Scanning Electron Microscopy Coupled Energy-Dispersive X-Ray Spectroscopy

Method Introduction

Scanning electron microscopy (SEM) coupled energy-dispersive X-ray spectroscopy (SEM-EDS) combines the benefits of two valuable analytical techniques: SEM, a versatile visualization technique, and energy-dispersive X-ray spectroscopy (EDS), a powerful method for elemental analysis. During SEM analysis, the surface of a specimen is scanned in a raster pattern with an electron beam. Atoms on the sample surface interact with the electron beam and emit secondary electrons (SE) from their shell as well as back-scatter electrons (BSE) from the beam itself. SE- and BSE-detectors collect and process the electron signals, allowing for a visualization of the sample surface down to the nanometer scale.

SEM usually operates at a high vacuum and with a high electron beam voltage to achieve maximum resolution. This requires the sample to be electrically conductive. If not, the sample must be coated with a conductive material, e.g., by sputter coating or by high vacuum evaporation.

Non-conductive specimens, such as biological samples, may be measured without coating by reducing the electron beam voltage and applying only a low or no vacuum. While this reduces image resolution, it can omit potential sample alteration during preparation.

Energy-Dispersive X-Ray Spectroscopy (EDS)

When secondary electrons are emitted from the sample upon interaction with the electron beam, higher-energy electrons fill their positions and emit energy in the form of X-rays. These X-rays are characteristic of the element from which they were emitted and can thus be used to map the elemental composition on the surface of a specimen. This information is very valuable for determining a specimen’s chemical identity and origin.

Applications

Applications of SEM-EDS include:

Visualization of subvisible particles isolated from liquid samples
Elemental analysis of subvisible particles isolated from liquid samples
Inspecting the structure and physical state of lyophilized products

Coriolis offers SEM-EDS as a standalone service or as part of a formulation development program (liquid and lyo), lyophilization process development, or during troubleshooting and root-cause analysis.

Quality and Biosafety Level

We provide all our analytical services with the highest quality standards. Experienced scientists carry out each project, and a scientific reviewer comprehensively checks every report or data presentation.

We offer this technology with the following quality and biosafety levels:

R&D level

We offer this method under R&D. Our GRP system assures the highest-quality research standards.

Up to biosafety level 2

This method can be applied to nucleic acids, viruses, cells, viral vectors, including lentiviruses and more.

Analytical Method Development, Qualification and Validation

For common sample types, we can often apply standardized methods with little setup effort. However, when needed, our experienced analytical experts create or optimize custom methods tailored to your active pharmaceutical ingredient, product type and development phase.

Method Development

Our method development approach tailors sample preparation, method settings and data analysis to the needs of your project and sample.

We include representative samples and, where available, suitable reference standards and stressed/degraded materials, allowing our analytical scientists to design a highly suitable, stability-indicating, robust and repeatable method. Upon request, we will compile a detailed description of the method for your records.

Method Qualification

Method qualification is the initial assessment of an analytical procedure’s performance to show its suitability for its intended purpose.

During method qualification, our analytical scientists perform documented testing demonstrating that the analytical procedure meets criteria in several categories. Criteria may include factors such as repeatability, specificity and robustness. We compile a qualification plan and report, including all relevant data.

Method Validation

Under GMP conditions, method validation confirms that an analytical procedure’s performance suits its intended purpose. Depending on the method’s scope, a broad range of method characteristics, such as specificity, accuracy, precision, limit of detection/limit of quantification (LOD/LOQ), linearity and range, is considered.

During method validation, our analytical scientists perform documented testing demonstrating that the analytical procedure consistently produces a result that meets the predetermined acceptance criteria. We compile a validation plan and report that includes all relevant data.

Depending on the development phase, a fit-for-purpose validation approach can be offered, adjusting the validation required efforts in a phase-appropriate way to meet the method’s needs.

Method Verification

Compendial method verification confirms that a compendial method (e.g., from Ph. Eur. or USP) is suitable and reliable for its intended purpose under the specific conditions of the laboratory.

Unlike full method validation, compendial method verification is often considered a partial validation since the method has already undergone extensive testing and validation during its inclusion in the compendium. The extent of method verification depends on the type of method.

During method verification, our analytical scientists perform documented testing demonstrating that the developed analytical method performs adequately for the specific product or matrix being tested and within the specific laboratory where the method will be employed.

Talk to Our Experts or Request a Quote

Our expert team is ready to answer your questions and guide you to the services best suited to your program’s modality, stage and challenge. If your needs are well-defined, we’ll begin the quotation process.

Related Services

Fourier transform infrared (FTIR) microscopy Raman microscopy Scanning electron microscopy coupled energy-dispersive x-ray spectroscopy (SEM-EDS)

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