University Of Cape Town Geology – Quadrupole ICP-MS

University Of Cape Town Geology – Quadrupole ICP-MS

University Of Cape Town Geology – Quadrupole ICP-MS

The ICP-MS facility is able to analyze a wide range of trace elements (Li to U, excluding elements such as H, C, O, N, and noble gases) in geological and other materials that can be dissolved in an acidic solution, or in the solid state in situ (at the sub-millimeter scale) using laser ablation.

Quantitative trace element measurements in solution mode are performed via calibration using multi-element synthetic certified standard solutions.  Precision, accuracy, and detection limits are determined through the analysis of USGS or other rock standards, as well as procedural blanks, processed with every sample batch.  Sample digestions and dilutions are performed in clean laboratory conditions.

Laser analyses of silicate minerals and glasses are calibrated using well-characterized, homogeneous solid standards, such as NIST glasses. Samples for laser ablation analysis are typically either polished thick sections or polished 25 mm diameter disc mounts.  Users should be aware that there are limitations on the size of samples that can be analyzed and no guarantees are made for measurements conducted on unpolished specimens.

Users should contact ICP-MS lab personnel to find out whether laser ablation or solution analysis is more appropriate for their analytical needs. Our ICP-MS instrument is a Thermo-Fisher X-Series II quadrupole ICP-MS (installed in 2009) with a New Wave UP213 solid-state laser ablation system. The spot size of the laser can be set to various diameters between 10 and 300 microns. The X-series II instrument is equipped with a 48-sample autosampler for automated solution analysis. The facility is operated by Chief Scientific Officer, Christel Tinguely and supervised by Dr. Phil Janney.

multi-collector ICP-MS

Two NuPlasma HR MC-ICP-MS equipment and two New Wave solid-state Laser Ablation systems (193nm and 213nm wavelengths) are installed in the multi-collector ICP-MS facility. It is vital that the material be homogeneous when introducing samples into solid forms via laser ablation or as solutions after appropriate chemical preparation.

Isotope ratios as geochemical tools

The goal of the MC-ICP-MS Facility is to offer a versatile isotope analysis service that can examine both liquid and solid materials. Sr, Nd, and Pb can currently be determined by solution, and Sr, Pb, Hf, B, and Li can be determined by laser ablation.

Rb, Sr, U, and Pb isotope dilution concentration measurements are being developed, along with high-precision isotope-dilution analysis for the concentration measurements of Sm and Nd. The analysis of the Hf and Fe isotope systems using solutions is expected to be established in the near future. The clean lab and instrument protocols to analyze more isotope systems (such as Si), as required by demand, will be established

Solution analysis

After chemical preparation, solution analysis normally needs at least 50ng of the target element. Prospective users are expected to first collect concentration data for the element(s) of interest to ensure that an appropriate amount of material is dissolved for solution analysis. ICP-MS, XRF, or another appropriate technique can be used to obtain these concentration data. Analysis of the same sample dissolution by quadrupole ICP-MS is the preferable technique where highly accurate concentration data are needed for exact age correction or geochronology. But if necessary, either the quadrupole ICP-MS or the MC-ICP-MS Facility can be used to do isotope dilution analysis.

Laser analysis

Plagioclase, clinopyroxene, bone, and teeth can all be used for in situ study of Sr and Pb isotope compositions using laser ablation. Li and B stable isotope systems in natural and synthetic glass samples can also be analyzed in situ using laser ablation. It is also possible to analyze zircon in situ for the compositions of the U-Pb and Hf isotopes. Zircons can either be analyzed in thin sections or after being removed from the sample and put in an epoxy disc; the latter method is preferred. Prior to analysis, it is possible to obtain suitable cathode luminescence photomicrographs to help with spot selection. The choice of spot size will depend on the elemental concentration of the target isotope system and the desired spatial resolution, which ranges from 10 to 250 microns.

For more information regarding the Quadrupole ICP-MS Lab, please contact:

Ms. Christel Tinguely
c.tinguely@uct.ac.za
​Laboratory:
Rm 1.05, Geological Science
(021) 650 3667

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