Is it possible to measure a concentration that is above the upper limit specified for a test?

Document ID

Document ID TE764

Version

Version 2.0

Status

Status Published

Published Date

Published Date 27/05/2017
Question
Is it possible to measure a concentration that is above the upper limit specified for a test?
Summary
Measure a concentration above the upper limit of a test
Answer
Add deionized or distilled water to the sample so that it is diluted to a concentration that can be measured. Run the test using the diluted sample, and then multiply the result by the dilution factor to find the concentration in the original sample (before dilution). Make sure reagents are added after the sample has been diluted to ensure that enough reagent is available to react with the parameter being measured. Some parameters such as ozone, sulfide, ferrous iron, and oxygen scavengers are not suitable for dilution because they will be partially consumed by reactions with oxygen or lost to the atmosphere. In these cases, it is best to use a test method with a higher range. If there are impurities in the dilution water, disinfectants such as chlorine will be consumed, and results will be lower than actual.