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.