Table 2.

List of the identified VOM using the NIST 08 spectra library

	Name of the volatile organic metabolite (VOM)	CAS-number	Chemical formula	tR [mins]	m/z	frequency [%]
						HNSCC	Healthy
1	Furan	110–00-9	C4H4O	5.53	68	100	100
2	Propanal	123–38-6	C3H6O	5.65	58	100	100
3	Acetone	67–64-1	C3H6O	5.90	43	100	100
4	3-Pentanol	584–02-1	C5H12O	5.97	59	100	92.7
5	1-Propanol	71–23-8	C3H8O	7.21	31	98.1	93.9
6	2-Methylfuran	534–22-5	C5H6O	7.46	82	100	100
7	3-Methylfuran	930–27-8	C5H6O	7.74	82	100	100
8	2-Butanone	78–93-3	C4H8O	7.84	43	100	100
9	2-Methylbut-3-en-2-ol	115–18-4	C5H10O	8.24	71	100	100
10	Acetic acid	64–19-7	C2H4O2	8.69	43	100	100
11	Benzene	71–43-2	C6H6	9.00	78	100	100
12	3-Methylbutanal	590–86-3	C5H10O	9.16	44	98.1	100
13	Thiophene	110–02-1	C4H4S	9.20	84	98.1	97.6
14	2-Methylbutanal	96–17-3	C5H10O	9.37	41	100	100
15	2-Ethylfuran	3208–16-0	C6H8O	9.64	81	100	100
16	2,5-Dimethylfuran	625–86-5	C6H8O	9.84	96	100	100
17	2-Pentanone	107–87-9	C5H10O	10.04	43	100	100
18	2,4-Dimethylfuran	3710–43-8	C6H8O	10.15	96	98.1	100
19	Methyl methacrylate	80–62-6	C5H8O2	10.23	55	100	100
20	2-Ethenylfuran	1487–18-9	C6H6O	10.65	105	100	100
21	Tetrahydro-2,2,5,5-tetramethylfuran	15,045–43-9	C8H16O	11.48	43	100	100
22	Dimethyl disulfide	624–92-0	C2H6S2	11.56	94	100	100
23	3-Methyl-2-pentanone	565–61-7	C6H12O	11.99	43	100	100
24	Toluene	108–88-3	C7H8	12.01	91	100	100
25	2-Methylthiophene	554–14-3	C5H6S	12.23	97	100	98.8
26	2-Ethyl-5-methylfuran	1703–52-2	C7H10O	12.53	95	100	100
27	3-Hexanone	589–38-8	C6H12O	12.93	43	100	100
28	2,3,5-Trimethylfuran	10,504–04-8	C7H10O	13.12	43	100	100
29	2-Hexanone	591–78-6	C6H12O	13.20	43	100	100
30	Hexanal	66–25-1	C6H12O	13.47	44	100	100
31	m-Cresol	108–39-4	C7H8O	14.01	108	100	100
32	2-Acetyl-5-methylfuran	1193–79-9	C7H8O2	14.31	109	100	100
33	5-Methyl-3-hexanone	623–56-3	C7H14O	14.71	57	100	100
34	4-Methyl-3-hexanone	17,042–16-9	C7H14O	14.94	57	100	100
35	Ethylbenzene	100–41-4	C8H10	15.38	91	100	100
36	2-Hexenal	6728–26-3	C6H10O	15.90	41	100	100
37	4-Heptanone	123–19-3	C7H14O	16.19	43	100	100
38	2-Methylbutanoic acid	116–53-0	C5H10O2	16.41	74	100	100
39	3-Heptanone	106–35-4	C7H14O	14.74	57	100	100
40	Styrene	100–42-5	C8H8	16.85	104	100	100
41	2-Heptanone	110–43-0	C7H14O	17.05	43	100	100
42	Heptanal	111–71-7	C7H14O	17.43	70	100	98.8
43	4-Methyl-2-heptanone	6137–06-0	C8H16O	19.00	43	100	100
44	3-Methyl-2-heptanone	2371–19-9	C8H16O	19.25	43	100	100
45	2-Ethenyltetrahydro-2,6,6-trimethyl-(2H)-pyran	7392–19-0	C10H18O	19.45	139	100	100
46	2-Methyl-5-(methylthio)-furan	13,678–59-6	C6H8OS	20.19	128	100	100
47	Dimethyl trisulfide	3658–80-8	C2H6S3	20.61	126	100	100
48	Benzaldehyde	100–52-7	C7H6O	20.95	77	100	100
49	Terpinolen	586–62-9	C10H16	21.35	93	98.1	100
50	1,4-Cineole	470–67-7	C10H18O	21.42	43	100	100
51	Octanal	124–13-0	C8H16O	21.61	43	100	100
52	D-Limonene	5989–27-5	C10H16	21.79	68	98.1	100
53	o-Cymol	527–84-4	C10H14	21.93	119	100	100
54	1,3,5-Trimethylbenzene	108–67-8	C9H12	22.21	105	100	100
55	Dihydro-5-methyl-2(3H)-furanone	108–29-2	C5H8O2	22.29	56	98.1	98.8
56	1,8-Cineole	470–82-6	C10H18O	22.34	43	100	100
57	Tetrahydro-2,2-dimethyl-5-(1-methyl-1-propenyl)furan	7416–35-5	C10H18O	22.60	43	100	100
58	Phenol	108–95-2	C6H6O	23.42	94	100	100
59	2,6-Dimethyl-7-octen-2-ol	18,479–58-8	C10H20O	24.13	59	100	100
60	Benzyl alcohol	100–51-6	C7H8O	24.50	108	100	100
61	Dehydro-p-cymol	1195–32-0	C10H12	24.63	117	100	100
62	Tetrahydrolinalool	78–69-3	C10H22O	25.06	73	92.5	96.3
63	Linalool	78–70-6	C10H18O	25.30	71	100	100
64	Nonanal	124–19-6	C9H18O	25.45	57	100	100
65	3,4-Dimethyl-2,5-furandione	766–39-2	C6H6O3	25.70	39	100	100
66	4-Tolualdehyde	104–87-0	C8H8O	25.81	91	100	100
67	p-Cresol	106–44-5	C7H8O	26.63	107	100	100
68	± − 4-Acetyl-1-methylcyclohexene	70,286–20-3	C9H14O	27.13	43	100	100
69	1-(1,4-dimethyl-3-cyclohexen-1-yl)-ethanone	43,219–68-7	C10H16O	27.74	109	98.1	100
70	Camphor	76–22-2	C10H16O	28.20	95	100	97.6
71	4-Terpineol	562–74-3	C10H18O	28.43	71	98.1	100
72	α-Terpineol	98–55-5	C10H18O	29.07	59	100	100
73	1,3-Di-tert-butyl-benzene	1014–60-4	C14H22	29.80	175	100	100
74	DL-Carvone	99–49-0	C10H14O	31.16	82	100	100
75	4-tert-Butyl-2-chlorophenol	98–28-2	C10H13ClO	33.49	169	100	100
76	4-tert-Butylphenol	98–54-4	C10H14O	33.57	135	100	100
77	1,2-Dihydro-1,1,6-trimethylnaphthalene	30,364–38-6	C13H16	33.82	157	100	100
78	β-Damascenone	23,726–93-4	C13H18O	35.03	69	100	100
79	7,8-Dihydro-α-ionone	31,499–72-6	C13H22O	36.00	136	96.2	100
80	3,4-Dehydro-β-ionone	1203–08-3	C13H18O	36.77	43	100	100
81	α-Calacorene	21,391–99-1	C15H20	38.86	157	100	100