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    • UV-visible absorbance spectra of purified and unpurified m-cresol purple samples in sodium hydroxide and sodium chloride solutions at pH 12

    Metadata Updated: September 30, 2025

    M-cresol purple is the most widely used pH indicator dye for seawater pH measurements. Impurities in the indicator are known to absorb strongly at one of the wavelengths used in spectrophotometric pH determination and lead to large biases in the pH measurements. This repository contains data and Matlab scripts to facilitate the implementation of a DD-SIMCA model for detecting residual impurities in purified m-cresol purple (mCP) relevant to climate quality seawater pH measurements. The model was trained on measurements of UV-visible absorbance spectra of purified mCP and tested on independent datasets consisting of purified and unpurified mCP samples. The repository contains demo scripts that will demonstrate the training and optimization of the DD-SIMCA model and reproduce the figures in the associated publication. A function is provided for users to classify new mCP samples with the model.The datasets consist of measurements of the UV-visible absorbance spectra (350 nm to 750 nm) of purified and unpurified m-cresol purple samples in sodium hydroxide and sodium chloride solutions at pH12 and an ionic strength of 0.7 mol/kg soln. The UV-visible absorbance measurements were collected on an Agilent Cary 100 spectrophotometer at NIST. A second dataset is included consisting of similar measurements of various purified m-cresol purple samples collected on an Agilent 8453 spectrophotometer at MBARI. This dataset was used to test the performance of the SIMCA model on samples measured on a different spectrophotometer. The SIMCA model and results are published in the manuscript "Detection of impurities in m-cresol purple with SIMCA for the quality control of spectrophotometric pH measurements in seawater."

    Access & Use Information

    Public: This dataset is intended for public access and use. License: See this page for license information.

    Downloads & Resources

    References

    https://doi.org/10.1016/j.marchem.2024.104362

    Dates

    Metadata Created Date September 30, 2025
    Metadata Updated Date September 30, 2025
    Data Update Frequency irregular

    Metadata Source

    Harvested from Commerce Non Spatial Data.json Harvest Source

    Other Data Resources

    Additional Metadata

    Resource Type Dataset
    Metadata Created Date September 30, 2025
    Metadata Updated Date September 30, 2025
    Publisher National Institute of Standards and Technology
    Maintainer
    Identifier ark:/88434/mds2-3055
    Data First Published 2024-04-02
    Language en
    Data Last Modified 2023-07-13 00:00:00
    Category Environment:Marine science, Chemistry:Analytical chemistry
    Public Access Level public
    Data Update Frequency irregular
    Bureau Code 006:55
    Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
    Schema Version https://project-open-data.cio.gov/v1.1/schema
    Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
    Harvest Object Id dc3ab264-0bec-43ef-b96a-32ed8154b9c3
    Harvest Source Id bce99b55-29c1-47be-b214-b8e71e9180b1
    Harvest Source Title Commerce Non Spatial Data.json Harvest Source
    Homepage URL https://data.nist.gov/od/id/mds2-3055
    License https://www.nist.gov/open/license
    Program Code 006:045
    Related Documents https://doi.org/10.1016/j.marchem.2024.104362
    Source Datajson Identifier True
    Source Hash 1edef08f37b5a1893259eff7cee5cda7b44c90f47b1d86d6149340877fb77007
    Source Schema Version 1.1

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