Rotronic provides guidance and solutions for water activity

products-servicesRotronic AG
March 6th 2018

 

Overview

Water Activity and Moisture Content are two very distinct parameters that are often confused and misused. Both affect pharmaceutical products and processes but in different ways.

In this product bulletin, Rotronic explains the differences between moisture content and water activity and provides an overview of the solutions that apply to measuring both.

Water activity vs moisture content

When one understands the differences between moisture content and water activity, it will be seen that different measurements must be applied to quantify them.

Moisture content is the overall proportion or quantity of water contained in a material, expressed as a percentage in terms of weight and traditionally measured through loss of weight on drying. This measuring method raises some issues: a low drying temperature may not remove all water while a high one may also remove non-water compounds.

More modern methods resolve these issues and use infra-red absorption. This way the water content is directly measured, the method is non-destructive and far quicker.

Water Activity (aW) is a measure of the free or ‘active’ water in a sample, and ranges between 0 and 1, with the latter representing pure water. As water activity measures the ‘free’ or ‘active’ water in a sample it is more relevant to growth of organisms, chemical processes, enzyme activity and physical parameters like size and clumping that are only affected by the water available for chemically interaction.

The significance of ‘free water’

Water can be bound in materials in two different ways.

  • Chemically Bound Water is bound so tightly that it cannot be utilized by bacteria, enzymes etc. It can be removed through high temperature heating.
  • Free Water is also removed through heating but is far more loosely bound through weak bonds, structural diffusion, capillary condensation and surface binding. It can be utilized by bacteria and can exchange with the environment.

A whole grape, for instance, would have the same moisture content as its two constituent halves. However, the aW would be far lower in a whole grape as much of the water is bound inside the grape skin and only ‘freed’ when the grape is cut open.

While Water Activity is related to Moisture Content, it is product and temperature specific and has special relevance to growth of organisms, chemical processes, enzyme activity and physical parameters.

Rotronic water activity measurement solutions

Rotronic offers a complete range of products for measurement of water activity that combine accuracy, high efficiency, compatibility and simple calibration.

Combine the measurement heads, insertion probes, benchtop display units and handheld instruments as you need.

Product overview

AwTherm HygroLab C1 HP23-AW-A HC2-AW-USB HC2-AW
Measurement unit Yes Yes Yes Yes
Display unit Yes Yes Yes
Stationary Yes Yes Yes Yes
Portable Yes
Interchangeable probe connector 4 2 Yes
Probe connector fitted Yes
USB port/connector Yes Yes Yes Yes Yes
Ethernet interface Yes
AwQuick function Yes Yes Yes Yes
HW4-P-Quick PC software Yes Yes Yes
Dew and frost point calculation Yes Yes Yes Yes
HW4 compatibility Yes Yes Yes Yes Yes
Temperature controlled Yes

 

AwTherm
AwTherm is a professional high-end laboratory analyzer for temperature-stabilized measurement of water activity in the food, pharmaceutical, cosmetics and other industries. The wide control range permits measurements to be integrated directly in the temperature-controlled manufacturing or storage process. Stabilizing the temperature prevents imprecise results due to external temperature influences. A removable measurement head allows the probe to be temperature calibrated or adjusted to achieve high precision.

HygroLab C1
The HygroLab C1 is a laboratory analyzer for measuring water activity, relative humidity and temperature with up to four interchangeable measurement heads. Ability to combine measurement heads and insertion probes makes this solution extremely flexible. The HygroLab C1 is easy and intuitive to use. The 4-channel benchtop display unit can be connected via USB or Ethernet with a PC running included Rotronic HW4 software that can be used to configure instruments and as a remote control for the complete system.

HygroPalm23-AW-A
This mobile laboratory unit is perfect for on-site water activity measurements to determine the stability and preservability of the sample being analyzed. HP23-AW-A can be used with up to two measurement heads or insertion probes. The HygroPalm can be controlled externally using the HW4 software running on a PC.

HC2-AW
This aW measurement head was developed for use in combination with the HygroLab C1 and the HP23-A-AW handheld analyzer. This digital probe enables quick and easy measurement of water activity. It can be calibrated via the HygroLabC1, HP23-A-AW or via the HW4 PC software. Compact sample makes it possible for humidity equilibrium to be reached quickly for all products being tested, while the metal housing ensures high temperature stability. All critical surfaces are made of chrome steel for minimal soiling.

HC2-AW-USB
Adding a USB interface to the HC2-AW measurement head allows it to be connected directly to a PC. It comes as a set that includes software or as a single instrument for addition to a system.

Resources

Click on Rotronic solutions in water activity for more information.
Click on Rotronic to contact the company directly.
Click on Products for more information on Rotronic measurement solutions.
Click on Water Activity White Paper for detailed and technical information.

Rotronic HygroLab C1 Water Activity Measurement can quantify ‘free’ water

Rotronic HygroLab C1 Water Activity Measurement can quantify ‘free’ water

Rotronic AWTherm allows temperature stabilized water activity measurements

Rotronic AWTherm allows temperature stabilized water activity measurements


Supplier Information
Supplier: Rotronic AG
Address: Grindelstrasse 6, CH-8303 Bassersdorf, Switzerland
Tel: +41 44 838 1144
Fax: +41 44 838 1487
Website: http://www.rotronic.com