Ozone Testing Kit Using Indigo Method Eliminates Need To Measure Reagent Volume

Ozone Testing Kit Using Indigo Method Eliminates Need To Measure Reagent Volume
Ozone Vacu-vials Kit from CHEMetrics

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The Ozone Vacu-vials Kit from CHEMetrics enables water producers to test for residual ozone following the disinfection process using the Indigo method.

Commonly used in Europe, ozone disinfection is gaining acceptance in the United States and other countries as water utilities move away from chlorination, says Henry Castaneda, vice president of marketing and technology, CHEMetrics.

“The problem with chlorination is it may form byproducts that have been known to be hazardous and in some instances suspect carcinogen precursors. In the case of ozone, it’s a compound that breaks down into oxygen.”

However, because ozone is a gas, it quickly separates from water, making it difficult to measure. Typically, two methods are used to measure ozone in the treatment process: DPD and the Indigo method.

“In the case of municipalities, if they’re trying to measure the effectiveness of the ozone-generating equipment, they are probably going to be reading about 1 or 3 ppm and using the DPD method to measure the residual ozone concentration,” Castaneda says. “If they happen to be chlorinating at the same time, typically they’re going to use the Indigo method.”

Using the DPD method, potassium iodide is added to the sample before analysis. Ozone reacts with the iodide, releasing iodine, which reacts with DPD (N, N-diethyl-p-phenylenediamine) to form a pink color.

With the Indigo method, the Indigo trisulfonate reagent immediately reacts with the ozone. The color of the blue reagent decreases in intensity in proportion to the amount of ozone present in the sample. The test reagent is formulated with malonic acid to prevent interference from up to at least 10 ppm of chlorine.

“What makes us distinctive is how we do the testing,” Castaneda says. “We use a liquid reagent in a vacuum-sealed ampoule to produce a color reaction. Most other techniques use a powder or tablet reagent that requires mixing and compromises the ozone concentration in the sample. Basically, the way it works is the ampoule, which looks like a pencil with a tapered tip, is placed at the bottom of the sample. When the tip is snapped, the ampoule aspirates the precise amount of sample. The operator does not have to measure sample volume.”

With Indigo chemistry, CHEMetrics’ self-zeroing technology eliminates the need to generate a reagent blank for each test. Only one ampoule is required per test.

Results can be read in any spectrophotometer that accepts a 13 mm cylinder, enabling operators to use existing laboratory equipment.
The Indigo Vacu-vials Kit has a range of 0 to 0.75 ppm. Additional kits are available for testing fluoride and other compounds by using different reagents. 800/356-3072; www.chemetrics.com.


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