Abstract
Microwave-assisted digestion using tetrafluoroboric acid (HBF4) was evaluated as a reduced-hazard alternative to hydrofluoric acid (HF) for elemental analysis of geological materials. Six geological reference materials spanning a range of lithologies and compositions relevant to sedimentary paleoenvironmental investigations (BHVO-2, SCo-2, SSAR-1, MESS-4, NOD-A-1, and ShBOQ-1) were digested using an automated microwave system and analysed for elemental concentrations by ICP-MS/MS. Near-quantitative recovery of refractory silicate- and oxide-associated elements, including Cr, Co, and Ni, indicates effective dissolution of resistant mineral phases, although minor under-recovery of Ti and Zr suggests that digestion may not have been fully quantitative for all refractory minerals. In contrast, Mg, Al, Ca, rare earth elements (REEs), and Th exhibited notably reduced recoveries, inferred to result from the precipitation of insoluble fluorides and oxides—a limitation common to fluoride-based digestion methods. Despite this, the method enables efficient microwave-assisted sample processing and is well suited for the determination of REE profiles and concentrations of light transition metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) and many trace elements (Be, Na, P, S, K, Nb, Sb, Ba, Tl, Pb, U) from geological materials, while presenting lower hazards relative to conventional HF-based digestion procedures.
References
Arslan, Z., & Lowers, H. (2024). Trace Silicon Determination in Biological Samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS): Insight into the Volatility of Silicon Species in Hydrofluoric Acid Digests for Optimal Sample Preparation and Introduction to ICP-MS. Minerals, 14(3), 299. https://doi.org/10.3390/min14030299
Axelsson, M. D., Rodushkin, I., Ingri, J., & Öhlander, B. (2002). Multielemental analysis of Mn–Fe nodules by ICP-MS: optimisation of analytical method. The Analyst, 127(1), 76–82. https://doi.org/10.1039/b105706p
Bédard, L. P., Savard, D., & Barnes, S. (2008). Total Sulfur Concentration in Geological Reference Materials by Elemental Infrared Analyser. Geostandards and Geoanalytical Research, 32(2), 203–208. https://doi.org/10.1111/j.1751-908X.2008.00881.x
Birdwell, J. E., & Wilson, S. A. (2021). Mineral Resources Program Energy Resources Program Geochemical and Mineralogical Properties of Boquillas Shale Geochemical Reference Material ShBOQ-1. https://doi.org/10.3133/fs20213048
Birdwell, J. E., & Wilson, S. A. (2021). Results from geochemical and mineralogical characterization of Boquillas Shale geochemical reference material ShBOQ-1. US Geological Survey (USGS) Data Release, 1005. https://doi.org/10.3133/fs20213048
Bollen, M. R., Blaser, P., Bruggmann, S., Wu, S., & Jaccard, S. L. (2026). Geological Reference Materials by Microwave Digestion with HBF4 [dataset]. The AuScope EarthBank Platform. https://doi.org/10.57744/LDLDB1186369
Chen, B., Krachler, M., Gonzalez, Z. I., & Shotyk, W. (2005). Improved determination of arsenic in environmental and geological specimens using HG-AFS. Journal of Analytical Atomic Spectrometry, 20(2), 95. https://doi.org/10.1039/b416142d
Chen, S., Wang, X., Niu, Y., Sun, P., Duan, M., Xiao, Y., Guo, P., Gong, H., Wang, G., & Xue, Q. (2017). Simple and cost-effective methods for precise analysis of trace element abundances in geological materials with ICP-MS. Science Bulletin, 62(4), 277–289. https://doi.org/10.1016/j.scib.2017.01.004
Cox, G. M., Jarrett, A., Edwards, D., Crockford, P. W., Halverson, G. P., Collins, A. S., Poirier, A., & Li, Z.-X. (2016). Basin redox and primary productivity within the Mesoproterozoic Roper Seaway. Chemical Geology, 440, 101–114. https://doi.org/10.1016/j.chemgeo.2016.06.025
Fiket, Ž., Mikac, N., & Kniewald, G. (2017). Mass Fractions of Forty-Six Major and Trace Elements, Including Rare Earth Elements, in Sediment and Soil Reference Materials Used in Environmental Studies. Geostandards and Geoanalytical Research, 41(1), 123–135. https://doi.org/10.1111/GGR.12129
Flanagan, F. J., & Gottfried, D. (1980). USGS rock standards; III, Manganese-nodule reference samples USGS-Nod-A-1 and USGS-Nod-P-1. https://doi.org/10.3133/pp1155
Govindaraju, K. (1994). 1994 Compilation of Working Values and Sample Description for 383 Geostandards. Geostandards Newsletter, 18(S1), 1–158. https://doi.org/10.1046/j.1365-2494.1998.53202081.x-i1
Hallmaier, M., Gutjahr, M., Lippold, J., Hemming, S. R., Gerber, L., Weber, M. E., & Eisenhauer, A. (2025). Authigenic Uranium Preservation and Bottom Water Oxygenation in the Scotia Sea. Geochemistry, Geophysics, Geosystems, 26(9), e2025GC012415. https://doi.org/10.1029/2025gc012415
Horsburgh, N. J., Finch, A. A., & Friis, H. (2023). Lanthanide and yttrium substitution in natural fluorite. Physics and Chemistry of Minerals, 50(2). https://doi.org/10.1007/s00269-023-01239-4
Hu, Z., & Gao, S. (2008). Upper crustal abundances of trace elements: A revision and update. Chemical Geology, 253(3–4), 205–221. https://doi.org/10.1016/j.chemgeo.2008.05.010
Javed, M. B., Grant-Weaver, I., & Shotyk, W. (2020). An optimized HNO3 and HBF4 digestion method for multielemental soil and sediment analysis using inductively coupled plasma quadrupole mass spectrometry. Canadian Journal of Soil Science, 100(4), 393–407. https://doi.org/10.1139/cjss-2020-0001
Jochum, K. P., Nohl, U., Herwig, K., Lammel, E., Stoll, B., & Hofmann, A. W. (2005). GeoReM: A New Geochemical Database for Reference Materials and Isotopic Standards. Geostandards and Geoanalytical Research, 29(3), 333–338. https://doi.org/10.1111/j.1751-908x.2005.tb00904.x
Jochum, K. P., Weis, U., Schwager, B., Stoll, B., Wilson, S. A., Haug, G. H., Andreae, M. O., & Enzweiler, J. (2016). Reference Values Following ISO Guidelines for Frequently Requested Rock Reference Materials. Geostandards and Geoanalytical Research, 40(3), 333–350. https://doi.org/10.1111/j.1751-908x.2015.00392.x
Kagami, S., & Yokoyama, T. (2021). Simultaneous Determination of Insoluble Fluoride-Forming and High Field-Strength Element Abundances in Rock Samples by ICP-QMS through Isotope Dilution-Internal Standardisation. Geostandards and Geoanalytical Research, 45(4). https://doi.org/10.1111/ggr.12394
Karandashev, V. K., Khvostikov, V. A., Nosenko, S. V., & Burmii, Zh. P. (2017). Stable Highly Enriched Isotopes in Routine Analysis of Rocks, Soils, Grounds, and Sediments by ICP-MS. Inorganic Materials, 53(14), 1432–1441. https://doi.org/10.1134/s0020168517140084
Klein, O., Zimmermann, T., Hildebrandt, L., & Pröfrock, D. (2022). Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution. Science of The Total Environment, 852, 158464. https://doi.org/10.1016/j.scitotenv.2022.158464
Krachler, M., Mohl, C., Emons, H., & Shotyk, W. (2002). Influence of digestion procedures on the determination of rare earth elements in peat and plant samples by USN-ICP-MS. Journal of Analytical Atomic Spectrometry, 17(8), 844–851. https://doi.org/10.1039/b200780k
Lee, S.-A., Kim, H., Kim, Y.-I., Otosaka, S., Bollen, M., Blaser, P., Haghipour, N., Yoon, T.-H., Joo, H. T., Jaccard, S. L., Eglinton, T. I., Kim, M., Kim, I.-N., Sun, X., & Jeong, J. (2026). Multi-Isotopic approach to trace the provenance and trajectory of sinking particles in the Ulleung Basin, East Sea (Japan Sea). Frontiers in Marine Science, 13. https://doi.org/10.3389/fmars.2026.1832231
Li, Z.-H., WoldeGabriel, G., & Marina, O. (2024). Tetrafluoroboric Acid Digestion for Accurate Determination of Rare Earth Elements in Coal and Fly Ash by ICP-MS Analysis. Minerals, 14(1), 72. https://doi.org/10.3390/min14010072
Maher, W. A., Krikowa, F., Foster, S. D., Ellwood, M. J., & Bennett, W. W. (2018). Antimony measurements in environmental matrices: seven considerations. Journal of Analytical Atomic Spectrometry, 33(5), 706–712. https://doi.org/10.1039/c7ja00391a
Marques, R., Prudêncio, M. I., & Russo, D. (2021). Rare earths and other chemical elements determined by neutron activation analysis in new reference USGS materials: carbonatite, nephelinite, syenite, granite, stream sediment and marine shale. Journal of Radioanalytical and Nuclear Chemistry, 327(3), 1229–1236. https://doi.org/10.1007/s10967-021-07605-2
Muratli, J. M., McManus, J., Mix, A., & Chase, Z. (2012). Dissolution of fluoride complexes following microwave-assisted hydrofluoric acid digestion of marine sediments. Talanta, 89, 195–200. https://doi.org/10.1016/j.talanta.2011.11.081
Okina, O. I., Lyapunov, S. M., & Dubensky, A. S. (2018). Influence of sample treatment after bomb digestion on determination of trace elements in rock samples by ICP-MS. Microchemical Journal, 140, 123–128. https://doi.org/10.1016/j.microc.2018.04.020
Pourmand, A., Dauphas, N., & Ireland, T. J. (2012). A novel extraction chromatography and MC-ICP-MS technique for rapid analysis of REE, Sc and Y: Revising CI-chondrite and Post-Archean Australian Shale (PAAS) abundances. Chemical Geology, 291, 38–54. https://doi.org/10.1016/j.chemgeo.2011.08.011
Quiroz, W., Astudillo, F., Bravo, M., Cereceda-Balic, F., Vidal, V., Palomo-Marín, M. R., Rueda-Holgado, F., & Pinilla-Gil, E. (2016). Antimony speciation in soils, sediments and volcanic ashes by microwave extraction and HPLC-HG-AFS detection. Microchemical Journal, 129, 111–116. https://doi.org/10.1016/j.microc.2016.06.016
Roué, L., Kurzweil, F., Wille, M., Wegwerth, A., Dellwig, O., Münker, C., & Schoenberg, R. (2021). Stable W and Mo isotopic evidence for increasing redox-potentials from the Paleoarchean towards the Paleoproterozoic deep ocean. Geochimica et Cosmochimica Acta, 309, 366–387. https://doi.org/10.1016/J.GCA.2021.05.013
Sekimoto, S., & Ebihara, M. (2017). Accurate Determination of Chlorine, Bromine and Iodine in U.S. Geological Survey Geochemical Reference Materials by Radiochemical Neutron Activation Analysis. Geostandards and Geoanalytical Research, 41(2), 213–219. https://doi.org/10.1111/ggr.12145
Shaheen, M. E., & Fryer, B. J. (2011). A simple solution to expanding available reference materials for Laser Ablation Inductively Coupled Plasma Mass Spectrometry analysis: Applications to sedimentary materials. Spectrochimica Acta Part B: Atomic Spectroscopy, 66(8), 627–636. https://doi.org/10.1016/J.SAB.2011.06.010
Takei, H., Yokoyama, T., Makishima, A., & Nakamura, E. (2001). Formation and suppression of AlF3 during HF digestion of rock samples in Teflon bomb for precise trace element analyses by ICP-MS and ID-TIMS. Proceedings of the Japan Academy, Series B, 77(1), 13–17. https://doi.org/10.2183/pjab.77.13
Vlastelic, I., & Piro, J. (2022). Volatilisation of Trace Elements During Evaporation to Dryness of HF-Dissolved Silicates (BHVO-2, AGV-1, BIR-1, UB-N): Open- Versus Closed-System Conditions. Geostandards and Geoanalytical Research, 46(3). https://doi.org/10.1111/ggr.12428
Wang, Z., & Becker, H. (2014). Abundances of Sulfur, Selenium, Tellurium, Rhenium and Platinum‐Group Elements in Eighteen Reference Materials by Isotope Dilution Sector‐Field ICP-MS and Negative TIMS. Geostandards and Geoanalytical Research, 38(2), 189–209. https://doi.org/10.1111/j.1751-908X.2013.00258.x
Webb, P. C., Potts, P. J., Thompson, M., & Gowing, C. J. B. (2017). GeoPT41A—an international proficiency test for analytical geochemistry laboratories–report on round 41A (Mineralised stream sediment, SSCO-1)/July 2017. International Association of Geoanalysts: Report.
Webb, P. C., Thompson, M., Potts, P. J., Gowing, C. J. B., & Wilson, S. A. (2017). GeoPT40—An international proficiency test for analytical geochemistry laboratories—Report on round 40 (Silty marine shale, ShWYO‐1)/January 2017. International Association of Geoanalysts: Report.
Willie, S., Nadeau, K., Pihillagawa Gedara, I., Yang, L., Clancy, V., Grinberg, P., Kumkrong, P., Mercier, P. H. J., Mihai, O., Tyo, D. D., Jiang, C., Kingston, D. M., Meija, J., Maxwell, P., & Mester, Z. (2014). MESS-4: Marine Sediment Certified Reference Material for total and extractable metal content. National Research Council Canada. https://doi.org/10.4224/crm.2014.mess-4
Yokoyama, T., Makishima, A., & Nakamura, E. (1999). Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion. Chemical Geology, 157(3–4), 175–187. https://doi.org/10.1016/s0009-2541(98)00206-x
Zimmermann, T., von der Au, M., Reese, A., Klein, O., Hildebrandt, L., & Pröfrock, D. (2020). Substituting HF by HBF4 – an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS. Analytical Methods, 12(30), 3778–3787. https://doi.org/10.1039/d0ay01049a
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Copyright (c) 2026 Michael R. Bollen, Patrick Blaser, Sylvie Bruggmann, Shuzhuang Wu, Samuel L. Jaccard