Question

Which of the following preservatives is most effective in acidic pH?

• A. Benzyl alcohol
• B. Sodium benzoate
• C. Chlorobutanol
• D. Phenol

Hint:

Sodium benzoate works best in acidic pH because it forms undissociated benzoic acid, which shows better antimicrobial action.

Answer 1

The Correct Option is B

Concept:
Preservatives are added to pharmaceutical preparations to prevent microbial growth. The effectiveness of many preservatives depends strongly on pH.

Step 1: Understanding sodium benzoate.
Sodium benzoate is the sodium salt of benzoic acid. It is most effective in acidic conditions because, at low pH, benzoate ions are converted into undissociated benzoic acid.

Step 2: Why acidic pH increases activity.
The undissociated form of benzoic acid can easily penetrate microbial cell membranes. After entering the microbial cell, it interferes with cellular functions and inhibits microbial growth.

Step 3: Checking the other options.
Benzyl alcohol is used as a preservative, but it is not the best-known answer for maximum effectiveness in acidic pH.
Chlorobutanol is also a preservative, but its use is not specifically linked as strongly with acidic pH.
Phenol is an antimicrobial agent, but sodium benzoate is the correct preservative for acidic pH.

Step 4: Final answer.
Therefore, the preservative most effective in acidic pH is Sodium benzoate. \[ \boxed{\text{Sodium benzoate}} \]