Generating an acceptable calibration curve is an important part of ICP analysis.
Maintaining confidence in that calibration throughout an analytical sequence requires additional quality-control checks.
In our guide to selecting ICP Calibration Standards for ICP-MS and ICP-OES, we covered how calibration standards establish the relationship between analyte concentration and instrument response. Once that calibration is established, laboratories may need additional standards to verify and monitor its performance.
ICP Quality Control Standards help laboratories answer those verification and performance questions.
Depending on the analytical method and laboratory quality program, QC workflows may include:
- Initial Calibration Verification (ICV) Standards
- Continuing Calibration Verification (CCV) Standards
- Interference Check Standards
- Instrument Check Standards
- Other performance or method-specific check solutions
Each answers a different analytical question.
What Is an Initial Calibration Verification Standard?
An Initial Calibration Verification (ICV) Standard is analyzed after calibration to independently confirm that the calibration produces acceptable results.
In practical terms, calibration establishes the relationship between concentration and response. The ICV provides a check of that calibration before the laboratory proceeds with the analytical sequence.
When required by the method or quality program, a laboratory may use an ICV manufactured from a source independent of the standards used to establish the calibration.
CPI offers Initial Calibration Verification (ICV) Standards for ICP-MS and ICP-OES calibration verification and laboratory QC.
What Is a Continuing Calibration Verification Standard?
An acceptable calibration at the beginning of an analytical sequence does not automatically mean it remains acceptable throughout the run.
A Continuing Calibration Verification (CCV) Standard is analyzed periodically during an analytical sequence to determine whether instrument calibration remains acceptable.
If the measured CCV result falls outside the laboratory's established acceptance limits, corrective action may be necessary before sample results can be reported.
CPI offers Continuing Calibration Verification (CCV) Standards as a distinct category within ICP Calibration Standards.
ICV vs. CCV: What's the Difference?
Although both verify calibration, their roles differ.
| Standard | Primary purpose | Typical point of use |
|---|---|---|
| ICV | Independently confirms initial calibration | After calibration |
| CCV | Checks whether calibration remains acceptable | Periodically during the analytical sequence |
The exact requirements, frequency, acceptance limits, and source requirements should always follow the laboratory's applicable analytical method and quality program.
What Is an ICP Interference Check Standard?
Calibration verification is only one component of analytical quality control. ICP measurements can also be influenced by interferences.
An Interference Check Standard helps a laboratory evaluate whether high concentrations of potentially interfering elements affect accurate determination of target analytes.
Depending on the analytical technique and method, measurement can be affected by:
- Spectral interferences
- Physical interferences
- Chemical interferences
- Matrix-related effects
Interference standards provide laboratories with a defined material for evaluating these effects within the appropriate analytical workflow.
CPI's Interference Check Standards support ICP-MS and ICP-OES workflows that require evaluation of potential spectral interference and instrument performance.
What Are Instrument Check Standards?
Instrument Check Standards serve another purpose: evaluating aspects of instrument performance.
CPI's Instrument Check Standards support applications including:
- Sensitivity
- Stability
- Performance verification
- Method checks
- Routine laboratory quality control
These should not automatically be treated as interchangeable with ICV, CCV, or interference solutions. The appropriate solution depends on what the analytical method is intended to evaluate.
What About ICP Tuning and Setup Solutions?
Instrument setup is another distinct part of the ICP workflow.
CPI's ICP Tuning and Setup Solutions support ICP-MS and ICP-OES applications including optimization, sensitivity checks, stability testing, setup verification, and performance checks.
Keeping these categories distinct creates a useful way to think about an ICP workflow: setup and tune → calibrate → verify calibration → monitor calibration → evaluate interference and performance.
The exact sequence and required solutions depend on the method and instrument.
Why QC Standard Selection Matters
A standard should be selected according to the analytical question it is intended to answer.
For example:
- Did the initial calibration produce acceptable results? An ICV may be appropriate.
- Has calibration remained acceptable during the run? A CCV may be appropriate.
- Could an interfering element be affecting the target analyte? An interference check standard may be appropriate.
- Is the instrument meeting a required performance criterion? An instrument or performance check solution may be appropriate.
Clear terminology also simplifies purchasing and inventory management. An analyst looking for a CCV should be able to identify a Continuing Calibration Verification Standard without sorting through broadly labeled ICP products.
Quality and Documentation
Reference materials used in QC should also be evaluated based on the documentation and quality requirements of the laboratory.
Relevant considerations can include:
- Traceability
- Certified values where required
- Measurement uncertainty
- Matrix
- Concentration
- Lot information
- Certificate of Analysis
- Stability or validity information
- Applicable manufacturing and testing quality systems
For CRMs, laboratories should review the producer's applicable ISO 17034 accreditation and scope. ISO/IEC 17025-accredited testing and calibration capabilities can also be relevant when evaluating how reference materials are manufactured, tested, and documented.
Accreditation applies to the relevant facility or laboratory—not to the individual reference material.
Frequently Asked Questions
Is an ICV the same as a calibration standard?
They serve related but different functions. Calibration standards establish the relationship between analyte concentration and instrument response. An ICV is used after calibration to independently confirm that the calibration produces acceptable results.
What does CCV stand for?
CCV means Continuing Calibration Verification. It is used periodically during an analytical sequence to determine whether calibration remains acceptable.
Are ICV and CCV standards used with both ICP-MS and ICP-OES?
CPI offers ICV and CCV standards for ICP-MS and ICP-OES applications.
What does an interference check standard evaluate?
It can help determine whether potentially interfering elements affect accurate determination of target analytes.
Standardize Your Standards—and Your QC
For more than 40 years, CPI International has supported scientists performing analytical testing.
Today, CPI's reference-standard offering includes dedicated categories for ICP Quality Control Standards, Initial Calibration Verification (ICV) Standards, Continuing Calibration Verification (CCV) Standards, Interference Check Standards, Instrument Check Standards, and ICP Tuning and Setup Solutions.
This organization helps laboratories select standards according to the analytical function they need to perform.
Explore CPI ICP Quality Control Standards for ICP-MS and ICP-OES.
Next in the series: Once the required calibration or QC function is established, formulation becomes the next consideration. Compare analyte combinations, concentrations, matrices, and custom formulations in Single-Element vs. Multi-Element & Custom ICP Standards: How to Select Concentration, Matrix and Analyte Combinations.