Department of Geological Sciences
288 Farm Lane, Room 206
East Lansing, MI 48824-1115
Phone: (517) 432-5522
Fax: (517) 353-8787
The Department of Geological Sciences at Michigan State University operates a state-of-the-art Thermo Scientific ICAP Q quadrupole Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). The ICP-MS is used in combination with a Photon Machines Analyte G2 193 nm excimer laser ablation system equipped with a 15 x 15 cm HelEx sample cell, for solid sample micro-analyses. In addition, a CETAC ASX 520 autosampler allows for liquid sample analyses.
The ICAP Q instrument is equipped with a collision cell, which minimizes interferences caused by argon molecules (e.g., 40Ar35Cl+on 75As+, 40Ar16O1H+ on 57Fe+) and substantially improves detection limits on interference-prone low mass isotopes.
The ICP-MS is capable of analyzing most elements, either as single elements or in multi-element analysis, with high precision and sensitivity. The analyses can be qualitative or quantitative.
The ICAP Q ICP-MS is located in the Food Safety and Toxicology building on the MSU campus in a clean laboratory. The clean environment of the room complements the high sensitivity of the instrument in being able to analyze low level concentrations (ppt).
The ICAP Q ICP-MS, see manufacturer’s webpage for more details.
The Photon-Machines Analyte G2 excimer laser and the HelEx sample holder, with multiple glass samples mounted. The use of a large cell and large sample holder reduces the need for sample holder exchange, while increasing the degree of automation and reducing the risk of atmospheric contamination. Another sample holder variant can hold up to 12 1-inch mounts and 6 petrographic thin sections. See manufacturer’s webpage for more details.
ICP-MS instruments have become popular in analytical laboratories owing to their versatility. In a few minutes, the ICP-MS can produce high quality data for elements with wide range of atomic masses, from 6Li to 238U. The best results are obtained for elements that have ionization potentials lower than those of the carrying gas (Ar, 15.8 eV) and that are free of isobaric interferences. The most common applications for ICP-MS are in biological, environmental, geological, and industrial fields. The following is a modest list of materials that can be analyzed by ICP-MS:
Archeological Applications: artifacts (e.g. ancient ceramics, bronze mirrors) and raw materials
Biological Applications: Animals: blood, bones, feathers, feces, hair, human breath, milk, red cells, serum, shells, stomach contents, teeth, tissues, urine, zooplankton.
Plants: barks, broccoli, fertilizers, fruits, garlic, grass, leaves, mushrooms, roots, tobacco, tea, tree rings, wood.
Foods: beverages, food packaging, juices, milk, metabolites, rice flour, sea food, wine.
Health sciences: chemotherapy drugs, illicit drugs, medicines, toxicology studies, metabolism studies, dietary supplements.
Earth Science Applications: fossils, minerals, meteorites, rocks, soil, waters.
Environmental Applications: atmospheric deposits (wet, dry), brines, car exhaust particles, coal fly ash, dust, gases from landfills, incinerator wastes, organic waste, oil pollution, paint, snow, sludge, washing powders.
Forensic Science: glass, illicit drugs and plants, soils, paint, metals.
Industrial Applications: alloys, automobile catalytic converters, ceramics, dyes, glass, lab gloves, nuclear industry products, paint, paper, petroleum based products, plastic, rare earth element compounds, steel, silica, superconductors, sulfides.
Laser-ablation ICP-MS: the principles
Samples are placed under vacuum in the HelEx laser sample chamber. A laser beam (here with a 193 nm wavelength) is focused on the sample surface (typically glass or mineral), and turns it into an aerosol. Laser beam energy and hit frequency are optimized for best signal intensity and stability. The sample chamber can move at a pre-set speed allowing ablations to be done along a raster of spots or a line along a surface (this technique yields better analytical precision). Alternatively, the sample stage remains immobile and the laser drills into the sample, allowing for micro-analysis of smaller samples such as minerals in rocks. Our laser beam size can vary from 160 microns to 5 microns, and is optimized based on sample size and analytical concentrations. A collection cup lies above the sample, where high-purity He carrier gas circulates, entraining the ablated material and conveying it to the mixing chamber of the ICP-MS.
In the mixing chamber, the He carrier gas and sample are mixed with high-purity argon and injected inside a quartz torch. Additional argon is introduced in the torch around the sample injector. An induction coil generates an electro-magnetic field such that the argon-sample mixture is ionized as a plasma. The plasma is introduced into the mass spectrometer through a set of cones (sampling cone and skimmer cone). Ions of interest are filtered through a set of lenses and carried to the quadrupole for detection. If necessary, prior to detection, ions circulate through a He-fluxed collision cell, where molecular compounds are disintegrated in order to reduce mass interferences with analyzed ions.
Solution mode ICP-MS is simpler as the laser ablation process is bypassed entirely. Instead, the solution is aspired and conveyed into a nebulizer by a peristaltic pump. There, it is mixed with argon and then introduced inside the torch for ionization. Automation of the sample introduction process is made possible by the use of an autosampler.
Data generation: the principles
Whether the instrument is used in solution or laser mode, the following steps are required in order to generate exploitable data:
- For each investigated element, the ICP-MS measures the abundance of one of its isotopes (generally expressed in counts per second, or cps). To relate measured intensities to actual concentrations, calibration must be performed at the beginning of the analytical session. Calibration is done using multiple standards with a matrix similar to that of the samples. Standards can consist of solutions spiked with precisely known amounts of one, or several, trace elements, solutions of reference materials of precisely known trace element compositions (e.g., NIST SRM 1640), and, for laser ablation, natural reference rock materials (e.g., USGS BHVO-1G), or artificial glass doped with precisely known amounts of trace elements (e.g., NIST SRM 612, USGS GSD-1G). We also use natural reference rock powders fluxed in lithium tetraborate similar to our samples analyzed for whole rock compositions. In solution mode only, standards can be diluted to extend calibration bounds and better reflect sample concentrations, if necessary.
- For each standard and sample analyzed, a few elements of previously known concentrations must be analyzed to precisely estimate possibly variable sample introduction parameters such as plasma uptake rate by the mass spectrometer cones, solution uptake rate by the autosampler, or ablation rate by the laser. These internal standards consist of a multi-element spike solution (e.g., a Sc-Ge-Y-In-Tb-Bi solution) added to the sample and standard solutions, for solution ICP-MS. In laser ablation, internal standards normally consist of major elements of which concentrations in the sample have previously been determined by X-ray fluorescence in our laboratories. Laser ablation internal standards may include Mg, Si, Ca, Ti, Fe. The intensities of the analytes are then normalized to the intensities of the internal standard elements. Using several internal standards better addresses uncertainties associated with variable isotopic masses, ionization and/or ablation characteristics of the analytes.
- To precisely assess quantification limits in the samples, a laboratory blank must be added within the analytical session. The blank must be chemically processed the exact same way as the samples so that possible contamination from the solvents or containers can be quantified and blank corrections applied to the samples.
- A pair of standards is periodically analyzed as unknowns throughout an analytical session, in order to monitor instrumental drift and, if necessary, correct the intensities obtained on the samples for instrumental drift. Instrumental drift means a change in sensitivity to an analyte, or practically, a change in the ratio measured between an analyte and its internal standard.
The joint X-ray Fluorescence and ICP-MS Laboratories at MSU offer a variety of analytical services, including elemental packages for rock and soil samples (Option 1 below).
The following schedule shows estimated fees. Additional discounts may be given for large numbers of samples or in-house sample preparation. Fees are subject to change at any time. Prices reflect a normal turn-around time of about one (1) month. Rush orders may require additional charges. Please consult Dr. Tyrone Rooney before officially quoting any prices.
Geological (rock and soil) samples by X-ray fluorescence and laser-ablation ICP-MS
Sample Preparation: All samples are analyzed as glass disks, prepared by fusion of finely-ground rock powders with lithium tetraborate. Samples may be submitted as powders or in bulk. Submit a minimum of 8 grams powder or 30 grams whole rock.
|Sample type||Cost per sample|
|Trimming/powdering of bulk samples||$5/sample|
|Li2B4O7 fusion (of powdered samples*)||$6.50/sample|
*Submitted sample powders should be fine enough so they are not “gritty” when rubbed between sheets of paper. Re-powdering of gritty samples will require an additional charge.
Users may also request to prepare their own samples at MSU, subject to a $2.00/sample materials charge.
|Elements||Academic or research||Commercial|
Major elements only* (XRF)
Major elements + 30 trace elements** (XRF + LA-ICP-MS)
*Standard major element package includes SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, CaO, Na2O, K2O, P2O5.
A minimum charge of $350 (academic) and $600 (commercial) will apply for all geological analyses involving LA-ICP-MS. This cost reflects the minimum time to tune the instrument, run standards, and data processing.
ICP-MS (solution) Samples
Samples must be free of solids, and in a matrix of 1-2% HNO3. A minimum of 10 mL should be submitted for each sample. It is preferred that the user provides standard solutions spanning the range of concentrations of elements of interest and that the samples and standards are spiked with a precisely known amount of spike solution of elements to be used as internal standards (please contact us with questions, and readsample preparation guidelines below). If standards are not provided, samples are not spiked, and/or concentrations are not known, additional sample preparation charges may apply (see below):
|Elements||Academic or research||Commercial|
|ICP-MS cost per hour (> 8 hours)||$200 ($150)||$300|
|Additional standard preparation or screening, per hour, one (1) hour minimum||$150||$300|
Laser ablation ICP-MS will be selected over solution ICP-MS for solid samples (e.g., fused powders, or in-situ analyses of minerals, glass, ceramics, etc.). Based on the relative complexity of analyses (number of ablations, standardization, data processing, etc.) rates will vary for solid sample introduction. The following rates are estimates only. Please contact us for further pricing. The minimum fee reflects protocol development and data processing.
|Elements||Academic or research||Commercial|
|LA-ICP-MS cost per hour||$175||$300|
|LA-ICP-MS minimum charge||$350||$600|
Laser Ablation Sample Preparation
In general, one of the largest benefits of laser ablation ICP-MS is that sample preparation is minimal, as long as the sample is relatively homogenous or the region of interest can be identified in the sample (e.g. minerals in thin section). It is much preferred that the concentration of at least one element is precisely known, such that it can be used as an internal standard. Please consult with lab manager for any special sample preparation required for specific types of samples, or specific standards that may be needed.
Solution Sample Preparation
Sample preparation is responsibility of the user. Always discuss the sample preparation procedure with the lab manager to make sure that the procedure is compatible with the ICP-MS. The following general rules should be followed:
- The solutions to be run in the ICP-MS should be 1% - 2% HNO3.
- Reagents used for the sample preparation should be double distilled or ultra pure. The high purity acids reduce contamination and background levels in the instrument.
- Total dissolved solids of solutions should be less than 0.1% (the total dissolved solids is the ratio of the sample weight to the solution volume).
- Blank solution:
The user should provide a procedural blank. This blank should be prepared by the same method used to prepare the unknowns. If the unknowns have not been processed by any digestion method, the blank would be diluted acid of similar characteristics to those of the unknowns. The procedure blank will be the first solution to be run to check the cleanness of the sample preparation procedure. If the blank produces unacceptably high counts, the analyses will not proceed. To avoid wasting samples, use only high purity reagents in all the stages of sample preparation. We need to keep the ICP-MS as clean as possible to be able to reach low levels of detection (ppt).
The user should provide a set of at least 4 standards for each run that have concentration range similar to that expected from the unknowns. These standards will be used to generate the calibration curves from which the composition of the unknown samples will be inferred. The user should discuss the number and type of standards most appropriate for the analysis with the lab manager.
For best results, the standards should have a similar matrix to the unknowns and be prepared by the same method. If samples and standards are not matrix-matched, the accuracy of results may be compromised.
If the composition of the sample is completely unknown, a qualitative scan must be run prior to the preparation of the standards.
There are two types of standards that are used in solution ICP-MS. One set of standards includes those solutions prepared from single or multi-element standards that are commercially produced. The second set of standards is known as SRM (standard reference material). SRMs are samples with well-defined compositions (working values) from analyses by many different laboratories.
An alternative calibration method is standard addition. Standard addition is one of the most precise methods for determining the composition of an unknown sample.
This calibration strategy consists of "spiking" the unknown solution with known amounts of the analyte(s) and comparing the signal response of the un-spiked and spiked unknown solutions.
When doing standard additions, the amount of unknown solution needed is doubled. One portion of the unknown solution should not be “spiked" and another portion of the unknown solution should be “spiked."
Internal standards (IS) are elements that are added to the blank, standards, and samples in known concentrations. The concentration of a given internal standard should be the same in all the solutions (i.e. blank, standards, and samples).
To select an internal standard keep in mind the following:
- the internal standard should not have isobaric interferences with the analyte(s)
- the samples and standard reference materials should have negligible concentrations of the IS
- when analyzing a group of elements with a wide range of masses, several internal standards should be used with a similarly wide range of masses (e.g. Be, In and Bi)
Internal standards are widely used in ICP-MS analyses to correct for variations in the instrument response as the analysis proceeds (drift) and to calculate the analyte concentrations of the samples (see principles above)