Monday, May 12, 2008

Going Green

Sample prep is vital to growing water testing uses

By John Sira and Lynn Jordan

Water is a critical natural resource for the entire planet. A clean water supply affects daily life in many ways, including as a drinking source for plants and animals. While industrial nations have built extensive treatment plants for drinking water, many developing nations still struggle with disease and illness, such as cholera, resulting from unsanitary drinking sources. As the United States becomes more environmentally conscious, the need for testing our water supply is increasing dramatically. State and federal agencies such as the U.S. Environmental Protection Agency have built extensive procedures for testing water. These procedures include testing everything from the drinking water supply to contaminants in our oceans, lakes, rivers and streams. Water testing will continue to grow throughout the world as techniques become more advanced and the instrumentation required becomes more accessible.

The water supply of the United States is monitored by multiple federal, state and local entities. Local public water works monitor and test the water that is plumbed into households and businesses. These agencies test the sources of our water for a wide variety of biological and chemical contaminants from many sources including pollution, illegal dumping, or even from something as simple as prescription medications that enter the water supply through our wastewater system. Typically, biological and chemical contaminants are unnoticeable without the use of sophisticated analysis techniques.

Analysis of trace-level contaminants is one of the most rapidly growing and advancing areas of water testing. In order to ensure accurate detection and analysis of contaminants, careful preparation of the sample is critical. The sample preparation process begins with the collection of the water sample. This step is done in the field, with someone taking a sample of the water to be tested from the river, stream, ocean or lake. The sample then enters the "cleanup" phase of the sample preparation process; two of the most common techniques are extraction and concentration.

Extraction techniques commonly performed include Solid Phase Extraction (SPE) or Liquid/Liquid Extraction. The purpose of both extraction techniques is to remove impurities from the sample so it is easier to detect the low level contaminants. These techniques essentially clean the sample of unwanted materials to allow for better detection of sample contaminants. Extractions can also be a form of sample concentration, resulting in a concentration of contaminates. Essentially, analytical laboratories use these extraction techniques to concentrate and purify samples prior to analysis.

SPE and Liquid/Liquid extraction can be performed manually or automated with a sample preparation workstation. Automation means all samples are handled identically and are not subject to operator variations. In turn, this consistency makes automated sample preparation more reliable and reproducible. Sample cleanup is not only critical in detection of low level contaminates but it also plays an important role for the analytical instrumentation used for detection of these contaminates. To detect such low-levels, the analytical instrumentation is very sensitive, and dirty samples not only impact the quality of the analysis but can also result in costly and unpredictable down time and repairs for the instrumentation.

Once a sample has been cleaned up through an extraction process, the sample extract is typically evaporated to dryness. The purpose of an evaporation step is to remove the extraction solvents, which would interfere with the separations and quantitation of contaminates. The evaporation step can be as simple as air drying a sample or using a heat source to evaporate and concentrate the sample. Many laboratories use commercially produced concentration devices. These devices typically use centrifugal force or a combination of heat and nitrogen gas to provide rapid evaporation and concentration. By using these concentration devices, evaporation time is greatly reduced. The faster the samples are cleaned up, the faster the final sample results are obtained.

Imagine a needle in a haystack. It's nearly impossible to find it using your bare hands but with the right tools and techniques, it can easily be accomplished. Further, it is crucial to do in order to ensure safety. This is analogous to finding trace levels of contaminants in a lake or a river. Proper sample preparation insures that harmful contaminants will be detected in the sample analysis.

John Siira is global evaporation and extraction product manager, and Lynn Jordan is applications scientist, at Caliper Life Sciences Inc. of Hopkinton. They can be reached at 508-435-9500.