Sunday, July 11, 2021

Calibration of Dissolution Test Apparatus

The calibration of dissolution apparatus can differ according to different Pharmacopoeias such as USP/BP/IP. According to the USP, the dissolution test consists of four standardized apparatus i.e. basket, paddle, reciprocating cylinder, and flow-through cell. The use of a certain standardized instrument for the drug (active pharmaceutical ingredient) to be analyzed is specified in the monograph.

Dissolution Testing is a quality control test used to evaluate the different dosage forms such as tablets, capsules, suppositories, and pessaries, etc. Every instrument needs to be calibrated for confirming the desired performance as per the standards, the calibration procedure of dissolution test apparatus types 1 and 2 are mentioned in the USP. There are two methods of calibration of dissolution test apparatus such as the physical parameter, and USP tablet calibrator. In physical calibration, check the level adjustment, vibration, shaft rotating speed (RPM), alignment, centering, wobble, depth of paddle/basket, timer, and temperature, etc. In performance verification parameter, dissolution calibration using USP Prednisone calibrator tablets are used with distilled water.


Calibration procedure of dissolution test apparatus:

  • Operate the instrument as per the standard operating procedure (SOP).
  • Materials needed to calibrate: Calibrated Vernier caliper, stopwatch, tachometer, thermometer, prednisone standard, prednisone tablets, water, methanol, Whatman filter paper, glassware, approved kit, and UV-spectrophotometer, etc.

Physical calibration:

Level adjustment of dissolution:

Be sure to level the dissolution test before calibrating using a bubble or spirit level. to adjust the level, rotate the leveling wheel which is provided at the bottom.

Basket calibration of dissolution:

Check each basket's physical characteristics such as the ID of the basket, appearance, external diameter of basket and ring, height, the height of coupling disk, and vent hole diameter, etc. All parameters must be within the range given in the monograph.
Parameter Limit
ID of screen 20.2±1.0 mm
Hole diameter 2.0±0.5 mm
External diameter screen 22.2±1.0 mm
External diameter of ring 25.0±0.02 mm
Total height 37.0 ±3.0 mm
Height of screen 27.0±1.0 mm
Height of coupling disk 5.1±0.5 mm
Distance from bottom 25±2 mm

Paddle calibration of dissolution:

Check each basket's physical characteristics such as paddle height, shaft diameter, upper and lower chord, thickness and distance from the bottom, etc. All parameters must be within the range given in the monograph.
Parameter Limit
ID of screen 20.2±1.0 mm
Hole diameter 2.0±0.5 mm
External diameter screen 22.2±1.0 mm
External diameter of ring 25.0±0.02 mm
Total height 37.0 ±3.0 mm
Height of screen 27.0±1.0 mm
Height of coupling disk 5.1±0.5 mm
Distance from bottom 25±2 mm

Timer calibration of dissolution:

Set a timer for 30 minutes, and turn on the instrument and stopwatch simultaneously, when the instrument is turned off, note the stopwatch reading and note down the observations. The acceptance limit for the timer should not deviate from ± 1 minute.

Spindle speed calibration of dissolution:

Attached the basket or paddle to the instrument and set the 50 RPM. Place the tachometer in contact with each spindle, start the revolution, and take a note of the reading. Or manually count the number of revolutions per minute. Repeat the same process for 100 and 150 RPM alternatively. The standard limit of speed is NMT 4.0 % of set RPM

Wobble test (Shaft of paddle/basket) of dissolution:

Make sure that the paddle/ basket shaft is clean and free of any particle, attached it to the instrument, and lower the apparatus. Place the Wobbling meter in each jar about 2 mm above the paddle/basket, such that the device does not come into contact with the paddle/basket. Operate the machine at 50 RPM and measure the Wobbling of each shaft and basket in mm. The wobbling for paddle/basket as per the USP standard is 2.0 mm.

Paddle/ basket depth calibration of dissolution:

Attached the paddle and basket in each spindle alternatively and lower the apparatus. Place the Vernier caliper/ depth gauge between the bottom of the tool and the bottom of the bowl. Measure the distance from the bottom edge of the paddle blade/basket to the innermost surface of the jar. The standard limit of depth is 25.0± 2mm.

Temperature calibration of dissolution:

Set the temperature of the water bath at 37oC, place the vessels in a water bath, and allow the dissolution medium to come to a temperature of 37oC.Using a calibrated thermometer, check that the temperature of the vessels is within range. Repeat the same procedure for 35, 37, and 40oC. The standard limit of temperature is ± 0.50C.

Chemical calibration:

Calibration of dissolution using prednisone tablets:

Sample: Prednisone tablets (Disintegrating type) 50 mg.
Dissolution medium: 500 ml purified water
Volume: 500 ml
Temperature: 37°C ± 0.5°C
Speed: 50 RPM
Duration: 30 minutes

Procedure for USP type-I dissolution: Set the all above parameters and perform the dissolution test for USP type-I using prednisone tablets (Disintegrating type). Calculate the content of prednisone using the analytical procedure of UV/HPLC at 242 nm. The acceptance criteria for USP type-I at 50 RPM are 45 to 75 % release.

Procedure for USP type-II dissolution: Maintain the same conditions as described under USP type-I and repeat the procedure as in USP type-I, however instead of paddles, use baskets. The acceptance criteria for USP type-I at 50 RPM are 35 to 65 % release.

Calibration of dissolution using salicylic acid tablets:

The calibration of dissolution test equipment using salicylic acid tablets (Non- disintegrating type) has been discontinued.

Why dissolution test apparatus calibration with salicylic acid tablets stopped?

Salicylic acid tablets are unstable and tend to stick together, and as a result, they fail to meet analytical standards. The salicylic acid tablets were therefore withdrawn from the calibration of the dissolution test apparatus.

What is the calibration frequency of the dissolution apparatus?

The physical calibration of the dissolution apparatus takes place every three months, while the chemical calibration takes place every six months.  

ANNEXURES:

Annexure 1: It is a format for recording temperature and rpm calibration data for the dissolution test apparatus.
Annexure 2: It is a format for recording wobble calibration data for the dissolution test apparatus.
Annexure 3: It is a calibration record format of dissolution test apparatus for prednisone tablet and salicylic acid tablet calibration.


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