Brandon Doss Dept of Chemistry & Biochemistry Introduction Ponderosa pine resin samples will be analyzed by GC-MS to determine whether attack by bark beetle alters the relative terpene composition of the resin. Seven terpenes will be monitored: α-pinene, β-pinene, myrcene, 3-carene, limonene, terpinolene, and longifolene. Fenchone is used as an internal standard. Sample Preparation Resin samples are prepared as 0.25g/mL solutions in dichloromethane. Dichloromethane was chosen as a solvent because of its strong dissolving power towards the resins, and because it has a very low boiling point, which makes it a good choice for gas chromatography. The samples were further diluted in dichloromethane to a resin concentration of 2.5e-3g/mL (2,500ppm) prior to analysis by GC-MS. Each sample was spiked with 9.5e-5g/mL (95ppm) of fenchone as an internal standard. Terpene Identification A stock terpene solution was prepared to establish the retention order and identification of the compounds by GC-MS. 10uL of each terpene was added to 930uL of hexane. This was further diluted by a factor of 100 in dichloromethane prior to GC-MS analysis. Figure 1 shows the chromatogram of the stock solution. All terpenes are well resolved from each other and from the internal standard with the exception of limonene and terpinolene. After comparison of the Kovat’s retention index1(NIST) and analysis of an extracted ion chromatogram for m/z=136, Figure 2, it was determined that these two components are co-eluting.

Pine Resin Terpene Analysis by GC-MS. Instrumentation Varian Saturn 3900 GC Varian Saturn 2100T Ion-Trap MS Figure 1. Terpene standard solution by GC-MS.

Figure 2. Extracted ion chromatogram of terpene standard, m/z=136.

The peak at 14.5min is nearly twice the height and area of its counterparts, suggesting that two components are eluting at the same time. Notice the absence of fenchone (m/z=152) and the substantial decrease of the longifolene signal (m/z=204).

Data Analysis There will be no absolute measurement of terpene concentration in this study, rather the concentration of individual terpenes will be measured against the internal standard component, fenchone. Although the absolute terpene concentrations will be unknown, the concentration of fenchone is well specified and thus provides a point of reference for a relative interpretation of the data. We will monitor the ratio of terpene signal to fenchone signal in each sample. For example, the ratio of a-pinene to fenchone in BSC3 is 5.02, Figure 3. We will monitor this ratio in BSB3 to see how it changes. Figure 3.