Dispersive liquid-liquid microextraction combined with gas chromatography for extraction and determination of class 1 residual solvents in pharmaceuticals.

The present study reports a new method for analyzing class 1 residual solvents (RSs), 1,1-dichloroethene (1,1-DCE), 1,2-dichloroethane (1,2-DCE), 1,1,1-trichloroethane (1,1,1-TCE), carbon tetrachloride (CT), and benzene (Bz), in pharmaceutical products using dispersive liquid-liquid microextraction (DLLME) combined with gas chromatography-flame ionization detection (GC-FID). Unlike common DLLME methods, solvents of high boiling point were selected as dispersive and extraction solvents in order to prevent their chromatographic peaks from overlapping with those of analytes that have short retention times. Therefore N,N-dimethyl formamide (DMF) and 1,2-dibromoethane (1,2-DBE) were chosen as dispersive and extraction solvents, respectively. Analytical parameters of the proposed method were determined and good linearities and broad linear ranges (LRs) were obtained. Taking 500 mg samples, limit of detections for the tested pharmaceuticals were obtained as 0.11, 0.03, 0.05, 0.05, and 0.006 μg g(-1) for CT, 1,1-DCE, 1,2-DCE, 1,1,1-TCE, and Bz, respectively, which are considerably much lower than their permissible limits in pharmaceuticals.