DETERMINATION OF NONYLPHENOL POLYETHOXYLATES AND THEIR CARBOXYLIC-ACID METABOLITES IN SEWAGE-TREATMENT PLANT SLUDGE BY SUPERCRITICAL CARBON-DIOXIDE EXTRACTION

A supercritical fluid extraction (SFE) method was developed for the ex traction of nonylphenol polyethoxylate (NPnEO) non-ionic surfactants f rom dried sewage treatment plant sludge. Extraction was carried out at 80 degrees C and 5100 p.s.i. with carbon dioxide using water as a mod ifier. The ethoxylates were analyzed by gradient high-performance liqu id chromatography (HPLC) with an APS Hypersil column and a fluorescenc e detector (230 nm excitation and 300 nm emission). This SFE method wa s more time-efficient and it produced higher recovery than Ihe traditi onal Soxhlet extraction and steam distillation techniques used for NPn EO in sewage sludge. The same procedure was also applicable to the coe xtraction of nonylphenoxyacetic (NP1EC) and nonylphenoxyethoxyacetic ( NP2EC) acids, which were metabolites of the ethoxylates under aerobic conditions. Following an off-line methylation, analysis of the acids w as achieved by CC-MS in selected ion monitoring mode. In a brief surve y of sludge samples collected from nine sewage treatment plants across Canada, very high levels of nonylphenol mono-(NP1EO, 28-304 mu g/g) a nd di-ethoxylates (NP2EO, 4-118 mu g/g) were found. In contrast, the t otal polyethoxylate concentration (from 3 to 17 ethoxy units) vias gen erally less than 50% of the sum of NP1EO and NP2EO in the same sample. NP1EC and NP2EC were found in only three of the seven samples tested, with concentrations ranging from 4 to 38 mu g/g. (C) 1997 Elsevier Sc ience B.V.