Cream Matrix Research Articles

Extraction of acyclovir from pharmaceutical creams for HPLC assay. Optimization and validation of pretreatment protocols

Abstract Three simple protocols for the extraction of acyclovir from its pharmaceutical creams based on ultrasonication, ultrasonication with heating and magnetic stirring were evaluated and compared. Extraction kinetics were studied at different time intervals (5, 10, 15, 30 and 60 min) and the extraction efficiency was determined by HPLC. The effect of concentration of aqueous NaOH as the extraction medium and the stirring speed were also studied and optimized. Best results were obtained with 50 mL of 0.01 mol L−1 aqueous NaOH with magnetic stirring speed of 500 r.p.m. HPLC analysis involved rapid separation of acyclovir from the cream matrix using a 100 × 4.6 mm i.d. monolithic column and UV detection at 254 nm. Magnetic stirring produced the best results in terms of extraction efficiency with an average extraction yield of 100.8%, n = 16 at an optimum extraction time of 15 min. The selected protocol was validated for within and day-to-day precision and ruggedness.

Characterization of antioxidants using a fluidic chip in aqueous/organic media

Application of antioxidants in the cosmetic industry demands control of the efficiency of ROS-scavenging within the cream matrix. Our goal was to construct a system for the simultaneous detection of superoxide and hydrogen peroxide and their possible scavengers. DMSO is a good solvent for many cosmetic products, and thus the system should work in mixed aqueous-organic media. The fluidic chip developed consists of an ROS-generation chamber, a mixing section and a compartment for the biosensor chip. This electrode chip had two sensors: one sensor for each species. Cytochrome c was used as the sensing protein. Both the superoxide and the hydrogen peroxide sensors demonstrated sufficient sensitivity in DMSO-buffer mixtures within the concentration range 0.4 nM-1.2 nM (superoxide) and 50 microM-1000 microM (hydrogen peroxide). The influence of the flow conditions on the generation of ROS was investigated and the optimal parameters for the antioxidant detection were evaluated. The efficiency of ROS-scavenging was tested with typical antioxidants of enzymatic and non-enzymatic origin, as well as complex cosmetic creams.

Air cell microstructuring in a high viscous ice cream matrix

Ice cream is a complex multiphase system consisting of ice crystals, air cells and fat globules embedded in a high viscous freeze concentrated matrix phase. The microstructure of these constituents has significant impact on the consumer quality characteristics and its specific manipulation is of great interest. While in the frozen state the structure is dominated by the ice crystals after thawing the foam characteristics become important. Ice cream foam stability is correlated to the sensed creaminess and can be improved with smaller air cells and reduced coalescence. In contrast to the common approach addressing this goal by changed recipes this contribution proposes an additional process step which allows efficient dispersion of the air cells by high shear forces. Disruption of air cells by shear is efficiently done at high matrix viscosities, which are directly related to the amount of frozen water and therefore the temperature. Conventionally scraped surface heat exchangers (freezers) are used for whipping and freezing of an ice cream premix. With outlet temperature of − 5 to − 8 ° C these devices operate at relatively low ice cream viscosities. Here the ice cream is processed in a low temperature extruder (LTE) after a classic freezer which cools it further to below − 12 ° C. This way shear forces exceeding those in the conventional system by 2–3 orders of magnitude can be applied. The maximum air cell diameter x 90 , 3 is reduced from 52 to 19 μ m. Beside the air structures the extrusion process induces also changes in the fat structures. High shear forces are also able to form an optimized network of agglomerated fat globules, which further stabilizes the foam. These structural changes have a significant impact on the foam related quality characteristics of ice cream as is proven by measurements of the rheological behaviour during thawing and melt down tests.

Release of Hydrocortisone from a Cream Matrix: Dependency of Release on Suspension Concentration and Measurement of Solubility and Diffusivity

The principal object of the present research was to investigate the sensitivity of drug release from a semisolid system to the manner of its preparation and to the concentration of drug placed within it. Established theory indicated that release should be concentration dependent, with the specific dependency determined by whether the drug in the system is fully in solution or is present substantially as suspended matter. To purposefully explore these relatively untested performance expectations, the total amount of drug in the formula was varied from a low concentration of 0.25% to a high concentration of 3%. Conditions were established such that release conformed to release from a semi-infinite medium into a receptor sink. At every concentration, release profiles were well reproduced in replicate samples and, where multiple lots of a kind were employed, from lot to identical lot. In all cases square root of time release kinetics were observed. Moreover and without exception, the square root of time release rate from run to run was directly proportional to the square root of the total concentration of hydrocortisone placed in the formulations. The amount released per square root of time per square root of total concentration was nearly identical from run to run irrespective of total concentration. The overall behavior fit theoretical expectations for suspensions having only a small fraction of the drug they contain in solution. That this condition prevailed even at the lowest 0.25% hydrocortisone strength was proven by independently measuring hydrocortisone's solubility (0.02%). Measurement of solubility permitted estimation of the effective diffusivity of the drug through the cream (2 × 10−7 cm2/s).

Analysis of Zinc Undecenoate and Undecenoic Acid in Athlete's Foot Cream

ABSTRACT A validated method has been developed to quantify the amount of zinc undecenoate and undecenoic acid in a commercial athlete's foot cream matrix by liquid-liquid extraction followed by gas chromatography and titration method. Gas chromatography was used to analyse the total amount of undecenoic acid and a titration method was used to quantify the amount of zinc ion present in the mixture.

Determination of Ro 14-4767 (Loceryl™) by LC using automated column switching with ultraviolet and electrochemical detection

Ro 14-4767, Loceryl is a member of a new class of antimycotics, and a number of dosage forms are being developed for its topical application. The active, impurities and its major oxidation products are amenable to ultraviolet detection at wavelengths of approximately 220 nm. As new delivery systems and lower strengths have been developed, it was recognized that a more sensitive detection method may be necessary to support product development. Ro 14-4767, Ro 14-3168 (impurity) and diastereomers are readily oxidized at potentials of 0.8 V (vs Ag/AgCl) at a glassy carbon electrode. Electrochemical detection substantially improved the sensitivity relative to UV detection. However, detection of impurities and oxidation products by either UV or electrochemical detection exhibited interference problems from the cream matrix. Employing column switching eliminated the interference problem from the cream matrix and adding tetrahydrofuran to the mobile phase (acetonitrile and pH 7.0 phosphate buffer) significantly increased the selectivity and sensitivity for both UV and electrochemical detection. The method requires the use of two pumps to continually deliver the mobile phase through both detectors before and after valve switching, preventing the baseline from shifting during a stop in the flow to the electrochemical detector. Quantitative recovery of the active, the potential degradation products, and Ro 14-3168 from a placebo cream using column switching and UV detection has been demonstrated. Utilizing this methodology it is possible to quantitate 0.1% of the formulation label claim for the potential degradation products and Ro 14-3168. Electrochemical detection provides greater selectivity in that only Ro 14-3168, Ro 14-4767 and its diastereomers are detected. However, the sensitivity of detection relative to UV is enhanced. The method is linear in the range of 50 to 150% of the working standard solution for 0.01% and 0.001% active concentration of the cream. The column switching technique can be automated for reproducible assay of a large number of samples.