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Use of two sulfonthalein dyes in the extraction‐free spectrophotometric assay of tramadol in dosage forms and in spiked human urine based on ion‐pair reaction
Author(s) -
Vinay Kanakapura B.,
Revannasiddappa Hosakere D.,
Rajendraprasad Nagaraju,
Ramesh Pavagada J.,
Xavier Cijo M.,
Basavaiah Kanakapura
Publication year - 2012
Publication title -
drug testing and analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.065
H-Index - 54
eISSN - 1942-7611
pISSN - 1942-7603
DOI - 10.1002/dta.247
Subject(s) - chemistry , chromatography , bromocresol green , tramadol , urine , absorbance , extraction (chemistry) , molar absorptivity , detection limit , tramadol hydrochloride , dichloromethane , analgesic , pharmacology , medicine , organic chemistry , biochemistry , physics , solvent , optics
Tramadol is a centrally acting analgesic used in the prevention and treatment of moderate to severe pain. Two sensitive, selective, and rapid spectrophotometric methods are described for the determination of tramadol in its dosage forms and in spiked human urine. The methods are based on formation of yellow ion‐pairs between tramadol and two sulfonthalein dyes; bromocresol purple (BCP) and bromocresol green (BCG) in dichloromethane medium followed by absorbance measurement at 400 and 410 nm, respectively. Under the optimum conditions, tramadol could be assayed in the concentration ranges, 1–15 and 1–16 µg ml −1 with correlation coefficient greater than 0.999 in both cases. The molar absorptivity values are calculated to be 1.84 × 10 4 and 1.97 × 10 4 l mol −1 cm −1 for BCP and BCG methods, respectively; and the corresponding Sandell sensitivity values are 0.0143 and 0.0134 µg cm −2 . The limits of detection (LOD) and quantification (LOQ) have also been reported. The stoichiometry of the reaction was found to be 1:1 in both cases and the conditional stability constant (K f ) values of the ion pairs have been calculated. The within‐day and between‐day RSD were 0.9–1.96% and 1.56–3.21%, respectively. The methods were successfully applied to the determination of tramadol in tablets and injections and also in spiked human urine with good recoveries. The procedures are simple, accurate, and suitable for quality control application. Copyright © 2011 John Wiley & Sons, Ltd.