Serving Scientists Since 1994

Equipment Qualification

Calibrating Your Dissolution Tester

There have been a number of changes relating to equipment qualification over the past few years. Today there is basically a choice between running the USP qualification which involves both physical testing and running a calibrator tablet, or calibrating to physical parameters only, the ASTM Physical testing parameters.

In response to the ASTM proposals, the USP published a 'USP Dissolution Toolkit'  which suggests tighter physical parameters in addition to the calibrator tablets, Prednisone.

One argument put forward is that if a dissolution tester is mechanically perfect, then there is no need to run calibrator tablets, technically that might be correct, except there are a number of external parameters that can have an effect on the dissolution test which fall outside simple physical testing. One of these is the operator, and a reasonable argument can be made that operators should be able to run the calibrator tablets as part of their training to ensure that they are competent to perform everyday tests on other pharmaceutical products.

An excellent article by Gregory Martin and Vivian Gray, published in Dissolution Technologies Journal discusses Dissolution Instrument Qualification and Common Pitfalls and is well worth reading.


Mechanical Calibration

In terms of the mechanical calibration requirements, both the ASTM guidelines and the USP Toolkit require reasonably tight specifications. This is required to maintain a good correlation between each testing position. 


Calibration Parameter ASTM Mechanical Calibration Specifications USP Toolkit Specifications
Shaft Wobble

≤1.0 mm runout, 2 cm
above the paddle or

≤1.0 mm runout, 1 cm
above the paddle or

Shaft Verticality

<0.5° from vertical at
2 points 90° apart

<0.5° from vertical at
2 points 90° apart

Basket Wobble

≤1.0 mm runout at
bottom of basket

≤1.0 mm runout at
bottom of basket


≤1.0 mm, at 2 mm and
60 mm above basket or
at 2 mm and 80 mm
above paddle

≤2.0 mm, not more
than 2 cm below the
flange of the vessel

Vessel Verticality

<1.0° from vertical at
2 points 90° apart

<0.5° from vertical at
2 points 90° apart

Height of basket or
paddle, above
bottom of vessel

25 ± 2 mm 25 ± 2 mm

Rotational Speed
(50 rpm)

±2 rpm ±1 rpm
Temperature 37 + 0.5 °C

37 ± 0.5 °C, range not
more than 0.4 °C


Prednisone Calibrator Tablets

The Prednisone Calibrator tablets are available from the country USP representative. The Pass/Fail criteria are lot dependent and published with the tablets as are the CV% allowed between vessels. 

Prednisone is very sensitive and can fail for a number of reasons. If a failure occurs then there may be implications for any tests performed since the last calibration and so it is important to keep everything about the tester in top condition and constantly checked.

Failures due to poor degassing, vibration, vessels, physical tester parameters and poor storage are not uncommon.


Storage and Use of Calibrator Tablets

  • Keep tablets in a dessicator until just before use.
  • Remove tablets and brush off excess powder.
  • Use Forceps or gloves - never touch Prednisone with bare fingers
  • Use immediately - do not allow the tablets to sit on a bench awaiting use as they will degrade very quickly
  • Do not use broken tablets
  • Drop on a stationary paddle to avoid chipping or breakage


Validation Logbooks

It is highly advisable to maintain a logbook for each dissolution tester, to include all serial numbers, locations and all procedures on the equipment. It helps you should things go wrong and enables traceability at all times.


Calibration Frequency

In general, equipment calibration is repeated every six months.

If the tester is moved for any reason it will need to be re-calibrated

If only paddles or only baskets are used, then it is not necessary to calibrate for both methods


Variables That Can Effect Dissolution Tests

As mentioned at the top of this page, variables can be physical or operator related. The table below is not exhaustive but provides some insight into some of these parameters.

Physical Variables Operator Variables

Drive Belts
Current Surges
Instrument Geometry (Verticality)
Bath Maintenenance
Shaft Wobble
Basket Maintenance
Basket and Vessel Cleanliness
Vessel Errors
Rotation Speed
Paddle/Basket Height



Correct Apparatus Set-Up
Medium Degassing
Medium Preparation
Sample Handling
Sample Introduction
Sampling Technique
Sample Preparation
Standards Preparation 

As you can see there are a lot of parameters to consider. In the following pages we will aim to examine some of these.


Next Page - Basic Set-Up & Care 


Associated Products

Validation Tools