β phenethylamine

L-norepinephrine hydrochloride, (±)−dopamine hydrochloride, serotonin hydrochloride, epinephrine hydrochloride, tryptamine, (±)−octopamine hydrochloride, (±)−synephrine, tyramine hydrochloride, β-phenethylamine, D,L-metanephrine hydrochloride, adenine riboside, 4-aminobutyric acid, L-tyrosine, L-tryptophan, L-tryptophan-d5 (TRP-D5) and 4-aminobutyric acid-2,2,3,3,4,4-d6 (GABA-D6) were purchased from Sigma-Aldrich Corporation (Milan, Italy). The deuterated internal standards, (±)−norepinephrine-2,5,6,α,β,β-d₆ HCl (NE-D6), 2-(3,4-dihydroxyphenyl)ethyl-1,1,2,2-d₄-amine (DA-D4), serotonin-α,α,β,β-d₄ creatinine sulfate complex (5HT-D4), (±)−epinephrine-2,5,6,α,β,β-d₆ (E-D6), tryptamine-α,α,β,β-d₄ HCl (TRY-D4), (±)−p-octopamine-α,β,β-d₃ HCl (OCT-D3), 2-(4-hydroxyphenyl)ethyl-1,1,2,2-d₄-amine HCl (TYRA-D4), and 2-phenyl-d₅-ethylamine (β-PEA-D5) were obtained from CDN Isotopes (Pointe-Claire, Quebec, Canada). The L-tyrosine-ring-d4 (TYRO-D4) was from Cambridge Isotope Laboratories, Inc. (Tewksbury, MA, USA). The purity of all analytes and labeled internal standards was ≥98%.
Water was purified with a Milli-Q Elix purification system (Millipore, Bedford, MA, USA). High-purity MS-grade solvents (formic acid, methanol, and acetonitrile) were obtained from Fluka (Milan, Italy) and used without further purification.

Bacon samples were obtained from the supermarkets of Chengdu (Sichuan), Hunan (Changsha), Hubei (Wuhan), Guangdong (Guangzhou), Shanxi (Xian), and Gansu (Lanzhou) of China at the March of 2017. All samples were collected in three replicates, and stored at -20°C. The standard substances (histamine, tyramine, tryptamine, β-phenethylamine, putrescine, cadaverine, and 1, 7-dimethylheptane) were purchased from Sigma–Aldrich Co., LLC (St. Louis, MO, United States). Other chemicals were bought from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).