Evaluation tests for creams are crucial in pharmaceutics to determine the quality, stability, and effectiveness of topical formulations. Key parameters such as pH, viscosity, spreadability, homogeneity, and sterility are analyzed to ensure the product meets pharmaceutical and cosmetic quality standards. Understanding these tests helps pharmacy students and professionals develop safe, effective, and high-quality cream formulations
Test For Evaluation of Cream
1. Uniformity of weight
2. Sterility (For Sterile cream)
3. Irritancy study
- Mark an area of 1 sq.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 24hrs and reported.
4. Determination of pH
- Measured by a standard digital pH meter at room temperature.
5. Physical appearance
- Observed by its colour, roughness and graded.
6. Spreadability
Adequate amount of sample is taken between two glass slides and a weight of 100gm is applied on the slides for 5 minutes. Spreadability can be expressed as,
S= m*l/t
Where, m = weight applied to upper slide.
l = length moved on the glass slide.
t = time taken
7. Saponification value & Acid value (If oily base is used)
Saponification value: 2gm of substance refluxed with 25ml of 0.5 N alcoholic KOH for 30 min, to this 1ml of phenolphthalein added and titrated immediately, with 0.5N HCl, note the reading as ‘a’. Repeat the operation omitting the substance being examined. Note the reading as ‘b’
Saponification value = (b-a)*28.05/w
Where,
w = weight of substance in gram.
Acid value: 10gm of substance is dissolved in accurately weighed 50 ml mixture of equal volume of alcohol and solvent ether, the flask was connected to reflux condenser and slowly heated, until sample was dissolved completely, to this 1ml of phenolphthalein added and titrated with 0.1N NaOH, until faintly pink colour appears after shaking for 30 seconds.
Acid value = n*5.61/w
Where,
n = the no. of ml of 0.1 N KOH solution.
w = the weight of substance in gram.
8. Viscosity
- Viscosity of creams can be determined by using Brookfield Viscometer.
9. Homogeneity
- The formulation was tested for the homogeneity by visual appearance and by touch.
Conclusion
Proper evaluation of cream formulations is essential to guarantee their stability, consistency, and performance in pharmaceutical and cosmetic applications. Through tests like pH, viscosity, spreadability, and sterility checks, formulators ensure the cream meets required quality parameters. Understanding these evaluation methods not only helps pharmacy students in practical learning but also supports the development of safe and effective topical products.
Cream Evaluation in Pharmacy – Multiple Choice Questions
1. Which of the following tests is performed to ensure a cream is free from microbial contamination?
A) Spreadability test
B) Sterility test
C) Viscosity test
D) pH determination
Answer: B) Sterility test
2. What is the purpose of the irritancy study in cream evaluation?
A) To check color and texture
B) To determine spreadability
C) To assess potential skin reactions
D) To measure viscosity
Answer: C) To assess potential skin reactions
3. How is the pH of a cream typically measured?
A) By visual inspection
B) Using a standard digital pH meter
C) By spreading between glass slides
D) By titration with HCl
Answer: B) Using a standard digital pH meter
4. Which parameter is evaluated by placing a cream sample between two glass slides and applying a weight?
A) Viscosity
B) Homogeneity
C) Spreadability
D) Acid value
Answer: C) Spreadability
5. What does the saponification value measure in a cream with an oily base?
A) Acid content
B) Viscosity
C) Degree of esterification of fats
D) pH
Answer: C) Degree of esterification of fats
6. Which instrument is commonly used to determine the viscosity of a cream?
A) Digital pH meter
B) Brookfield Viscometer
C) Reflux condenser
D) Glass slide apparatus
Answer: B) Brookfield Viscometer
7. Homogeneity of a cream is assessed by:
A) Measuring spreadability
B) Visual inspection and touch
C) Sterility test
D) pH measurement
Answer: B) Visual inspection and touch
8. Which formula is used to calculate spreadability (S)?
A) S = m × l × t
B) S = m × l / t
C) S = t × l / m
D) S = m + l – t
Answer: B) S = m × l / t
9. The acid value of a cream indicates:
A) Amount of free fatty acids present
B) pH of the cream
C) Viscosity of the cream
D) Spreadability of the cream
Answer: A) Amount of free fatty acids present
10. Uniformity of weight in creams is tested to ensure:
A) Consistent dose in each application
B) Proper viscosity
C) Correct pH
D) Good spreadability
Answer: A) Consistent dose in each application
FAQs- Cream Evaluation in Pharmacy
1. What are the main types of tests performed for cream evaluation in pharmaceutics?
Answer: Cream evaluation includes physical tests (appearance, homogeneity, spreadability, viscosity), chemical tests (pH, saponification, acid value), and biological tests (sterility, irritancy).
2. How does spreadability affect patient compliance in topical creams?
Answer: Better spreadability ensures even application with minimal effort, improving patient compliance and ensuring effective delivery of active ingredients.
3. Why is Brookfield Viscometer preferred for viscosity measurement in creams?
Answer: The Brookfield Viscometer provides precise, reproducible measurements of cream viscosity, which reflects its consistency, stability, and ease of application.
4. How is the irritancy study standardized in cream evaluation?
Answer: A 1 sq.cm area on the dorsal hand is marked, cream is applied, and the skin is observed for erythema, edema, or irritation at regular intervals for up to 24 hours.
5. What does the saponification value indicate about an oily cream base?
Answer: It indicates the amount of alkali required to saponify the fats or oils in the cream, reflecting the chemical composition and quality of the lipid component.
6. How is homogeneity quantitatively assessed in creams?
Answer: While often evaluated visually and by touch, homogeneity can also be assessed by microscopic examination or by measuring uniform distribution of active ingredients.
7. Why is pH testing critical for topical creams?
Answer: pH testing ensures the cream is compatible with skin, preventing irritation or chemical instability and maintaining the effectiveness of active ingredients.
8. What is the role of acid value determination in cream evaluation?
Answer: Acid value measures the amount of free fatty acids in the cream, which affects stability, shelf-life, and potential skin irritation.
9. Can sterility testing be skipped for non-sterile creams?
Answer: Yes, sterility testing is required only for sterile creams intended for wound care or mucosal application. Non-sterile creams are tested for microbial limits instead.
10. How do evaluation tests ensure compliance with pharmaceutical standards?
Answer: By systematically testing parameters like pH, viscosity, spreadability, sterility, and homogeneity, creams are verified to meet quality, safety, and efficacy standards before patient use.