0.1 N NaOH Standardization as per USP
Importance of Standardization
Standardization is a critical step in analytical chemistry to ensure the accuracy and reliability of results. In pharmaceutical analysis, standardization of titrants is essential to determine the concentration of active pharmaceutical ingredients (APIs) and excipients. The United States Pharmacopeia (USP) provides guidelines for the standardization of 0.1 N NaOH, a commonly used titrant in pharmaceutical analysis.
Principle of 0.1 N NaOH Standardization
The standardization of 0.1 N NaOH is based on the reaction between NaOH and potassium hydrogen phthalate (KHP). KHP is a primary standard, meaning its purity is well-established and can be used to standardize other substances. The reaction involves the neutralization of KHP with NaOH:
KHP + NaOH → NaKP + H2O
Procedure for 0.1 N NaOH Standardization
Step 1: Preparation of KHP Solution
- Weigh accurately about 2-3 grams of KHP into a 100 mL beaker.
- Add about 50 mL of boiled and cooled water to the beaker.
- Stir the mixture until the KHP is completely dissolved.
Step 2: Titration of KHP Solution with 0.1 N NaOH
- Pipette 20-25 mL of the KHP solution into a conical flask.
- Add 2-3 drops of phenolphthalein indicator to the flask.
- Titrate the KHP solution with 0.1 N NaOH until the color of the solution changes from colorless to pink.
- Record the volume of 0.1 N NaOH required for the titration.
Step 3: Calculation of 0.1 N NaOH Concentration
- Calculate the weight of KHP (in grams) that reacted with 0.1 N NaOH.
- Calculate the normality of NaOH using the formula:
Normality of NaOH = (Weight of KHP / Equivalent weight of KHP) x (1000 / Volume of NaOH required)
- The equivalent weight of KHP is 204.22 g/mol.
- Calculate the concentration of NaOH (in M) using the normality value.
Acceptance Criteria
- The normality of 0.1 N NaOH should be between 0.095 and 1.05 N.
- The concentration of NaOH (in M) should be within ± 2% of the theoretical value.
Conclusion
The standardization of 0.1 N NaOH is a critical step in pharmaceutical analysis. The procedure outlined above follows the guidelines set forth by the USP and ensures the accuracy and reliability of results. By following this procedure, analysts can ensure that their 0.1 N NaOH titrant is of high quality and suitable for use in pharmaceutical analysis.
