Determination of Dechlorane compounds in aqueous samples using ultrasound-assisted dispersive liquid-liquid microextraction and gas chromatography-electron-capture negative ion-mass spectrometry

A simple and solvent-minimized procedure for the rapid determination of chlorinated flame retardants, Dechlorane compounds: syn- and anti-Dechlorane Plus (syn- and anti-DP), Dechlorane (Dec) 602, Dec 603 and Dec 604, in aqueous samples is described. The method involves the use of ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) prior to their determination by gas chromatography-electron-capture negative ion-mass spectrometry (GC-ECNI-MS) operating in the selected-ion-monitoring (SIM) mode. The parameters affecting the extraction efficiency of analytes from water samples were systematically investigated. The best extraction conditions involved the rapid injection of a mixture of 1.0 mL of acetonitrile (as a dispersant) and 60 mu L of carbon tetrachloride (as an extractant) into 10 mL of water sample containing 0.5 g of sodium chloride in a conical bottom glass tube. After ultrasonication for 1.0 min and centrifugation at 5000 rpm (5 min), the volume of the sedimented phase was adjusted to 20 mu L and the analytes were then determined by GC-ECNI-MS analysis. The limits of quantitation (LOQs) ranged from 0.08 to 0.3 ng L-1. The precision for these analytes, as indicated by relative standard deviations (RSDs), was less than 9% for both intra- and inter-day analyses. Accuracy, expressed as the mean extraction recovery, was between 75 and 92%. A preliminary result revealed that trace levels of Dechlorane compounds were detected in various water samples with total concentrations ranging from 0.6 to 0.9 ng L-1.