Table 1. Combined MALDI MS, SIMS, and CE–ESI MS Results for Rhamnolipid and Quinolone Species Detected from the WT P. aeruginosa Biofilm^a.

		CE-ESI MS			MALDI MS				SIMS
compound ID	molecular formula	[M + H]+ observed	[M – H]− observed	ΔM (neg)	[M + H]+ observed	[M + Na]+ observed	[M – H + 2Na]+ observed	ΔM	[M + H]+ observed	[M + Na]+ observed	[M – H + 2Na]+ observed	ΔM
HHQ (2-heptyl-4-quinolone)	C16H22NO	244.170	242.152	–0.003	244.18			0.01	244.17			0.00
PQS (2-heptyl-3-hydroxyquinolone)	C16H21NO2	260.164	258.148	–0.002	260.17			0.01	260.16			–0.01
HQNO (4-hydroxy-2-heptylquinolone-N-oxide)	C16H21NO2	260.165	258.148	–0.002	260.17			0.01	260.16			–0.01
C9:1-NHQ (2-nonenyl-4-quinolone)	C18H23NO		268.168	–0.002	270.19			0.01
NHQ (2-nonyl-4-quinolone)	C18H25NO	272.202	270.184	–0.002	272.21			0.01	272.20			0.00
C9:1-PQS (2-nonenyl-3-hydroxyquinolone) C9:1-NQNO (4-hydroxy-2-nonenylquinolone-N-oxide)	C18H23NO2	286.180	284.161	–0.005	286.19			0.01	286.18			0.00
C9-PQS (2-nonyl-3-hydroxyquinolone) NQNO (4-hydroxy-2-nonylquinolone-N-oxide)	C18H25NO2		286.178	–0.003	288.20			0.01	288.19			0.00
C11:1-UHQ (2-undecenyl-4-quinolone)	C20H27NO								298.21			–0.01
Rha-C10	C16H30O7	335.208	333.187	–0.005		357.21	379.19	0.02			379.16	–0.01
Rha-C8-C10	C24H44O9		475.289	–0.002		499.31		0.02		499.28		–0.01
Rha-Rha-C10	C22H40O11	481.256	479.247	–0.002		503.27	525.25	0.02
Rha-C10-C10	C26H48O9		503.321	–0.001		527.34	549.33	0.02		527.30		–0.02
Rha-C10-C12:1	C28H50O9		529.337	–0.001		553.38		0.04		553.33		–0.01
Rha-C10-C12	C28H52O9		531.355	0.002		555.38		0.03		555.33		–0.02
Rha-Rha-C8-C10	C30H54O13		621.351	0.002		645.38		0.03		645.34		–0.01
Rha-Rha-C10-C10	C32H58O13		649.379	–0.001		673.42	695.41	0.04		673.40		0.02
Rha-Rha-C10-C12	C34H62O13		677.411	–0.001		701.46	723.44	0.05		701.40		–0.01

^aBold text indicates species confirmed by MS/MS. Rhamnolipid abbreviations are explained elsewhere.^29,33