|
Sl. No. | Reagent/s used | Methodology | λ
max (nm) | Linear range, g mL−1 and ε, l mol−1 cm−1 | Reaction time, min | Remarks | Ref. |
|
(1) | (a) Methyl orange.
| Extracted ion-pair complex was measured.
| 420
| 10–50 (ε = 1.02 × 104)
| 2
| Involves strict pH control and extraction step.
|
[5] |
(b) Ferric chloride, 2,2′-bipyridyl | Complex formed between reduced Fe(II) and 2,2′-bipyridyl measured. | 490 | 4–20 (ε = 1.0 × 104) | 5 | Heating required, multistep reaction. | |
|
| (a) 2,6-Dichloro quinone-4-chlorimide (DCQC)
| Oxidative coupling product measured.
| 610
| 5–25 NA
| NA
| Narrow linear range.
| |
(2) | (b)1,2-Napthoquinone-4-sulphonic acid (NQS).
| Color produced by replacement of imino group of RTB by sulfonate group of NQS measured.
| 480
| 15–75 NA
| NA
| Narrow linear range.
| [6] |
| (c) Brucine, sodium metaperiodate. | Oxidative coupling product measured. | 530
| 8–40 NA | NA | Narrow linear range. | |
|
| (a) Ferric chloride,1,10-phenanthroline.
| Complex formed with 1,10-phenanthroline, ferric chloride measured.
| 510
| 2–10 (ε = 3.85 × 104)
| 10
| Heating required, multi step reaction, narrow linear range.
| |
(3) | (b) Folin-Ciocalteu reagent, sodium hydroxide.
| Reduced FC-reagent was measured.
| 610
| 2–10 (ε = 3.5×103)
| 5
| Narrow linear range.
| [7] |
| (c) Alizarin red | Extracted ion-pair complex was measured. | 425
| 4–20 (ε = 5.4 × 103) | 2 | Involves strict pH control and extraction step. | |
|
(4) | 7,7,8,8- Tetracyanoquinodimethane (TCNQ) | Charge transfer complex measured | 744
| 10–100 NR | 15 | Heating required, reagent is expensive.
| [8] |
|
| (a) Bromophenol blue (BPB)
| | 425
| 0.8–16 (ε = 1.76 × 104)
| 5
| | |
(5) | (b) Bromocresol purple (BCP)
| Extraction free ion-pair complexes measured. | 425
| 1–20 (ε = 1.96 × 104) | 5 | Simple, rapid, sensitive, selective, and no heating step. Use of single reagent and no extraction step involved. | |
| (c) Bromothymol blue (BTB) | | 420 | 1.2–24 (ε = 1.63 × 104) | 5 | | |
|
(6) | NBS (a) JG
|
Resulting color measured | 620
| 0.5–8 (ε = 3.03 × 104)
| 15
|
Highly sensitive, no heating or extraction step, inexpensive instrumental setup, use of ecofriendly chemicals, and aqueous system | |
(b) CMG | 540 | 1.5–30 (ε = 1.15 × 104)
| 15
| |
|
(7) | (a) p-Chloranilic acid (p-CA)
| Radical anion was measured.
| 530
| 14–245 (ε = 1.30 × 103)
| Instantaneous
| Single-step instantaneous reaction, no heating or extraction step, no pH control, wide linear dynamic ranges. | Present methods |
(b) 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) | Radical anion was measured. | 590 | 4–70 (ε = 5.22 × 103)
| Instantaneous
|
|