How to Calibrate an Infrared Spectrophotometer

Learn how to calibrate an infrared spectrophotometer.
••• Photodisc/Photodisc/Getty Images

As is the case when using any scientific instrument, you need to make sure the instrument is in good working order before using it to analyze a sample. Checking the response of the instrument for a known sample verifies that the instrument is properly calibrated. Spectrophotometers require periodic calibration to ensure correct response of the instrument. Infrared (IR) spectrophotometers use polystyrene as a calibration standard. A scan of the instrument with a piece of polystyrene in the sample holder will verify the presence of peaks seen on the IR spectra and the relative intensity of the peaks.

    Turn on the spectrophotometer and allow it to warm up for at least 10 minutes. The warm up time is required for the source to stabilize. Without a stable source, you can’t rely on the spectra obtained. The analytical signal relies on attenuation of the source radiation by the sample.

    Run the calibration standard by placing a piece of polystyrene film in the sample holder. Without a test run using a sample of known spectra called a standard, you have no certainty that the spectrophotometer is working correctly.

    Retrieve the spectra for the polystyrene sample. Compare the spectra with the one in a standard reference of IR spectra. Make sure that all the peaks expected exist on the test spectra. The location of the peaks must line up with the wavelength of absorption.

    Check the spectra to make sure that the strength of the signal is within 95 percent of maximum for the strongest peak. If the strongest peak in the spectra is more or less than full scale, adjust the attenuation to deliver the correct signal strength.

    Calibrate the IR spectrophotometer often. A minimum frequency of calibration should include a scan just before and one just after your work for the day.

    Things You'll Need

    • Polystyrene film
    • Reference spectra of polystyrene

Related Articles

Ace Your Middle School Science Fair with These Science...
Types of Spectrometers
How to Calculate Limit of Detection (LOD)
How to Convert PPM to NTU
How to Calculate Absorbance
How to Use a Spectrophotometer
How to Test Copper Purity
How Do Ultrasonic Sensors Work?
How to Create Bar Charts From Likert Scale Results
Use of a Colorimeter
How Does an Atomic Absorption Spectrometer Work?
How to Convert Hertz to Nanometers
How to Interpret XRF Data
How Does IR Spectroscopy Work?
How to Calibrate an FTIR Spectrometer
How to Measure the Ohm Value for an Inductor
How to Calculate Capacitance for AC Coupling
How to Calculate Thermocouple Sensitivity
How to Detect Potassium Nitrate
What Are the Advantages & Disadvantages of Diode Lasers?