ABSTRACT
A rapid and simple method for simultaneous determination of Chlorpheniramine Maleate (CPM) and Phenylpropa-nolamine Hydrochloride (PPM) by first derivative UV spectrophotometry has been developed in combined pharmaceutical dosage forms. The proposed method was successfully applied for the determination of drugs in physical mixture and commercial formulations and results showed good linearity, precision and reproducibility.
ABSTRACT
A rapid and simple method for simultaneous determination of Chlorpheniramine Maleate (CPM) and Phenylpropa-nolamine Hydrochloride (PPM) by first derivative UV spectrophotometry has been developed in combined pharmaceutical dosage forms. The proposed method was successfully applied for the determination of drugs in physical mixture and commercial formulations and results showed good linearity, precision and reproducibility.
ABSTRACT
Se evaluó la fotoestabilización de la riboflavina en disolución acuosa a través de solapamiento espectral. En estudios previos se determinó que la longitud de onda a 445 nm promueve la degradación de la riboflavina, por eso se escogieron los colorantes que mejor eficiencia de absorción presentaran a esta longitud de onda. El estudio de fotoprotección consistió en determinar y comparar las constantes de velocidad (k0) de las reacciones de fotodegradación de la riboflavina en disoluciones (80 µM) en presencia y ausencia de colorantes a diferentes concentraciones: tartrazina (40, 58, 71 y 187 µM), amarillo ocaso (80, 160, 442 y 1 600 µM) y amarillo de quinoleína (80,133, 160 y 1 600 µM). Las cinéticas se realizaron irradiando las muestras en una cámara de simulación solar a 250 W.m-2, a diferentes tiempos y cuantificando la riboflavina residual, mediante cromatografía líquida de alta resolución. Las constantes de velocidad (k0) se determinaron mediante el método integral. En ausencia de colorantes la fotodegradación de la riboflavina obedece a una cinética de orden cero (k0= 0,0012 mg.mL-1×min-1) con un 79,9 por ciento de degradación tras 20 min de exposición a la luz. En presencia de colorantes la estabilidad de la riboflavina mejora significativamente con el aumento de la concentración del colorante empleado; sin embargo, se encontró que el amarillo de quinoleína a bajas concentraciones (< 160 µM) incrementó la degradación de la riboflavina, mientras que en la concentración más alta estudiada, redujo 6 veces la k0, lo cual sugiere que interacciones químicas se están llevando a cabo. La mayor fotoprotección se obtuvo con el amarillo ocaso a la concentración legal permitida, donde la concentración de la riboflavina se mantuvo inalterada tras 30 min de irradiación. El estudio muestra que debido a la alta capacidad fotosensibilizante de la riboflavina, la técnica de fotoprotección por solapamiento espectral no se pueda usar de forma genérica, pues no solo se puede esperar un efecto fisicoquímico de solapamiento sino que pueden generarse interacciones fotoquímicas.
The photostabilization of Riboflavin (RF) in aqueous solution was evaluated through spectral overlap. Previous studies established that wavelength at 445nm promoted RF degradation; hence dyes that exhibited high absorption performance at 445 nm were selected. The photoprotection study consisted in determining and comparing the rate constants (k0) of the RF photodegradation reactions in solutions (80 µM), both in presence and absence of dyes at different concentrations: tartrazine (40, 58, 71 y 187 µM), sunset yellow (80, 160, 442 y 1 600 µM) and quinoline yellow (80, 133, 160 y 1600 µM).The kinetics were estimated by irradiating the samples in a solar simulation chamber at 250 W×m-2 and at different times; then the residual RF was quantified by HPLC method. The rate constants (k0) were determined by the integral method. When dyes are absent, the RF photodegradation is due to zero order kinetics (k0= 0.0012 mg×mL-1×min-1) with 79.9 percent degradation after 20 min of exposure to light. When dyes are present, the RF stability improves significantly with increasing concentration of the dye; however, it was found that quinoline yellow at low concentrations (<160 µM) increased the EF degradation, whereas at the highest studied concentration, k0 was reduced 6 times, suggesting that chemical interactions occurred. Most photoprotection was obtained from the sunset yellow at allowable concentration where RF concentration was unchanged after 30 min of irradiation. The study showed that the high photosensitizing capacity of riboflavin hindered the generic use of photoprotective technique through spectral overlapping, because physical-chemical effect of overlapping may be expected in addition to occurrence of photochemical interactions.