COLORIMETRIC METHOD

COLORIMETRIC METHOD

1. BCDA COLLEGE OF PHARMACY AND TECHNOLOGY NAME : AMIT MIA ROLL NO : 20101921032 REG.NO: 212010201910019 SUBJECT: PHYSICAL PHARMACEUTICS 1(CA1) CODE: PT 316 TOPIC: COLORIMETRIC METHOD TO DETERMINE pH

2. CONTENTS INTRODUCTION Principle Method Precautions Advantage Disadvantage Reference

3. COLORIMETRIC METHOD : Colorimeter method is used to determine the P H of the solution up to +- 0.2 units in the range of P H 3 to 11.0 based on the colour changes. INTRODUCTION

4. C olorimeter

5. PRINCIPLE The principle involves the comparison of color of the test solution with that of the standard solution of the definite pH values colors are developed by adding universal indicator to both test and standard solution.

6. Several standard solutions are available commercially, which are premixed solution of buffer and indicator. CAPILLARIES : The buffer solution and universal indicator are mixed and placed in capillary tubes. A set of such standard solution is known as capillators . COMPARATORS : For large volumes, comparators are used, The test sample is also mixed with universal indicators.

7. METHOD Standard buffer solution of known PH values ranging from 3.0 to 11.0 are prepared with 1.0 PH intervals. A few drops of the universal indicators are added to each buffer solution different color produces. A few drops of indicators are added to the test solution. The color of unknown solution is matched with the standard colors produced by buffer solution. Based on the approx. PH value obtained in step (d), the PH interval is reduced to a narrow range. Steps from (b) to (d) are repeated and the exact PH of test solution reported.

8. PRECAUTIONS : Standard solution must be protected from light to prevent color fading. All tubes should be of same dimensions.

9. ADVANTAGE Colorimetric method is less expensive. It is useful for the study of acid base reactions in non aqueous solution. DISADVANTAGE It is particularly Used when the solution is not colored or not turbid. Errors may result by the presence of salts , protein etc. This method is less accurate and less convenient.

10. REFFERENCE C.v.s subrahmonyam ,DR. Ashok A hajare .