Liquid Impingement Techniques

Microbiological Monitoring

• Microorganisms can be found everywhere that air can be found. Bacteria spores have even been found in the jet stream, high above the Earth. Because pharmaceuticals have to be manufactured in sterile environments to avoid contamination, the air in pharmaceutical plants is typically monitored on an ongoing basis for microorganisms. Liquid impingement techniques are sometimes used for this purpose.

The Technique of Liquid Impingement

• Liquid impingement devices use suction to pump air through a tube with a narrow opening into a flask containing a liquid. The narrow opening causes the air to speed up as it is sucked through the tube. When the air strikes the liquid, its direction changes, and microorganisms present in the air are left behind in the liquid. The microorganisms can then be identified and counted in a culture of the liquid. A liquid impingement device can also work by causing air to bubble through the liquid in the collection flask.

Disadvantages

• Liquid impingement does have certain disadvantages. Microorganisms can suffer cellular damage from the liquid. If the liquid is allowed to sit for too long, some microorganisms may reproduce, affecting the accuracy of the sample count. In addition, glass is generally not used in pharmaceutical plants, but most liquid impingement devices are made of glass.

Variations

• Alternative techniques for liquid impingement are sometimes preferred to the traditional method. For example, the Coriolis and SAS-PCR devices are not made of glass, so they are more suitable for a controlled space such as a pharmaceutical manufacturing area. The Coriolis device uses centrifugal forces to expel microorganisms from the air onto the walls of a flask. The SAS-PCR device is designed to increase the amount of time in which the liquid is in contact with the air.