S. No. Reagent/s used Methodology λmax (nm) Linear range
(µgmL-1)
LOQ
(µg mL-1)
Reaction time Remarks Ref.
1. p-Chloroanilic acid Pink coloured C-T complex was measured. 519 10-200
(€=1.28×103
L mol-1cm-1)
- Instantaneous Less sensitive 14
2. 0.1 M NaOH LMT in NaOH was measured. 305 2-50 - - 21
3 a) BCG/Dichloromethane Ion-pair extraction 410 1.5-15 1.3 5 min Tedious extraction procedure involved and Less sensitive 22
b) Alcoholic KOH Ion-pair breaking 620 0.5-5.0 0.59 Instantaneous
4 a) BPB/CHCl3 Ion-pair extraction 420 2.5-25 µg mL-1 0.15 5 min Tedious extraction procedure involved  
b) Ethanolic H2SO4 Ion-pair breaking 420 50-400 ng mL-1 0.003 Instantaneous 23
  c) Ethanolic KOH 600 10-80 ng mL-1 0.0005
5 a) BCP/dichloromethane Ion-pair extraction 410 2.0-20.0 µg mL-1 0.8 5 min 24
b) Ethanol Ion-pair breaking 410 150-1500 ng mL-1 0.06 Instantaneous
c) Ethanolic KOH 600 50-600 ng mL-1 0.02
6 a) Bromocresol green/CHCl3 Ion-pair extraction NA 0.15-19.8 µg mL-1 NA NA 25
b) Bromocresol purple/CHCl3 NA 0.15-19.8 µg mL-1 NA NA
c) Chlorophenol red/CHCl3 NA 0.05–34.1 µg mL-1 NA NA
7 a) 0.1 M H2SO4 LMT in 0.1 M H2SO4 was measured. 225 0.5-5.0
(€=8.65×104
L mol-1cm-1)
0.02 - Very simple, and wide linear dynamic ranges. Present work.
b) Methanol LMT in methanol was measured. 225 1.25-12.5
(€=2.11×104
L mol-1cm-1)
0.09 -
NA. Not available
Table 6: Performance characteristic of the existing spectrophotometric methods and the proposed methods.