Table 1:
Table of lipid classes, their head groups, most prevalent precursor ion, and class-specific diagnostic fragments generated from the lipid head group.
| Lipid Class | Chemical Structure | Precursor Ion | Diagnostic Fragments |
|---|---|---|---|
| Fatty acid (FA) |
|
[M−H]− | (see note)** |
| Phosphatidylcholine (PC) |
|
[M+H]+ |
m/z 184.0733 NL 183.0661 |
| [M+CH3COO]− | NL 74.0368 | ||
| Phosphatidyl-ethanolamine (PE) |
|
[M+H]+ | NL 141.0191 |
| [M−H]− |
m/z 140.0118 m/z 196.0380 |
||
| Phosphatidylserine (PS) |
|
[M+H]+ | NL 185.0089 |
| [M−H]− |
m/z 152.9958 NL 87.0320 |
||
| Phosphatidylglycerol (PG) |
|
[M+NH4]+ | NL 189.0402 |
| [M−H]− |
m/z 152.9958 m/z 171.0063 |
||
| Phosphatidic acid (PA) |
|
[M+NH4]+ | NL 115.0035 |
| [M−H]− | m/z 152.9958 | ||
| Phosphatidylinositol (PI) |
|
[M+NH4]+ | NL 277.0563 |
| [M−H]− |
m/z 241.0119 m/z 223.0013 m/z 152.9958 m/z 259.0224 |
||
| Ceramide with d18:1 backbone |
|
[M+H]+ | m/z 264.2685 |
| Diacylglycerol (DAG) |
|
[M+NH4]+ | NL (FA+NH3) |
| Triacylglycerol (TAG) |
|
[M+NH4]+ | NL (FA+NH3) |
| Sphingomyeline with d18:1 backbone (SM) |
|
[M+H]+ | m/z 184.0733 |
| [M+CH3COO]− |
m/z 168.0431 NL 74.0368 |
||
| Cardiolipin |
|
[M−H]− | m/z 152.9958 |
| Acylcarnitine |
|
[M+H]+ |
m/z 85.0284 NL 59.0735 |
| Bile Acid |
|
[M−H]− | R1′, R2′, R3′ = H or OH If R4′ = OH, fragment varies If R4′ = NHCH2CO2H, m/z 74.0248 If R4′ = NH(CH2)2SO3H, m/z 124.0074 m/z 79.9574 |
NL = neutral loss.
*
Functional group R is saturated or unsaturated acyl chain.
**
Free fatty acids are generally not fragmented in common collision-induced dissociation (CID) experiments. For the convenience of multiple reaction monitoring detection, precursor ion mass is also used as fragment ion mass, i.e. for palmitate, FA 16:0, use transition: 255.2 → 255.2. Table is organized from resources: 206–208