Rtx 5ms

The pesticide analyses were performed using GC–MS QP 2010 plus (Shimadzu, Kyoto, Japan). Chromatographic separation was conducted with a fused silica capillary column Rtx-5MS, crossbonds 5% diphenyl and 95% dimethylpolysiloxane (30 m × 0.25 mm I.D., film thickness of 0.25 m, J & W Scientific, Folsom, CA, USA). Helium (purity ≥ 99.999%) was used as carrier gas at a constant flow of 1.0 mL/min. The temperature program was set initially at 100 °C for 2.5 min; ramp to 200 °C at a rate of 15 °C/min; 250 °C at 10 °C/min and finally to 300 °C at a rate of 6 °C/min being held for 2 min with total run time of 24 min. Injector temperature was maintained at 280 °C, and the injection volume was 1.0 µL in a splitless mode. Mass spectrometric parameters: electron impact ionization mode with an ionizing energy of 70 eV, injector temperature 250 °C, interface temperatures 230 °C, ion source temperature 200 °C. The mass spectrometer was operated in the selective ion monitoring (SIM) mode and the characteristic ions are given in Table 5. Full-scan data were acquired in the range of m/z 50–900 to obtain the fragmentation spectra of the analytes. The fragments of the ions monitored in SIM mode were selected based on good selectivity and high sensitivity.

The derivatized samples were analyzed using GC-MS (QP2020, Shimadzu, Kyoto, Japan). Rtx-5 MS with a fused silica capillary column (30 m × 0.25 mm ID, J&W Scientific, Folsom, CA, USA) was used for the separation of metabolites. The front inlet temperature was set to 230°C. The column temperature was isothermally held at 80°C for 2 min, increased by 15°C/min to 330°C, and isothermally held for 6 min. The transfer line and ion source temperatures were 250°C and 200°C, respectively. Ionization was achieved with a 70 eV electron beam. The flow rate of helium gas through the column was 1 mL/min. Twenty scans per second were recorded over the mass range of 85–500 m/z. Chromatograms and mass spectra were acquired using Shimadzu GC solution (Shimadzu, Kyoto, Japan).

The derivatization steps of extracted rice koji samples were as described by Lee et al. [11 (link)]. GC–TOF–MS analysis was conducted on an Agilent 7890A GC system (Santa Clara, CA, USA) with a Pegasus HT TOF-MS (Leco Corporation, St. Joseph, MI, USA). The carrier gas (helium) was used with an RTx-5MS (30 m length × 0.25 mm inner diameter, J&W Scientific, Folsom, CA, USA) at a constant flow rate of 1.5 mL/min. The temperatures of the injector and ion source were maintained at 250 and 230 °C, respectively. The oven temperature was maintained at 75 °C for 2 min and then increased to 300 °C at 15 °C/min, which was sustained for 3 min. Then, 1 μL of sample was injected with a mass scan range of m/z 50–800. All sample analyses were performed with three analytical replicates.

For GC-TOF-MS analysis, the redissolved samples were dried using a speed vacuum concentrator. The dried samples were derivatized as follows: (1) the oximation was performed by adding 50 µL of 20 mg/mL methoxyamine hydrochloride in pyridine to the dried samples and incubating at 30 °C for 90 min (2) the silylation was performed by mixing 50 µL of MSTFA to the mixture and incubating at 37 °C for 30 min. The derivatized samples were filtered using Millex GP 0.22 µm filters (Merck Millipore, Billerica, MA, USA).
GC-TOF-MS analysis was performed using an Agilent 7890A GC system (Santa Clara, CA, USA) equipped with Rtx-5MS (length 30 m, inner diameter 0.25 mm, J&W Scientific, Folsom, CA, USA) coupled with an Agilent 7693 autosampler and a Pegasus^® HT TOF-MS (LECO Corp., St. Joseph, MI, USA). The analysis parameters were adapted from a previous study [2 (link)]. Three biological replications were analyzed for each sample.

The gas chromatography time-of-flight mass spectrometry analysis was performed on an Agilent 7890A gas chromatograph system (Santa Clara, CA, USA) with a Pegasus HT TOF-MS (Leco Corp., St. Joseph, MI, USA). A Rtx-5MS (30 m length, 0.25 mm inner diameter, J&W Scientific, Folsom, CA, USA) was used to provide the carrier gas helium (He) at a constant flow rate of 1.5 mL/min. Each derivatized sample (1 µL) was injected into the GC-system under split mode (5:1). The injector and ion source temperatures were keeped at 250 °C and 230 °C, respectively. The oven temperature was set at 75 °C for 2 min and then increased to 300 °C at 15 °C/min, which was sustained for 3 min. The detector voltage was 1650 V, and mass scan range was 50–1000 m/z. Three analytical replications were conducted for each FSP sample.