GC column effluent splitter for problematic solvents introduced in large volumes: Determination of di-(2-ethylhexyl) phthalate in triglyceride matrices as an application

Introduction of solutions of up to several milliliters by on-column injection of large volumes or by coupled HPLC-GC may cause problems with GC detectors (FID, AFID, MS). For instance, dichloromethane forms large amounts of hydrochloric acid and carbon black in FIDs. A column effluent splitter was developed for keeping the major portion of the solvent vapors away from the detector; approximately 99% of the vapor is vented while the remaining 1% of vapor is used for detecting the widths of the solvent peaks. During analysis, the split ratio is reversed by a strong increase of the resistance to the gas flow through the split exit line. The system was used for the determination of di-(2-ethylhexyl)-phthalate (DEHP) in triglyceride matrices of various foods. Direct determination by HPLC is not sufficiently sensitive, whereas direct analysis by GC is hindered by the triglycerides. Solutions of fats or oils were pre-separated on a silica column using dichloro-methanelcyclohexane 1:l with addition of 0.05 % acetonitrile as eluent. The HPLC fraction containing the DEHP was transferred to GC through a loop-type interface using concurrent solvent evaporation. Detection limits were around 0.1 ppm.