Positive and negative ion mode

DB = Double bond

Lipid classes

Type of overlap

Example

PE O - LPE

PE O = LPE

[PE O-26:1+H]+ = [LPE 26:1+H]+

PC O - LPC

PC O = LPC

[PC O-26:1+H]+ = [LPC 26:1+H]+

Positive ion mode

DB = Double bond

Lipid classes

Type of overlap

Example

PC-PE

PC = PE + 3CH2

[PC 32:0+H]+ = [PE 35:0+H]+

[PC 32:0+Na]+ = [PE 35:0+Na]+

PC-PA

[PC+H]+ = [PA+5CH2+DB+NH4]+

[PC 32:0+H]+ = [PA 37:1+NH4]+

PE-PA

[PE+H]+ =[PA+C2H4+DB+NH4]+

[PE 34:1+H]+ = [PA 36:2+NH4]+

PS-PG

[PS+H]+ = [PG+2DB+NH4]+

[PS 34:1+H]+ = [PG 34:2+NH4]+

SM - CerPE

SM = CerPE + 3CH2

[SM d34:1+H]+ = [CerPE d37:1+H]+

Negative ion mode

DB = Double bond

Lipid classes

Type of overlap

Example

PC-PS*

[PC+HCOO]- = [PS+3CH2-DB-H]-

[PC 33:1+HCOO]- = [PS 36:0-H]-

PC-PS

[PC+CH3CO2]- = [PS+4CH2-DB-H]-

[PC 32:1+CH3COO]- = [PS 36:0-H]-

all lipid classes forming acetate/formate adducts*

[X+CH2+HCOO]- = [X+CH3COO]-

[PC 34:1+HCOO]- = [PC 33:1+CH3COO]-

[Cer d35:1+HCOO]- = [Cer d34:1+CH3COO]-

*Acetate salts of LC-MS grade can be contaminated with trace amounts of formate, which can lead to false-positive identification. Methanol can be oxidized to formic acid during electrospray ionization.