Applications of On-Line Precolumn Technology to Water Quality Control

Abstract

On-line precolumn technology is applied to the analysis of organics in water samples with relatively low organic contamination (e.g. drinking water or certain surface waters). Two precolumns in series, one packed with a bonded C₁₈ silica and the other with the polymer-based PRP-1 are used for the organic concentration and it is shown that a range of organics of medium to low polarity can thus be determined from sample volumes up to 500ml. With such a volume and depending on the breakthrough volume values measured with the two adsorbents, very apolar compounds are extracted by the C₁₈ precolumn alone whereas the moderately and relatively polar compounds are recovered from both C₁₈ and PRP-1 precolumns. Hence, the ratio of amounts preconcentrated on C₁₈ and on PRP-1 precolumns and the variations of this ratio with the sample volume are useful information for the identification of solutes. In complex mixtures, simple identification of a solute by its retention time during the analytical gradient is not sufficient and needs confirmation. In addition, three detection modes (UV absorbance, fluorescence and electrochemistry) are carried out after the C₁₈ analytical column and comparisons of the chromatograms from each detector can also confirm a possible identification. Applications to the research of moderately polar pollutants at the ppb level in drinking water and relatively polar herbicides in river water are presented.