Proposal

Abstract

For my solution mode ICP-MS analytical project, I am determining the concentrations of rare earth elements within rock and groundwater samples. These samples were collected from an area in the Hill Country of Central Texas near Hamilton pool, on a property called Mirasol Springs. Measuring rare earth elements using ICP-MS requires careful planning. To ensure the data are reliable, interferences must be accounted for by tuning the instrument, using standards, and interference equations. As part of this project, I will be analyzing the effectiveness of Ce tuning solution by running the samples after high vs low signal production of CeO during tuning.

The REE’s studied in this project include 139Lu, 140Ce, 141Pr, 146Nd, 149Sm, 157Gd, 159Tb, 163Dy, 165Ho, 166Er, 169Tm, 172Yb and 175Lu. The project will compare the accuracy of each analytical method using a standard. If the standards demonstrate that the two methods of analysis have different levels of accuracy, then the results will have to account for the differences in accuracy.

Hypothesis

As for the analytical part of the project:

I hypothesize that there will be several oxide interferences on the rare earth elements when using less Ce tuning solution.

As for the chemical makeup of the samples:

Because the samples being tested are sands, limestones and shales deposited in a marine environment, the chemical makeup of the samples will reflect past deposition of REE’s. The environment in the area of study experiences very little disturbance, so there is likely little to no outside influence on the concentration of REE’s. Therefore, the REE concentrations in groundwater are likely to reflect the REE concentrations from the geologic units.

Project significance

My analytical project will demonstrate the importance of having precise methods of analysis for rare earth elements. The samples must be kept in a sterile environment. Blanks, calibration standards and internal standards must be used to ensure that the data are reliable. The equipment should be tuned. Intereferences must be considered and accounted for. My project will demonstrate the significance of each of these steps, specifically regarding REE’s.

Methods

Sample collection:

The rock samples analyzed in this project were collected by Brian Hunt via air rotary drilling. I selected 5 representative samples from his cores, one sample from each unit in the project area. These units include the Upper Glen Rose Limestone, Lower Glen Rose Limestone, Hensel Sand, Cow Creek Limestone, Hammett Shale and Sycamore Sand.

Sample prep:

Rock samples will be dissolved in HF and microwaved, then nitric acid will be added, and the sample will be dried again. Water will be added to dilute the sample (as defined by Barbaro, et. al. 1995). Because HF was added to the sample, special materials need to be used when doing analysis via solution ICPMS. Therefore, a PFA nebulizer, spray chamber, and injector connector will be used. A Pt injector will attach to the torch, and the torch will be made of high purity quartz glass (ESI 2024). The ICPMS analytical methods followed by Barbaro (1995) will be used for the rock samples.

For each of the methods, an ultrasonic nebulizer will be used to have higher detection limits, since REE’s often have low detection limits. Argon gas will be used in the nebulizer, and argon will be used in the plasma to create ions. To account for oxide or polyatomic intereferences, a CRC will be used. There should be no isobaric interferences (Jose, et. al. 2024).

Timeline and Budget