📌 Limit Test Series – Part 2🔬 Limit Test for Chlorides (IP) – Complete Student Guide

📌 Limit Test Series – Part 2

🔬 Limit Test for Chlorides (IP) – Complete Guide for Pharmacy Students

Subject: Pharmaceutical Analysis

Course: B.Pharm | D.Pharm | Pharm.D

Series: Limit Test Series

✨ Introduction

In pharmaceutical analysis, limit tests are used to control the presence of small amounts of impurities that may affect the quality and safety of pharmaceutical substances.

The Limit Test for Chlorides is a commonly asked and practically important test in pharmacy exams. It ensures that chloride impurities do not exceed the prescribed pharmacopoeial limit.

This blog explains the principle, reagents, procedure, observation, acceptance criteria, and exam-oriented points in a simple and clear manner.

🧪 What is the Limit Test for Chlorides?

The limit test for chlorides is a semi-quantitative test used to detect and control chloride ions present as impurities in pharmaceutical substances.

The test is based on the comparison of turbidity produced by the test solution with that of a standard solution.

⚗️ Principle of Limit Test for Chlorides

The test is based on the reaction between chloride ions and silver nitrate in the presence of nitric acid, resulting in the formation of silver chloride, which produces turbidity.

Chemical Reaction:

Cl⁻ + AgNO₃ → AgCl ↓ (White turbidity)

If the turbidity produced in the test solution is not greater than that of the standard solution, the sample passes the test.

🧫 Reagents Required

Reagent

Purpose

Silver Nitrate Solution

Forms silver chloride precipitate

Nitric Acid

Provides acidic medium

Standard Chloride Solution

For comparison

Distilled Water

Solvent

🧪 Procedure

🔹 Preparation of Test Solution

Dissolve the given sample in distilled water

Add nitric acid to acidify the solution

Add silver nitrate solution

Mix well and allow to stand for 5 minutes

🔹 Preparation of Standard Solution

Take a known volume of standard chloride solution

Add the same reagents in the same quantity

Maintain identical conditions as the test solution

👀 Observation

Observe the turbidity produced in:

Test solution

Standard solution

✅ Acceptance Criteria

✔️ The turbidity of the test solution should not be greater than the turbidity of the standard solution.

Less or equal turbidity → Pass

Greater turbidity → Fail

📚 Exam-Oriented Important Points

The limit test for chlorides is a turbidity comparison test

White precipitate formed is silver chloride

Acid used in the test is nitric acid

Silver nitrate acts as the precipitating agent

The method is specified in the Indian Pharmacopoeia (IP)

❓ Viva & MCQ-Based Questions

What is the principle of the limit test for chlorides?

Which acid is used in the chloride limit test?

Why is turbidity compared instead of weight?

Name the precipitate formed in the test.

📈 How This Blog Helps Students

Easy language for quick revision

Perfect for practicals, viva, and exams

Helpful for Pharmaceutical Analysis subject

Suitable for notes and PDF conversion