A New Non-Extractive Ion-Pair Spectrophotometric Method for the Assay of Albendazole

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. RezumatLucrarea prezintă o nouă metodă spectrofotometrică non-extractivă de dozare a albendazolului (ABZ) ca pereche de ioni cu roșu de Congo (CR). Perechea de ioni (ABZ-CR), solubilă și stabilă, cu maxim de absorbție la 294 nm s-a obținut folosind o concentrație de CR de 2•10 -8 M și soluție tampon Britton-Robinson (BR) cu pH = 2,5. Metoda este liniară pe domeniul de concentrații 2,5 -4,7 µg/mL, cu limita de detecție de 0,09 µg/mL și limita de cuantificare de 0,28 µg/mL. Metoda a fost aplicată la dozarea substanței farmaceutice ABZ. Deoarece CR este un indicator cu proprietăți farmacologice și folosit ca model în studiile de biochimie, studiul a avut în vedere și stabilirea mecanismului de interacțiune cu ABZ. Modificările spectrale și constantele fizico-chimice (conductivitate, constantă dielectrică) au aratat că perechea de ioni ABZ-CR se formează la suprafața agregatelor de CR prin interacțiuni electrostatice și transfer de sarcină.

UV-Spectrophotometric Determination of the Active Pharmaceutical Ingredients Meloxicam and Nimesulide in Cleaning Validation Samples with Sodium Carbonate

“…The existing J 2023, 6 249 spectrophotometric methods for the determination of nimesulide are summarized in Table 1 and those for meloxicam in Table 2. Water/chloroform Hexadecyl-trimethylammonium bromide 404 6-20 1 0.7 [13] Water/chloroform Bromocresol green 412 2-18 5 0.6 [14] Water/chloroform Bromocresol purple 410 2-16 4 0.5 [14] Water/chloroform Bromothymol blue 407 2-18 3 0.5 [14] Water/chloroform Brilliant blue G 502 2-18 5 0.5 [14] Water/chloroform Methyl orange 482 2-14 3 0.7 [14] Water p-N,N-dimethyl phenylene diamine dihydrochloride, chloramine-T 540 10-50 0.8 0.6 [15] Water p-N,N-dimethyl phenylene diamine dihydrochloride, These methods were checked for rapidness, simplicity and usage of the reagents common for pharmaceutical laboratory; it was found that the simplest methods (that allowed the determination of nimesulide and meloxicam content directly in the aqueous solutions without lengthy phase separation steps and sample or reagent preparation and that used only very common reagents available in any pharmaceutical laboratory) were based on the formation of the colored deprotonated forms of nimesulide and meloxicam in alkaline environments. Both these active pharmaceutical ingredients exhibited an acid-base behavior and, in the presence of NaOH, formed the intensively colored yellow solutions.…”