Evaluating the Accuracy of Elemental Analysis of Soil and Rock Prepared by Microwave Acid Digestion
Faculty Mentor
Carmen Nezat
Document Type
Poster
Start Date
10-5-2023 9:00 AM
End Date
10-5-2023 10:45 AM
Location
PUB NCR
Department
Environmental Science
Abstract
The EWU Environmental Geochemistry Lab recently attained a microwave digestion system (CEM MARS 6) to transform solid samples (e.g., soil, crushed rock, plant material) into liquid form in order to be analyzed using current instrumentation in the lab. The microwave system provides a safer, faster, and consistent treatment of samples than the standard hot plate method of digestion. In this study, we evaluate the accuracy of these methods, especially the potential for contamination when analyzing trace amounts of metals. Certified reference materials (CRMs from USGS and NIST) were digested in Teflon vessels using concentrated, trace metal-grade nitric acid. The digests were diluted with ultrapure water, filtered through 0.45µm membranes, and analyzed for elements such as calcium (Ca), iron (Fe), potassium (K), lead (Pb) and zinc (Zn) using an Inductively Coupled Plasma - Optical Emission Spectrometer (ICP-OES). Procedural blanks were prepared using the same procedure as the samples. Results indicate insignificant Pb and Zn contamination: concentrations in the procedural blanks were less than 1% of those in heavy metal-contaminated soil references and were very low in the procedural blanks and heavy metal-poor rocks. Concentrations of Ca, Fe, Mg, and K in the procedural blanks were less than 1% of those in the naturally-occurring rock references; Na concentrations were higher and more variable (4-19%). The next step is to compare measured amounts of digested CRMs to their certified values.
Recommended Citation
Desimone, Carson, "Evaluating the Accuracy of Elemental Analysis of Soil and Rock Prepared by Microwave Acid Digestion" (2023). 2023 Symposium. 46.
https://dc.ewu.edu/srcw_2023/res_2023/p1_2023/46
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Evaluating the Accuracy of Elemental Analysis of Soil and Rock Prepared by Microwave Acid Digestion
PUB NCR
The EWU Environmental Geochemistry Lab recently attained a microwave digestion system (CEM MARS 6) to transform solid samples (e.g., soil, crushed rock, plant material) into liquid form in order to be analyzed using current instrumentation in the lab. The microwave system provides a safer, faster, and consistent treatment of samples than the standard hot plate method of digestion. In this study, we evaluate the accuracy of these methods, especially the potential for contamination when analyzing trace amounts of metals. Certified reference materials (CRMs from USGS and NIST) were digested in Teflon vessels using concentrated, trace metal-grade nitric acid. The digests were diluted with ultrapure water, filtered through 0.45µm membranes, and analyzed for elements such as calcium (Ca), iron (Fe), potassium (K), lead (Pb) and zinc (Zn) using an Inductively Coupled Plasma - Optical Emission Spectrometer (ICP-OES). Procedural blanks were prepared using the same procedure as the samples. Results indicate insignificant Pb and Zn contamination: concentrations in the procedural blanks were less than 1% of those in heavy metal-contaminated soil references and were very low in the procedural blanks and heavy metal-poor rocks. Concentrations of Ca, Fe, Mg, and K in the procedural blanks were less than 1% of those in the naturally-occurring rock references; Na concentrations were higher and more variable (4-19%). The next step is to compare measured amounts of digested CRMs to their certified values.
