Table 1.

Main fragments and Kovats RIs of 145 compounds in our library that were produced using MCF and ECF derivatization for GC/TOF-MS analysis.

No.	Compounds	MCF Derivatives		ECF Derivatives		Notes	No.	Compounds	MCF Derivatives		ECF Derivatives		Notes
		main fragments (m/z)#	RI	main fragments (m/z)#	RI				main fragments (m/z)#	RI	main fragments (m/z)#	RI
1	(±)-2-Methylpentanoic acid	88, 43, 57, 71, 101	885	74, 43, 102, 55, 87	947	c	75_1	L-2-Hydroxyglutaric acid (m)	85, 47, 144	1241	85, 131,159, 57, 203	1684	bcd
2_1	2-Hydroxybutyric acid (m)	59, 45, 73, 117, 100	1108	59, 131, 87, 159, 176	1250	abc	75_2	L-2-Hydroxyglutaric acid (s)	71, 59, 99, 131, 175	1502	85, 57, 159	1314
2_2	2-Hydroxybutyric acid (s)	59, 41, 89, 69	851	59, 41, 75, 89, 103	919		76	L-Alanine	70, 102, 129, 59, 42	1132	116, 44, 70, 88, 144	1279	abcd
3	2-Methylhexanoic acid	88, 43, 57, 69, 101	966	74, 43, 102, 56, 85	1029		77	L-Alpha-aminobutyric acid	84, 56, 116, 72, 103	1217	130, 58, 102, 86, 74	1362	abcd
4_1	2-Phenylglycine (m)	77, 132, 51, 164, 104	1657	132, 178, 77, 105, 205	1785		78	L-Asparagine	127, 59, 83, 95, 146	1407	141, 69, 95, 56, 113	1537	abcd
4_2	2-Phenylglycine (s)	77, 132, 51, 105, 191	1439	132, 77, 91, 105, 177	2029		79	L-Aspartic acid	86, 59, 128, 160, 96	1481	188, 70, 142, 100, 88	1661	abcd
5	2-Phenylpropionate	105, 77, 164, 51, 63	1219	77, 105, 178, 63, 91	1295		80	L-Cysteine	160, 59, 116, 132, 146	1707	220, 74,102, 132, 174	1885	abcd
6_1	3-(3-Hydroxyphenyl)-3-hydroxypropanoic acid (m)	91, 178, 59,134, 238	1751	120, 91, 77, 149, 194	1886	abc	81_1	L-Cystine (m)	160, 59, 100, 132, 192	2382	74, 188, 90, 174, 220	2793
6_2	3-(3-Hydroxyphenyl)-3-hydroxypropanoic acid (s)	120, 77, 91, 107, 180	1595	91, 119, 120, 65, 50	1082		81_2	L-Cystine (s)	160, 59, 192, 100, 76	2601	74, 146, 174, 188, 102	2545
7	3-Aminoisobutanoic acid	88, 56, 96, 115, 144	1262	102, 56, 74, 112, 129	1402	bc	82	L-Glutamic acid	114, 142, 174, 59, 82	1599	128, 84, 156, 56, 202	1772	abcd
8_1	3-Hydroxybutyric acid (m)	43, 74, 59, 87, 103	874	60, 43, 71, 87, 117	944	abc	83_1	L-Glutamine (m)	141, 109, 59, 68, 82	1546	155, 83, 56, 111, 43	1667
8_2	3-Hydroxybutyric acid (s)	59, 69, 100, 85, 75	1124	69, 114, 131, 159, 99	1274		83_2	L-Glutamine (s)	128, 84, 56, 143, 70	1152	84, 56, 128, 173, 156	1934
9	3-Hydroxyhippuric acid	179, 92, 135, 107, 208	2174	121, 149, 92, 193, 223	2365		84	L-Histidine	81, 59, 139, 194, 210	2084	81, 136, 154, 238, 254	2272	abcd
10_1	3-Hydroxyisovaleric acid (m)	43, 59, 85, 117, 74	891	43, 59, 85, 131, 103	959	abc	85	L-Homoserine	56, 100, 115, 83, 70	1378	100, 56, 70, 129, 115	1473	abcd
10_2	3-Hydroxyisovaleric acid (s)	73, 44, 56, 117, 90	1149	43, 59, 83, 128, 173	1301		86	Linoleic acid	55, 67, 81, 95, 294	2096	67, 55, 81, 95, 109	2158	ac
11	3-Hydroxyphenylacetic acid	121, 59, 91, 78, 180	1657	107, 77, 180, 135, 90	1784	abc	87	L-Isoleucine	115, 144, 88, 70, 59	1370	101, 129, 158, 70, 112	1499	abc
12	3-Indoleacetonitrile	121, 59, 78, 224, 165	1682	107, 77, 135, 180, 252	1808	d	88_1	L-Kynurenine (m)	146, 92, 119, 248, 205	2355	146, 92, 119, 262, 205	2477	bd
13	3-Indolepropionic acid	130, 203, 77, 115, 143	1934	130, 217, 143, 115, 77	2031	ac	88_2	L-Kynurenine (s)	117, 90, 63, 145, 173	1847	146, 120, 92, 65, 175	2459
14	3-Methyl-2-oxovaleric acid	57, 41, 85, 69, 144	972	57, 41, 85, 102, 158	1047	abc	89	L-Lactic acid	59, 103, 43, 130, 87	1030	45, 73, 117, 145, 56	1167
15	3-Methylindole*	130, 131, 77, 51, 103	1416	130, 131, 77, 51, 103	1430	c	90	L-Leucine	88, 115, 144, 128, 69	1357	158, 102, 43, 112, 69	1483	abcd
16	3-Methylpentanoic acid	74, 43, 59, 101, 55	899	88, 60, 43, 70, 55	964	bc	91	L-Lysine	142, 212, 244, 59, 88	2021	156, 56, 84, 102, 128	2207	abcd
17_1	4-Hydroxybenzoic acid (m)	135, 59, 77, 92, 107	1581	121, 138, 65, 93, 166	1731	abc	92	L-Methionine	115, 61, 147, 128, 162	1621	129, 61, 101, 175, 114	1737	abcd
17_2	4-Hydroxybenzoic acid (s)	121, 65, 93, 152, 74	1472	121, 152, 65, 93, 193	1658		93_1	L-Norleucine (m)	88, 69, 144, 59, 112	1406	69, 56, 112, 158, 86	1538	cd
18_1	4-Hydroxycinnamic acid (m)	161, 59, 89, 133, 236	1883	147, 120, 91, 192, 164	2041	bc	93_2	L-Norleucine (s)	69, 112, 59, 83, 128	1171	158, 230, 74, 86, 114	1746
18_2	4-Hydroxycinnamic acid (s)	147, 91, 119, 178, 65	1760	147, 120, 91, 192, 164	1926		94_1	L-Phenylalanine (m)	91, 162, 65, 128, 146	1730	91, 176, 65, 128, 77	1850	abcd
19	4-Hydroxyphenylpyruvic acid	135, 77, 92, 107, 180	1449	121, 65, 93, 77, 51	1531	bc	94_2	L-Phenylalanine (s)	91, 162, 65, 128, 77	1528	91, 128, 176, 65, 148	1586
20	4-Methylhexanoic acid	74, 43, 55, 87, 115	996	41, 61, 74, 101, 129	1064	bc	95	L-Proline	128, 59, 82, 187, 68	1408	142, 70, 98, 114, 215	1526	abcd
21	5-Dodecenoic acid	74, 55, 67, 96, 138	1520	88, 55, 96, 138, 180	1592	abcd	96_1	L-Serine (m)	86, 42, 58, 145	1434	114, 60, 74, 102, 204	1727
22	5-Hydroxy-L-tryptophan	204, 117, 145, 350, 90	2894	146, 218, 117,174, 346	2824	b	96_2	L-Serine (s)	56, 144, 86, 70, 103	1542	86, 60, 132, 74, 102	1495
23	Adipic acid	59, 55, 114, 101, 74	1248	111, 55, 73, 83, 157	1398	abcd	97_1	L-Tryptophan (m)	130, 77, 103, 276, 185	2410	130, 77, 103, 304, 258	2534	abcd
24	Alpha-Hydroxyisobutyric acid	73, 43, 59, 117, 101	1040	59, 43, 87, 131, 159	1169	bc	97_2	L-Tryptophan (s)	130, 77, 103, 244, 185	2163	130, 77, 103, 258, 185	2218
25	Alpha-Linolenic acid	55, 67, 79, 93, 107	2100	79, 67, 55, 93, 108	2186	ac	98_1	L-Tyrosine (m)	121, 236, 59, 165, 77	2201	107, 192, 264, 74, 91	2408	abcd
26	Aminoadipic acid	114, 59, 156, 188, 124	1698	170, 98, 55, 128, 216	1870	abc	98_2	L-Tyrosine (s)	121, 165, 59, 77, 91	1985	107, 135, 192, 264, 77	2118
27	Arachidic acid	74, 87, 43, 55, 283	2337	88, 43, 101, 55, 73	2404	ac	99	L-Valine	115, 98, 130, 55, 87	1270	144, 55, 101, 72, 129	1409	abcd
28	Arachidonic acid	79, 55, 67, 91, 203	2276	79, 55, 67, 91, 105	2335	abc	100	Malic acid	59, 75, 85,113, 101	1393	71, 43, 89, 117, 127	1587	abc
29	Behenic acid	74, 87, 43, 55, 311	2552	88, 43, 101, 55, 69	2614	acd	101	Malonic acid	59, 101, 74, 42, 69	939	115, 43, 88, 60, 133	1066	bc
30	Beta-Alanine	101, 56, 70, 74, 88	1222	115, 70, 98, 56, 88	1375	bc	102	m-Cresol	77, 91, 166, 107, 122	1256	180, 108, 77, 91, 136	1357	cd
31	Butyric acid	74, 43, 71, 59, 87	719	71, 43, 88, 60, 101	837	abc	103	Melatonin*	160, 173, 117, 145, 232	2477	173, 160, 145, 117, 232	2510
32	Capric acid	143, 55, 87, 101, 129	1332	88, 101,73, 55, 157	1396	abcd	104	Methylsuccinic acid	59, 129, 101, 41, 69	1062	115, 43, 73, 87, 143	1204	bcd
33	Caproic acid	74, 43, 59, 55, 87	934	60, 43, 88, 73, 101	998	abc	105	Myristic acid	74, 87, 43, 55, 101	1728	88, 41, 55, 73, 101	1789	ac
34	Caprylic acid	74, 87, 43, 55, 101	1118	88, 41, 55, 70, 101	1192	abc	106	Myristoleic acid	55, 74, 87, 110, 137	1712	55, 69, 88, 101, 124	1777	abcd
35	Cinnamic acid	131, 103, 77, 51, 162	1409	103, 131, 77, 176, 147	1502	abc	107	N-acetyltryptophan	130, 77, 103, 201, 260	2412	130, 215, 77, 103, 143	2463	abc
36	cis-Aconitic acid	59, 153, 184, 125, 98	1453	112, 84, 139, 167, 213	1640	abc	108	Nervonic acid	55, 69, 83, 97, 111	2710	55, 69, 83, 97, 111	2778	acd
37_1	Citraconic acid (m)	59, 126, 68, 98, 53	1108	112, 84, 141, 68, 96	1267	bc	109	Nicotinic acid	78, 106, 51, 137	1137	78, 51, 106, 123, 151	1218	bc
37_2	Citraconic acid (s)	127, 59, 99, 69, 53	1089	113, 85, 141, 157, 171	1237		110	N-Methylnicotinamide*	78, 51, 106, 135, 136	1458	78, 51, 106, 135, 136	1478	b
38	Citramalic acid	43, 85, 117, 59, 75	1111	131, 43, 85, 103, 58	1252	abc	111	Nonadecanoic acid	74, 87, 55, 143, 312	2224	88, 101, 157, 115, 326	2333	acd
39_1	Citric acid (m)	143, 101, 59, 43, 175	1485	112, 84, 139, 167, 212	1639	abcd	112	Norvaline	88, 130, 55, 98, 115	1310	144, 55, 72, 98, 129	1450	cd
39_2	Citric acid (s)	59, 101, 143, 69, 126	1384	57, 71, 115, 157, 85	1511		113	Oleic acid	55, 74, 83, 97, 296	2106	55, 69, 88, 96, 111	2163	abcd
40_1	D-2-Hydroxyglutaric acid (m)	85, 57, 69, 144	1243	85, 57, 159, 101	1311	bc	114_1	Ornithine (m)	128, 59, 88, 115, 198	1913	142, 70, 56, 96, 212	2093	abc
40_2	D-2-Hydroxyglutaric acid (s)	71, 59, 99, 131, 175	1504	85, 131, 159, 57, 203	1683		114_2	Ornithine (s)	128, 59, 139, 70, 96	1651	142, 70, 56, 113, 129	1761
41	Docosahexaenoic acid	79, 91, 67, 55, 105	2488	79, 91, 41, 67, 55	2544		115	Ortho-Hydroxyphenylacetic acid	91, 121, 78, 133, 148	1587	106, 134, 78, 180, 208	1706	b
42	Docosapentaenoic acid	55, 67, 79, 91, 105	2468	79, 91, 67, 55, 105	2529	ac	116_1	Oxoglutaric acid (m)	115, 55, 59, 87, 130	1272	101, 129, 55, 73, 158	1390	abc
43	Docosatrienoic acid	55, 67, 79, 95, 108	2523	79, 67, 55, 95, 108	2585	ac	116_2	Oxoglutaric acid (s)	115, 55, 59, 87, 143	1229	101, 129, 55, 73, 157	1379
44	Dodecanoic acid	74, 87, 43, 55, 101	1538	88, 41, 55, 73, 101	1603	abcd	117	Palmitic acid	74, 87, 43, 55, 101	1919	88, 43, 101, 55, 73	1982	abcd
45	Dopamine	117, 201, 164, 166, 94	1074	117, 94, 201, 166, 129	1093	abcd	118	Palmitoleic acid	55, 41, 69, 74, 87	1905	55, 41, 69, 88, 236	1963	abcd
46	Eicosapentaenoic acid	55, 67, 79, 91, 105	2273	79, 67, 91, 55, 105	2355	abc	119	p-Cresol	77, 107, 121, 166, 91	1263	108, 77, 91, 180, 135	1366	c
47	Eicosatrienoic acid	55, 67, 79, 93, 107	2302	67, 79, 55, 93, 107	2367	abc	120	Pelargonic acid	74, 87, 43, 55, 101	1224	88, 41, 55, 73, 101	1299	abcd
48	Eicosenoic acid	55, 69, 79, 97, 111	2323	55, 69, 83, 97, 111	2386	abc	121	Pentadecanoic acid	74, 87, 43, 55, 213	1824	88, 41, 55, 73, 101	1884	ac
49	Epinephrine	117, 201, 166, 164, 94	1074	117, 94, 201, 166, 129	1093		122	Phenol	65, 78, 152, 108, 93	1146	94, 66, 77, 166, 121	1245	abcd
50	Erucic acid	55, 41, 69, 74, 83	2534	97, 55, 69, 83, 320	2605	abc	123	Phenylacetic acid	91, 65, 150, 51, 119	1181	91, 65, 164, 51, 119	1251	abc
51	Ethylmethylacetic acid	88, 57, 41, 101, 69	800	57, 74, 85, 102, 115	876	abcd	124	Phenylethylamine	91, 65, 147, 104, 179	1521	91, 102, 65, 147, 193	1588	d
52	Fumaric acid	59, 85, 54, 114, 144	1020	99, 127, 55, 71, 82	1181	abc	125_1	Phenyllactic acid (m)	91, 131, 162, 59, 103	1636	131, 91, 103, 148, 176	1768	abc
53	Gamma-Aminobutyric acid	102, 59, 88, 112, 143	1362	116, 56, 84, 69, 130	1504	abcd	125_2	Phenyllactic acid (s)	91, 65, 162, 103, 77	1393	131, 91, 162, 103, 121	1709
54	Glutaric acid	59, 100, 129, 42, 55	1132	87, 42, 115, 143, 55	1284	bc	126	Phenylpyruvic acid	59, 90, 121, 75, 105	1735	118, 90, 192, 63, 147	1878
55	Glutathione	142, 98, 70, 82, 59	1576	84, 128, 56, 156, 202	1770	abc	127_1	p-Hydroxyphenylacetic acid (m)	121, 59, 78, 91, 224	1673	107, 77, 135, 180, 252	1809	abcd
56_1	Glyceric acid (m)	43, 59, 87, 69, 102	1238	61, 91, 133, 105, 116	1653	abc	127_2	p-Hydroxyphenylacetic acid (s)	121, 149, 65, 138, 93	1488	107, 77, 135, 166, 238	1747
56_2	Glyceric acid (s)	59, 91, 75, 103, 133	1463	61, 91, 133, 161, 205	1343		128	Pimelic acid	55, 74, 115, 43, 69	1357	101, 55, 69, 129, 171	1500	bc
57	Glycine	88, 115, 147, 44, 59	1128	102, 56, 74, 130, 175	1287	abc	129	Pipecolic acid	91, 174, 218, 65, 142	2099	91, 174, 218, 65, 156	2203	b
58	Glycolic acid	45, 59, 74, 117, 89	1002	103, 45, 59, 76, 131	1147	abc	130	Propionic acid	57, 88, 42	649	57, 74, 45, 102, 84	696	abc
59	Heptadecanoic acid	74, 87, 43, 55, 241	2021	88, 41, 101, 55, 73	2083	acd	131_1	Purine (m)	120, 133, 178, 80, 93	1548	120, 93, 148, 192, 66	1613	d
60	Heptanoic acid	74, 43, 55, 87, 101	1020	88, 43, 60, 73, 101	1091	abc	131_2	Purine (s)	178, 59, 65, 80, 107	1720	120, 192, 93, 66, 133	1810
61_1	Hippuric acid (m)	105, 77, 51, 134, 161	1713	105, 77, 51, 134, 161	1781	abcd	132	Putrescine	88, 56, 44, 69, 128	1442	142, 102, 56, 70, 186	1856	ac
61_2	Hippuric acid (s)	105, 77, 51, 136, 92	1092	105, 77, 51, 122, 150	1171		133	Pyroglutamic acid	84, 41, 56, 143	1393	84, 41, 56, 157	1466	bc
62_1	Homocysteine (m)	59, 82, 115, 174, 142	1612	128, 56, 175, 234, 102	2032		134	Pyruvic acid	43, 89, 117, 57, 75	954	84, 56, 128, 173, 156	1963
62_2	Homocysteine (s)	59, 114, 82, 174, 147	1824	133, 56, 161, 88, 115	1599		135_1	Salicyluric acid (m)	120, 92, 176, 235, 204	1898	120, 92, 176, 249, 204	1958	abd
63	Homogentisic acid	117, 94, 166, 201, 82	2010	117, 94, 201, 82, 166	1093	abc	135_2	Salicyluric acid (s)	44, 120, 56, 92, 77	2092	120, 92, 149, 193, 295	2272
64	Hydrocinnamic acid	91, 104, 164, 51, 77	1288	91, 104, 77, 51, 178	1365	abc	136	Serotonin	204, 117, 145, 260, 90	2438	146, 159, 218, 174, 231	2909
65	Hydroxyphenyllactic acid	59, 121, 161, 77, 236	2090	192, 107, 120, 147, 264	2327	b	137	Stearic acid	74, 87, 43, 55, 101	2123	88, 41, 101, 55, 73	2188	abc
66	Hydroxypropionic acid	45, 58, 71, 88, 103	1314	45, 87, 117, 102, 71	935	d	138	Suberic acid	55, 74, 97, 69, 138	1464	55, 69, 83, 139, 185	1598	bcd
67	Indole*	90, 117, 63, 50, 74	1311	117, 90, 63, 50, 74	1328	c	139	Succinic acid	55, 59, 87, 45, 116	1029	101, 55, 73, 129, 45	1175	abc
68	Indoleacetic acid	130, 189, 77, 103, 51	1839	130, 77, 103, 203, 51	1898	abc	140_1	Tartaric acid (m)	59, 85, 44, 115, 159	1689	115, 88, 71, 63, 131	1909	abc
69	Indoleacrylic acid	170, 143, 115, 215, 63	2213	170, 143, 115, 215, 89	2343	d	140_2	Tartaric acid (s)	59, 101, 145, 69, 85	1454	115, 133, 88, 105, 160	1061
70	Isobutyric acid	43, 59, 71, 87, 102	680	71, 43, 88, 116, 101	809	abc	141	Tetracosanoic acid	74, 87, 43, 55, 339	2751	88, 43, 101, 55, 73	2804	ac
71	Isocaproic acid	74, 43, 55, 88, 101	905	88, 43, 101, 55, 73	969	bc	142	trans-Cinnamic acid	131, 103, 162, 77, 51	1409	131, 103, 77, 176, 147	1503	abcd
72_1	Isocitric acid (m)	115, 55, 143, 83, 99	1515	101, 129, 55, 157, 85	1636	abcd	143	Tryptamine	130, 143, 218, 103, 77	2185	130, 143, 232, 103, 77	2293	abcd
72_2	Isocitric acid (s)	59, 129, 75, 101, 157	1725	129, 157, 101, 55, 185	1941		144	Valeric acid	74, 43, 57, 87, 101	842	73, 41, 57, 88, 60	914	ac
73	Isovaleric acid	74, 43, 59, 101, 85	797	88, 60, 70, 41, 115	878	abc	145	Vanillic acid	165, 59, 79, 121, 196	1759	151, 168, 123, 196, 268	1898	bc
74_1	Itaconic acid (m)	59, 69, 99, 127, 113	1092	113, 86, 141, 68, 157	1230	bc
74_2	Itaconic acid (s)	157, 59, 125, 98, 113	1387	90, 117, 189, 63, 133	1661

Note: a–c, compounds identified in human serum (a), urine (b), feces (c) samples by two independent parameters of MS and Kovats-RI; d, compounds identified in intracellular extract of E. coli. m: main peak; s: secondary peak.

^*These compounds cannot derivatize with MCF/ECF and elute as prototype.

^#The top 5 ions for each compound were ordered by the decreasing intensity.