The current fee for using the ICP-MS facility is $490/day plus 44% overhead (215$/day) for URI and external users for routine analyses without operator. Additional charges are added for special applications requiring technical assistance.
The reagents used in all stages of sample preparation should be double distilled or ultra pure. The high purity acids will keep background levels in the instrument low allowing to reach detection of parts per billion (ppb) or parts per trillion (ppt) levels. If running solutions (usually 1 %-2 % HNO3 or 1% -2% aqua regia), the total dissolved solids (i.e. the ratio of the sample weight to the solution volume) should normally be less than 0.1 % - unless special nebulizers are used. The sample preparation procedure should be discussed with the lab manager to make sure that the procedure is compatible with the ICP-MS.
There are two types of standards that are used in ICP-MS: laboratory standards prepared from single or multielement standards that are commercially produced or Standard Reference Materials (SRMs) whose composition (working values) is a compilation of analyses of many different laboratories. These standards will be used to generate the calibration curves from which the composition of the unknown samples will be inferred. For the best results, the standards should have a similar matrix to the unknowns and prepared by the same method. If the composition of the sample is completely unknown, a qualitative scan can be run easily prior to the preparation of the standards.
Full procedure blanks represent low levels of elements of interest present in the reagents used to prepare the samples and are subtracted from the unknowns. 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 the similar characteristics to those of the unknowns. The procedure blank will be run to check the cleanness of the sample preparation procedure.
For quantitative ICP-MS analysis, calibration is most commonly achieved by external standarization. The signal intensities of all analyte isotopes are measured in a blank as well as in one or more artificial or natural standards with known analyte concentrations that cover the concentration range of interest. The relationship between the blank-corrected standards on a diagram of signal intensity vs concentration is used to establish a calibration curve that may be used to calculate the concentration of the analytes in samples of unknown composition.
Alternative means of calibration include the methods of standard addition and isotope dilution. Standard addition calibration provides an effective way to minimize sample-specific matrix effects through the use of sample solutions that have been 'spiked' with a known concentration of each analyte elements. The method of isotope dilution requires samples to which a known amount of a 'spike' of an enriched isotope solution of known isotopic composition has been added.
Although ICP-MS instrument generally provides relatively stable signals for extended periods of time, instrument drift ( i.e. temporal variation, most commonly a decrease, of signal intensity with time) does occur and has to be corrected. This drift correction may be achieved by internal standardization, i.e. the normalization of all data to a non-analyte isotope present in the same or known concentrations in all samples and standards. Ideally, internal standards should be species with masses without interferences in the matrix. Common internal standard isotopes are 9Be, 45Sc, 89Y, 103 Rh, 115In and 209Bi. In the case of laser ablation ICP-MS, internal standardization is used to correct for differences in the ablation characteristics between different materials.