METTLER TOLEDO
 

No sample reaction before DSC and TGA measurement!

Aug 18, 2008
The sample robot for DSC 1 and TGA/DSC 1 can remove the protective crucible lid from the crucible or pierce the lid of hermetically sealed aluminum crucibles immediately before measurement. This unique feature prevents sensitive pharmaceutical samples from taking up or losing moisture or volatile components between weighing-in and measurement. It also protects oxygen-sensitive samples from oxidation.
Sample robot for DSC 1 and TGA/DSC
Robotic solution – Precise and reliable like a Swiss watch

Sample changers are often used in the pharmaceutical industry when large series of samples have to be measured for screening or quality control purpose. The advantage is that all the samples can be prepared at the same time and the analyses performed overnight. Especially in lengthy experiments, the samples ready on the turntable are however exposed to atmospheric conditions for longer periods.


During this time the samples may lose volatile components such as moisture, or conversely, if hygroscopic, absorb moisture. Both processes have a direct influence on the characteristics of the sample material and the accuracy of the analytical results.
There are two ways to prevent such effects from occurring with samples stored on the turntable of the sample robot:
  1. The samples are hermetically sealed in aluminum crucibles and the lid is not pierced until just before the measurement. To do this, the sample robot must be equipped with the crucible lid piercing kit (see Fig. 1). This method is particularly suitable for the determination of moisture, for example in pharmaceutical substances.
  2. The samples are stored in ceramic crucibles with special aluminum lids. The sample robot removes the lid during the measurement. The following experiments performed with polyamide 6 illustrate the effect of sample storage in an open crucible and demonstrate the importance of the crucible lid piercing kit

To see the robot in action and piercing the hermetically sealed crucible, click here for the video.


Figure 1: The TGA weight loss curves of a moist sample
Figure 1: The TGA weight loss curves of a moist sample. The continuous black lines show the curves of the samples sealed with 0.35 mm hole lids (Samples B), and the dashed red lines show the curves of hermetically sealed samples (Samples A) that were pierced automatically with a 0.1 mm needle immediately before measurement.

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