Macro and Micro Analytical Methods Development

Science Center Objects

The Macro and Micro Analytical Methods Development Project (MMAMD) provides access to the expertise of highly experienced research scientists and state of the art analytical instrumentation to develop new and unique analytical capabilities to solve complex problems beyond routine analysis.

photo collage of lab equipment, field work, and sample data

USGS reference material matrix sampling, geochemical reference materials, analytical laboratory equipment, and sample data. 
(Public domain.)

Science Issue and Relevance

Many projects funded by the Minerals Resources Program and other USGS mission areas use chemical analysis as a tool to study a variety of mineralogical, ecological, environmental, and biological processes. Routinely, the success of these projects is reliant upon access to state-of-the-art instrumentation and methods of analysis. The Macro and Micro Analytical Methods Development Project provides access to the expertise of highly experienced research scientists and state of the art analytical instrumentation to develop new and unique analytical capabilities to solve complex problems beyond routine analysis. Generally macro analytical methods examine the bulk elemental, chemical, or mineralogical composition of a sample while micro analytical methods use specialized sample introduction devices or instrumentation to examine how the elements or minerals are spatially distributed in a sample. Both macro and micro analytical methods use a variety of analytical instrumentation including: Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Raman Spectroscopy, and Cavity Ring-Down Spectroscopy (CRDS). Development of new, state-of-the-art analytical methods can be applied to topical studies in energy and minerals, environmental health, ecosystems, land resources use, water quality, and natural hazards. For many projects carried out by the USGS, there are no commercial laboratories that can provide the unique types of geochemical analyses or the high quality data required to carry out the project objectives.

Methodology to Address Issue

Our scientists ascertain what types of new and emerging analytical techniques USGS will need with the next several years to support programmatic research efforts and to develop those techniques using existing instrumentation or by obtaining the necessary equipment and instrumentation. Another key goal of the project is to evaluate the need for and develop new natural matrix geochemical standard reference materials that are used by USGS and other scientists to calibrate analytical instrumentation, validate methods and models, and monitor laboratory performance. Project members also develop methods for specialized analyses via reimbursable projects for other DOI and U.S. government agencies. The Project is responsible for maintaining the availability of analytical instrumentation, laboratories, techniques and staffing for use by multiple USGS projects and for maintaining specialized in-house capabilities for use in characterization of difficult to analyze sample matrices beyond the capabilities of the contract laboratory.

lab analytical equipment

A selection of analytical equipment in Geology, Geophysics, and Geochemistry Science Center laboratories.
(Public domain.)

New Macro Analytical Methods Development - This task provides for the coordinated research and development of new analytical methods needed to meet the needs of projects administered under the Mineral Resources Program and other USGS projects as needs arise. Project staff work on analytical techniques including inductively coupled plasma-atomic emission spectrometry (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), ion chromatography, liquid chromatography, hydride generation atomic absorption, and specific element instrumentation such as mercury, carbon, and sulfur analyzers. Other areas of investigation include development of new or improved sample preparation methodologies such as specialized hot plate or microwave-assisted digestions and extractions to improve efficiency and data quality.

One of the primary goals of this task is to develop and validate analytical protocols for difficult-to-analyze samples that are beyond the capabilities of routine commercial laboratories. Development of new analytical protocols is performed in anticipation of future analytical needs of USGS projects, so that state-of-the-art analytical methods will be available to project staff as they are needed. Current areas of focus include:

  1. Development and validation of new analytical methodologies including High Resolution Dynamic Reaction Cell (DRC) and/or Kinetic Energy Discrimination (KED) Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) for analysis of typical geological samples to improve detection limits and accuracy eliminating common interferences on elements,
  2. Development and validation of direct analysis of powdered samples for trace elements using Energy Dispersive X-ray Fluorescence (EDXRF),
  3. Development and validation of new analytical methods for interference-free analysis of rare earth elements in waters, soils, and sediments using alternative sample introduction devices, dynamic reaction cell ICP-MS, and/or high resolution (HR) ICP-MS,
  4. Continued development of speciation methods using the high performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) system for determination of different forms of arsenic, selenium, and chromium species in aqueous species,
  5. Continued investigation and validation of new methods for the preservation and extraction of inorganic species of arsenic, selenium, and chromium from a wide variety of sample types, including fire ashes, soils, sediments, and air filters, including improved or modified hexavalent chromium extraction methods,
  6. Investigation and development of isotope dilution methodologies for the accurate determination of elements in geochemical reference materials,
  7. Continued development and validation of new and improved analytical methods using dual-view ICP-AES to improve detection limits and elimination of interferences using Multicomponent Spectral Fitting (MSF) techniques,
  8. Further develop novel in-situ microanalytical techniques for determining trace concentrations in heavy metals in surface water environments in virtual real-time mode using field deployable instrumentation that operates in unattended mode.
reference materials

USGS provides geochemical reference materials for use by scientists in all areas of earth science. Reference materials are routinely used in the calibration of analytical instrumentation, development of new extraction methodologies, and as quality control samples which monitor laboratory performance. For more information on this program please see our Fact Sheet.
​​​​​​​(Public domain.)

Geological Reference Materials - This task develops and produces geochemical reference materials in support of USGS mineral exploration and development activities. Geological reference materials are crucial for USGS projects and laboratories to ensure the highest possible accuracy of their chemical analyses.

Geologic reference materials are developed using matrix matched geologic sample types currently under investigation. Well characterized reference materials are a key component in evaluating laboratory accuracy and precision, as these materials are routinely used in laboratory quality assurance programs. We provide reference materials for methods development on new sample types or methods of analysis, which in turn allow the transition from qualitative to quantitative analysis. We foster development of new preparation techniques to meet specific project needs and collaborate with government, private, and international partners to develop new reference materials that benefit USGS activities.

The major areas of investigation are listed below.

  1. Replacement of existing USGS powdered reference materials which serve as the backbone to many quality control programs.
  2. Development of new reference materials for microanalysis, particularly focusing on the development of a) glass materials from different alumino silicate rock types and b) pressed powders from significant geologic matrix types (phosphates, gypsum, barite, sulfides, carbonates).
  3. Development of new reference materials from sample types important in rare earth element source materials (carbonatite, alkaline dike).
  4. Develop plans for the preparation of several shale gas reference materials in collaboration with industry.
  5. Begin developing a series of new geologic reference materials designed to assist in the mineralogical analysis of geologic materials by X-ray diffraction (XRD).
  6. Prepare customized geologic reference materials for private and government customers (ex. mine waste, ore material, baseline sediments, soils, lunar simulant).
scientists in laboratory

USGS scientists in the laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) laboratory in Denver, CO.
​​​​​​​(Public domain.)

Laser Ablation ICP-MS Trace Element Microanalysis - The laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) task involves the continuing advance of in-situ methods for trace element analyses for Mineral Resource Program goals. Direct, in-situ analyses provide a detailed look at the chemical story preserved in minerals, rocks, biological and environmental samples. Our work provides broad support across numerous USGS projects and to outside collaborators. Focus areas include the direct assessment of the residence and mode of occurrence of critical metals in a variety of deposit types and waste products, utilization of trace element signatures and zoning within minerals to better decipher mineral deposit origins, and detailed examination of the role of microchemistry and complex residence of metals on the geometallurgy and processing of geologic materials for economic recoveries.

Our objectives are to maintain the laboratory as a leading analytical facility providing analyses for core USGS projects, be responsive (and proactive) to the changing needs of projects and scientists in areas where microanalyses can help solve problems, and to integrate and understand the complimentary nature of both traditional bulk chemical methods as well as the important necessary microanalytical tools. We utilize the known and newly developing potential of trace element microanalysis for the determination of trace elements in minerals and other solid media useful to attain programmatic goals. We work closely with the Geological Reference Materials task and the other microanalytical techniques in this project.

pyrite grain photomicrograph

Pyrite grain with δ34S isotopic composition.
(Credit: Michael Pribil, USGS. Public domain.)

MC-ICP-MS equipment

USGS multi-collector inductively coupled plasma-mass spectrometer in Denver, CO. 
(Credit: Michael Pribil, USGS. Public domain.)

Multi-Collector ICP-MS - The objectives for the multi-collector inductively coupled plasma-mass spectrometer (MC-ICP-MS) lab are to continue the development of new methodologies for analysis and application of isotope systems in both solution and solid (laser) form for the applications in mineral and environmental research in support of Mineral Resources Program and USGS goals. The primary objective is to better understand the potential insight that non-traditional and traditional stable isotopes can provide for the Program's environmental, economic and geological studies. The infancy of multi-collectors still warrants the need for thorough method development with a focus on chromatographic separation for solution sample introduction and in situ laser ablation introduction. These new methods will have immediate application in the Mineral Resources Program and the multi-collector field. The lab will continue to establish new ties within the USGS and with other State, Federal agencies and Universities. Current research endeavors are below.

  • In situ S isotope ratios by laser ablation MC-ICP-MS for geological applications
  • Sr in situ laser ablation of fish otoliths and whole otolith by solution
  • Development of in situ Pb isotope glass reference material
  • Source correlation using multiple isotope systems
  • Hg isotope systematics in mineral deposits and ecosystems
analytical equipment in lab

Analytical equipment, including gas chromatographs and spectrometers, in the USGS microbial geochemistry laboratory in Denver, CO.
​​​​​​​(Credit: Christopher Mills, USGS. Public domain.)

Method for Assessing the Microbial Geochemistry of Mineral Deposits and Their Impact on Surrounding Environments - The transport and fate of metals are inextricably linked to the carbon cycle. Natural organic compounds chelate metals which is key to the sequestration and transport of metals in aquatic environments. Many types of microorganisms in soil, sediment, and water environments link the oxidation of organic carbon and the reduction of metals. Others mediate the oxidation or methylation of metals. Many of the processes that release metals into the environment from mineralized deposits or mine waste are exclusively mediated or are accelerated by microbial activity. In addition, microbial activity can mitigate (e.g. Cr[VI] reduction) or exacerbate (e.g. mercury methylation) trace metal pollution. Microorganisms also respond to toxic concentrations of trace metals and changes in microbial community structure can be an indicator of impacts to ecosystem health. Organic biomarker molecules isolated from environmental matrices can indicate the types and abundances of microorganisms present. Some indicator molecules provide measures of viable microorganisms while others can integrate long-term occurrence of microbial processes.

We maintain and develop expertise in microbial biogeochemistry and associated analytical methods and instrumentation to support research on processes that distribute and sequester trace metals from mined and unmined mineralized deposits. The methods will be applied to geochemical exploration research and on environmental impacts of mining. We will develop methods that utilize gas chromatography-mass spectrometry to measure microbial abundance and characterize microbial communities.

Raman Spectroscopy for Metal Speciation in Minerals - Currently the best available method for the direct quantification of chromium(VI) in environmental solids (e.g. soils, rocks, mine wastes, manufacturing residues, and materials in the built environment) is synchrotron-based X-ray absorption near edge spectroscopy (XANES), a technique with very limited availability and no potential for application on a routine basis. Several laboratory-based techniques now exist that show promise for routine quantification of chromium(VI) in solids at trace levels: Raman spectroscopy, wavelength-dispersive X-ray fluorescence (WD-XRF), and laboratory-based XANES. The individual capabilities of each of these techniques for chromium(VI) quantification and chromium speciation in solids will be assessed in this task by analyzing selected representatives of an extensive set of samples prepared under a previous project. Raman spectroscopy is a spectroscopic technique used to observe vibrational, rotational, and other low-frequency modes in a system and is commonly used in chemistry to provide a fingerprint by which molecules can be identified. Raman spectroscopy could provide an alternative method to X-ray absorption near edge structure XANES for the determination of oxidation state of elements (e.g. arsenic and chromium) directly in the solid. This would allow studies to be performed more easily with lab-based instrumentation.

Our objectives are:

  • Use microbeam techniques to identify chromium-bearing phases in soils contaminated with chromite-ore processing residue, in naturally-weathered serpentinite soils, and in primary serpentinite / peridotite rock.
  • Test the feasibility of above-mentioned laboratory-based techniques to quantify chromium(VI) species in solid phases and microvolumes of solution.
X-ray Diffractometer

X-ray diffractometer in the USGS powdered x-ray diffraction laboratory in Reston, VA.
(Credit: Nadine Piatak, USGS. Public domain.)

XRD lab

USGS powdered x-ray diffraction laboratory in Reston, VA.
(Credit: Nadine Piatak, USGS. Public domain.)

Research Mineralogy - We provide research, development, and application of mineralogical analysis and support of topical projects within the USGS. The task includes x-ray mineralogy, thermogravimetric analysis coupled with quadrupole mass spectrometry, qualitative and semi-quantitative x-ray fluorescence spectroscopy and related analytical techniques for mineralogical studies in support of Mineral Resources Program and Energy Resources Program projects. The powder x-ray diffraction laboratory in Reston, VA provides qualitative and quantitative powder x-ray diffraction (XRD) and energy-dispersive x-ray fluorescence (EDXRF). Capabilities include identification and quantification of crystalline and amorphous phases, and crystallographic and atomic structure analysis for a wide variety of sample media.

Task goals are to 1) ensure availability of state-of-the-art mineralogical analyses for scientists funded by the Mineral and Energy Resources Programs, 2) develop new methods and new applications of existing methods, and 3) minimize duplication of skills and equipment by sharing laboratory facilities with both Mineral and Energy Resources Programs.

 

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