Experiment Sample preparation methods are shown in Figure 1. We sampled 1 g of the inside surface of the cardboard packaging for a commercial pancake batter mix into a vial, added 10 mL hexane and ethanol (1:1 volume ratio), and soaked it overnight. Then we collected the solvent into another vial and added 0.5 mL water. Next, we collected the top supernatant and added Na2SO4. After 1 hour, we collected the final supernatant and measured it via GCxGC–HRTOF–MS. Measurement conditions are shown in Table 1.