VOLUMETRIC SOLUTION PREPARATION AND STANDARDISATION AS PER USP

Purpose

To describe the procedure for “Preparation and Standardization of Volumetric Solutions”

Scope

This procedure is applicable for “Preparation and Standardization of Volumetric Solutions”

Procedure:

Precautions:

·         Solutions of limited stability/unstable should be prepared on the day of use or otherwise specified and standardized before use.

·         To minimize volumetric error, the temperature should be same for the volumetric apparatus, the material being prepared, the solvents being used to prepare the volumetric solutions.

·         For Blank determination where it is directed that “any necessary correction” be made by blank determination, the determination should be done using the same quantities of the same reagent treated in the same manner as the solution or mixture containing the portion of the substances under examination but omitting the substances under examination.

·         Volumetric solution should be prepared and standardized at room temperature.

·         Keep the bottle of the standardized solution always closed to protect it from Contamination.

·         Dispense a required quantity of the standardized solution in a clean dry container.

·         Do not dip any pipette in the stock solution or replace the dispensed quantity back in the stock solution to prevent contamination.

·         Always wear protective goggles, gloves and a lab coat

·         When diluting acid, add small volumes of the acid to large volumes of water to disperse heat whilst mixing thoroughly. During pouring of the liquid, pouring down the sides prevents splashing.

·         Work near a running supply of water. If the acid contacts the skin, it must be washed off rapidly with copious amounts of tap water (however with large spills onto the skin, wipe off excess first).

Have a supply of neutralizer (sodium carbonate or bicarbonate) in case of acid spill. It should be first isolated to prevent it spreading and the area evacuated in case of fumes. Sand and a bucket can be used to clear acid for neutralization. Handle the flammable solvents with extra care and proper safety measures.

Preparation: VOLUMETRIC SOLUTION PREPARATION AND STANDARDISATION AS PER USP

·         Volumetric Solution’s validity shall be of one month from the date of preparation.

·         Standard procedures shall be followed for preparation and standardization of volumetric solutions.

·         Detailed method of preparation of volumetric solutions mentioned in Volumetric Solutions Preparation & Standardization method.

·         The volumetric solutions must be prepared by accurately weighing a suitable quantity & dissolving in specified solvent to produce the specified volume as mentioned in the respective General Test Procedure (GTP)/ Pharmacopoeia.

·         Weaker solutions are prepared and standardized using proportionate amounts of the reagent or by making an exact dilution of a stronger solution.

·         Volumetric solutions prepared by dilution should be re-standardized either as directed for the stronger solution or by comparison with another volumetric solution having known ratio to the stronger solution.

·         The water used in the preparing volumetric solutions complies with the requirement of the monograph on purified water unless otherwise specified.

·         Analyst shall check the expiry & Re- standardization date before using any volumetric solution, and shake the solution well in order to mix the drops of water condensed on the top and sides of the bottles with the solution in the bottle.

·         Use freshly boiled and cooled purified water for preparation of unstable solutions such as potassium permanganate, sodium thiosulphate.

·         All volumetric solution shall be stored in transparent / amber colored glass bottles (as shown in picture below) whichever is suitable for the storage and stability of prepared solution.

·         For volumetric solution preparation of sodium hydroxide plastic bottles to be used for the storage of the volumetric solution.

Allocation of VS No.:

For numbering of volumetric solutions given below procedures shall be followed:

VS/YY/XX,

Where,

VS           :               Volumetric Solution

YY           :               last 02 digits of the year

XX           :               VS Number

Standardization: VOLUMETRIC SOLUTION PREPARATION AND STANDARDISATION AS PER USP

Volumetric solutions must be standardized by titration against a primary standard or by titration with a standard solution that has been recently standardized against a primary standard.

Re-standardization:

Restandardize the volumetric solutions after 15 days or when as required. During re-standardization of volumetric solution calculate the variance by following formula:

Initial molarity – New molarity

Variance % = ----------------------------------------------------- x 100 = …………. %

Initial molarity

Acceptance Criteria:

·         All the VS when standardized shall not deviate more than +/- 10 % of the standard value (strength). All the volumetric solutions shall be titrated in triplicate set & the RSD shall not be more than 0.2 %.

·         Variance shall be less than 1.0% when all the VS are Restandardize. All the volumetric solutions should be titrated in triplicate set & the RSD shall not be more than 0.2 %.

·         Molarity of volumetric solution recorded to 4th decimal for 0.1 to 1.0 M/N solutions & for solution of 0.01 or less than 0.1 M/N the molarity should be determined up to 5th decimal.

·         VS that show evidence of deterioration e.g. Sedimentation, discoloration or crystallization will be discarded and freshly prepared and standardized VS shall be used for analysis.

Labelling:

All the bottles should be labeled indicating the name & the strength of the solution date of preparation, signature of the person who prepared & standardized it, date of standardization, standardization due on date, use before date., Molarity/Normality, Batch No of VS as per label

4.8          Storage:

·         Volumetric Solutions shall be stored below 25°C / or specified in respective SOP.

·         Volumetric solution of Silver nitrate should be kept in amber coloured bottles protected from light.

Usage:

·         When a solution is to be used in an assay in which

·         the end point is determined by an electrochemical process (like: potentiometrically) the solution shall be standardized in the same way.

·         The apparatus shall be chosen and use with care. A burette shall be of such size that the titrant volume represents not less than 30 % of the nominal volume. Where less than 10 ml of titrant shall be measured with a 10 ml burette or suitable burette.

·         For viscous fluids like syrups, the pipette or flask shall be washed clean, after draining, and the washing added to the measured portion.

·         The capacity tolerance for volumetric flask, transfer pipette, and burette are those should be Class A and calibrated.

·         Any VS shall not to be used after 01 month from its preparation date. Expired Volumetric Solution shall be discarded as per specified procedure and recorded

·         For those volumetric solutions whose stability data not available, shall be prepared freshly for use. These volumetric solutions shall not be stored for further use. VOLUMETRIC SOLUTION PREPARATION AND STANDARDISATION AS PER USP

Records:

·         All entries related to drying/ weighing shall be done in related log books.

·         Records are to be maintained for each solution starting with the value determined when the solution was prepared & continuing with the values determined throughout the shelf life of the solutions. This record shall be retained for at least 2 years after the solution has expired.

·         All volumetric solutions prepared and standardized shall be listed for their observed molarity or normality and their next due date preparation / Restandarization

·         Validity and standardization details of volumetric solution shall be prepared and approved as per format

References

European Pharmacopoeia           

Indian Pharmacopoeia