Dissolution Method for Multivitamin Tablets

Vitamin–Mineral Dosage Forms:

Combinations of water-soluble vitamins (Water-Soluble Vitamins Tablets) and combinations of oil- and water-soluble vitamins (Oil and Water-Soluble Vitamins Tablets) is determined by measuring the dissolution of a single index vitamin from the water-soluble vitamins present. Riboflavin is the index vitamin when present in the formulation. 
For formulations that do not contain Riboflavin, Pyridoxine is the index vitamin. If neither riboflavin nor pyridoxine is present in the formulation, the index vitamin is niacinamide (or niacin), and in the absence of niacinamide (or niacin), the index vitamin is thiamine. If none of the above four water-soluble vitamins is present in the formulation, the index vitamin is ascorbic acid.

Multivitamin Tablets contains following Active Ingredients:
Ascorbic Acid BP 15mg
Cholecalciferol BP 300IU
Niacinamide BP 7.5mg
Vitamin-A Acetate BP 2500IU
Riboflavin BP 0.5mg
Thiamine Mononitrate BP 1mg

Dissolution Condition:
Medium: 0.1 N hydrochloric acid ; 900 mL. 
Apparatus: II ( Paddles ) 
Speed: 75 RPM 
Time: 60 minutes. 
Temperature : 37°C ± 0.5°C 

Preparation of Medium: 
Dilute 51mL of Conc. HCl in 6L of water. Mix well. 

Standard Solution: 
Transfer 10mg Riboflavin secondary reference standard to 100 mL volumetric flask, add 70 mL dissolution medium, sonicate to dissolve and make up to volume with dissolution medium. Dilute 0.6 mL of resulting solution to 100mL with dissolution media. 

Sample Solution: 
Place 900 mL of dissolution medium maintained at 37 ± 0.5°C in 6 dissolution vessels separately. Fix the paddle to the shaft & bring it into the position. Place 1 tablet each into 6 dissolution vessels. Operate the instrument at 75 RPM for 60 minutes. At the end of 60 minutes, Withdraw from each of the vessels about 10mL, combine equal volumes of the filtered solutions of the 6 individual specimens withdrawn, and determine the amount of riboflavin dissolved, based on the average of 6 units tested. 

Chromatographic Conditions: 
Column : 150 mm × 4.6 mm, C18, 5 µm 
Flow Rate : 1 mL/minute 
Column Temperature : 30°C 
Detection Wavelength : 280 nm 
Injection Volume : 20 µL 

Mobile Phase:
Water : Methanol : Acetonitrile : Glacial Acetic Acid ( 75 : 16.5 : 7 : 0.8, v/v) containing 140 mg of Sodium Hexane Sulphonate per 100 ml. 

Inject standard preparation in five replicate & record the chromatogram. Inject sample preparation in duplicate, record the chromatogram. 

% Dissolution of Riboflavin by using the formula:

                                  At = Average Area of Sample solution 
                                  As = Average Area of Standard solution 
                                  Ws = Weight of Standard 
                                  V = Volume of Medium 
                                  P = Potency of Standard 
                                  L = Label Claim

Not less than 75% of the labeled amount of riboflavin is dissolved in 1 hour.

NOTE: Analysts have to perform Method Validation as per Regulatory Guidelines.

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