Skip to Content

ICP Calibration Standards: Selecting Standards for ICP-MS and ICP-OES

August 27, 2026 by
ICP Calibration Standards: Selecting Standards for ICP-MS and ICP-OES
Alissa Morse

ICP-MS and ICP-OES laboratories routinely measure multiple elements across a wide range of concentrations.

The analytical capability of the instrument, however, does not eliminate the need for an accurate reference point.

ICP calibration standards contain known analyte concentrations used to establish the relationship between concentration and instrument response. Selecting an appropriate standard requires consideration of the analytical method, elements, concentrations, matrix, compatibility, stability, and intended calibration or QC function.

The correct solution may be a single-element reference material, multi-element calibration standard, ICV or CCV standard, or a formulation developed specifically for the laboratory's method.

As covered in our Guide to Inorganic Standards and Certified Reference Materials, selecting the appropriate reference material starts with understanding its intended analytical purpose, certification requirements, traceability, matrix, and stability.

What Is an ICP Calibration Standard?

An ICP calibration standard provides known concentrations of one or more elements for establishing or verifying calibration in an ICP analytical method.

For example, an ICP-MS laboratory can prepare a series of working solutions from a concentrated reference standard and use the resulting instrument responses to generate a calibration curve.

Within CPI's ICP calibration standards portfolio, laboratories can find:

These categories reflect an important point: not every ICP standard serves the same analytical purpose.

ICP-MS Calibration Standards

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) provides highly sensitive multi-element measurements.

Reference materials used in ICP-MS workflows can include:

Because ICP-MS can measure elements at very low concentrations, contamination control and starting-material purity are particularly important considerations when selecting reference materials.

Matrix selection matters as well. The acid composition of an ICP-MS calibration standard should be compatible with the analytical method, sample-preparation procedure, instrument components, and analytes being measured.

ICP-OES Calibration Standards

Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES)—also known as ICP-AES—is widely used for multi-element analysis.

Standards commonly used by ICP-OES laboratories include:

Multi-element standards allow multiple analytes to be introduced in the same calibration solution. That can reduce the number of individual standards a laboratory needs to combine.

It does not mean, however, that any group of elements can simply be mixed together.

Chemical compatibility, analyte concentration, acid matrix, oxidation state, and long-term stability all need to be considered when developing multi-element formulations.

Single-Element or Multi-Element?

This is one of the most practical decisions in ICP standard selection.

Single-Element ICP Standards

A single-element reference material gives the laboratory maximum flexibility over the final calibration or QC solution.

Single-element standards can be particularly useful when:

  • Only a few elements are required
  • Analyte concentrations differ substantially
  • Elements are chemically incompatible
  • Analytical methods change frequently
  • Independent individual standards are desirable

CPI's Single Element ICP Standards include Peak Performance™ standards and CRMs for ICP-MS and ICP-OES calibration, trace-metals analysis, and QC.

Multi-Element ICP Standards

A multi-element standard combines multiple analytes into one solution.

When an appropriate stable formulation can be produced, this approach can reduce:

  • Pipetting
  • Preparation time
  • Number of standards handled
  • Opportunities for preparation errors
  • Laboratory waste

For laboratories repeatedly running the same method, a properly formulated multi-element standard can simplify routine preparation.

Why Does Matrix Matter in ICP Calibration?

Concentration isn't the only value on a standard that matters.

The matrix can directly affect whether a standard is appropriate for its intended analytical use.

Common matrices for inorganic standards include:

  • Nitric acid (HNO3)
  • Hydrochloric acid (HCl)
  • Mixed nitric and hydrochloric acid
  • Hydrofluoric acid-containing matrices
  • Water
  • Other method-specific matrices

Nitric acid is commonly used for many inorganic elemental standards because it is compatible with a wide range of metals and analytical applications.

Some elements may be better suited to hydrochloric-acid matrices, while small amounts of HF can be required to stabilize certain elements or mixtures.

When HF-containing standards are used, laboratories should verify that the relevant sample-introduction components and laboratory procedures are appropriate for solutions containing hydrofluoric acid.

Element Compatibility Matters Too

A multi-element ICP standard requires more than combining individual stock standards. The formulation must remain chemically compatible and stable at the specified concentrations and matrix.

Potential issues include:

  • Precipitation
  • Hydrolysis
  • Adsorption
  • Oxidation or reduction
  • Complex formation
  • Matrix incompatibility
  • Concentration-dependent instability

A mixture that remains stable at one concentration may not necessarily remain stable at a substantially higher concentration.

That becomes particularly important when a laboratory is considering a custom formulation.

When Does a Custom ICP Calibration Standard Make Sense?

If laboratory personnel repeatedly prepare the same calibration mixture from several stock solutions, a custom standard can reduce routine preparation steps while matching the method's required analytes, concentrations, matrix, and volume.

A laboratory can specify parameters including:

  • Elements
  • Concentration of each analyte
  • Matrix
  • Solution volume
  • Packaging
  • Required certification
  • Analytical method or application

A custom multi-element formulation can reduce routine preparation steps and opportunities for dilution or transcription errors.

CPI custom standards allow laboratories to order the concentration, matrix, and volume their methods require rather than adapting a method around a predefined formulation.

Frequently Asked Questions About ICP Calibration Standards

What concentration should an ICP calibration standard be?

There is no universal concentration. The appropriate concentration depends on the analytical method, expected sample concentrations, instrument working range, and dilution procedure.

Concentrated stock solutions such as 1,000 µg/mL can be used to prepare lower-concentration working standards, while custom formulations can be produced closer to method-specific concentrations.

What matrix should I use for an ICP-MS or ICP-OES standard?

The matrix should be compatible with the analytes, analytical instrument, sample-preparation method, and samples being analyzed.

Can several elements be combined into one ICP standard?

Often, yes—but chemical compatibility, analyte concentration, matrix, oxidation state, and long-term stability need to be considered first.

Standardize Your Standards

CPI International has been supporting scientists for more than 40 years and provides ICP Calibration Standards, dedicated ICP-MS Calibration Standards, ICP-OES Calibration Standards, and Single Element ICP Standards for analytical laboratories.

CPI also provides custom formulations when an off-the-shelf solution does not match the laboratory's analytical requirements.

Explore CPI ICP Calibration Standards for ICP-MS and ICP-OES.

Next in the series: Calibration is only the beginning of an analytical sequence. Next, learn how laboratories verify calibration and monitor analytical performance in ICV, CCV, Interference & Instrument Check Standards: A Guide to ICP Quality Control.

Read Next
Inorganic Standards & Certified Reference Materials: A Guide for Analytical Laboratories