Development of an In-Line System for the Analysis of 4,4′-DDT in Water

An in-line system for trace persistent organic pollutants (POPs) in water was developed by using a laboratory-made hollow fiber membrane (HFM) unit connected with a high-resolution gas chromatograph-mass spectrometer (HRGC-MS). The semivolatile organic compound, 4,4′-Dichlorodiphenyl trichloroethane (4,4′-DDT), was chosen as a representative of a persistent organic compound. The synthetic water contaminated with 4,4′-DDT was passed through the HFM unit, the extraction occurred by the analyte pervaporated and permeated, then stripped into HRGC-MS. Several factors were investigated for the high extraction efficiency. The best performance was obtained at sample and stripping gas flow rates of 6 and 9 mLmin⁻¹, respectively, and desorption temperature of 60°C. At this temperature, the diffusion rate was enhanced by 15 times over 25°C. A wide linear dynamic range was obtained, i.e., 0.10–1.0 mgL⁻¹, with a limit of detection (LOD) of 90 μgL⁻¹. The extraction efficiency of 4,4′-DDT in real water samples was in the range of 83–94%. Real water samples were analyzed and 0.6 μgL⁻¹ of 4,4′-DDT was found in unregistered bottled water and 7.0 μgL⁻¹ in tap water.

Key Words:

• 4,4′-DDT
• POPs
• Water
• Pervaporation
• In-line

ACKNOWLEDGEMENTS

This work was supported by the Royal Golden Jubilee Ph.D. Program under the Thailand Research Fund, the Postgraduate Education and Research Program in Chemistry (PERCH). The department of Chemistry, Faculty of Science and Graduate School, Prince of Songkla University are gratefully acknowledged.