Raman Analysis | EUROLAB

What Is Raman Analysis?

Raman spectroscopy is based on a very small fraction of monochromatic laser light directed at the sample scattering with a change in energy due to molecular vibrations. These energy differences form a spectrum specific to the molecule.

Purpose of Raman Analysis

The purpose is to identify a material's molecular structure without damaging the sample. Giving a strong signal in aqueous media and being able to measure through packaging are clear advantages over FTIR.

Which Products Is Raman Analysis Applied To?

Polymer and composite materials
Polymorph differentiation in pharmaceutical active ingredients
Pigment, paint and artwork materials
Microplastic particle identification
Carbon materials and graphene structures

In Which Sectors Is Raman Analysis Used?

ChemistryPharmaceuticalsFoodCosmeticsEnvironmentPlasticsEnvironment

Standards Related to Raman Analysis

European Pharmacopoeia 2.2.48 (Raman spectroscopy)
ASTM E1840 (Raman wavenumber calibration)
ISO 24187-type microplastic examination guidelines

Raman Analysis Conditions

Lazer dalga boyu: It is selected according to the sample; If there is fluorescence, a longer wavelength is preferred
laser power: It is limited to a level that will not burn the sample.
Spectral range: According to the analyzed bond vibrations
Calibration: Wavenumber calibration with reference material

Equipment for Raman Analysis

Raman spectrometer and laser source
Raman microscope (for micro-Raman measurements)
Spectral library
Sample positioning stage

Sample Requirements for Raman Analysis

Most samples require no preparation; the measurement is non-destructive
Measurement through transparent packaging is possible in most cases
Dark-coloured and fluorescent samples can present difficulty
Particles must be presented on a filter for microplastic examination

Duration of Raman Analysis

A single-point measurement takes seconds to minutes. In mapping studies, duration increases in proportion to the area examined.

Raman Analysis Procedure

1The sample is placed at the measurement position.
2Laser wavelength and power are selected.
3Focusing is performed and the spectrum is recorded.
4The fluorescence background is corrected.
5Identification is made by comparing the spectrum with the library.
6Component distribution is derived via area scanning if required.

Raman Analysis Acceptance Criteria

The acceptability of the identification result is assessed against the product's declared composition or the pharmacopoeial monograph.

Evaluation of Results

Identification relies on the spectrum's characteristic bands agreeing with the reference. If fluorescence is strong the spectrum can be suppressed; in that case confirmation with a different laser wavelength or FTIR is required.

Raman Analysis Report

Sample description, receipt date and laboratory number
Method applied and reference standard, if any
Instrument and measurement conditions
Sample preparation steps
Measurement results and units
Measurement uncertainty (if requested)
A statement that the results relate only to the sample submitted for testing

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

European Pharmacopoeia raw material identification requirements
EU single-use plastics and microplastics regulations

Pages Where This Method Is Used

Analytical Methods — What Does This Group of Methods Do?

The section below describes the field that the Raman Analysis test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Analytical method pages are pages about a MEASUREMENT TECHNIQUE rather than about a test. The difference matters: "salt spray testing" is a test and answers one question; "ICP-MS" is a technique and is used in dozens of different tests. Sometimes the user is looking not for the test but for the technique — because the method name is what appears in their specification.

This distinction becomes decisive in choosing a laboratory. When a customer asks for "heavy metal analysis", the real question is by which technique it will be done: XRF is fast and non-destructive but does not distinguish compounds; AAS is economical for a single element; ICP-OES screens multiple elements; ICP-MS sees trace levels. The same sample gives results with different detection limits and different uncertainties across the four techniques.

Method selection is made against three criteria. DETECTION LIMIT: is the concentration sought within the range the method can see? MATRIX COMPATIBILITY: is the sample matrix (plastic, food, soil, metal) one the method can handle, and is pre-treatment required? SPECIFICATION LINK: does the product standard or legislation mandate a particular method? The third often overrides the first two — the specification binds the method.

Method pages build a CHAIN. A technique is linked to the test pages where it is used, to the standards those tests rest on, to the legislation those standards are tied to and ultimately to market access regimes. The example chain in the source document works like this: XRF → metal analysis → RoHS compliance → heavy metal restriction → coating pages. Whichever link the user enters from, they reach the others.

Sample preparation is the invisible half of the result in this family and is a greater source of error than the technique itself. The digestion method, degree of grinding, extraction solvent and dilution ratio change the result markedly. The same sample on the same instrument gives a different result with different preparation; the definition of the method therefore covers preparation too.

Calibration and verification are the third determining component. An instrument is calibrated with certified reference material, the calibration curve is verified periodically and a control sample is run in each batch. Without these steps, a number produced is not traceable even if the instrument is working correctly.

Method groups in this field

Elemental analysis
ICP-OES, ICP-MS, AAS and XRF. They differ in detection limit, matrix tolerance and multi-element capacity.
Chromatography
GC, GC-MS, HPLC, LC-MS/MS and ion chromatography. It separates a mixture into its components and measures each separately.
Spectroscopy
FTIR, Raman, UV-Vis and optical emission. For material identity, functional group identification and alloy composition.
Thermal analysis
DSC, TGA, DMA and dilatometry. Transition temperatures, composition, decomposition and dimensional behaviour.
Microscopy and imaging
Optical microscopy, SEM-EDS, radiography and tomography. Structure, defects and elemental distribution.
Classical (wet) chemistry
Titration, gravimetry and colorimetry. Used as a reference method and in confirming instrumental results.

Commonly confused in this field

XRF is a screening tool; it sees elements and does not distinguish compounds. A decision on a restricted compound requires confirmation by wet chemistry.
The phrase "not detected" is not proof of absence; it is read together with the detection limit of the method.
The specification binds the method. A technically better method is not accepted if the specification calls for another.
Sample preparation is part of the result; a report that does not state the preparation is not reproducible.
Results obtained by different techniques cannot be compared directly; their detection limits and uncertainties differ.
A method page is not a test page; which method applies to which test comes from the product standard.

Which decisions these results support

Matching the method written in the specification to the laboratory's scope
Method selection according to detection limit and matrix compatibility
Confirming an instrumental result with a reference method
Eliminating deviations arising from sample preparation

Related Tests

Frequently Asked Questions About Raman Analysis

Raman or FTIR?

The two are complementary. Symmetric and non-polar bonds give a strong signal in Raman, and polar bonds in FTIR. Raman is generally more suitable for aqueous samples, and FTIR for thin films and coatings.

Is the sample damaged?

The method is non-destructive, but high laser power can cause local heating in dark-coloured samples. Power is therefore limited.