*2.1.2 Preparation sample HS-SPME*

HS-SPME Coffee Powder: 4 g of powder was weighed in a septic-sealed gas vial (20 mL); the resulting headspace was sampled for 40 min at 40°C with a 350 rpm agitation rate using a PDMS/DVB SPME fiber. By sampling 5 L of a 1000 mg/L solution of n-C13 in DBP in a 20 mL headspace vial and agitating it at 3 mL for 20 min at 50°C, the internal norm was preloaded to the fiber.
