Prof. Dr. Anton Wallner

Head Accelerator Mass Spectrometry and Isotope Research
Phone: +49 351 260 3274

Chemistry Labs

Rare radioisotopes are determined with AMS in all sorts of different materials including geological (rock, river sand, marine sediments,...), environmental (water, ice, soil, organic matter,...), anthropogenic (steel, concrete, air or water filters,...) and even extraterrestrial (meteorite, lunar soil) materials. Sample sizes may range from several milligrams to kilograms of material. In the chemistry labs we extract and isolate the element(s) of interest by different wet chemical methods. The resulting target material of a few mg is pressed into sample holders for AMS measurement.

One of the most frequent separation procedures performed in our chemistry labs is the extraction of 10Be and 26Al from geological samples:

Rock to target ©Dr. Konstanze Stübner

Sample Processing


Heavy liquids ©Dr. Konstanze Stübner

Quartz purification for in-situ 10Be and 26Al. For many geological applications of in-situ 10Be and 26Al in quartz, the first processing steps consist of crushing and grinding rock samples and sieving to a suitable grain size fraction (e.g., 250-500 μm). Paramagnetic and heavy minerals are removed by Frantz magnetic and heavy-liquid separation, respectively (check out USGS Open-File Report 2016-1022 for a comprehensive explanation of these techniques). Chemical leaching in HCl or acetic acid removes any calcite present in the sample.

Sample leaching ©Dr. Konstanze Stübner

The resulting mineral separate consists mostly of quartz and feldspar. Feldspar can be chemically removed by repeated leaching in a HCl-H2SiF6 mixture (Merchel et al., 2019) or by froth floatation (Sulaymonova et at., 2018). Quartz is further purified by leaching in diluted (2-4%) HF, which also etches the quartz grains and removes 'meteoric' (i.e., atmospherically produced) 10Be.

Sample dissolution ©Dr. Konstanze Stübner

About 20 g of cleaned quartz is weighted, spiked with a 9Be carrier, and dissolved in concentrated HF at room temperature. We use the Phena EA 9Be carrier with a concentration of (2246±11) μg 9Be/(g solution) and a 10Be/9Be ratio of ∼1E-16 (Merchel et al., 2013). To bring the sample solution into chloride form HClO4 is added, the solution is boiled down on a hotplate, and the residue is dissolved in HCl.

Pressure digestion ©Dr. Konstanze Stübner

Meteoric 10Be samples, deep-sea Mn crusts, and other samples. For meteoric 10Be applications, Be is extracted from the reactive Fe,Mn-oxyhydroxide phases on the surface of the mineral grains by leaching soil or sediment samples with a solution of NH2OH⋅HCl in acetic acid (Bourles et al., 1989, Gutjahr et al., 2007). Some materials can be dissolved in HCl (e.g., iron meteorites or deep-sea Mn crusts and nodules) or in HNO3/H2O2 (e.g., organic samples); for other materials total fusion, e.g., by microwave digestion, may be necessary to bring the sample into solution.

Column chemistry and hydroxide precipitation

Hydroxide precipitation ©Dr. Konstanze Stübner

Once the sample is in solution, we use a combination of ion exchange chromatography and hydroxide precipitation to separate the element(s) of interest from the matrix. Some elements (Fe, Mn, Be, Al, Ti) form insolable hydroxides at pH≥8, which can be separated from the elements that stay in solution (Na, K, Ca, B) (e.g., Ochs and Ivy-Ochs, 1997).

Column chemistry ©Dr. Konstanze Stübner

We use Dowex 1x8, mesh 100-200 anion exchange resin (see here for a brief introduction to ion exchange chromatography) to separate Fe and Dowex 50Wx8, mesh 100-200 cation exchange resin to separate Be and Al. For actinide (Pu, U, Cm, Am) separation we use different extraction chromatographic resins including Eichrom TEVA, UTEVA, TRU and DGA resins.

Be-hydroxide ©Dr. Konstanze Stübner

After chemical processing, the sample consists of <1 mg of the target element in its hydroxide form. For actinide analysis or carrier-free Be measurements, the last processing step is a co-precipitation of the target element with a carrier Fe-solution. Other chemical separation techniques are used for the preparation of Ca, Cl, or I samples.

Target materials and target preparation

Target pressing ©Dr. Konstanze Stübner

The sample is transferred to a quartz crucible and dried at 80°C, then calcinated in the muffel oven to transform the hydroxides into oxides (e.g., 1 h at 900°C). For Be and Al analysis the oxides are weighted and mixed with metal powder (Nb:BeO ∼4:1; Ag:Al2O3 ∼1:1). The sample material is then pressed into a cathode for AMS measurement.

Capabilities in the chemistry labs:

  • Chemical processing of quartz-rich samples for in situ 10Be and 26Al applications
  • Chemical processing of sediment samples for meteoric 10Be applications
  • Chemical processing of different sample materials for actinide analysis (i.e., 236U, 239/240Pu, 244Pu, 241Am)
  • Equipped for working with hydrofluoric acid (HF)
  • Dedicated lab for 36Cl- and 129I-samples in a Cl- and S-free environment
  • Equipped for different chemical digestion methods including pressure digestion and microwave digestion
  • Different precision balances including an ultra-microbalance
  • Equipped for target preparation for HVEE and NEC machines
Target preparation tool ©Dr. Konstanze Stübner

Former Users