Ms. Rizk et al., SPECTROPHOTOMETRIC DETERMINATION OF LIGNOCAINE IN PURE FORM AND IN PHARMACEUTICAL PREPARATIONS, Analytical letters, 30(15), 1997, pp. 2743-2753
Two spectrophotometric methods have been developed for the determinati
on of lignocaine in pure raw material or in formulated dosage form. On
e of these methods is based on the extraction of the ion-associate for
med with reineckate salt by nitrobenzene or chloroform/acetone [solven
t mixture, 1:1 (v/v)] and the absorbance is measured at 525 nm and at
pH 5. Beer's law is obeyed in the range 0.2-2.0 mg/mL. The other metho
d depends on the oxidation of lignocaine by Ce(IV), the excess of Ce(I
V) is reacted with chromotrope 2B or chromotrope 2R where the red colo
ur of the reagent decreases. The absorbance is measured at 510 and 530
nn and the methods are found useful in the concentration ranges 0.5-2
.5 and 1.1-3.4 mu g/mL, respectively. In another approach iron (II) is
added to the excess Ce(IV) followed by the reaction with thiocyanate,
salicylate or o-phenanthroline. The developed colours are measured at
450, 520 and 510 nm with concentration ranges 1.5-12.3, 1.8-10.6 and
0.5-4.3 mu g/mL, respectively. It is evident that the use of the thioc
yanate method is more preferable due to its wider usable concentration
range.