Instrumentation

Multi-Collector ICP-MS
Thermal Ionization Mass Spectrometers
High Resolution ICP-MS
Laser-Equipped Noble Gas Mass Spectrometer
Stable Isotope Ratio Mass Spectrometers

Multi-Collector ICP-MS (MC-ICP-MS)

Introduction

MC-ICP-MS combine a plasma source capable of ionizing most of the elements in the periodic table with a mass spectrometer capable of producing the flat top peaks necessary for precise isotope ratio measurement. These instruments have provided new and/or improved analytical opportunities for the measurement of radioactive, radiogenic and stable isotope ratios of elements ranging from Li to U.

The PCIGR houses a Nu Plasma MC-ICP-MS, which fulfills multiple roles: it is used to analyse a wide range of both radiogenic (Nd, Hf and Pb) and stable (Li, Fe, Cu, Zn, Mo & Cd) isotopes serving both as a research tool and an educational resource. As of November 2006 the PCIGR Nu has made over 21,000 analyses.

The Instrument (Nu Instruments - Nu Plasma)

The Nu Plasma is equipped with a plasma source capable of ionizing most elements. An electrostatic analyzer, a 25cm radius magnet and two zoom lenses are used to focus the ion beam into a fixed array of 12 Faraday cups and 3 ion-counting systems. Initial instrument sensitivity has been improved by the addition of an 80-litre primary pump that significantly improves pumping at the interface. Sensitivity is further enhanced by use of a Nu Plasma DSN 100 desolvating nebulisation system (DSN-100) in order to run in dry plasma conditions. The entrance slit is adjustable and can be used to increase instrument resolution sufficiently to partially resolve ⁴⁰Ar¹⁴N and ⁴⁰Ar¹⁶O from ⁵⁴Fe and ⁵⁶Fe and enable measurement of Fe isotope ratios under “pseudo high resolution” conditions.

Radiogenic Isotopes

Stable Isotopes

Thermal Ionization Mass Spectrometers (TIMS) - (Thermo Finnigan TRITON-TI and VG 54R)

The Triton TIMS was installed in April 2002 and is used by the geochemical tracer lab for high-precision analyses of radiogenic isotopes that can be measured to better precision than on the Nu Plasma. The Triton is equipped with 9 Faraday cups and one ion counter and a special matrix system for data integration that cancels out individual collector gain (virtual amplifier), thus allowing for the acquisition of high-precision analyses (<5x10-6 for 87Sr/86Sr and 143Nd/144Nd on 135 ratios [2sd, internal precision]). The barrel carries 21 samples that run automatically for routine analyses (Sr, Nd) at a pace of a barrel every 2-3 days.

Since completion of the installation in October 2002, the Triton has analyzed:
1260 Sr isotopic compositions
1151 Nd isotopic compositions
37 Pb isotopic compositions.
We are now on barrel number 157 (17/18 samples and 4/3 standards per barrel).

We replaced the H3 collector in October 2003 and the running means for the standards were :
NBS 987: 0.710252 ± 12 (n=77)
La Jolla: 0.511853 ± 11 (n=91)
Then in September 2005, all the inserts of the collectors were replaced; our new running means for the standards are:
NBS 987: 0.710246 ± 17 (n=89)
La Jolla: 0.511852 ± 12 and 0.348406 ± 8 (n=50)

The Isomass VG54R single-collector TIMS was purchased in 1982 with NSERC support and underwent major upgrades in 1987 and 1995. It is currently configured with a Faraday collector and Daly multiplier, the latter for low level U-Pb analyses
(<1 ng radiogenic Pb), digital voltmeter and an automated 16-sample turret. The PCIGR geochronology lab can routinely
separate a wide range of minerals for conventional U-Pb analysis including zircon, baddeleyite, monazite, titanite, allanite, garnet, apatite and rutile from mafic through felsic rock samples.

Since Since PCIGR was established in January, 2002, the VG54R has produced:
2903 U-Pb isotope dilution analyses from 510 rock samples
678 sulphide mineral common Pb isotopic compositions
912 U-Pb standard and blank analyses

High Resolution ICP-MS (HR-ICP-MS) - (Thermo Finnigan ELEMENT2)

The new high resolution single collector ICP-MS (HR-ICP-MS), a Finnigan Element2, is capable of analyzing elements in solution at concentrations as low as parts per quadrillion (ppq) and has a dynamic range of over 9 orders of magnitude. Most interferences can be resolved at the analysis step, minimizing the need for excessive sample processing.

There are numerous labs with ICP-MS instruments in Canada, but our facility stands out by its versatility and ability to adapt to different users and by its full capacity to realize high-resolution analysis. The Element2 is employed by multiple users every week; each with a different application and matrix (seawater, fresh water, porewater, soil, rock, etc.). The transition from one application to another is smooth and efficient. To date, users of the Element2 have mainly been employing straightforward nebulization ICP-MS (IDMS has also been used extensively). Recent applications include low-level trace element concentrations in rocks and USGS standards, PGE concentrations in mantle xenoliths, Cu concentrations in trace metal clean artificial seawater (used in culturing phytoplankton), an assessment of metal mobility in lake sediments contaminated with mine tailings, and the characterization of As species in biological tissues and water samples.

Up-to-now (before the relocation of all the instruments to the EOS building), the Element2 has analyzed about 800 samples for trace element profiles (REEs/HFSE or both) for mineral separates such as apatites, fluorites, feldspars, clinopyroxenes, complete trace elemental profiles for komatiites, basalts, granites, diorites, peridotites, anorthosites, including at least 13 different reference materials for lithophile, chalcophile, and siderophile elements in different rock matrices. About 40 PGE analyses and approximately 240 Nd and Os isotope ratios were also measured on that instrument.

The Element is also extremely useful for our everyday lab quality control (lab blanks, reagent blanks, column calibration, exact sample contents for MC-ICP-MS analyses).

Laser-Equipped Noble Gas Mass Spectrometer - (Micromass VG 5400)

The noble gas mass spectrometer (NGMS) is a VG4500 from Micromass (now GV) and is a well-proven instrument for analysis of all the noble gases. This instrument is the newest model of NGMS currently available in Canada and, uniquely to our instrument, is also capable of and calibrated for He analysis. Sample heating for step-heating Ar extraction is accomplished utilizing either a 30W MR-10 infrared CO2 laser from New Wave Merchantek or a computer-controlled resistance furnace built by Modifications Inc. Development of (U-Th)-He dating is underway utilizing laser-heating of mineral grains for He extraction and the Element2 for determining U and Th concentrations.

The installation of the VG5400 was completed in the summer of 2003. 894 step-heating dates have been realized (comprising well over 10,000 analyses; i.e., single steps or total fusion dates) since then, among which 40% were measured after the move.

Stable Isotope Ratio Mass Spectrometers -
(ThermoFinnigan Delta plus and Delta plusXL)

The light stable isotope facility houses two ThermoFinnigan isotope ratio mass spectrometers that are fed by four analytical streams. An elemental analyzer (EA) and Finnigan Gas Bench are connected to the Delta plus mass spectrometer. The thermal combustion elemental analyzer (TC/EA) and gas chromatography combustion interface (GC-C) are connected to the Delta plus XL. The EA, TC/EA and GC/C are connected via Finnigan ConFlo III interfaces. The Delta plus XL is also equipped with a Dual Inlet interface for off line analysis and developmental work.

The Gas Bench is used for automated acid digestion and analysis of 13C and 18O isotopes in carbonate minerals (calcite, dolomite, magnesite, hydromagnesite, siderite, ankerite) and analysis of gases, and dissolved inorganic carbon (DIC) in fluids. Sample and standard mineral powders are treated with phosphoric acid in sealed glass exetainers that have been flushed with helium. The CO2 produced is introduced into the mass spectrometer in continuous flow mode, using helium as the carrier gas. The gas from the sample is run along with reference CO2 gas of known composition. DIC is analysed on the gas bench by putting 600 microlitres of the sample water in a sealed exetainer. The exetainer is flushed with helium to replace air in the headspace and to sparge CO2 dissolved in the water. Phosphoric acid is added, the sample is shaken then left to equilibrate for one hour. The CO2 produced is introduced into the mass spectrometer in continuous flow mode.

The TC-EA is used for sample pyrolysis and continuous flow analysis of 2H and 18O water and 2H in minerals. The TC/EA is at present only being used for liquid samples, although solids can also be analysed. Liquids are introduced by autosampler into the furnace tube at 1450 oC and pyrolyzed. The component hydrogen and oxygen gases are carried to the mass spectrometer in helium carrier, via a Finnigan Conflo III interface.

The EA is used for analysis of 13C and 15N in solid samples, including organisms, hair, sediments, and coal. Samples are placed in tin cups and introduced to the elemental analyzer with an AS autosampler. The sample is combusted in the presence of oxygen at 1000 degrees Celsius. Combustion gases are then carried in a stream of helium through a reduction column, a water trap and finally a GC column where the gases are separated. Final combustion products N2 and CO2 are introduced to the DeltaPlus by the Conflo and d15N and d13C are determined. For some d13Corg analyses, samples are treated first with 10% HCl and dried before placing the samples into tin cups.

The GC/C system was recently delivered and installation is scheduled to be completed in January 2006. This system measures compound specific stable isotope ratios of carbon, nitrogen, oxygen and hydrogen in gases, liquids, organic volatile compounds and biomolecules. It is includes a HP 6890 gas chromatograph, a micro combustion furnace, a reduction furnace, a reactor for thermo-chemical conversion of gas chromatograph uluates, and an autosampler.

The Delta Plus