Different Dissolution Testing Apparatus

                               

Different Dissolution Testing Apparatus

Dissolution is the process by which a solid solute enters a solution. In the pharmaceutical industry, it may be defined as the amount of drug substance that goes into solution per unit time under standardized conditions of liquid/solid interface, temperature and solvent composition. Drug dissolution testing plays an important role as a routine quality control test, for characterizing the quality of the product and also plays a major role in drug development. Dissolution testing is an official test used by pharmacopeia’s for evaluating drug release.

Table No. 1: List of the Official Dissolution Apparatus and their uses

S. No.	Official Name	Main features of the apparatus	Uses	Rot. speed
1	USP Apparatus 1	Basket	Tablets, capsules, Floating dosage forms	50-120 rpm
2	USP Apparatus 2	Paddle	Tablets, capsules, enteric forms	25-50 rpm
3	USP Apparatus 3	Reciprocating cylinder	Extended release drug product	6-35 rpm
4	USP Apparatus 4	Flow through cell	Implants, powders, suspensions	N/A
5	USP Apparatus 5	Paddle over disk	TDDS, Ointments	25-50 rpm
6	USP Apparatus 6	Cylinder 6	TDDS	N/A
7	USP Apparatus 7	Reciprocating disk	Extended release drug product	30 rpm

          

Apparatus I- Basket Apparatus:

·       Unless otherwise specified in the individual monograph, use 40- mesh cloth.

·       Useful for: Capsules, Beads, Delayed release / Enteric Coated dosage forms , Floating dosage forms

·       Standard volume: 900/1000 ml

 

 Apparatus-II - Paddle Apparatus

 

Method of first choice the dosage unit is allowed to sink to the bottom of the vessel before rotation of the blade is started. A small, loose piece of no reactive material such as not more than a few turns of wire helix may be attached to dosage units that would otherwise float. Other validated sinker devices may be used.

·       Useful for: Tablets, Capsules, Beads, Delayed release, enteric coated dosage forms

·       Standard volume: 900/1000 ml.

Apparatus III – Reciprocating cylinder:

 

The assembly consists of a set of cylindrical, flat-bottomed glass vessels; a set of glass reciprocating cylinders; stainless fittings (type 316 or equivalent) and screens that are made of suitable nonsorbing and nonreactive material (polypropelene) and that are designed to fit the tops and bottoms of the reciprocating cylinders; and a motor and drive assembly to reciprocate the cylinders vertically inside the vessels.

The vessels are partially immersed in a suitable water bath of any convenient size that permits holding the temperature at 37 ± 0.5 during the test.

The dosage unit is placed in reciprocating cylinder & the cylinder is allowed to move in upward and downward direction constantly. Release of drug into solvent within the cylinder measured.

·       Useful for: Tablets, Beads, controlled release formulations.

·       Standard volume: 200-250 ml/station.

Apparatus IV – flow through cell

 

The assembly consists of a reservoir and a pump for the Dissolution Medium; a flowthrough cell; a water bath that maintains the Dissolution Medium at 37 ± 0.5. The cell size is specified in the individual monograph.

The pump forces the Dissolution Medium upwards through the flow-through cell. Place the glass beads into the cell specified in the monograph, Place 1 dosage unit on top of the beads or, if specified in the monograph, on a wire carrier and then assemble the filter head, and fix the parts together by means of a suitable clamping device.

By introducing the pump the Dissolution Medium warmed to 37 ± 0.5 through the bottom of the cell to obtain the flow rate specified in the individual monograph. Collect the elute by fractions at each of the times stated, Perform the analysis as directed in the individual monograph.

·       Useful for: Low solubility drugs, Micro particulates, Implants, Suppositories, Controlled release formulations

·       Variations: (A) Open system & (B) Closed system

 

Apparatus V–Paddle over disk:

Use the paddle and vessel assembly from Apparatus 2 with the addition of a stainless steel disk assembly designed for holding the transdermal system at the bottom of the vessel. Other appropriate devices may be used, provided they do not sorb, react with, or interfere with the specimen being tested. The disk assembly for holding the transdermal system is designed to minimize any “dead” volume between the disk assembly and the bottom of the vessel, the disk assembly holds the system flat and is positioned such that the release surface is parallel with the bottom of the paddle blade, the vessel may be covered during the test to minimize evaporation.

·       Useful for: Transdermal patches

·       Standard volume: 900 ml.

 Apparatus VI–cylinder:

Use the vessel assembly from Apparatus 1 except to replace the basket and shaft with a stainless steel cylinder stirring element and to maintain the temperature at 32 ± 0.5 during the test. The dosage unit is placed on the cylinder at the beginning of each test, to the exterior of  the cylinder such that the long axis of the system fits around the circumference of the cylinder & removes trapped air bubbles. Place the cylinder in the apparatus, and immediately rotate at the rate specified in the individual monograph.

Apparatus VII – Reciprocating Holder:

The assembly consists of a set of volumetrically calibrated solution containers made of glass or other suitable inert material, a motor and drive assembly to reciprocate the system vertically and a set of suitable sample holders. The solution containers are partially immersed in a suitable water bath of any convenient size that permits maintaining the temperature, inside the containers at 32 ± 0.5. For Coated tablet drug delivery system attach each system to be tested to a suitable sample holder (e.g., by gluing system edge with 2-cyano acrylate glue onto the end of a plastic rod or by placing the system into a small nylon net bag at the end of a plastic rod or within a metal coil attached to a metal rod).

Semisolid Drug Products - Performance Tests

A.    Vertical Diffusion Cell

The vertical diffusion cell (VDC) system is a simple, reliable, and reproducible means of measuring drug release from semisolid (cream, ointment, and gel) dosage forms. Typically, 200–400 mg of a cream, ointment, or gel is spread evenly over a suitable synthetic, inert support membrane. The membrane, with its application side up, is placed in a VDC (typically a 15-mm diameter orifice), e.g., a Franz cell. Diffusive communication between the delivery system and the reservoir takes place through an inert, highly permeable support membrane. The membrane keeps the product and the receptor medium separate and distinct. Membranes are chosen to offer the least possible diffusional resistance and not to be rate controlling. The release rate experiment is carried out at 32 + 1 Deg C, except in the case of vaginal creams when the temperature should be 37 +1 Deg C

B.     Special Immersion Cell

The Immersion Cell is a test system designed for ointments, creams, lotions, etc., for quality control purposes. It can be used on a standard dissolution system in combination with small volume paddle and a flat bottom mini dissolution vessel. The ointment is sealed in a delivery chamber where it can only move into the solution through a membrane.