Determination of trace level nitroaromatic explosives in wastewater by stir bar sorptive extraction coupled to gas chromatography

A novel poly (phthalazine ether sulfone ketone, PPESK) stir bar was prepared. The method for analyzing trace level nitroaromatic explosives in aqueous samples by stir bar sorptive extraction coupled to GC through thermal desorption was developed. The stir bar can be placed into thermal desorption unit after extraction at 250°C, so the sensitivity of the method can be enhanced because the analyses are completely transferred into GC column. The PPESK stir bar was proved to show one order of magnitude higher extraction capacity than the corresponding PPESK fiber and two orders of magnitude higher extraction efficiency than PDMS stir bar. The limits of detection (LODs) were in the range of 0.008-0.022μg/L. The repeatability of the method (RSD) was from 6.9% to 15.9%, and the linear ranges were 0.06-10.0μg/L with correlation coefficients of 0.9962-0.9998 except for TNT. By using the optimized extraction method, the wastewater samples produced in explosive production process were analyzed. The recoveries were from 88% to 100% for low concentration sample and from 61% to 88% for diluted high concentration sample. The RSDs of the repeatability of real sample application were lower than 11%.