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Transmission Raman Spectroscopy (TRS™) is an ideal method for quantitative analysis of mixtures such as tablets, capsules, powders, liquids and suspensions

TRS, Conventional Raman and Near-Infrared

Raman spectroscopy is highly chemically specific, but conventional Raman methods rely on data collected from backscattering, which limits analysis of samples such as tablets and capsules to their surfaces. The surface is often not representative of the bulk in a tablet or capsule – even without coatings or capsule shells in the way.

Transmission Raman spectroscopy probes the whole content through ≥10mm of sample. The TRS method works by illuminating the sample on one side and collecting the transmitted light on the other. The resulting transmission Raman spectrum is highly representative of the entire sample mixture, enabling sensitive, accurate and fast quantitative measurement of the whole object in one quick measurement.

Transmission Raman data is representative of the entire object. Conventional Raman data is typically limited to surface subsampling

Transmission Raman data is representative of the entire object. Conventional Raman data is typically limited to surface subsampling

Unlike other spectroscopic methods, such as Near-Infrared, TRS is typically insensitive to tablet coatings and capsule shells, so no sample preparation is required. TRS is also insensitive to typical variations in particle size, sample compaction and moisture.

TRS in Pharmaceutical Analysis

Transmission Raman is ideally suited to fast, quantitative analysis of pharmaceutical final dosage forms and mixtures. At GMP manufacturing facilities content uniformity (CU) testing is required prior to product release but HPLC, the industry’s “standard” technique, has significant drawbacks; HPLC methods are time-consuming, consumable costs are high and specially-trained operators are required to chemically prepare the materials.

Cobalt's TRS100™ instrument was developed for rapid non-destructive content uniformity testing of tablets, capsules and powders. TRS measurements typically take seconds per sample and the chemically-rich TRS information gives the relative quantities in the mixture. This works even with multiple APIs, polymorphs and excipients in a single measurement. Unlike HPLC, CU testing with the TRS100 incurs no sample preparation, wet chemistry or consumable costs.

Transmission Raman Applications

TRS100 instruments are already in use at many global pharmaceutical manufacturers for CU testing and R&D applications, but TRS applications extend to many areas of the manufacturing process.

TRS Applications include:

  • Quantification of mixtures in tablets, capsules and powders
  • Polymorph content analysis
  • Stability monitoring
  • Process validation for manufacturing

If you would like to discuss the potential benefits of TRS technology for your application, get in touch at

The Second International Pharmaceutical Seminar on Transmission Raman Spectroscopy

The second international seminar and user meeting on the use of Transmission Raman Spectroscopy (TRS) in pharmaceutical analysis will be hosted by Cobalt at Oxford University in the UK on Tuesday December 5th 2017.