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Crustal Geophysics and Geochemistry Science Center

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Solution ICP-MS Laboratory

Photo of ELAN DRC II ICP-MS  and HPLC system in the Solutuions Laboratory.
ELAN® DRC II Quadrupole ICP-MS and Series 200 HPLC System

Photo of ELAN DRC-e ICP-MS and autosampler.
ELAN® DRC-e Quadrupole ICP-MS and S-10 Autosampler
The solution ICP-MS Laboratory uses dedicated quadrupole ICP-MS instrumentation to perform analyses on a wide variety of sample types. Several standard sample preparation procedures are available for routine matrix types, including soils, rocks, and biological specimens. All quadrupole ICP-MS systems are equipped with Dynamic Reaction Cell Technology to reduce interference effects on sample results. Specialized techniques, such as the use of desolvation systems, are also used to minimize interferences during sample analysis.


Sample Preparation Techniques

4-Acid Digestion

Photo of geological samples undergoing 4-acid digestion.
4-Acid Digestion of geological samples.
Sample decomposition using this multi-acid digestion technique is suited to dissolve certain rock types, soils, and sediments. This method uses a combination of nitric, hydrochloric, hydrofluoric and perchloric acids. As with any technique there are going to be exceptions. The method does not fully dissolve refractory or resistant minerals and some secondary minerals. Examples of incomplete digestion are as follows: Ba in barite, Cr in chromite, Ti in rutile, Sn in cassiterite, Al in corundum, and rare earth elements in monazite. Samples that contain elements in high concentrations where normally the element is a trace constituent will have to be diluted (i.e., Mg in dolomite, Pb in galena, Zn in sphalerite, Cu in chalcopyrite). This dilution increases the lower reporting limits.

Sodium Peroxide Sinter

Photo of samples being prepared with the sodium peroxide sinter method.
Samples being prepared via Na2O2 sinter method.
For the determination of the rare earth elements (REE) La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb in geologic materials, the REE are made soluble in the sample material by sintering with sodium peroxide (Na2O2), leaching with water, and acidifying with nitric acid. Lutetium is added as an internal standard for oxide correction. Rhodium and Iridium are added on line as internal standards to correct for matrix effects and instrumental drift.

Microwave Digestion

Photo of Multiwave 3000 Microwave digestion system.Multiwave 3000 Microwave digestion system and Teflon vessels.
Photo of Teflon vessels.
Close-up photo of teflon vessels.
For biological or organic samples, difficult to digest samples, or for samples where the volatile elements need to be preserved, microwave digestion is a preferred sample preparation technique. Using a specially-designed laboratory microwave digestion system, the temperature and pressure inside the vessels can be precisely controlled. This provides reproducible results and a high degree of reliability and safety. In this technique, small amounts (< 0.5 gram) of sample are digested with small amounts of high-purity acids and/or peroxide in closed Teflon vessels. The temperature and pressure are controlled automatically using a computer interface. Once the digestion is complete, the samples are allowed to cool and are then diluted with high-purity water.

More details on the methodologies used by the laboratory can be found in the following document: http://pubs.usgs.gov/of/2002/ofr-02-0223/.

The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.

For further information contact Ruth Wolf (rwolf@usgs.gov).

Mineral Resources Program
Eastern Central GMEG Alaska Minerals Information Crustal Geophysics and Geochemistry Spatial Data