Table 3.

Mean molecular mass, elemental groupings, and formula categorization of molecular formulae which correlated positively (r > 0, p < 0.01) with optical indices FI, freshness index, HIX, SUVA₂₅₄, S_275−295, S_350−400, and S_R.

Mean m/z (Da)	All Formulae		FI		Freshness		HIX		SUVA254		S275−295		S350−400		SR
	408	%	383	%	385	%	450	%	413	%	382	%	407	%	379	%
Total no. formulae	6716	100	1447	21	1869	27	2170	32	2162	33	1711	25	360	5	1635	24
CHO only	2960	100	125	4	362	12	1341	45	1429	49	320	11	35	1	372	13
CHON	2494	100	925	37	1016	40	683	28	388	16	912	36	312	12	734	29
CHOS	1531	100	530	34	641	42	195	13	359	25	599	39	9	1	634	41
CHOP	251	100	31	14	55	24	43	17	16	7	42	18	8	3	42	18
Contains N,S and/or P	3756	100	1322	44	1507	50	829	28	733	26	1391	46	325	10	1263	42
Black carbon	587	100	6	1	8	1	181	30	324	56	8	1	8	1	10	2
Polyphenols	1140	100	42	4	50	4	575	50	675	60	49	4	56	5	52	5
Highly unsaturated	3668	100	942	25	1129	30	1355	37	1135	32	1078	29	274	7	954	26
Unsaturated aliphatics	909	100	301	34	503	56	10	1	7	1	447	50	17	2	487	54
Saturated fatty acids	100	100	3	3	23	23	9	8	2	2	17	17	2	2	16	16
Sugars	37	100	3	9	4	12	13	36	8	22	2	6	3	8	1	3
Peptides	275	100	150	56	152	57	27	9	11	4	110	41	0	0	115	43

Mean m/z is the intensity-weighted average mass (Da). Listed integers reflect the number of molecular formulae and percentages in parentheses represent the percent of peak intensity contributed by each classification of molecular formulae.