PURIFICATION AND CHARACTERIZATION OF BROMOCRESOL PURPLE FOR SPECTROPHOTOMETRIC SEAWATER ALKALINITY TITRATIONS

Author

Taymee A. Brandon, The University Of MontanaFollow

Graduation Year

2016

Graduation Month

May

Document Type

Thesis

Degree Name

Bachelor of Science

School or Department

Chemistry and Biochemistry, Department of

Major

Chemistry

Faculty Mentor Department

Chemistry and Biochemistry, Department of

Faculty Mentor

Dr. Michael DeGrandpre

Faculty Reader(s)

Dr. Michael DeGrandpre

Keywords

ocean acidification, indicator, flash chromatography, hplc

Subject Categories

Analytical Chemistry | Environmental Chemistry

Abstract

The topic of my research is the purification of the sulfonephthalein indicator bromocresol purple (BCP). BCP is used as an acid-base indicator in seawater alkalinity determinations. Impurities in sulfonephthalein indicator salts often result in significant errors in pH values³. High-precision inorganic carbon (i.e. CO₂) measurements are necessary to document the changes in ocean chemistry and pH due to anthropogenic CO₂­ uptake by the earth’s oceans³. In order to reduce the error in seawater pH determinations and the general understanding of the CO₂ cycle, BCP must be purified and characterized. Previous work has described the use of flash chromatography to efficiently produce large batches of purified indicator, so this method was used for BCP purification³. Since BCP is purified at a level useful for seawater pH calculations, the chemical can be characterized by more accurately calculating the constants associated with it¹. The spectrophotometric pH values obtained by measuring absorbance ratios are directly related to indicator molecular properties, such as molar absorptivity ratios and protonation characteristics². Once the accuracy of these values is improved, future and archived spectrophotometric pH data can be calculated using the improved indicator equilibrium and molar absorptivity values². The available purification method of BCP will advance the understanding of ocean acidification in systems where the chemical is used.

Honors College Research Project

1

Recommended Citation

Brandon, Taymee A., "PURIFICATION AND CHARACTERIZATION OF BROMOCRESOL PURPLE FOR SPECTROPHOTOMETRIC SEAWATER ALKALINITY TITRATIONS" (2016). Undergraduate Theses, Professional Papers, and Capstone Artifacts. 97.
https://scholarworks.umt.edu/utpp/97