Qp2010 plus gas chromatograph mass spectrometer

GC/MS-analysis was performed on a QP2010 Plus Gas Chromatograph/Mass Spectrometer (Shimadzu, Duisburg, Germany) equipped with a fused silica capillary column (Equity TM-5; 30 m × 0.25 mm, 0.25 μm film thickness; SUPELCO, Bellafonte, PA) and a quadrupol detector working with electron impact ionization at 70 eV. One μl of the solution containing TBDMS amino acids was injected in 1:10 split mode at an interface temperature of 260°C and a helium inlet pressure of 70 kPa. The column was developed at 150°C for 3 min and then with a temperature gradient of 10°C min⁻¹ to a final temperature of 260°C that was held for 3 min. With a sampling rate of 0.5 s, selected ion monitoring was used. Data were collected using the GC/MS solution software (Shimadzu). All samples were measured three times. ¹³C-Excess and isotopologue abundances were calculated as described before (Lee et al., 1991 (link); Eylert et al., 2008 (link)) including: (i) determination of the TBDMS-derivate spectrum of unlabeled amino acids, (ii) determination of mass isotopologue distributions of labeled TBDMS-amino acids, and (iii) correction of ¹³C-incorporation concerning the heavy isotope contributions due to the natural abundances in the TBDMS-moiety and the amino acid atoms.

The Shimadzu TD-20 thermal desorption system was used for the low-temperature, slow-heat-rate thermal decomposition of lignin. The GC/MS analysis of the lignin decomposition products was performed using a Shimadzu QP-2010 Plus gas chromatograph–mass spectrometer (Kyoto, Japan). The thermal desorption parameters were as follows: helium was used as the carrier gas flowing at 30 mLmin⁻¹, and the volatile and semi-volatile products of lignin decomposition were trapped on the Tenax TA sorbent (Sigma Aldrich, Steinheim, Germany) in a cooling trap at −10 °C. The lignin sample weight was varied from 0.6 mg to 8.1 mg. Thermal decomposition was carried out in the range of 150–400 °C in 50 °C increments. The duration of the process was varied from 5 to 60 min.
The GC separation parameters were constant during all experiments. The GC was equipped with a HP-5MS fused-silica capillary column (30 m × 0.25 mm i.d., 0.25 µm f.t.). The gas flow was 1.0 mLmin⁻¹ with the split ratio of 30:1. The GC oven temperature program began at 40 °C and then increased at a heating rate of 3 °C/min to 200 °C followed by a post-run program at 320 °C for 3 min. The MS was operated in EI mode (70 eV) at 230 °C. The components were identified using the NIST and Wiley libraries.

Samples R1a, R1b and R2a were subjected to a transesterification procedure in accordance with a procedure previously reported in the literature [13 (link)]. In brief, about 100.0 mg of the samples was dissolved in 0.2 mL of MeOH. Then, MeONa was added (24.1 mg, 0.9 mmol) and the mixture was stirred for 3 h at room temperature. After this time, the crude compound was diluted with AcOEt (25 mL) and washed with water (3 × 10 mL). The combined organic layers were dried over Na₂SO₄, filtered, concentrated under a vacuum and then were subjected to GC/MS analyses. GC/MS analyses were performed with QP-2010-Plus Gas Chromatograph Mass Spectrometer (Shimadzu Italia S. r. l., Milan, Italy) using a “silica fusa” Rix^®-5ms column (Restel^®) (30 m, 0.25 mm ID, 0.25 µm) (Restel S.r.l., Cernusco Sul Naviglio, Milan, Italy), with a flow of 1.0 mL/min. The temperature varied from 100 °C to 250 °C in 10′.