Journal cover Journal topic
Ocean Science An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 2.539 IF 2.539
  • IF 5-year value: 3.129 IF 5-year
    3.129
  • CiteScore value: 2.78 CiteScore
    2.78
  • SNIP value: 1.217 SNIP 1.217
  • IPP value: 2.62 IPP 2.62
  • SJR value: 1.370 SJR 1.370
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 48 Scimago H
    index 48
  • h5-index value: 32 h5-index 32
Discussion papers
https://doi.org/10.5194/os-2019-126
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-2019-126
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 09 Jan 2020

Submitted as: research article | 09 Jan 2020

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).

Impact of impurities in bromocresol green indicator dye on spectrophotometric total alkalinity measurements

Katharina Seelmann1, Martha Gledhill1, Steffen Aßmann2, and Arne Körtzinger1,3 Katharina Seelmann et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 2Kongsberg Maritime Contros GmbH, Kiel, Germany
  • 3Christian-Albrechts-Universität zu Kiel, Kiel, Germany

Abstract. Due to its accurate and precise character, the spectrophotometric pH detection is a common technique applied in measurement methods for carbonate system parameters. However, impurities in the used pH indicator dyes can influence the measurements quality. The work described here focuses on influences from impurities in the pH indicator dye bromocresol green (BCG) on spectrophotometric seawater total alkalinity (AT) measurements. First, a high-performance liquid chromatography (HPLC) purification method for BCG was developed. A subsequent analysis of BCG dye from four different vendors with this method revealed different types and quantities of impurities. After successful purification, AT measurements with purified and unpurified BCG were carried out using the novel autonomous analyzer CONTROS HydroFIA® TA. Long-term measurements in the laboratory revealed a direct influence of impurity types and quantities on the drift behavior of the analyzer. The purer the BCG, the smaller was the drift increment per measurement. Furthermore, we could show that a certain impurity in some indicator dyes changed the drift pattern from linear to non-linear, which can impair the AT measurements during a long-term deployment of the system. Laboratory performance characterization experiments revealed no improvement of the measurement quality (precision and accuracy) by using purified BCG as long as the impurities of the unpurified dye do not exceed a quantity of 2 % (relationship of peak areas in the chromatogram). However, BCG with impurity quantities higher than 6 % provided AT values, which failed fundamental quality requirements. Concluding, to gain optimal AT measurements, an indicator purification is not necessarily required as long as the purchased dye has a purity level of at least 98 %.

Katharina Seelmann et al.
Interactive discussion
Status: open (until 05 Mar 2020)
Status: open (until 05 Mar 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Katharina Seelmann et al.
Katharina Seelmann et al.
Viewed  
Total article views: 134 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
98 33 3 134 1 2
  • HTML: 98
  • PDF: 33
  • XML: 3
  • Total: 134
  • BibTeX: 1
  • EndNote: 2
Views and downloads (calculated since 09 Jan 2020)
Cumulative views and downloads (calculated since 09 Jan 2020)
Viewed (geographical distribution)  
Total article views: 72 (including HTML, PDF, and XML) Thereof 71 with geography defined and 1 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Cited  
Saved  
No saved metrics found.
Discussed  
No discussed metrics found.
Latest update: 27 Jan 2020
Publications Copernicus
Download
Short summary
We investigated the impact of indicator dye impurities on spectrophotometric seawater measurements, especially how they may influence the drift behavior and the measurement quality of an autonomous analyzer using this indicator. These measurements are important for ocean carbon observations. This work revealed that impurities up to a quantity of 2 % do not influence the measurement drift and quality. Higher impurity levels lead to a changing drift behavior and quality deteriorations.
We investigated the impact of indicator dye impurities on spectrophotometric seawater...
Citation