Organic substances contained in the water

Dissolved organic carbon (DOC) or total organic carbon (TOC)  

Acidification can also be effected sampling, and before deep-freezing. 

Phenols Preservation by adding 5 ml 35 % hydrochloric acid and 1 g copper sulphate per litre of water. Transport in refrigerated condition. 

Chlorinated hydrocarbons Transport in refrigerated condition in specially cleansed, gas-tight sealed glass bottles. 

Polycyclic aromatic hydrocarbons Transport specially cleansed glass bottles. 

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In order to determine TOC/DOC, the organic substances contained in the water sample are oxidized with UV rays or by wet-chemical means, or burnt... 

In the analysis of air for pollutants, for example, some of the compounds may be present in too low concentrations to be analysed straightaway. In such a case, it becomes necessary to raise concentrations of those compounds to the level where the required analysis becomes practical. Situation of a different type may arise in certain other analyses. Thus in the analysis of river water for metals that are present in trace concentrations, erroneous results are obtained because of the interference caused in the analysis by organic compounds contained in the sample. In a situation like this interfering substances have to be removed before the analysis can be performed. Also, many analyses now carried out daily in the clinical and forensic laboratories all over the world involve separation as an integral part of the procedure. 

Generally, soaps are readily biodegradable up to a concentration of 1000 mg/1. Soaps with shorter alkyl chains are faster degraded. In addition, they do not inhibit the biodegradation of other organic substance contained in domestic waste-water. Soaps are readily biodegradable under anaerobic conditions. Non-soluble calcium soaps show the same behaviour if the particle size is small enough. 

Solid substances and organic substances contained in water (such as mineral oils, detergents and humic acids) reduce the service life of the separation column and should therefore be separated off before the analysis. 

The amount of potassium permanganate consumed in the chemical oxidation of organic substances contained in water, this amount being quoted in "mg/1 KMnOzjL" as well as in "mg/1" as the corresponding oxygen equivalent. 

Oxidizability and chemical oxygen demand, like biological oxygen demand, do not provide an exact figure for the total amount of organic substances in water. However, they are used as characteristic values, whose usefulness has been proved in practice, for the evaluation of the total organic substances contained in a sample of water. 

The industrial stream to be treated, the feed, will not be an analytical grade solute dissolved in water, but often contains several known and unknown substances, both organic and inorganic. To be able to make an initial selection of possible solvents, it is necessary to make a classification of the individual substances present in the feed and of the groups of substances with chemical similarities, for instance, paraffins, aromatics, salts, or others. The following questions have to be answered ... 

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