The Radiogenic Isotope and Geochronology Laboratory (RIGL) is located in the Webster Physical Science Building on the WSU Pullman campus. The infrastructure includes a 900 ft2 Class-1000 clean lab dedicated to sample dissolution and chromatography separation for geochronological analysis, a ThermoScientific NeptunePlus MC-ICPMS, and a Teledyne Analyte Excite laser ablation system paired with a ThermoScientific Element2 single collector high-resolution ICPMS, as well as supporting mineral separation and mounting laboratories. All facilities are located on the same floor, forming a comprehensive analysis center for geochemistry and geochronology in the School of the Environment of Washington State University.
Clean Lab
RIGL’s clean lab consists of three fully HEPA filtered rooms with a total area of 900ft2 equipped with Milli-Q ultra-clean water filtration system and exhaust hoods. Since its establishment, the laboratory has provided a variety of collaborative scientific services and training for WSU students, national and international visiting researchers in the broader geological community, and scientists from multidisciplinary backgrounds.
The clean lab is devoted to the preparation of solution-based geochronological and isotope analysis. All acids are distilled either by quartz or by Savillex sub-boiling distillation units one or two times as needed. Depending on the target material to be dissolved, the sample digestion either takes place in a Savillex beaker on a hot plate or in a PTFE vessel locked in a steel jacket heated in the dedicated oven for high-temperature high-pressure rock/mineral digestion. Support equipment includes precision balance, a sonicator bath, and a centrifuge. Eight polypropylene heat boxes connected directly to acid exhaust allow for contaminant-free multiple open beaker dry-downs on the hot plates throughout the sample dissolution.
Element separations are performed on solutions using different combinations of chromatographic separation columns. RIGL’s clean lab stocks basic cation/anion exchange resins and a selection of specialty resins, which facilitate the extraction of Rb, Sr, Sm, Nd, Lu, Hf, and Pb from rocks, minerals, and biological samples and provide the flexibility for customized sample processing to meet various analysis interests.
Laser Ablation System
The Analyte Excite 193-nm ArF Excimer laser ablation system (Cetac/Telydyne Technologies) coupled to inductively coupled-plasma mass spectrometers (LA-ICPMS) is used for analysis of solid-state materials.
The laser can be dynamically focused to spot sizes of 1.0μm to >150μm and delivers short pulses (less than 5ns) of high energy ultraviolet laser (up to 9J/cm2) at a repetition rate of up to 300Hz, allowing for flexible micro-sampling of solid materials. The laser ablation system is equipped with a two-volume ablation cell which provides full flexibility in sample size, rapid signal washout, high and uniform sensitivity throughout, allows for pre-programmed, unattended running of hundreds of zircon spot analyses and mapping (imaging) of elemental concentration over areas of minerals.
The main applications are isotopic composition analyses, such as Hf or Nd isotopes in analyte-rich accessory minerals such as zircon, monazite, titanite, and apatite, U–Pb geochronology of zircon, monazite, and titanite, and space-resolved quantitative analyses of trace elements in minerals (e.g., pyroxene, garnet) or biologic samples (e.g., fish otoliths). Planar polished surfaces of thin sections or resin-blocks are necessary for analysis using LA-ICP-MS. The instruments are carefully maintained by lab personnel who set up and tune the instruments before users analyze their samples.
Multi-Collector ICP-MS
The multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS) combines the high-resolution and precise measurement of a mass spectrometer and the superior ionization efficiency of an inductively coupled plasma source. These advantages make the MC-ICPMS capable of analyzing a wide range of elements, including high ionization potential elements (e.g., Hf) and non-traditional stable isotopes (e.g., Cu).
A Thermo Scientific Neptune Plus MC-ICPMS is housed at RIGL. The Neptune Plus is a double-focusing MC-ICPMS with the optional Jet Interface. With the Jet Interface, a 10 to 20 times higher sensitivity can be achieved. The detection system of our instrument consists of eight moveable faraday cups and one central detector that can be used as an electron multiplier or faraday. Users can adjust the cup configuration for the needs of analytical tasks. These features allow us to maintain highly precise and accurate measurements as well as reduce sensitivity loss.
Our Neptune Plus MC-ICPMS can also be attached to an Apex Ω desolvating nebulizer for maximizing signal intensity along with minimizing oxides and interferences. The apex nebulizer, which can be compatible with HF and prevent solvent precipitation, provides ultra-fast rinse-out for high sensitivity ICP sample introduction.
The Neptune Plus MC-ICPMS at RIGL has been routinely used for Sr, Nd, Hf, and Pb isotope solution measurements and other non-traditional stable isotopes (Fe, Cu, Zn, Ti, Sn, Mo). Multiple masses are simultaneously collected by the Neptune Plus instrument, which allows for interference and mass bias corrections. Based on the long-term reproducibility of solution standard at RIGL, the precision of parent-daughter ratio is estimated to be ~ 0.5% (Lu-Hf: Vervoort et al., 2004; Sm-Nd: Bouvier et al., 2008).
In addition to solution work, high-precision in-situ Hf and Nd analyses on zircon, monazite, titanite, and apatite is routinely performed in our lab. The in-situ data are collected using the Neptune Plus MC-ICPMS coupled to the Analyte Excite 193 nm laser system. For some samples with spatiotemporal complexity or small grain size, we also offer the laser ablation split stream method (LASS) to couple age and tracer isotope information. The LASS instrument involves the Neptune Plus MC-ICPMS (for Hf or Nd isotope measurements) and Element 2 (for U-Pb age or trace element determinations) equipped with the Analyte Excite 193 nm laser system.
High-Resolution ICP-MS
The Thermo Fisher Scientific Element 2 high-resolution ICP-MS is capable of analyzing trace and ultra-trace multi-element concentration (as low as parts per trillion) and the determination of isotope ratios. The instrument is equipped with a double-focusing magnetic sector field mass analyzer based on a reverse Nier-Johnson geometry, which allows high-speed multi-element analysis.
At RIGL, the Element 2 is mainly employed for trace element analysis, both in digested inorganic solutions and solid-state materials, and for U-Pb geochronology of zircon, titanite, monazite, and apatite. Solution samples are introduced by a direct nebulization system using a spray chamber. Preparation of samples is carried out in our specialized clean laboratory. Solid state material analysis is performed with connection to the Analyte Excite 193-nm laser ablation system
The Element 2 is also employed for the lab’s quality control measurements, including lab blanks, reagent blanks, column calibration, and concentration determination for isotope dilution analysis.