A NEW NON-EXTRACTIVE ION-PAIR SPECTROPHOTOMETRIC
METHOD FOR THE ASSAY OF ALBENDAZOLE
MARINELA FLOREA 1, IOANA CLEMENTINA CONSTANTINESCU 1*, MIHAELA VIOLETA GHICA 2, LĂCRĂMIOARA POPA 2, CORINA-CRISTINA ARAMĂ 1, ANGELA NEDELCU 1
“Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, 6 Traian Vuia Street, 020956, Bucharest, Romania
1Department of Analytical Chemistry,
2Department of Physical and Colloidal Chemistry
*corresponding author: constantinescu_clementina@yahoo.com
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Abstract:
The paper presents a new non-extractive spectrophotometric method for the assay of albendazole (ABZ) as ion pair with
Congo red (CR). A soluble and stable ion pair (ABZ-CR) with an absorption maximum at 294 nm was obtained using a 2·10-8 M
CR concentration and Britton Robinson (BR) buffer with pH = 2.5. The method is linear in the range 2.5 - 4.7 μg/mL, with
limits of detection and quantification of 0.09 μg/mL and 0.28 μg/mL, respectively. The proposed method was applied to the
assay of ABZ in bulk pharmaceutical substance. Because CR is a dye with pharmacological applications used as model in
biochemical studies, the research also focused on the mechanism of interaction with ABZ. Spectral changes and physicochemical
constants (conductivity, dielectric constant) indicated that ABZ-CR ion pairing takes place at the surface of CR
aggregates by electrostatic and charge transfer interactions.

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