Reagent

λ_max

pH

Molar absoptivity

(L mol⁻¹ cm⁻¹)

Beer’s law range

Reference

2-Hydroxy 4-ydroxy valerophenone

420

1.5 × 10³

[26]

3,5-Dibromo-4-hydroxyphenylfluorine

470

-

3.6 × 10⁴

2 - 20

[27]

O,O’-Bis (2ethyl)dithiophosporic acid

503

Acid medium

9.6 × 10⁴

0.5 - 4.0

[28]

3-Hydroxy-2-(4methoxyphenyl)-6-propionyl4H-chromen-4-one

416

5.56 × 10⁴

0 - 2.5

[19]

2,4-Dihydroxybenzaldehyde-isonicotinoylhydrazone

[29]

Cinnamaldyde4hydroxybenzoylhyrazone (CMBH)

404

6.82 × 10⁴

0.047 - 5/0

[30]

4-Hydroxy benzaldehyde thiosemicarbazone

365

6

1.25

0.03837 to 0.3837

[31]

3,4-Dihydroxy-benzaldehyde thiosemicarbazone

365

3 - 5

2.5 × 10³

0.19 - 1.3

[32]

Benzoylacetone-benzoylhydrazone

447

6.3 × 10⁵

0.05 - 2

[33]

8-Hydroxyquinoline-5 sulfonic acid

540

3.0 - 4.5

0.52

3 - 13

[3]

Bromopyrogallol red

625

1.3 × 10⁵

0.06 - 0.8

[34]

5,7-Dibromo-8-hydroxyquinoline

401

0.05 - 1.0 M H₂SO₄

4.13 × 10(3)

0.1 - 50

[35]

DTBP + AP₁

534

4.8 - 5.9

5.35

0.3 - 22

Present

method