Gc solutions software

The data analysis for the calibration curves, QCs and sample concentrations was carried out using Shimadzu GC solutions software. Microsoft Excel was used to carry out statistical analysis using averages, standard deviations (SDs), p-values and t-tests. A paired two-tailed t-test was employed to check the significance of differences between the mean values, with values ≤0.05 indicating a significant difference between means. Values were compared on an individual basis comparing the duplicate values of each sample (a total of four measurements and three degrees of freedom). The entire sample population data were analysed using SPSS software version 26. The population data were tested with the Kolmogorov–Smirnov test for normality. For sample subsets that were not normally distributed, a non-parametric test Wilcoxon matched-pair signed rank test was used to analyse the significance of difference, with a p-value of <0.05 indicating a significant difference. Coefficient of variance (CV) was used as a measure of variability, as a high CV typically equates to a high variation of duplicate values in relation to the SD and the mean. SD was calculated using the function:
$\sigma =\sqrt{\frac{\sum {\left(X-\mu \right)}^2}{n}}$ where $\sigma$ is the population SD, ∑ is the sum, μ is the population mean and n is the number of values within the data set. CV was calculated using:
$CV=\frac{SD}{\mathit{Mean}}\times 100\%$

The samples were ground into powder using liquid nitrogen with mortars and pestles. Then, 0.5 g of powder was transferred into a tube containing 1 mL of MTBE with 0.01 ng/mL tetradecane as an internal standard. The tube was vortexed for 3 min at maximum speed, incubated at 24 °C with rotation at a speed of 50 rpm for 1 h, and then dried using Na₂SO₄ and filtered through a 0.22 mm-mesh filter.
GC/MS analysis was performed using GC/MS-QP2010Ultra apparatus (Shimadzu Corporation, Kyoto, Japan) with an HP-5 MS column. The column temperature was programmed as follows: holding at 40 °C for 3 min, 40 °C to 280 °C at 10 °C/min, and holding for 2 min. The ion source and transfer line temperatures were 230 °C and 280 °C, respectively; the electron ionization was 70 eV; and the mass scanning was performed from 45 to 450 m/z with 5 scans/s. The results were qualitatively and quantitatively analyzed using the GC Solutions software (Shimadzu Corporation, Kyoto, Japan) with NIST (2017) and the PESTEI3 library.