Table 1.
Retention times and compound specific selected reaction monitoring (SRM) parameters for some of the ceramides analyzed in this study. The methods comprised of two segments, and all the peaks are displayed in the first segment. In each method to attain maximum sensitivity only 5–7 ceramides were included, in which precursor ion to double dehydrated product ion arising from sphingoid base is monitored.
| Ceramide Analyte | Precursor [M+H]+ → Product ion | Retention Time (min) | Collision Enery (V) |
|---|---|---|---|
| Method 1 | |||
| d18:1Δ4 c12:0 (ISTD) | 482.48 → 264.24 | 1.76 | 25 |
| d14:1Δ4 c14:0 | 454.43 → 208.29 | 1.77 | 25 |
| d14:1Δ4 c16:0 | 482.48 → 208.29 | 1.76 | 25 |
| d14:1Δ4 c18:1 | 508.49 → 208.30 | 1.75 | 26 |
| d14:1Δ4 c18:0 | 510.49 → 208.30 | 1.74 | 26 |
| d14:1Δ4 c20:0 | 538.50 → 208.30 | 1.73 | 36 |
| d14:1Δ4 c22:0 | 566.52 → 208.30 | 1.72 | 36 |
| Method 2 | |||
| d18:1Δ4 c12:0 (ISTD) | 482.48 → 264.24 | 1.76 | 25 |
| d14:1Δ4 c24:1 | 592.57 → 208.30 | 1.71 | 27 |
| d14:1Δ4 c24:0 | 594.58 → 208.30 | 1.70 | 27 |
| d16:1Δ4 c14:0 | 482.46 → 236.30 | 1.75 | 25 |
| d16:1Δ4 c16:0 | 510.49 → 236.30 | 1.74 | 26 |
| d16:1Δ4 c18:0 | 538.52 → 236.30 | NI | 26 |
| Method 3 | |||
| d18:1Δ4 c12:0 (ISTD) | 482.48 → 264.24 | 1.76 | 25 |
| d16:1Δ4 c20:0 | 566.55 → 236.30 | 1.71 | 26 |
| d16:1Δ4 c22:0 | 594.58 → 236.30 | 1.68 | 27 |
| d16:1Δ4 c24:1 | 620.59 → 236.30 | 1.81 | 28 |
| d16:1Δ4 c24:0 | 622.60 → 236.30 | 1.77 | 28 |
*
10 μL of solution was injected by an auto-sampler for LC-ESI-MS/MS experiments. A universal tuned tube lens value from polytyrosine calibration was used.