Valorization of Food Waste to Produce Eco-Friendly Means of Corrosion Protection and “Green” Synthesis of Nanoparticles

Table 4

LC-MS analysis results of the aqueous grape pomace extract.

RT^a (min)	Compound	RI^b	[M-H]^−c	Percentage (%)
2.26	Benzoic acid^a,b,c	1162	121	4.1
5.81	3-Hydroxybenzoic acid^a,b,c	1563	137	5.2
6.01	4-Hydroxybenzoic acid^a,b,c	1625	137	5.5
8.49	(2E)-3-(4-Hydroxyphenyl)prop-2-enoic acid (p-coumaric acid)^a,b,c	1938	163	10.6
8.42	3, 4, 5-Trihydroxybenzoic acid (gallic acid)^a,b,c	1943	169	5.5
10.37	(2E)-3-(4-Hydroxy-3-methoxyphenyl)prop-2-enoic acid (ferulic acid)^a,b,c	2091	193	3.7
10.42	3-(3, 4-Dihydroxyphenyl)-2-propenoic acid (caffeic acid)^a,b,c	2130	179	3.9
11.81	3-(4-Hydroxy-3, 5-dimethoxyphenyl)prop-2-enoic acid (sinapic acid)^a,b,c	2241	223	3.2
12.74	Delphinidin-3-O-glucoside^a,c	—	464	8.5
12.99	Cyanidin-3-O-glucoside^a,c	—	457	6.6
15.27	Malvidin-3-O-glucoside^a,c	—	491	6.4
16.33	(2R,2ʼR,3R,3ʼS,4R)-2, 2ʼ-Bis(3, 4-dihydroxyphenyl)-3, 3ʼ,4, 4ʼ-tetrahydro-2H,2ʼH-4,8ʼ-bichromene-3, 3ʼ,5, 5ʼ,7, 7ʼ-hexol (procyanidin B1)^a,c	—	579	8.8
16.88	(2R,3S)-2-(3, 4-Dihydroxyphenyl)-3, 4-dihydro-2H-chromene-3, 5, 7-triol (catechin)^a,b	2859	289	1.8
18.76	Epicatechin^a,b,c	2836	289	2.7
19.92	Quercetin-3-O-galactoside^a,c	—	363	4.9
21.46	Kaempferol-3-O-glucoside^a,c	—	447	5.9
21.85	2-(3, 4-Dihydroxyphenyl)-3, 5, 7-trihydroxy-4H-chromen-4-one (quercetin)^a,b,c	3163	301	4.6
21.98	3, 5, 7-Trihydroxy-2-(4-hydroxyphenyl)-4H-chromen-4-one (kaempferol)^a,c	—	285	2.1

^aRT: retention time; STD: standard compound; NIST 14 (compound identified by RI comparison with library). ^bRI: Kovats retention indices (RI) determined using a commercial hydrocarbon mixture (C9–C25) on the HP-5MS column (compound identified by Kovats retention indices comparison with literature values). ^cMS: compound identified by mass spectra comparison with the Wiley library.