Elemental analysis identifies and quantifies metals and other elements in pharmaceutical raw materials, finished products, and other regulated materials. For applications requiring high sensitivity and precise quantification, inductively coupled plasma (ICP) techniques offer powerful analytical capabilities.
ICP analysis uses a high-temperature plasma to atomize, excite, or ionize elements within a prepared sample. Depending on the analytical technique, these elements can then be measured using mass spectrometry or optical emission spectroscopy. Industries such as pharmaceuticals, mining and metallurgy, cosmetics, and oil and gas use ICP analysis to identify and measure the elemental and trace-metal composition of liquid, solid, or gas samples.
One of the most sensitive techniques is inductively coupled plasma mass spectrometry (ICP-MS), which combines an inductively coupled plasma source with a mass spectrometer. ICP-MS supports multi-element analysis at trace and ultra-trace concentrations, making it particularly useful for elemental impurities testing and other applications requiring low detection limits.
How Does Inductively Coupled Plasma Analysis Work?
An inductively coupled plasma is a high-temperature ionized gas capable of converting elements within a sample into atoms and ions. Argon is commonly used to create and sustain the plasma.
During ICP analysis, radiofrequency energy is applied through a coil surrounding the torch. This energy interacts with the argon gas to create and maintain the plasma. Temperatures within the plasma are high enough to desolvate, vaporize, atomize, and ionize components of the introduced sample.
What happens next depends on the analytical technique. In ICP-MS, the resulting ions are transferred to a mass spectrometer for separation and detection. In ICP optical emission spectroscopy (ICP-OES), characteristic light emitted by excited atoms and ions is measured.
These approaches allow laboratories to identify and quantify multiple elements within a sample, although the appropriate analytical method depends on factors such as the sample matrix, target elements, expected concentrations, and required sensitivity.
Sample Preparation and Introduction
Accurate ICP analysis begins before a sample enters the instrument. Sample preparation is an important part of developing a method that is appropriate for the material and analytical objective.
Liquid samples may require dilution or other preparation before introduction. A nebulizer typically converts the prepared liquid into an aerosol. The spray chamber helps remove larger droplets so that a fine aerosol can be carried into the plasma.
Solid samples generally require additional preparation for conventional ICP-MS analysis, which typically introduces samples in liquid form. Digestion may be needed to bring target elements into solution, with the preparation method determined by the sample matrix and the elements being measured.
Contamination control is particularly important when analyzing elements at trace or ultra-trace concentrations. Reagents, laboratory equipment, containers, and the surrounding environment can potentially introduce elements that affect measurements. Appropriate blanks, standards, and quality controls can help identify and manage these effects.
For this reason, sample preparation should be developed as part of the overall analytical method rather than treated as a separate step.
What Is ICP-MS?
Inductively coupled plasma mass spectrometry, or ICP-MS, combines the ionization capabilities of an ICP source with the selective detection capabilities of mass spectrometry. It is widely used when an application requires sensitive multi-element analysis.
After a sample enters the plasma, its components undergo processes that ultimately produce ions. These ions pass through an interface that transfers them from the atmospheric-pressure plasma into the lower-pressure environment of the mass spectrometer.
Ion optics help guide and focus the ions before they reach the mass analyzer. Depending on the ICP-MS configuration, a quadrupole or another type of mass analyzer separates ions according to their mass-to-charge ratio. The detector then measures the ions, producing signals that can be related to elemental concentrations through calibration.
This combination of plasma ionization and mass-based separation gives plasma mass spectrometry several useful capabilities. ICP-MS can analyze numerous elements during a single analytical run, achieve low detection limits for many analytes, and provide isotope-specific information when required.
These capabilities make ICP-MS particularly valuable for pharmaceutical elemental impurities testing, where multiple elements may need to be evaluated at low concentrations.
How an ICP-MS Instrument Measures Elements
The ICP-MS analytical process can be understood as a sequence of connected stages.
First, appropriate sample preparation converts the material into a form that can be introduced into the instrument. The sample aerosol then enters the inductively coupled plasma, where high temperatures facilitate atomization and ionization.
The resulting ions pass through interface cones that help transfer them into the vacuum system of the instrument. Ion optics guide the ions toward the mass analyzer, where they are separated based on mass-to-charge ratio. Finally, the detector measures the ions and generates an analytical signal.
Calibration standards with known concentrations establish the relationship between instrument response and analyte concentration. The laboratory can then use this calibration to quantify the target elements in test samples. Each stage can influence the quality of the final result, which is why ICP-MS testing involves more than operating the instrument itself.
ICP Interferences and Quality Controls
Although ICP analysis is highly sensitive, analytical interferences can affect measurements if they are not appropriately evaluated and controlled.
Spectral interferences occur when another species produces a signal that overlaps or interferes with the target analyte. ICP-MS instruments may use collision or reaction technologies to address certain types of interference.
Non-spectral effects can also occur. Differences in sample matrices, high concentrations of dissolved materials, or other sample characteristics may influence ionization, transport, or detector response.
Internal standards can help laboratories monitor and compensate for certain variations in instrument response and sample behavior. Analytical programs may also incorporate calibration standards, blanks, quality control samples, and other controls appropriate to the method.
Evaluating these factors is especially important when plasma mass spectrometry is used to quantify elemental impurities at low concentrations.
ICP-MS vs. ICP-OES and Atomic Absorption
Several analytical techniques can be used to measure metals and other elements, and each operates differently. ICP-MS uses an inductively coupled plasma to generate ions and a mass spectrometer to separate and measure those ions according to their mass-to-charge ratios. This approach provides sensitive multi-element analysis and can offer isotope-specific measurements.
ICP-OES also uses inductively coupled plasma, but the measurement principle differs. Rather than separating ions by mass, ICP-OES measures characteristic wavelengths of light emitted by excited atoms and ions.
Atomic absorption spectroscopy uses another approach, measuring the absorption of specific wavelengths of light by atoms of the target element. Choosing among these techniques depends on the elements being analyzed, expected concentrations, sample matrix, required detection limits, analytical range, and applicable testing requirements. An analytical laboratory can evaluate these factors when determining an appropriate method.
Applications of ICP Analysis in Pharmaceutical Testing
For pharmaceutical and life sciences organizations, ICP analysis can support several stages of development, manufacturing, and quality testing.
One major application is elemental impurities testing. Metals and other elemental impurities can originate from raw materials, manufacturing equipment, catalysts, packaging components, container closure systems, or other sources. Analytical testing can help characterize and quantify these elements.
ICP-MS can also support raw material testing. Depending on the material and specification, testing may be used to identify or quantify particular elements before a raw material is used in pharmaceutical manufacturing.
Other applications may include trace metals and heavy metals analysis, product development, investigations, and extractables and leachables studies. For example, ICP-MS may be used when evaluating metals potentially associated with materials used in pharmaceutical packaging or delivery systems.
The flexibility of plasma mass spectrometry also allows laboratories to develop methods for a variety of matrices. Liquids may be relatively straightforward to introduce, while complex matrices and solid samples can require more extensive preparation and method development.
Method Development, Validation, and Quality Considerations
A well-designed ICP method begins with an understanding of the analytical objective. Laboratories need to consider which elements must be measured, their anticipated concentrations, the nature of the matrix, and the sensitivity required.
Method development may involve establishing appropriate sample preparation, instrumental parameters, calibration ranges, internal standards, and approaches to potential interferences.
Validation demonstrates that a method is suitable for its intended purpose. Depending on the method and applicable requirements, characteristics such as accuracy, precision, specificity, linearity, range, limit of detection (LOD), and limit of quantitation (LOQ) may need to be evaluated.
Quality controls incorporated into routine testing can then help demonstrate that the analytical system continues to perform as expected.
Understanding and Reporting ICP Analysis Results
ICP results are generally reported as concentrations using units appropriate for the application. Correct interpretation may require accounting for dilution factors and other aspects of sample preparation.
LOD and LOQ are also important concepts. The LOD reflects the lowest amount or concentration that can be reliably detected under defined conditions, while the LOQ represents the level at which an analyte can be quantitatively determined with suitable performance.
Results may then be evaluated against established specifications, regulatory limits, or other acceptance criteria. For regulated testing, interpreting a numerical result within the context of the validated method and applicable requirements is as important as generating the measurement itself.
ICP Analysis and Elemental Testing at BA Sciences
Understanding what is ICP analysis is only the beginning of developing an appropriate elemental testing program. Method selection, sample matrix, target elements, required sensitivity, regulatory expectations, and sample preparation all need to be considered when determining the appropriate analytical approach.
BA Sciences provides elemental analysis capabilities for pharmaceutical, biopharmaceutical, and medical device organizations. Our services include ICP-MS testing for elemental impurities, trace metals, heavy metals, and pharmaceutical raw materials, as well as analytical method development and validation.
With more than 30 years of analytical laboratory experience, BA Sciences operates as a cGMP-compliant, FDA/DEA-registered, and ISO/IEC 17025:2017-certified laboratory.
Whether a program involves routine elemental analysis, development of an ICP-MS method, testing of complex or solid samples, or evaluation of elemental impurities, BA Sciences can help develop an analytical approach based on the specific material and testing requirements.
Contact BA Sciences to discuss ICP-MS testing, elemental analysis, method development, validation, or other analytical testing needs.