Journal
FRONTIERS IN MARINE SCIENCE
Volume 5, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fmars.2018.00177
Keywords
m-Cresol Purple; brackish water; estuaries; spectrophotometric pH measurements; traceability; primary standard; TRIS buffer
Funding
- BONUS, the joint Baltic Sea research and development programme [185]
- European Union's Seventh Programme for research, technological development and demonstration
- German Federal Ministry of Education and Research [03F0689A, 03F0773A]
Ask authors/readers for more resources
Spectrophotometric pH measurements allow for an accurate quantification of acid-base equilibria in natural waters, provided that the physico-chemical properties of the indicator dye are well known. Here we present the first characterization of purified m-Cresol Purple (mCP) directly linked to a primary pH standard in the salinity range 5-20. Results were obtained from mCP absorption measurements in TRIS buffer solutions. The pH(T) of identical buffer solutions was previously determined by Harned cell measurements in a coordinated series of experiments. The contribution of the TRIS/HCI component to the ionic strength of the buffer solutions increases toward lower salinity: This was taken into account by extrapolating the determined pK(2)e(2) to zero buffer concentration, thereby establishing access to a true hydrogen ion concentration scale for the first time. The results of this study were extended with previous determinations of pK(2)e(2) at higher and lower salinity and a pK(2)e(2) model was fitted to the combined data set. For future investigations that include measurements in the salinity range 5-20, pH(T) should be calculated according to this pK(2)e(2) model, which can also be used without shortcomings for salinities 0-40 and temperatures from 278.15 to 308.15 K. It should be noted that conceptual limitations and methodical uncertainties are not yet adequately addressed for pH(T) determinations at very low ionic strength.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available