Determination of meclizine hydrochloride by ion-pair extraction with methyl orange.

A method, based on ion-pair extraction, is described for the quantification of meclizine hydrochloride in various pharmaceutical dosage forms, for content uniformity determination, and for concentration monitoring in dissolution and bioavailability studies. Methyl orange, dissolved in pH 2.8 MacIlvaine buffer, gave excellent recovery of meclizine after its isolation from aqueous solutions of gelatin, urine, and blood serum. The chloroform-extracted molecular species appeared to be a 1:1 ion-pair. Beer's law was obeyed for a wide concentration range. Because the extracted species seemed well defined and stable and since a surface or an interphase adsorption phenomenon was not a problem, the reported method is considered sensitive, accurate, precise, rapid, and simple.

Soft gelatin capsules II: Oxygen permeability study of capsule shells.

A method is reported for studying the effects of several factors at room temperature on the oxygen permeability of soft gelatin capsule shell films. The method involves the use of a permeability cell assembly and the spectrophotometric determïnation of oxygen with an alkaline pyrogallic acid solution. Factors investigated were relative humidity, plasticizers, equilibrium water, an insoluble additive, and film thickness. Results from the effects of film thickness and oxygen partial pressure correlated well with the permeability equation. For greatest stability of encapsulated oxygen-labile materials, it is recommended that the soft gelatin capsule shells be prepared with a low plasticizer concentration and that the finished capsules be stored at low relative humidity.

Separation and ultraviolet absorbance techniques for determining dihydrotachysterol in pharmaceutical preparations.

Three separation techniques and ultraviolet (UV) spectrophotometry are described for dihydrotachysterol (DHT). The absorbance procedure eliminates the necessity of establishing a regular baseline, which is advantageous in certain cases. The relative absorbance values obey Beer's law in the range of 1-10 mug DHT/ml ethanol. An absorbance ratio check ensures the applicability of the method with respect to the degree of allowable interference present. The absorbance ratio values at the indicated wave-lengths at this concentration range and in the absence of any interferences are relativiely constant. The UV absorbance could serve as the common final determinative step for the other techniques, either singly or in combination, for quantitating DHT in preparations that require varying degrees of cleanup through extraction, saponification, and thin layer chromatography. The respective mean per cent recoveries and their relative standard deviations for a 50 mug DHT standard sample treated by the 3 techniques are 99.6 -+/ 0.5, 98.5 -+/ 1.1, and 97.3 -+/ 3.3%. Content uniformity determination of DHT in tablets and in soft gelatin capsules is also presented, and precautions are discussed.