinical-medical diagnosis. Some of the methods that use UPW and distilled water include:

  • High Performance Liquid Chromatography (HPLC) Vials on a tray inside the injection section of a High Performance Liquid Chromatography (HPLC) machine
  • Liquid Chromatography – Mass Spectrometry (LC-MS)
  • Gas Chromatography – Mass Spectrometry (GC-MS)
  • Graphite Furnace Atomic Absorption Spectroscopy (GFAAS)
  • Polymerase chain reaction (PCR)
  • Immunochemistry (ICC)
  • Mammalian cell culture
  • Clinical analysers
  • Trace analysis

Business customers can visit our online shop to buy ultrapure water from one of the UK’s leading chemical suppliers. With a range of pack sizes available, you’re sure to find the right product for your needs.

Original post: What Is Ultrapure Water?. No Republication or Redistribution allowed without written consent. Contact ReAgent Chemicals for more information.

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