Table 1. Flavored reference e-liquids.

Name	Category	Taste/smell	Formula	Reported concentration (mg/mL)	Concentration used in this study (mg/mL)
Ethyl butyrate	Ester	Pineapple	C6H12O2	11.1	11.1
Ethyl maltol	Sugar alcohol	Cotton candy	C7H8O3	27.1	27.1
Hexyl acetate	Ester	Apple	C8H16O2	2.5	2.5
Sucralose	Sugar substitute	Sweetener	C12H19Cl3O8	1–5	2.0
Triacetin	Triester of glycerol and acetic acid	Velvety / smoky	C9H14O6	N/K	11.6

Flavors are described using their names, chemical and physical properties, and reported [28, 29] and actual concentration used in this study. The reference e-liquids are prepared using a published research on standard development [26]. Uncertainty value of measurement is ± 0.1 mg.