Analysis of Organic Matter in Water of Low TO C (Total Organic Carbon) Content by Chromatographic Techniques

Abstract

The problems encountered when analyzing organic pollutants in drinking water stem from the large number of unknown compounds at very low concentration.

The concentration of the organics is carried out on n-alkyl silica, after a rigorous cleaning, or by liquid-liquid extraction. The complexity of these extracts renders a direct analysis by gas chromatography coupled with mass spectrometry impossible; hence, a pre-separation step is required.

Reversed and normal phase chromatography have been investigated with these extracts. The former leads to informative fingerprints but subsequent identification is difficult.

Normal phase liquid chromatography is more suitable and a separation by chemical classes of increasing polarity is applied to water extracts. The eluent is fractionated, each fraction is then gently evaporated and subsequently analyzed by GC. Identification is then possible by coupling with mass spectrometry.

These procedures are used to follow the change in organic matter during the two last steps of the drinking water treatment: ozonation and filtration on active charcoal. Another application is the analysis of humic extracts.