Table 1. Comparison between measured and theoretical m/z values in averaged product ion spectra of phosphatidylethanolamine (PE) 34 : 1 and phosphatidylcholine (PC) 31 : 1.

	m/zmeasured	Relative intensity	Formula	m/ztheoretical	Δm/z	Δppm
(a) 1st largest clique, n=1641) PE(34 : 1) ([M+H]+), Fig. 1(c)
Prec	718.5376		C39H77NO8P	718.5381	−0.00053	−0.74
Frag	95.0852	25	C7H11	95.0855	−0.00030	−3.11
	109.1010	21	C8H13	109.1012	−0.00020	−1.85
	121.1010	16	C9H13	121.1012	−0.00016	−1.30
	135.1166	17	C10H15	135.1168	−0.00019	−1.42
	239.2371	20	C16H31O	239.2369	0.00018	0.75
	265.2529	24	C18H33O	265.2526	0.00029	1.09
	308.2949	22	C20H38NO	308.2948	0.00012	0.40
	577.5187	1000	C37H69O4	577.5190	−0.00039	−0.67
	578.5222	524	C36H69O4 [13C]	578.5224	−0.00019	−0.33
	579.5257	112	C37H72O2P	579.5264	−0.00070	−1.21
	718.5380	104	C39H77NO8P	718.5381	−0.00012	−0.17
	719.5413	63	C38H77NO8P[13C]	719.5415	−0.00013	−0.18
(b) 2nd largest clique, n=641) PC(31 : 1) ([M+H]+)
Prec	718.5375		C39H77NO8P	718.5381	−0.00059	−0.83
Frag	124.9995	60	C2H6O4P	124.9998	−0.00036	−2.90
	184.0731	1000	C5H15NO4P	184.0733	−0.00022	−1.19
	185.0765	72	C4H15NO4P[13C]	185.0767	−0.00011	−0.59
	718.5379	294	C39H77NO8P	718.5381	−0.00028	−0.39
	719.5416	166	C38H77NO8P[13C]	719.5415	0.00012	0.17
Average					−0.00020	−0.76
Standard deviation					0.00026	1.09

¹⁾ The number of product ion spectral data points used to construct the averaged spectra.