Table 1
Multiple reaction monitoring (MRM) settings for the analysis of melanin pyrolysate by GC/MS/MS
| Time segment | Retention time [min] | Compound (Type*) | MRM transition | Collision energy [V] | |
|---|---|---|---|---|---|
| Precursor Ion [m/z] | Product Ion [m/z] | ||||
| 1 | 9.7 | Thiazole (P1) | 85 | 58 | 15 |
| 58 | 57 | 12 | |||
| 11.1 | Toluene (NS1) | 92 | 91 | 15 | |
| 91 | 65 | 16 | |||
| 2 | 16.2 | Styrene (NS2) | 104 | 77 | 27 |
| 104 | 78 | 15 | |||
| 103 | 77 | 14 | |||
| 3 | 19.2 | Phenol (NS3) | 94 | 65 | 26 |
| 94 | 66 | 16 | |||
| 22.1 | Methylphenol (NS4) | 108 | 107 | 16 | |
| 107 | 77 | 16 | |||
| 4 | 24.9 | 1,2-Benzenediol (NS5) | 110 | 63 | 30 |
| 110 | 64 | 20 | |||
| 110 | 92 | 15 | |||
| 25.8 | Benzothiazole (P2) | 135 | 108 | 18 | |
| 108 | 82 | 12 | |||
| 5 | 26.9 | Indole (NS6) | 117 | 89 | 30 |
| 117 | 90 | 16 | |||
| 90 | 63 | 27 | |||
| 6 | 28.2 | 4-Hydroxybenzothiazole (P3) | 151 | 96 | 23 |
| 151 | 123 | 12 | |||
| 123 | 96 | 10 | |||
| 28.5 | Methylindole (NS7) | 130 | 77 | 27 | |
| 130 | 103 | 14 | |||
| 103 | 77 | 10 | |||
| 7 | 29.3 – 29.9 | 2,3-Dihydro-5H-1,4-benzothiazin-5-one (P4) and its isomers (P4′ and P4″) | 165 | 110 | 18 |
| 165 | 136 | 22 | |||
| 136 | 109 | 16 | |||
| 8 | 30.7 – 30.9 | Methyl-2,3-dihydro-5H-1,4-benzothiazin-5-one (P5, P5′) | 179 | 110 | 15 |
| 179 | 150 | 20 | |||
| 178 | 109 | 20 | |||
| 31.2 | 4-Hydroxy-6-ethylbenzothiazole (P6) | 179 | 164 | 15 | |
| 164 | 109 | 20 | |||
| 164 | 136 | 15 | |||
Fig. 1
Reconstructed total ion current MRM chromatogram of the pyrolysate of melanin isolated from FFPE primary melanoma (panels A and D) and FFPE melanoma lymph node metastases (panels B and E). Panels C and F show the pyrograms of synthetic eumelanin from L-3,4-dihydroxyphenylalanine (L-DOPA) with 10% incorporation of pheomelanin units. For peak designation see Table 1.