| Abstract
| - Enormous amounts of sewage sludge are worldwidegenerated and released into the environment. Analysis ofthe most common and/or toxic chemicals in sludgeshould be mandatory before deciding its destination.Surfactants and some of their breakdown products areinvariably the most common organic contaminants in domesticsewage sludge. For determining these compounds, wehave developed a method based on extraction with subcriticalwater followed by liquid chromatography−mass spectrometry. On extracting surfactants and their metabolitesfrom 50 mg of sludge, the efficiency of the water extractiondevice was evaluated in terms of pH of the extractant,temperature, and time of the static extraction. The bestextraction conditions were obtained by using carbonatebuffer (pH 9.4) at 200 °C as extractant, 10 min of static extractionat the pressure of 100 bar followed by 17 min of dynamicextraction. Analyte collection was performed by insertinga solid-phase extraction cartridge downstream the extractioncell. Compared to 16-h Soxhlet extraction with methanol,this procedure was remarkably more efficient in extractinganionic surfactants and acidic metabolites of nonylphenolethoxylates (NPECs). A short survey was conducted toestimate concentration changes of target compounds after14-d sludge anaerobic digestion. Results showed that 54−74% of both neutral and weakly acidic ethoxylate specieswere removed after residence of the sludge in the digester.On the contrary, little, if any, removal of anionic surfactantswas observed after the digestion treatment. As expected,the level of nonylphenol increased under anaerobic conditions.
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