Green extraction and IC analysis of trace impurities in TATB through deep eutectic solvents

1,3,5-trinamino-2,4,6-trinitrobenzene (TATB) as an important insensitive high explosive has excellent safety performance due to strong hydrogen bonds. Ionic impurities including sulfate ions (SO₄^2-), nitrate ions (NO₃^-) and chloride ions (Cl^-) formed during the preparation of TATB have negative effects on TATB-based explosives. However, strong hydrogen bonds result in extremely low solubility of TATB in traditional solvents, which poses a huge obstacle to extract and detect the impurities in TATB for quality control. In this study, a green extraction method based deep eutectic solvent (CS-1) was firstly developed for the extraction of trace impurities in TATB. After the dissolution of TATB in CS-1 solvent, water (H₂O) was used as a green hydrogen bond donor to differentiate the solubility between TATB and its ionic impurities. Through the above strategy, TATB was efficiently removed and the impurities were selectively extracted in CS-1 solvent. Meanwhile, Ca(OH)₂ as a precipitant was investigated to eliminate the background interference of F^- ions in CS-1 solvent through forming the precipitate of CaF₂. Further, the extraction of deep eutectic solvent was combined with ion chromatography (IC) to develop an analytical method for trace impurities. This method displays excellent separation, high sensitivity and good repeatability toward four ionic impurities (Cl^-, NO₂^-, NO₃^- and SO₄^2-). Compared to traditional methods (DMSO method and oxygen flask combustion method) with low extraction ability, indirect detection and dangerous pretreatment, this method provides direct, convenient and accurate detection of anionic impurities in TATB, and displays better application for quality control of TATB.