Tech Team · Kintek Solution

To make KBr pellets for FTIR spectroscopy, the process involves mixing a small amount of the sample with potassium bromide (KBr) powder, typically in a ratio of 1:100. The mixture is finely ground to ensure homogeneity and then compressed using a hydraulic press to form a transparent pellet. This pellet is then ready for analysis in an FTIR instrument. The key steps include proper mixing, grinding, and applying the correct pressure to achieve a pellet that is suitable for infrared spectroscopy.

Key Points Explained:

1. Mixing the Sample with KBr:

   • The first step involves mixing the sample with KBr powder. The typical ratio is 1 part sample to 100 parts KBr. This ensures that the sample is sufficiently diluted to be within the detection range of the FTIR instrument while maintaining transparency.

2. Grinding the Mixture:

   • After mixing, the combination is ground to a fine powder. This step is crucial for achieving a homogeneous mixture, which is essential for accurate FTIR analysis. For harder samples, it may be necessary to grind the sample first before adding the KBr and grinding again.

3. Preparing the Pellet Die:

   • A pellet die is used to form the KBr mixture into a pellet. The die typically consists of two stainless steel disks with a precut cardboard spacer. The finely ground mixture is placed into the cutout hole of the cardboard spacer.

4. Compressing the Pellet:

   • The assembled die is then placed into a hydraulic press. Pressure is applied until it reaches a specified level, usually around 20,000 psi. This high pressure ensures that the KBr and sample mixture forms a solid, transparent pellet.

5. Finalizing the Pellet:

   • After compression, the disks are removed, and the pellet is carefully extracted. The resulting pellet is then ready to be inserted into the FTIR sample holder for analysis.

6. Considerations for Pressure:

   • The pressure applied during compression can vary, typically between 15 and 40 tons, depending on the specific requirements of the sample and the equipment used. Ensuring the correct pressure is applied is vital for producing a pellet that is both transparent and suitable for spectroscopic analysis.

By following these steps meticulously, one can produce high-quality KBr pellets that are ideal for FTIR spectroscopy, ensuring accurate and reliable results.

Summary Table:

Step	Description
1. Mixing	Mix sample with KBr powder in a 1:100 ratio for proper dilution and transparency.
2. Grinding	Grind the mixture to a fine powder for homogeneity, essential for accurate FTIR.
3. Preparing the Die	Use a pellet die with stainless steel disks and a cardboard spacer.
4. Compressing	Apply 20,000 psi pressure using a hydraulic press to form a solid, transparent pellet.
5. Finalizing	Extract the pellet carefully for FTIR analysis.
6. Pressure Considerations	Adjust pressure (15-40 tons) based on sample and equipment requirements.

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