Is the ultra low range version of TNT843 for Phosphorus USEPA compliant?

Document ID

Document ID TE12890

Published Date

Published Date 04/07/2021
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Question
Is the ultra low range version of TNT843 for Phosphorus USEPA compliant?
Summary
Information on the compliance of TNT843 using 5 cm path length cell for ULR.
Answer
Similarly to the explanation for the High Range Chlorine method (see also: What documentation is available to support the use of the DPD Chlorine methods for reporting? ) the William Telliard letter from 2003 ( which can be downloaded here  page 11) states that an extension of the calibration range of a compliant method is within the scope of the method and does not require regulatory approval provided that the upper limit of the linear range of the instrument or analytical system is not exceeded.

Or worded specifically in regards to the ULR TNT843: USEPA TNTplus Phosphorus - Spectrophotometric Measurement of Phosphorus in Water and Wastewater  is equivalent to EPA method 365.3/SM 4500-P E under the ATP rule and is therefore compliant. Modifications to extend the range by using a longer path length (following this method document: 10209 Spectrophotometer ULR, TNTplus 843) should not require any additional approval to also be compliant.

As always in regards to regulatory questions, check with your regulator if you have any questions.

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