Table 1.
Improvements in sensitivity using sulfuric acid compared to formic acid additive to reagent mixture. Standards were derivatized with sodium carbonate (100 mM), BzCl (2% (v/v) in acetonitrile), and an internal mixture that contained 20% (v/v) acetonitrile with 1% (v/v) formic acid or sulfuric acid.
| Analyte | Retention Time (min) |
Concentration (nM) |
Formic Acid Peak Area |
Sulfuric Acid Peak Area |
Increase with Sulfuric (%) |
|---|---|---|---|---|---|
| ACh | 1.2 | 50 | 9409 | 8219 | 87 |
| Tau | 2.3 | 2000 | 17373 | 17723 | 102 |
| Hist | 2.3 | 200 | 78624 | 81494 | 104 |
| Ser | 2.6 | 5000 | 19108 | 20770 | 109 |
| Asp | 2.8 | 200 | 1118 | 1324 | 118 |
| Gly | 2.9 | 5000 | 4163 | 4695 | 113 |
| Glu | 3.1 | 2000 | 19442 | 23809 | 122 |
| GABA | 3.7 | 200 | 23076 | 30285 | 131 |
| Ado | 4.6 | 200 | 8894 | 12443 | 140 |
| 5HIAA | 5.2 | 500 | 12758 | 16814 | 132 |
| HVA | 5.3 | 500 | 54869 | 69455 | 127 |
| NM | 5.5 | 20 | 13240 | 31391 | 237 |
| DOPAC | 5.9 | 500 | 158474 | 261578 | 165 |
| 5HT | 5.9 | 20 | 2221 | 10703 | 482 |
| NE | 6.0 | 20 | 5974 | 28457 | 476 |
| 3MT | 6.0 | 20 | 16229 | 71462 | 440 |
| DA | 6.4 | 20 | 21510 | 100588 | 468 |