|
| Sl. No. | Reagent/s used | Methodology | λ
max
(nm) | Linear Range, μg mL−1 and , l mol−1 cm−1 | , μg mL−1 | Reaction time, min | Remarks | Ref. |
|
| (1) | (a) Vanillin | Condensation product measured | 376 | 80–360 () | NR | 30 | Less sensitive, measurements at shorter wavelengths for (a) and (c), heating required for (b) and (c). | |
| (b) Ninhydrin | Condensation product measured | 569 | 40–280 () | NR | 5 | [16] |
| (c) p-benzoquinone | Condensation product measured | 369 | 80–320 () | NR | 5 | |
| (2) | Acetylacetone and formaldehyde | Condensation product measured | 415 | 20–140 () | NR | 20 | Heating required, less sensitive | [17] |
| (3) | (a) Iodine | Triiodide ion measured | 360 | 6–30 () | 0.39 | — | Shorter wavelength and less sensitive (a) Expensive reagent used (b) Less sensitive | |
| (b) 7,7,8,8- tetracyano- quinodimethane | Radical anions measured | 842 | 8–24 () | 0.48 | 20 | [18] |
| (c) DDQ | -do- | 456 | 12–36 () | 1.20 | — | |
| (d) Chloranilic Acid | -do- | 535 | 60–200 () | 7.59 | — |
| (e) Tetracyano ethylene | -do- | 412 | 40–140 () | 3.54 | 15 |
| (f) Chloranil | -do- | 521 | 40–120 () | 3.33 | 20 |
| (4) | Ninhydrin | Colored product measured | 405 | 50–300 | NR | 5 | Heating required, less sensitive | [19] |
| (5) | (a) Ninhydrin | Condensation product measured | 568 | 2–30 () | 0.15 | 20 | | [20] |
| (b) 7,7,8,8- tetracyano- quinodimethane | Charge transfer complex measured | 439 | 4–30 () | 0.04 | 15 | Heating require Expensive reagent used. | |
| (6) | NQS | Automated flow injection using piezoelectric pumping | 480 | Up to 150 | 11.0 and 9.8 | — | Less sensitive and complicated experimental setup | [22] |
| (7) | (a) Picric acid | Ion-pair complex measured | 415 | 1.25–15 () | 0.23 | 10 | Simple, sensitive selective, no heating step and inexpensive reagents used. | This work |
| (b) 2,4-Dinitrophenol | -do- | 420 | 2–18 () | 0.75 | 10 | |
|
