The GC conditions were as follows: injector temperature, 250 ◦ C; detector temperature, 280 ◦ C, carrier gas, H2; split ratio, 1/50 to 1/25; temperature program, 120 ◦ C for 1 min, followed by an increase of 10 ◦ C min−1 to 175 ◦ C, 175 ◦
C for 10 min, followed by an increase of 5 ◦ C min−1 to 210 ◦ C, 210 ◦ C for 15 min, then the temperature raised at a rate of 5 ◦ C min−1 to 230 ◦ C, 230 ◦ C for 5 min.