Table 1: Comparison of the proposed and the existing visible spectrophotometric methods.

Sl. no.Reagent/sMethodology , nmBeer’s law range µg mL−1
(ε in L mol−1 cm−1)
Remarks Reference

1(a) Brucine-sodium metaperiodateOxidative coupling product was measured5204.0–20.0
NA
Less sensitive, multistep reaction [28]
(b) Citric acid-acetic anhydride5808.0–24.0
NA
2Sodium nitroprusside acetaldehydeInner molecular complex formed was measured5524.0–20.0
(1.10 × 104)
Less sensitive, requires rigid pH control[29]
3Cobalt thiocyanateExtracted ternary complex formed by reaction with drug was measured629.416.0–48.0
(3.97 × 103)
Less sensitive, involves extraction step[30]
4Tropaeolin-OOOExtracted ion-pair complex was measured482.52.0–10.0
(2.08 × 104)
Requires rigid pH control; involves liquid-liquid extraction; use of organic solvents[31]
5(a) Chloranil in 1,4-dioxane CT-complex measured5485.0–25.0
(1.00 × 104)
Less sensitive, involves heating step, time consuming [32]
(b) Chloranil and acetaldehyde66020.0–60.0
(3.19 × 104)
6p-Chloranilic acidCT-complex measured5209.28 × 102
20–184
Less sensitive; use of organic solvents[33]
7Folin reagentChromogen formed by reaction with drug was measured455.616.0–48.0
(3.85 × 103)
Less sensitive, strict pH control, time consuming[34]
8Folin-Ciocaltaeu reagentReduced FC-reagent was measured7602.0–6.0
NA
Narrow linear range, less sensitive[35]
9 Bromate-bromide-
(a) Methyl orangeUnreacted bromine was measured5080.2–1.6
(1.90 × 105)
Narrow linear range, multistep reaction, time consuming [36]
(b) Indigo carmine6102.0–12.0
(2.71 × 104)
10NBS  No rigorous control of experimental conditions, no heating or extraction step, no use of organic solvents or toxic chemicals, and sensitive with wide linear dynamic rangeProposed methods
(a) Potassium Iodide Tri-iodide ion measured Starch-iodine complex measured370 0.6–15.0 
(b) Potassium Iodide-starch5700.2–4.0 

NBS: N-bromosuccinimide. NA: not available.