EPMA Laboratory

Rhodes University’s Electron Probe Micro Analyzer (EPMA) Laboratory has a tradition in microanalysis since 1972, when a second hand Camscan of Cambridge Instruments was installed. Our new 2011 model JEOL JXA-8230 EPMA is the third instrument, replacing our decomissioned JEOL JXA-733 that had been purchased in 1985.

Electron microprobe analysis, as EPMA is commonly known, provides precise quantitative chemical analysis of elements in small volumes (~1 to 10 cubic micrometers or more) of solid specimens. Samples are polished sections of inorganic solids (e.g.  natural rocks, mineral concentrates, gems, synthetic products, glasses, alloys,  bones, fossils, etc.).

Our EPMA is setup to quantify all elements from Be to U using four automated wavelength-dispersive spectrometers (WDS) in point, line or grid analysis. In scanning mode medium- to small-scale element mappings can be produced. Microfabrics and zonation patterns of luminescent minerals can be investigated using a cathodo-luminescence detector.

We provide two analytical and three imaging modes of operation:

(i)     Full quantitative mode: All detectable major and minor elements are quantified on a spot of
        ca. 1 μm diameter or larger. Trace elements more abundant than ca. 30 ppm can be analysed
        separately.

(ii)    Elemental distribution maps: Lateral variations of element concentrations are analysed at
        high resolution in a two-dimensional maps.

(iii)   Backscattered electron (BSE) imaging (compositional image).

(iv)   Secondary Electron (SE) imaging (particle geometry and topography).

(v)   Cathodo-luminescence imaging (variations in luminescence; quartz, zircon, carbonate, etc.).

The laboratory is managed by Dr Gelu Costin who joined Rhodes University in 2009 after sevaral years of successful analytical work for the RRUFF data base at the University of Arizona. He normally operates the instrument. Dr Steffen Büttner runs the instrument in Gelu Costin's absence and for external academics on collaborative basis.

Contact information

JEOL JXA-8230 Superprobe

Purchased in late 2011 the instrument was commissioned in March 2012. The funding for the new equipment was provided by NRF's National Equipment Programme and Rhodes University.

Our EPMA has the following technical configuration:

• W and LaB₆ electron gun.

• Computer automation operating through PC compatible JEOL software on Windows XP platform.

• Four wavelength-dispersive spectrometers (WDS);

• One FCS type spectrometer* with 4 crystals: LDE1, LDE2, TAP and PETJ.

• Two L type spectrometers with 2 crystals each: TAP, LiF (gas-flow counter) and LiFL, PETL (xenon counter), respectively.

• One XCE type spectrometer with 2 crystals: PETL, TAPL.

• Secondary-electron (SE) and backscattered-electron (BSE) detectors:

• Matrix corrections include ZAF and other methods

• “MiniCL” Gatan CL imaging system (visible range - 185 nm - 850 nm)

• Accelerating voltage: 0.2 to 30 kV

• Integrated visible-light microscopy: reflected, transmitted and cross-polarised light at 400X

• Auto-focus system for optimal sample positioning

• Carbon coating: Q150T E High Vacuum Evaporator with film thickness monitor module

Academic and commercial utilization

The EPMA laboratory is primarily setup for igneous, metamorphic, sedimentary and ore mineral analysis. In addition to rocks and minerals, we conduct analyses of metals and alloys, ceramics, glass, teeth and bones, and other natural and artificial solids. Particularly we are available to render analytical services to the minerals exploration and mining industry.

 Analytical services

• Standard quantitative analysis of elements from F to U in inorganic solid materials as point or area analysis, line scans or grids.

• Light element quantification from Be to O

• Trace element quantification (down to 10-30 ppm, depending on the analyzed element)

• Quantitative element mapping

• Qualitative element analysis (WDS scan)

• High resolution (1-10 microns scale) BSE/SE imaging

• Virtual WDS for testing various unusual calibrations

• EDS analysis is available via an Oxford Instruments Si(Li) detector system operating at Rhodes University’s Electron Microscopy Unit.

Analytical Costs

Pricing for 2013 (in SA Rands):

*Supervised (by operator) / unsupervised (experienced user).

**Pricing for after hours sessions or overnight runs are for unsupervised instrument use.

Weekend and public holiday time slots requiring operator help are charged at double rates.

*** Pricing excluding VAT.

Sample specifications

Standard size (46x26 mm) polished thin sections or polished cylindrical specimens (22 or 25 mm diameter) can be routinely analyzed. Large sample holders can accommodate custom sample sizes (maximum sample size: L100 x W100 x H50 mm).  

Standards

Our current standard collection includes more than 160 standards (minerals and glasses) to cover silicate, carbonate, PGM, sulphide, oxide, REE bearing mineral analysis.

1) SPI Supplies:

http://www.2spi.com/catalog/standards/spiweb/spimin.shtml (53 mineral standards)

http://www.2spi.com/catalog/standards/spiweb/spimet.shtml (44 metal standards

2) Agar Scientific: registered Standard No. 8462 (30 standards)

3) Various other standards (Smithsonian Institution, University of Arizona, etc.).