Fourier transform infrared spectrometerFTIR is a high-sensitivity analytical instrument based on the principle of interference, widely used in material composition analysis, structural identification, and reaction process monitoring. To ensure the accuracy of test results and long-term stability of the equipment, the following key points should be noted during use:
1、 Preparation before operation
Environmental condition control
Temperature and humidity: The laboratory temperature should be stable at 20-25 ℃, and the humidity should be ≤ 60%. Excessive humidity can cause fogging on the surface of optical components such as beam splitters and detectors, affecting signal strength; Temperature fluctuations may cause interferometer displacement, resulting in baseline drift of the spectrum.
Vibration and dust prevention: The instrument should be placed on a shock-absorbing platform, away from vibration sources such as centrifuges and air conditioning outdoor units. Regularly clean the instrument casing and sample chamber to prevent dust from entering the optical system.
Corrosion and electromagnetic interference prevention: Avoid using in environments containing corrosive gases (such as H ₂ S, Cl ₂) or strong electromagnetic fields (such as large motors, high-frequency generators) to prevent corrosion of optical components or interference with electronic signals.
Instrument preheating and self inspection
Preheating time: After starting up, it is necessary to preheat for more than 30 minutes to achieve thermal equilibrium of the detector (such as DTGS or MCT) and reduce noise interference.
Self check program: Run the built-in self check function of the instrument to check whether key components such as interferometers, lasers, detectors, etc. are working properly. If self inspection fails, contact an engineer for repair.
Sample preparation
Solid samples: When using the KBr compression method, the sample needs to be mixed and ground with KBr in a ratio of 1:100~1:200 to ensure that the particles are small and uniform (particle size ≤ 2 μ m) and avoid scattered light interference.
Liquid samples: When using NaCl or KBr salt window plates, it is necessary to ensure that the samples are non corrosive (such as strong acids or bases) to prevent the salt window plates from dissolving or breaking.
Gas sample: A dedicated gas cell should be equipped and the gas flow rate should be controlled (usually ≤ 100mL/min) to avoid pressure fluctuations affecting the stability of the spectrum.
2、 Standardized operation
Parameter setting optimization
Resolution selection: Choose the appropriate resolution based on the characteristics of the sample. Conventional analysis can choose 4cm ⁻¹, while high-precision structural identification needs to be increased to 2cm ⁻¹ or lower, but it will prolong the scanning time.
Scanning frequency setting: Increasing the scanning frequency (such as 32-64 times) can improve the signal-to-noise ratio, but it needs to balance the testing efficiency. For weak signal samples, the scanning time can be extended to 128 times.
Gain adjustment: dynamically adjust the detector gain based on the sample signal strength to avoid signal overload (causing clipping distortion) or too weak (insufficient signal-to-noise ratio).
Optical path alignment and calibration
Laser reference inspection: Regularly check the laser reference signal (usually located around 15798cm ⁻¹) to ensure its intensity is stable and peak shape is symmetrical. If the laser signal is abnormal, the interferometer needs to be readjusted.
Energy calibration: Use standard samples (such as polystyrene film) for energy calibration to verify whether the energy distribution of the instrument is uniform across the entire wavelength range (4000-400cm ⁻¹).
Sample testing process
Background scanning: Before placing the sample, scan the blank background (such as pure KBr film or air cell) to eliminate interference signals such as environmental CO ₂ and water vapor.
Sample placement: Ensure that the sample is perpendicular to the detection light path and avoid signal attenuation caused by tilting. For transmission mode, the sample thickness needs to be controlled within the range of 0.1~1mm.
Avoid cross contamination: When replacing samples, thoroughly clean the sample compartment and compression mold to prevent residual samples from affecting subsequent test results.
3、 Post operation maintenance
Cleaning and Storage
Cleaning of optical components: Use specialized lens paper or dust-free cloth to gently wipe optical components such as beam splitters and detector windows to avoid scratching the surface. It is strictly prohibited to use organic solvents (such as acetone, ethanol) for direct cleaning.
Sample compartment sealing: After the test is completed, promptly close the sample compartment door to prevent dust from entering. When not in use for a long time, a desiccant (such as silica gel) should be placed in the sample chamber to keep the interior dry.
Software and Data Management
Data backup: Regularly export test data to external storage devices to prevent data loss caused by instrument failure.
Software update: Pay attention to software update notifications released by instrument manufacturers, upgrade in a timely manner to fix vulnerabilities and optimize performance.
Regular maintenance plan
Quarterly maintenance: Check the dynamic calibration accuracy of the interferometer, replace desiccants, clean the instrument casing and ventilation openings.
Annual maintenance: Contact professional engineers to conduct a comprehensive overhaul of the instrument, including laser life assessment, detector performance testing, and optical path realignment.
4、 Safety precautions
Laser safety: The He Ne laser (wavelength 632.8nm) embedded in FTIR belongs to Class II laser, avoiding direct viewing of the laser beam and preventing eye damage.
High voltage protection: Some FTIR systems are equipped with high-pressure gas tanks (such as CO ₂ lasers), and protective goggles must be worn during operation to ensure that the gas leak alarm device is functioning properly.
Chemical safety: When handling corrosive or toxic samples, it is necessary to operate in a fume hood and wear protective gloves and goggles. After the testing is completed, dispose of the discarded samples according to the specifications.