Infrared (IR) spectroscopy is a powerful tool for analyzing the molecular structure of various samples.
The methods of sampling preparation in IR vary depending on the state of the sample—whether it's solid, liquid, or gas.
For solid samples, there are several common techniques that ensure the sample is transparent to IR radiation.
Let's explore these techniques in detail.
What are the methods of sampling preparation in IR? (3 Key Techniques Explained)
1. Mull Technique
The Mull technique involves mixing a finely crushed solid sample with Nujol, a liquid paraffin that serves as a mulling agent.
The sample is pulverized in a mortar and pestle.
Then, it is mixed with one or two drops of Nujol to form a thick paste.
This paste is applied onto salt plates and placed in the path of the IR beam for spectral recording.
Nujol is advantageous because it has low absorption in the IR region, allowing for clear transmission of the sample's IR spectrum.
2. Nujol Method
Similar to the Mull technique, the Nujol method also uses Nujol as a dispersing medium.
The powdered sample is mixed with Nujol to create a slurry.
This slurry is then applied between two KBr crystal plates.
This method is particularly useful for powder samples and requires minimal sample pretreatment.
The slurry is sandwiched between the plates to ensure even distribution and minimal air gaps, which could otherwise interfere with the spectral readings.
3. KBr Pellet Method
In the KBr pellet method, the solid sample is mixed with potassium bromide (KBr) in a 1:100 ratio by weight.
The mixture is then compressed using a hydraulic press to form a transparent pellet.
This pellet is primarily transparent to infrared light and contains a dilute sample quantity suitable for FTIR detection.
The KBr pellet method is widely used for its effectiveness in preparing samples for detailed molecular structure analysis.
Each of these methods ensures that the solid samples are prepared in a manner that optimizes their transparency to IR radiation, allowing for accurate and detailed spectral analysis.
The choice of method depends on the specific characteristics of the sample and the requirements of the analysis.
Continue exploring, consult our experts
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