Does sample temperature effect the UV lamp in the phosphonate test?

Document ID

Document ID TE7034

Version

Version 3.0

Status

Status Published

Published Date

Published Date 07/31/2018
Question
Does sample temperature effect the UV lamp in the phosphonate test?
Summary
Phosphonate UV lamp test
Answer
Mercury lamps are sensitive to cool temperatures because the bulb temperature determines the vapor pressure. The lamp can be over-cooled to the point that full output in the mercury spectrum is never achieved. Chilled water will decrease the operating voltage and interfere with the proper evaporation of Mercury. A Mercury-Xenon lamp contains a specific amount of Mercury and a small amount of Xenon is added at a pressure above one atmosphere. The Xenon is necessary to facilitate starting and sustaining the arc until the Mercury is fully vaporized. It also reduces the warmup period. Normal warmup time for a Mercury-Xenon lamp is about 10-15 minutes.

If the phosphonate test (method 8007) is yielding low results, check to see if the entire UV lamp shaft is emitting light. If not, the sample temperature is directly effecting the output of the mercury spectrum and the sample should be warmed to room temperature or the lamp should be allowed to warm for 10-15 minutes prior to use.

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