ANALYTICAL METHODS FOR SKIN CREAMS

Physical Properties
The Cream was observed for color, odour and appearance.

Test for Thermal Stability
The formulated cream was inserting into glass bottle with the help of spatula, and taped to settle to the bottom. Filled up to two-third capacity of bottle and insert plug and tighten the cap. Filled bottle was kept erect inside the incubator at 45 ˚ ± 1° for 48 hrs. The sample passed the test, if on removal from the incubator shows no oil separation or any other phase separation.

Test for microbial growth in formulated creams
The formulated creams were inoculated on the plates of agar media by streak plate method and a control was prepared by omitting the cream. The plates were placed in to the incubator and are incubated at 37 0C for 24 hours. After the incubation period, plates were taken out and check the microbial growth by comparing it with the control

Spreadability
The Spreadability was expressed in terms of time in seconds taken by two slides to slip off from the cream, placed in between the slides, under certain load. Lesser the time taken for separation of the two slides, better the Spreadability. Two sets of glass slides of standard dimensions were taken. The herbal cream formulation was placed over one of the slides. The other slide was placed on the top of the formulation, such that the cream was sandwiched between the two slides weight was placed upon the upper slides so that the cream between the two slides was pressed uniformly to form a thin layer. The weight was removed and the excess of formulation adhering to the slides was scrapped off. The upper slide allowed slipping off freely by the force of weight tied to it. The time taken for the upper slide was noted.
Spreadability= m ×l /t
m = weight tied to the upper slide (30g) l =length of glass slide (5cm) t =time taken in seconds.

Irritancy
Test Mark an area (1sq.cm) on the left hand dorsal surface. The cream was applied to the specified area and time was noted. Irritancy, erythema, edema, was checked if any for regular intervals up to 24 hrs and reported.

Wash ability
A small amount of cream applied on hand & washed under running tap water.

Viscosity
Viscosity of formulated cream was determined by book field viscometer at 100 rpm using spindle No 7.

pH of the cream
The pH of various formulations was determined by using digital pH meter. About 1 g of the cream was weighed and dissolved in 100 ml of distilled water and stored for two hours. The measurement of pH of each formulation was done in triplicate and average values were calculated.

Phase separation
The formulated cream was kept intact in a closed container at 25 – 300 C not exposed to light. Phase separation was observed carefully every 24 hrs for 30 days. Any change in phase separation was checked.

Moisture absorption studies
About 50 mg of cream was taken on a watch glass. A beaker was taken with full of water and was kept in a desiccator without adsorbents and allowed to get saturated. Watch glass with cream was introduced into the dessicator. It was left for 24 hrs.