TABLE 1.
Color index registration numbers, absorption maxima, purity, and calculated molar extinction coefficients of the sulfonated azo dyes useda
| Azo dye | Color index no. | Dye purity (%) | Absorption maximum (nm) | Extinction coefficient (mM−1 cm−1) |
|---|---|---|---|---|
| Acid black 1 (naphthol blue black) | 20470 | 85 | 618 | 53.2 |
| Acid black 24 | 26370 | 50 | 560 | 20.1 |
| Acid black 52 (Palatines fast black) | 15711 | 25 | 565 | 63.2 |
| Acid blue 113 | 26360 | 70 | 557 | 20.1 |
| Acid red 1 | 18050 | 60 | 530 | 21.1 |
| Direct red 81 | 28160 | 50 | 509 | 55.2 |
| Direct yellow 4 (brillant yellow) | 24890 | 70 | 404 | 74.2 |
| Direct yellow 50 | 29025 | 60 | 398 | 38.3 |
| Amaranth (acid red 27) | 16185 | 90 | 520 | 22.6 |
a
The dyes were purchased from Aldrich or Sigma and not further purified. The absorption maxima were determined in NaK phosphate buffer (pH 7.4, 54 mM). The molar extinction coefficients were calculated at the dye purities indicated.