Table 1.

Mass spectrometry assay methods for quantification of polymyxin B.

Study	Quantification Instrument/Method	Internal Standard	Precursor Ion → Product Ion Transitions (m/z)	Biomatrix	Solvents Utilized (Mobile Phases)
Cao et al. 2008 [25]	HPLC	N/A	PB1: 602.4, 401.9 PB2: 595.4, 397.2	Human plasma	Acetonitrile/tetrahydrofuran/ water (50:25:25, v/v)
Cheng et al. 2010 [23]	LC-MS/MS	Fibrinopeptide B (human)	PB1: 602.5 → 241.2 PB2: 595.6 → 227.5 PE1: 578.5 → 227.2 PE2: 585.6 → 241.3 Fibrinopeptide B: 786.3 → 187.3	Rat plasma	Acetonitrile with 0.1% FA, water with 0.1% FA
Thomas et al. 2012 [21]	LC-MS/MS	N/A	PB1: 602.6 → 241.1 PB2: 595.5 → 227.1	Human Plasma	Acetonitrile, water with 0.1% FA
He et al. 2013 [22]	UPLC-MS/MS	Carbutamide	PB1: 402 → 101 PB2: 397 → 101 PB3: 398 → 101 Ile-PB1: 402 → 101 Carbutamide: 272 → 74	Mouse Serum, ELF	Acetonitrile, water with 0.1% FA
Cheah et al. 2014 [24]	LCMS	Colistin in acetonitrile/water (50:50, v/v)	PB1: 401.85 PB2: 397.20 CA: 390.55 CB: 385.95	Bacterial growth media	Acetonitrile, water with 0.1% FA
Meng et al. 2016 [30]	LC-MS/MS	CB-182,753 (proprietary semi-synthetic cyclic peptide)	PB1: 602.6 → 241.2 PB2: 595.9 → 227.2 PB1-1: 602.6 → 241.2 CB-182,753: 614.4 → 532.6	Human plasma, urine	Acetonitrile with 1% FA in methanol (50:50), water with 0.1% FA, water/acetonitrile/methanol (10:45:45)
Covelli et al. 2017 [20]	LC-MS/MS	PE2 (i.e., Colistin B)	PB1: 402.3 → 100.9 PB2: 397.5 → 100.9 PE2: 386.2 → 100.9	Human and rat plasma	Acetonitrile/methanol (50:50) with 0.5% FA and 0.01 TFA, water with 0.5% FA and 0.01% TFA
Hee et al. 2017 [26]	LC-MS/MS	N/A	PB1: 602.6 → 101.2 602.6 → 241.2 PB2: 595.6 → 101.2 595.6 → 227.2 PB3: 595.6 → 101.2 595.6 → 227.2 Ile-PB1: 602.6 → 101.2 602.6 → 241.2	Human plasma	90% Acetonitrile with 0.1FA, water with 0.1% FA and 0.1% TCA

Abbreviations: PB1 = polymyxin B1, PB1-1 = polymyxin B1-1 (component of PB), PB2 = polymyxin B2, PE2 = polymyxin E2, CA = colistin A, CB = colistin B, ELF = epithelial lining fluid, FA = formic acid, TFA = trifluoroacetic acid.