The application of semipermeable membrane devices to the detection and monitoring of 4-nonylphenol in aquatic systems

• Main Author: Suffredine, Lori Jean
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/10026

The surfactant 4-nonylphenol (4-NP) is a component of many industrial and domestic cleaning products, and has been demonstrated to elicit estrogenic effects in organisms. 4-NP enters waterways through surface runoff and as a microbial breakdown product in secondary sewage treatment plant (STP) effluents. This research project examined the feasibility of applying a passive concentrator called the semipermeable membrane device (SPMD) to the collection and concentration of 4-NP from water. A derivatization method was developed to improve peak separation by GC-FID and provide better integration of peaks. Laboratory tests with SPMDs indicated they could be used successfully to sequester waterborne 4-NP. An established acetylation method for chlorinated phenolics was then applied to the 4-NP present in SPMD dialysates. The results indicated that only a small portion of the 4-NP was undergoing reaction. A procedure specific to 4-NP in STP effluents and sludges was attempted next, but the results confirmed that only partial derivatization was occurring. An experiment designed to track the progress of 4-NP through the acetylation reaction determined that the majority of the target analyte was remaining in the hexane-based SPMD dialysate, where it was unavailable for reaction with acetic anhydride in the water based potassium carbonate solution. Subsequent attempts at derivatization continued to yield only partial acetylation of the 4-NP. Solvent exchange procedures, aimed at transferring the target analyte from hexane to a water-miscible solvent, produced no improvement. A method which incorporated a methanol solvent exchange with substantially reduced solvent volumes appeared promising with laboratory samples, but failed to yield satisfactory results when applied to SPMD dialysates. Finally, successful acetylation of 4-NP in hexane was achieved using a method designed to acetylate analytes in an organic solvent. A replicate test conducted using the new acetylation method provided unexpected insights into the reasons for the difficulties encountered with achieving complete derivatization. The replicate test results suggested that the length of time taken to perform the acetylation procedure was critical to derivatization success. Subsequent experiments confirmed that although the initial reaction favored formation of the acetylated product, if left in contact with base, an equilibrium was established between acetylated and nonacetylated 4-NP. Preliminary testing with secondary sewage treatment plant effluent confirmed that the conventional SPMD system successfully sequestered waterborne 4-NP. Resulting dialysates had estimated NP concentrations of 4 to 5 mg/L. When performed under controlled conditions, the derivatization procedure developed in this research project quantitatively acetylated NP present in hexane-based SPMD dialysates. Final cleanup of acetylated dialysates using 5% deactivated silica gel isolated NP into the second eluting fraction, but failed to separate it from a significant number of background interferences. Further field testing and additional cleanup methods are needed to complete the techniques developed in this project and confirm their application under actual field conditions.