How to Use an Infrared Spectrometer

Infrared spectroscopy uses small amounts of sample.
••• chemical experience image by Sergey Galushko from

An infrared (IR) spectrometer is a device used in chemistry labs to determine the identity of a molecule. A beam of infrared light scans the sample and detects differences in the vibrational frequencies between the bonded atoms. A computer is attached and used to display the data, and the data then is compared to a table of standards to determine the types of bonds present.

    Ready your tools. Turn on the IR spectrometer and computer, allowing them to warm up for at least 10 minutes. If the sodium chloride plates are cold, leave them in their container and let them come to room temperature.

    Put on protective gloves. This prevents skin contact with any chemicals.

    Prepare sample plates. Place one to two drops of sample on one sodium chloride plate. Solid samples need to be diluted with four to five drops dichloromethane before being placed on plate.

    Cover the sample plate with the other sodium chloride plate. For solid samples, wait until sample has dried onto the first sodium chloride plate. There is no need to use a second plate for solid samples.

    Place the sample in the path of the sensor to scan it.

    Scan the sample using the computer's specific program.

    Clean the plates after each sample has been scanned. Wash the plates with 1mL dichloromethane and drying them with delicate task wipes, such as Kimwipes.

    Things You'll Need

    • Gloves
    • Sodium chloride plates
    • Chemical sample
    • Dichloromethane
    • Delicate task wipes
    • IR standards


    • Observe safety precautions when you work with unknown chemicals.

      Using water to clean plates will cause them to dissolve. Humid environments also can cause sodium chloride plates to dissolve slowly.

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