Tapping into the Latest Water Testing Methods

The quality and quantity of the water we drink has a direct impact on our health and well-being. Water carries nutrients and oxygen to our cells, regulates body temperature, removes waste, aids breathing and cushions joints and vital organs. The human body, which is about two-thirds water, loses roughly 10 cups (2.37 l) every day through perspiration, respiration and other bodily functions. This water must continually be replaced to sustain life and maintain optimum health.

On earth as well as within living organisms, water is in constant circulation. Long before it fills our glass, water evaporates from the oceans, falls onto the land as rain and snow, and either makes its way back to the oceans or is collected for human consumption. However, in its natural state, very little of this water is pure enough for us to drink. River and lake water contain organic matter, and groundwater often contains concentrations of mineral salts. Agricultural runoff, factory waste products and waterborne sewage systems add chemical and bacterial pollutants to many water sources.

Good enough to drink

To ensure a regular supply of pure drinking water, fresh water is collected from springs, rivers and wells, then stored, purified and distributed. Purification is the most important step and water treatment plants around the world use a variety of processes to remove contaminants. Sedimentation and filtration are used to remove solid particles and some types of bacteria. Aeration increases the amount of dissolved oxygen in the water and aids natural purification. Disinfection processes such as chlorination and ozonation are used to kill harmful microoganisms.

Ozonation is the chemical reaction that occurs when ozone is added to water. Ozone (O₃) is formed when oxygen (O₂) is struck by a source of energy. Because ozone breaks down into oxygen fairly quickly, it is a strong oxidizing agent that sterilizes water (in part by eliminating organic waste) and also reduces color and odor. However, ozonation is a chemical reaction that can create byproducts such as bromate, a potential carcinogen, with a U.S. Environmental Protection Agency (USEPA) Maximum Contaminate Level (MCL) of no more than 10 parts per billion (ppb) in drinking water. Bromate is formed during the ozonation of water that contains bromide, which commonly occurs in coastal regions where water sources are subject to salt water intrusion. To ensure water safety, it is essential to measure bromate in ozonated drinking waters at sub-ppb levels.

Detecting bromates in drinking water

The USEPA currently specifies the use of ion chromatography (IC) with conductivity detection as the approved method for detection of bromate in drinking water. In this process, IC is used to separate the bromide from other substances in the water, while a conductivity detector is used to measure the ionic components as they pass through a column. The conductivity detector measures concentration gradients by tracing the electrical currents conducted by various substances. Because this detection method is nonspecific, it cannot be used to distinguish between chloride and bromide, which are very similar. This makes it necessary to remove chloride from the sample before it is subjected to IC, a time-consuming and tedious process. To eliminate this pretreatment step, scientists have been evaluating inductively coupled plasma mass spectroscopy (ICP-MS) as an alternative ion-selective detector for IC analysis.

Since the late 1980s, scientists have used ICP-MS to perform trace multielement analysis, finding applications in a number of different fields. Because ICP-MS provides the resolution necessary to separate the bromide and chloride ion, it eliminates the need for pretreatment of the sample. However, because there were no commercially available means of coupling ICP-MS to chromatography, traditional approaches were cumbersome, labor intensive and not readily automated.

Increasing testing efficiency

To meet this need, Agilent developed the first fully integrated solution specifically designed for the rigors of automated trace-element speciation, comprising an Agilent 1100 Series HPLC system, coupled to a 7500 Series ICP-MS and real-time Plasma Chromatographic software (see diagram, below).

In early 2001, this system was used to investigate the fully automated, routine analysis of bromate in drinking water. The instrumentation used in the study was found to surpass all the performance criteria specified in the methodology, achieving a method detection limit of 0.14 ppb. To access more complete information about this study, you may view or download the application note "Automated Real-Time Determination of Bromate in Drinking Water Using LC-ICP-MS and EPA Method 321.8." ( 415 kbytes )

For more information

ICP-MS is one of the fastest growing techniques in analytical chemistry. For more information about this technique and Agilent's state of the art instrumentation, please visit the ICP-MS section of our Web site. Information about this and other products and solutions for chemical and biochemical researchers can be found on the main page of the Chemical/Life Sciences section of our Web site.

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