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How to use Fourier transform infrared microscopy for material analysis?
Date: 2025-09-10Read: 2
Fourier Transform Infrared Microscope (FTIR Microscope) is an advanced analytical tool that combines Fourier Transform Infrared Spectroscopy (FTIR) and microscopy techniques, capable of conducting chemical composition analysis and structural identification of samples in small regions.
1、 Instrument principle and advantages
Fourier transform infrared microscope converts the light source into interference light through Michelson interferometer, and after illuminating the sample, obtains the spectrum through Fourier transform. Its advantages include:
-High sensitivity: The detection limit can be as low as 10 nanograms, and a few nanograms of sample can obtain high-quality infrared spectra.
-Micro area analysis capability: Microscope measurement aperture can reach 8 microns or smaller, and can perform micro area analysis on heterogeneous samples.
-Sample preparation is simple: reflection spectra can be directly measured for opaque samples.
-Non destructive testing: During the analysis process, the original shape and crystal structure of the sample can be maintained, and the sample is not damaged.
2、 Sample preparation
-Solid samples: For thin film samples, the size should exceed 5mm; for block samples, the surface should be as horizontal as possible; The powder sample should be as uniform as possible, and the sample size should not be less than 10mg.
-Liquid sample: The liquid sample should be as uniform as possible, and the sample size should not be less than 0.5mL.
-Special samples: For small samples or samples that require tedious preprocessing using conventional infrared spectroscopy, infrared microscopy can be used for convenient and fast detection.
3、 Spectral collection and analysis
1. Transmission spectroscopy: The sample needs to be cut into very thin slices, with a thickness of about 15 microns, and the sample must be flat.
2. Reflectance spectroscopy: including attenuated total reflection (ATR) and grazing angle analysis, usually without sample preparation, with sensitivity up to the sub nanogram level.
3. Microscope imaging: Modern FTIR microscopes are equipped with computer-controlled microscope stages and video imaging systems, which can display two-dimensional images of samples and highlight areas containing specific functional groups using "pseudo color".
4、 Application examples
-Polymer analysis: FTIR microscopy is particularly important in polymer analysis, as it can identify polymers, additives, and determine the presence of impurities.
-Food packaging materials: can be used to analyze food packaging materials composed of multiple layers of different polymers and identify the polymer composition of each layer.
-Drug analysis: can be used for controlling the uniformity of active ingredients in drug tablets.
-Environmental monitoring: can be used for identification of microplastic particles.
5、 Operation skills and precautions
-Microscope optical path adjustment: Microscopic observation and infrared spectroscopy analysis share the same optical path, making it easy to locate the sample to be analyzed by the microscope.
-Sample requirement: The sample must not contain strong acids or bases.
-Intelligent software and automation functions: Some advanced FTIR microscopes are equipped with intelligent software that can automate functions such as sample loading, observation, focusing, illumination, and depth adjustment, reducing user intervention and improving analysis efficiency.
Through the above methods and techniques, Fourier transform infrared microscopy can provide accurate and efficient solutions for material analysis, widely used in multiple fields including polymers, food packaging, drug development, and environmental monitoring.