Traditional methods of quantitative analysis are often ill-suited to determining the bulk chemistry of high salinity brines due to their corrosive and clogging properties. Such methods are also often difficult to apply remotely in planetary environments. However, Raman spectroscopy can be used remotely without physical contact with the fluid and is not affected by many ionic brines. Developing methods to study aqueous solutes is vital to future study of brines on Mars and other planetary bodies, as they can reveal important information about modern and ancient near-surface aqueous processes. Both sodium carbonate standards and unknown samples from carbonate mineral dissolution experiments in high salinity brines were analyzed using a 532 nm laser coupled to an in Via Renishaw spectrometer to collect carbonate spectra from near-saturated sodium chloride and sodium sulfate brines. A calibration curve was determined by collecting spectra from solutions of known carbonate concentrations mixed with a pH 13 buffer and a near-saturated NaCI or NazS04 brine matrix. The spectra were processed and curve fitted to determine the height ratio of the carbonate peak at 1066 cm-1 to the 1640 cm-1 water peak. The calibration curve determined using the standards was then applied to the experimental data after accounting for dilutions. Concentrations determined based on Raman spectra were compared against traditional acid titration measurements.
McGraw, L. (2016, April). Development of a Rapid, Nondestructive Method to Measure Aqueous Solutes in High Salinity Brines Using Raman Spectroscopy. Poster session presented at the University of Oklahoma's Undergraduate Research Day, Norman, OK.