Determination of Phenolics in the Aquatic Environment

Summary

Different methods based on chromatography are summarized for trace level determination of phenolics. Hydrophilic phenols can be isolated from water samples with steam distillation, continuous liquid extraction, or on ion exchange resins, or extracted as lipophilic ion pairs. Procedures, based on in situ conversion of hydrophilic phenols into hydrophobic derivatives in combination with an extraction step, have been found to be useful. In addition, hydrophobic phenols are easily concentrated from water samples by batch liquid/liquid extraction or reversed phase adsorption. Phenols, present in sediment and sewage sludge, can be extracted either as undissociated phenols with organic solvents or as phenolates with alkaline aqueous solutions. The isolation of phenols from organism tissues are usually carried out with a mixture of semipolar and unpolar organic solvents. Clean-up procedures, involving batch partitioning at different pH values, are usually sufficient. Extracts with a high content of organic material require a more thorough and selective clean-up. For the quantification of phenolic compounds, capillary gas chromatography is a commonly used powerful tool. Conversion of phenols into unpolar derivatives are often applied before the gas chromatographic determination. For many non-halogenated phenols, the sensitivity can be drastically increased after the conversion into halogenated derivatives when using the electron capture detector. Other chromatographic methods have been less used for trace levels determination of phenols, mainly due to less sensitivity and selectivity compared to gas chromatography. However, liquid chromatography in combination with electrochemical detection have been demonstrated to be a promising technique.