Chemistry of water -Part 12-

Water analysis:

To reach correct analytical results, and obtain accurate values, we must be very careful during the sampling process because it is a very important and essential process, and any change in the physical or chemical properties of water when sampling can make our results erroneous.
Before sampling, the purity of the bottles to be used for this purpose must be ascertained. They are also cleaned with a sulfuric acid solution after being cleaned with a concentrated potassium permanganate solution. After that, they are washed several times with distilled water, and upon obtaining the sample, these bottles are washed three times with the water to be examined, and this point is very necessary. Finally, it must be ensured that there are no air bubbles inside the vial in which the sample is located, and then close it tightly.

• Bottle material:

• The sampling bottle's material should not react with the water being tested; hence its composition is crucial. The nature of the elements to be dosed determines which product should be used since there is no perfect material.

• Plastic bottles are widely used to take water samples, despite their adsorption of organic compounds and metal compounds, and plastic is a material that allows some dissolved gases to pass through. Despite that, when taking samples for the analysis of radioactive elements, polyethylene is frequently advised.

• For the collection and storage of water with a high gas content, glass is preferred. Also, for the dosage of the major ions, glass and Pyrex can as well be used. Nevertheless, trace elements like silica from glass and boron from Pyrex can dissolve in water.
  
  Pyrex measuring cup

• One benefit of using polyvinyl sampling bags is that they are only ever used once. However, if these bags are exposed to light for an extended period of time, they produce chlorine.

• Finally, mineral bottles are not recommended for preserving water samples.

References:

• [General and inorganic chemistry book- M. Shkhashirou- H. Birqdad- Y. Qodsi- University publications. Algeria]

• [AQUAPROX- Livre: Traitement des eaux de refroidissement. Imprimé en France par EMD S.A.S- 53110 Lassay-les-Chateaux. N° d'imprimeur: 15566- Dépot légal: juin 2006. N° 842- Cyclus print 90°]

• [GÉOCHIMIE DES EAUX CONTINENTALES- Nathalie Gassama. ISBN 9782340-047402 ©Ellipses Édition Marketing S.A., 2021. 8/10 rue la Quintinie 75015 Paris]

• [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]