Self-operator

         Academic/Research

            Commercial

ICP-MS cost per hour (> 8 hours)

$150 

          $200 (150)

                     $300

($125)

Additional standard preparation or screening, per hour, one (1) hour minimum            

n/a

                $150

                      $300

NOTE: All self-operator rates apply to users that prepare samples and standards UNESP and have sufficient.

Standards and Sample Preparation

The Platform ICP-MS is equipped with a variety of sample introduction systems that allow the analyses of solid, aqueous and gas samples.  The most common means of sample introduction are pneumatic nebulization of aqueous liquids via a concentric nebulizer and laser ablation of solid samples.

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).  The solutions to be run in the ICP-MS should be 1% - 2% HNO3.

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.

SOLUTION SAMPLE PREPARATION

1. 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.

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 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.

2. 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 Platform ICP-MS as clean as possible to be able to reach low levels of detection (ppt).

3. Calibration

Common calibration strategies for ICP-MS analyses are internal standards, external standard calibration, standard additions, or isotope dilution.

3.1. Internal standards

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).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. To select an internal standard keep in mind the following: a. the internal standard should not have isobaric interferences with the analyte(s); b. the samples and standard reference materials should have negligible concentrations of the IS; c. 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. In and Bi). 

3.2. External calibration

There are two types of external calibration. One uses a set commercially produced standards and the other uses a set of well characterized reference materials that have similar matrix to the unknowns. In either case, the standards are used to create calibration curves that will be used to calculate the concentrations of the elements of interest. The advantage of using commercially produced standards to generate the calibration curves is that their concentration is well characterized.

In addition, the user can prepare solutions that cover the compositional range in the unknown samples. However, the user must be aware that the response of the ICP-MS is highly sensitive to matrix effects. The intensity of the signal at a given isotope not only depends on the abundance of that isotope, but also the matrix of the solution can enhance or suppress the response. The standard reference materials (SRM) should be prepared by the same method as the unknowns. These standards can be used for drift corrections and to calculate the analyte concentrations in the unknowns. The advantage of using SRMs to calculate the calibration curves is that the matrix effects are readily taken into consideration, as long as the SRMs have similar matrices as the unknown samples.

3.3. 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."

3.4. Isotope dilution

Isotope dilution is the optimum method of calibration. 

It requires that the sample be "spiked" with a solution of known elemental concentration, and whose isotopic composition has been enriched in one of the isotopes of the elements being analyzed. 

Isotope dilution can only be used if the analyte has two or more isotopes, and if there is a "spike" solution enriched in one of the isotopes of every element of interest.