Identification and Quantification of Related Impurities in 2-Chloroethyl Phenyl Sulfide for Industrial Use

Abstract

A combination of gas chromatography and mass spectrometry (GC-MS) was applied to separate and identify the relative substances in 2-chloroethyl phenyl sulfide (CEPS), an industrial intermediate formed in the synthesis of sulfinpyrazone. Six impurities, including 1,2-dichloroethane, thiophenol, diethylmalonate, tributylamine, diphenyl disulfide, and 1,2-dithiophenylethane, were verified. According to the production technique, the sources of all of these related impurities were analyzed, and some practical suggestions are put forward for their removal from or avoidance in CEPS. Furthermore, a technique involving high-performance liquid chromatography with UV detection (HPLC-UV) was developed to separate and determine thiophenol, the key impurity in CEPS. A linear standard curve was obtained for thiophenol in concentrations between 2.65 × 10−4 and 0.106 mg mL−1, and the detection limit of thiophenol was 1.32 × 10−4 mg mL−1. Excellent precision and accuracy were shown from the method validation, with relative standard deviations (RSDs) of less than 1.5% for both intra- and interday measurements, and recoveries between 95.4% and 97.0%. Based on the above merits, the proposed procedures of GC-MS and HPLC-UV can provide specific information on the impurities in CEPS, and therefore, these methods can be well applied to quality control in the industrial production of CEPS.