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Mass spectra of sulfonephthalein pH indicator dyes and their impurities

Published by National Institute of Standards and Technology | National Institute of Standards and Technology | Catalog Last Checked: August 03, 2026 at 03:49 AM | Dataset Last Updated: November 25, 2015
Sulfonephthalein pH indicator dyes have historically been noted for impurities originating from the synthesis process which lead to batch to batch differences in pH measurements. Uncertainties up to 0.1 pH units have been attributed to impurities in these reagents. In an effort to understand the extent of impurities in these dyes and the potential impact on the expanded uncertainty of pH measured by this technique, we have examined seven commercially available sulfonephthalein pH indicators using liquid chromatography-mass spectrometry (LC-MS): bromocresol green (BCG), bromocresol purple (BCP), bromothymol blue (BTB), cresol red (CR), meta-cresol purple (MCP), phenol red (PR), and thymol blue (TB). Peaks eluting from the LC (Figure 1) were subjected to fragmentation by mass spectrometry. The resulting dataset will aid in efforts to improve the synthesis or purification of these dyes.

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Complete Metadata
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contactPoint 
{
  "fn": "Benjamin Place",
  "hasEmail": "mailto:benjamin.place@nist.gov"
}
description Sulfonephthalein pH indicator dyes have historically been noted for impurities originating from the synthesis process which lead to batch to batch differences in pH measurements. Uncertainties up to 0.1 pH units have been attributed to impurities in these reagents. In an effort to understand the extent of impurities in these dyes and the potential impact on the expanded uncertainty of pH measured by this technique, we have examined seven commercially available sulfonephthalein pH indicators using liquid chromatography-mass spectrometry (LC-MS): bromocresol green (BCG), bromocresol purple (BCP), bromothymol blue (BTB), cresol red (CR), meta-cresol purple (MCP), phenol red (PR), and thymol blue (TB). Peaks eluting from the LC (Figure 1) were subjected to fragmentation by mass spectrometry. The resulting dataset will aid in efforts to improve the synthesis or purification of these dyes.
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identifier 3DF9EB5C7EEFBBE3E0531A570681B5811503
keyword 
[
  "mass spectrometry",
  "pH indicators",
  "seawater pH"
]
landingPage https://data.nist.gov/od/id/3DF9EB5C7EEFBBE3E0531A570681B5811503
language 
[
  "en"
]
license https://www.nist.gov/open/license
modified 2015-11-25 00:00:00
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publisher 
{
  "name": "National Institute of Standards and Technology",
  "@type": "org:Organization"
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references 
[
  "https://doi.org/10.6028/jres.122.021"
]
theme 
[
  "Chemistry:Analytical chemistry",
  "Environment:Air / water / soil quality",
  "Environment:Environmental health"
]
title Mass spectra of sulfonephthalein pH indicator dyes and their impurities

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