Gas analyses were carried out using a Clarus 690 gas chromatograph (Perkin Elmer, USA), which was additionally equipped with an ARNEL 4019 system (Perkin Elmer, USA) and a mass spectrometer (MS, SQ8S, Perkin Elmer, USA). The gas sample was injected using a syringe into the gas injection system, which was connected to multiple separation columns and injectors (thermal conductivity detectors (TCD) and mass spectrometer (MS)).