“…10,11) Furthermore, it was statistically demonstrated that this method was not affected by such variations as sampling years, trees, and fruiting positions as long as the plants were grown under set conditions. 12) However, it is often difficult to measure the isotope ratio by ordinary GC-MS when the molecular ion peak is very small or not detected. In GC-IR-MS specialized for the measurement of isotope ratios, the value is determined as the whole molecule isotopic ratio.…”