What is the most common reagent you find in all types of laboratories?

You got the answer right! Water.

Water can be found in every type of laboratory, be it medical, pharmaceutical, chemistry, and microbiological. These laboratories need different levels of water purity for the different levels of sensitivity of their analysis and experiments.

Water Purification Process

The whole water purification process is long and involves many steps. The most common purification processes used to decontaminate water of its impurities are the following:

1. Distillation – Water is heated and the condensed vapor is trapped and collected. However, there are still impurities found in distilled water such as silica, ammonia, and other organic compounds. Storage of distilled water is also important to keep it from contamination.

2. Reverse osmosis – Osmosis is the movement of water from higher concentration to lower concentration as caused by the osmotic pressure. In reverse osmosis, water is passed through a filter using a higher pressure than the osmotic pressure to separate the impurities.

3. Ion exchange – This process removes various metals particularly heavy metals present in water however ion exchange will retain microorganisms.

4. Activated carbon – Also known as adsorption media and works effectively removing chlorine in water by "a catalytic mechanism and dissolved organics by adsorption".

5. Ultraviolet disinfection – It uses ultraviolet light which is a powerful sterilizing agent to kill bacteria and other microorganisms.

6. Filtration – Filtration of water using different pore sizes ensure that other impurities which are of various sizes are also trapped and the water is uncontaminated.

These are just some of the water purification methods used and their progressions differ from system to system as well.

There are also different types of water according to their use in the laboratory. This is dependent on the purification process and more importantly on the quality of water that results after the long and careful methods of purification.

Types of Laboratory-grade Water

According to the Genetic Engineering and Biotechnology News, there are three main types of laboratory-grade water:

• Type 1. This is the ultrapure water which has very low levels of ions (resistivity 18.2), organic molecules, bacteria, and particles. It is commonly manufactured by combining purification technologies such as activated carbon, reverse osmosis, ion-exchange resins, ultraviolet photo-oxidation, filtration processes, and electrodeionization. It is used for analytical methods such as high-pressure liquid chromatography (HPLC), gas chromatography, and inductively-coupled plasma mass spectrometry (ICP-MS). However, it is very important for reagent as well as equipment preparation for molecular biology and cell culture.

• Type 2. This send type of water is known as pure water and may contain a minute amount of ions (resistivity above 5), organic molecules (up to 50 ppb of total organic carbon), and possibly a small amount of microorganisms. It is the type which is commonly used in preparing the usual reagents and buffers inside the laboratory.

• Type 3. Usually, generated by reverse-osmosis or ion-exchange this type of water is used for less sensitive applications such as qualitative analyses, glassware rinsing, and water baths.

Contrary to popular belief, tap water cannot be used for just about anything in the lab because of the impurities found in it. Organic and inorganic compounds, microorganisms, particles, and dissolved gases are present in tap water and these impurities can affect the results of the experiments.

There are different types of water corresponding to the different needs of a laboratory. Deionized water is good for most laboratory needs but there are certain analyses and experiments which are more sensitive and therefore, needs higher grade of lab water.