Research Article

Utility of p-Chloranilic Acid and 2,3-Dichloro-5,6-dicyano-p-benzoquinone for the Spectrophotometric Determination of Rizatriptan Benzoate

Table 1

Comparison of the proposed and the existing visible spectrophotometric methods.

Sl. No.Reagent/s usedMethodologyλ max (nm)Linear range,
g mL−1 and ε, l mol−1 cm−1
Reaction time, minRemarksRef.

(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′-bipyridylComplex formed between reduced Fe(II) and 2,2′-bipyridyl measured.4904–20
(ε = 1.0 × 104)
5Heating 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
NANarrow 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 redExtracted ion-pair complex was measured.425
4–20
(ε = 5.4 × 103)
2Involves strict pH control and extraction step.

(4)7,7,8,8- Tetracyanoquinodimethane (TCNQ)Charge transfer complex measured 744
10–100
NR
15Heating 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)
5Simple, rapid, sensitive, selective, and no heating step. Use of single reagent and no extraction step involved.
(c) Bromothymol blue (BTB)4201.2–24
(ε = 1.63 × 104)
5

(6)NBS (a) JG
Resulting color measured620
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) CMG5401.5–30
(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.5904–70
(ε = 5.22 × 103)
Instantaneous

NR: not reported; NA: not available.