What are likely Inorganic Impurities in Purified Water？
The most common inorganic impurities in purified water are residuals of the more commonions in feed water–sodium，calcium，iron，magnesium，chloride，sulphate，nitrate-andions weakly held on ion-exchange resin-silicates and borates.Bicarbonations will usually be present，aswell，well，well，produced by the dissolution of atmospheric CO2 in the product water on exposure to the environment。
Where do Inorganic Impurities come from？
Inorganicions are the most abundant of the impurities in the feed water used to supply water purification systems.These can carry over into the product purified water if they are not removed effectively.They can also be released fromion-exchange（IX）media within the purification system as the media IX paciared up。
What Applications do Inorganic Impurities affect？
Clearly，the presence of an impurity containing an element being determined will directly affect the accuracy of the results of elemental analysis.Other elements/compounds with overlapping spectral emissions or isotopic masses will also interfere withICP-OES and ICP-MSanalyses respectively.Higher concentrations of less soluble species can lead to degradation in spray characteristics for these techniques andAASand can degrade column and detector performance inHPLC.Impurityions can also affectionisation and form multi-atomions in ICP-MS and LC-MS
How are Inorganic Impurities Monitored？
The universal method of monitoring for ionic impurities in purified water is by measuring its electrical conductivity/resistivity.A resistivity of 18.2MΩ.cm is essential for ultrapure water containing the lowest levels of impurities but，due to the slight ionisation of water into hydrogen and hydroxylions，even with18.2MΩ.cm resistivity water，ppb levels of impurity ions may be present.The absence of trace ions canonly be assured by carrying out regular specific analyses，notably by ICP-MS，or using awater-purification system design which guarantees their removal，such as PureSure。
What Levels are Important？
The significance of impurities depends on the application.For ultrace analysis even very low（sub-ppb）levels of inorganicions can interfere significantly。Type1+water with a resistivity of 18.2MΩ.cm is essential。For less sensitive analyses high er impurity levels may be acceptable（Type2+or2with resistivity respectively of 10or1MΩ.cm）。
How does ELGA Remove Inorganic Impurities？
In ELGA systems typically over95%of ions are removed by high-rejection reverse osmosis membranes.Asubsequent storage reservoir is protected by CO2-removing vent-filtration.The remaining ions are removed by recirculation throughion-exchangecartridges.The purest，high-efficiency mixed bed resins are used throughout.The use ofPureSure-twin ion-exchange packs with resistivity monitoring both between the packs and in the product water–makes sure that the purification packs are exchanged before there is any chance of the second pack becoming less than100%effective。This guarantees that the minimum levels of impurity ions are achieved and maintained。The IX capacity is also maximised。
