Suitability of Laboratory Water Grades for different Laboratory Applications

A laboratory uses large quantities of water for numerous activities. Water grades for laboratory use discussed the different grades of water which are commonly used in the laboratory. Further, the parameters used to define purity have been discussed in the article Techniques for establishing purity of laboratory use water. The present article explores the typical applications for different types of water defined by ASTM.

Untreated Tap Water

Untreated tap water contains numerous impurities and is not covered under the ASTM classification. It is put to use for primary washing and cleaning of laboratory glass and plastic ware along with detergents or other agents. It also finds used for cooling in water distillation and for reflux cooling in laboratory extractions.. It is also used as a coolant in some instruments but it is recommended to use it only after demineralization and addition of anti- corrosive agents.

Distilled water

Distilled water has sufficient purity for most laboratory applications such as secondary washing and rinsing of laboratory ware, preparation of standard solutions and buffers and for use as blank in titrimetric and spectroscopic determinations.

Type – I water

Type- I water is also referred to as ultrapure grade water. It is used in analysis involving high sensitivity detection at low ppb or ppm levels where even trace level impurities can contribute to significant errors in analytical results. Some of the techniques for which Type- I water is recommended are:

• HPLC
• ICP – MS and ICP – AES
• GC – MS
• LC – MS – MS
• AAS using graphite furnace analysis
• Ion chromatography
• Preparation of ultrapure buffer solutions
• Total organic Carbon determinations
• Preparation of blanks and standards for above determinations
• Life science applications such as electrophoresis,endotoxin analysis in dialysis solutions and injectables and clinical studies

Type-II water

Type- II water is used for common laboratory applications and determinations carried out in ppm levels. Examples of such applications are:

• Preparation of pH standards and buffers
• As feedwater for preparation of Type- I water
• Electro chemical analysis using potentiometry, voltammetry, polarography and amperometry
• Flame atomic absorption spectroscopy
• Spectrophotometric analysis
• Media preparation for cell cultures
• Preparation of reagents and standards for analysis of water samples such as drinking water, lake and river waters.

Type- III water

Type- III water is suitable for common laboratory applications such as:

• Glassware washing
• Use in humidity chambers and environmental chambers
• Water baths
• Steam generation for use in autoclaves and sterilizers

Today water has become to be accepted as an indispensable resource in a laboratory but it’s use for different applications needs to be decided judiciously without compromising quality of results and at same time keeping in mind the cost involved in generation of high purity water grades.