E 2 octenal

Standard compounds of the highest available purity were used. Pentanal (PEN), hexanal (HEX), 2-pentyl-furan (2PF), 2,4-nonadienal (NON), pyridine (PYR), 1-octen-3-ol (OCT), (E)-2-octenal (OCA) and 2,4,6-trimethylpyridine (TMP) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Water was purified with a Milli-Q purification system A10 Gradient/Elix System (Millipore, Bedford, MA, USA). A standard stock solution of TMP at 0.1 mg L⁻¹ was prepared in Milli-Q water, stored in a sealed vial at 4 °C, and used as internal standard.

Standards of most volatile compounds were obtained from Sigma-Aldrich (Shanghai, China): 1-octen-3-ol (98%), (E)-2-octen-1-ol (97%), 1-heptanol (98%), propanal (97%), pentanal (98%), hexanal (98%), heptanal (97%), octanal (99%), (E)-2-octenal (97%), nonanal (99.5%), (E)-2-nonenal (97%), benzaldehyde (99.5%), 2-pentylfuran (98%), and 2,3-pentanedione (97%). The 3-methylbutanal (98%) was supplied by Aladdin (Shanghai, China). The n-alkanes (C₇-C₄₀, ≥97%, external standard) was obtained from o2si Smart Solutions (Shanghai, China). The 2-methyl-3-heptanone (99%) was supplied by Dr. Ehrenstorfer (Beijing, China) as an internal standard.

The Tan mutton used in this experiment was randomly obtained from the hind legs of Yanchi Tan sheep (30 ± 1 kg, 9 months age) from Ningxia Xinhai Food Co., Ltd. (Yanchi, China). The following chemicals were purchased from Sigma-Aldrich (Shanghai, China): 1,2-dichlorobenzene (internal standard, 99.7%) and n-alkanes (C₅-C₃₂, 98%), hexanal (95%), heptanal (97%), 1-heptanol (97%), benzaldehyde (99.5%), 2-methypyrazine (99%), (E)-2-undecenal (96%), pentanal (99%), octanal (99%), 1-hexanol (99%), 1-pentanol (99%), (E)-2-octenal (97%), nonanal (99.5%), (E)-2-nonenal (97%), 2-pentylfuran and 1-octen-3-ol (98%). Methanol (analytical grade) was purchased from Thermo Fisher Scientific Co., Ltd. (Shanghai, China).

A mixture of n-alkanes (C6–C10) dissolved in pentane was purchased from Fluka (Buchs, Switzerland) and α-pinene (≥95%) from Merck. All other reference compounds were supplied by Sigma-Aldrich (Munich, Germany): (E)-2-hexen-1-ol (≥ 95%), (E)-2-octenal (≥94%), (E)-2-nonenal (≥93%), hexyl acetate (99%), 1-decyne (98%), (Z)-3-hexenyl acetate (≥98%), (E)-2-decenal (analytical standard), 3-methyl-1-butanol acetate (isoamyl acetate) (≥97%), benzaldehyde (≥99%), nonanal (97%), (E)-2-hexenal (98%), (E)-2-octen-1-ol (97%), decanal (≥98%), 2,4-octadienal (96%), (E,E)-2,4-decadienal (analytical standard), (R)-(+)-limonene (97%), (E,E)-2,4-hexadienal (≥95%). Dichloromethane (anhydrous, ≥99.8%) and pentane (anhydrous, ≥99%) used as diluents were also from Sigma-Aldrich.
Samples of the reference compounds were prepared by dilution of the individual compounds in Dichloromethane, except for a mixture of alkanes which were diluted in pentane. The concentration of stock solutions of each compound was 0.1 mg mL⁻¹ but the final dilution of each standard was individually modified to obtain good reproducibility of retention times.

Quantitative calibration standards of 2, 10, 20, 100, and 200 ng/μl were made from (E)-2-octenal, (E)-2-decenal, and tridecane (all >94%, Sigma-Aldrich, Australia) diluted using dichloromethane. All calibration standards also contained tetralin (IS) added from a 10 μg/μl stock. (E)-2-octenal, (E)-2-decenal, and tridecane quantities from H. halys headspace samples were calculated using calibration linear equations. 4-Oxo-(E)-2-hexenal was prepared from 2-ethylfuran following Moreira and Millar [18 (link)]. To determine whether differences in defensive compound quantity between diapausing and diapause-disrupted H. halys were significant, non-parametric Mann-Whitney U two-tailed tests were performed, following Shapiro-Wilk tests for normality.

Beef from the hind legs of the Qinchuan cow was purchased from Yichuan's Xinbai market (Ningxia, China). The following chemicals were purchased from Sigma-Aldrich (Shanghai, China):1,2-dichlorobenzene (internal standard) and n-alkanes (C₇-C₄₀, ≥ 97%), hexanal (95%), heptanal (97%), 1-heptanol (97%), octanal (99%), (E)-2-octenal (97%), non-anal (99.5%), (E)-2-non-enal (97%), benzaldehyde (99.5%), (E, E)-2,4-decadienal (94%), 2-pentylfuran (98%), 2,5-dimethyl pyrazine (98%) and 1-octen-3-ol (98%). (E)-2-undecenal (l (94%), 2-pentylfuran (98%), 2,5-dime. (E, E)-2,4-non-adienal (95.8%) was from TCI Development Co., Ltd. (Shanghai, China). (E)-2-hexenal (97%) and (E)-2-heptenal (97%) were purchased from TCI (Shanghai, China). Methanol (analytical grade) was purchased from Thermo Fisher Scientific Co., Ltd (Shanghai, China).