5 Reasons Why To Use DSC and TGA for Testing Pharmaceuticals

Thermal analysis equipment can be found in many analytical, development, formulation and QC laboratories. Find out why this technique is that frequently used.

Thermal analysis equipment can be found in many analytical, development, formulation and QC laboratories. Find out in the following why this technique is that frequently used.

Reason 1: Wide application range

DSC (Differential Scanning Calorimetry) is well suited to characterize the physico-chemical properties (melting range, glass transition temperature, specific heat capacity) of APIs, excipients, formulations or packaging materials, to study polymorphism phenomena, interactions between the components of a physical mixture (compatibility), process induced transformations (PIT) or to determine the eutectic purity of a substance.

Thermogravimetric analysis (TGA) quantitatively detects mass losses and is therefore the method of choice for compositional analysis, for studying a sample´s behavior during pyrolysis or for deducing thermal stability.

Furthermore, kinetics evaluation can be performed based on thermal analysis data. In this way, first information about the shelf life of a drug product can be derived from its thermal stability using Kinetics NEO, even for different climatic conditions.

Using a combination of TGA and a gas analyzing system, e.g., FT-IR or GC-MS, it is possible to identify the gas species evolved from a sample material during heating and thus to elucidate the processes behind the mass losses.

Reason 2: Sample preparation with minimum effort

Most of the samples can be used as they are without any digestion, extraction, etc. Powder samples need just to be filled in the crucible or pan. For DSC measurements, it can be additionally useful to compact the powder to ensure good contact with the pan bottom.

Reason 3: Small sample masses

Some mg of sample – it may be solid, semi-solid or liquid – are usually sufficient to set up a thermal analysis experiment. Thus, DSC and TGA can perfectly be applied in the early development or pre-formulation stage where the sample amount is limited.

Reason 4: Fast but meaningful results

A typical heating rate for a thermal analysis experiment is 10 K/min – although modern instruments can realize heating rates between <0.1 and several hundred K/min. If only one heating of the substance is necessary, a DSC measurement is finished in approx. half an hour. Automated evaluation routines in the software (e.g., AutoEvaluation and/or Identify as part of the NETZSCH Proteus® software) can help get an overview of the sample´s behavior immediately after the measurement has been completed.

Reason 5: DSC and TGA are already established methods for testing pharmaceuticals

Both techniques are listed in various pharmacopeias such as USP, Ph. Eur. or JP. Concerning USP, DSC and TGA are described in chapter <891>; concerning Ph. Eur. in chapter 2.2.34.

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