A high-sample-throughput LC-GC method for mineral oil determination.

The present investigation deals with a method improvement to increase data throughput and reduce solvent consumption for both saturated and aromatic mineral oil hydrocarbon determination using a coupled liquid-gas chromatographic system. The starting point of this work was the method proposed by Biedermann, Fiselier, and Grob in 2009. A total time and solvent reduction of 34 and 23%, respectively, was obtained by speeding up the GC run and reducing the LC-reconditioning step. The band broadening, occurring in the LC column during stop-flow in the multitransfer mode, was assessed by comparing the variances of the perylene peak width recorded in the stop-flow and normal modes. Band broadening directly proportional to the stop time of the LC pumps was observed, however, it did not affect the analytical reliability. A series of real samples (paperboards and pasta) was analyzed obtaining comparable results using both the reference and proposed method, both in the normal and multitransfer modes.