Introduction and principles of common laboratory instrument analysis

August 12, 2022
August 12, 2022 Longchang Chemical

Introduction and principles of common laboratory instrument analysis

1.Infrared absorption spectrometer, IR

Analytical principle: absorption of infrared light energy, causing vibrational, rotational energy level jumps of molecules with changing dipole moments.

Representation of the spectrum: variation of relative transmitted light energy with frequency of transmitted light.

Information provided: location, intensity and shape of the peaks, providing the characteristic vibrational frequencies of functional groups or chemical bonds.

2. Ultraviolet absorption spectrometer, UV

Principle of analysis: absorption of UV energy, causing a jump in the electron energy level in the molecule.

Representation of the spectrum: variation of the relative absorbed light energy with the wavelength of the absorbed light.

Information provided: location, intensity and shape of the absorption peaks, providing information on the different electronic structures in the molecule.

3. Nuclear magnetic resonance spectrometry, NMR

Principle of analysis: nuclei with nuclear magnetic moments in an external magnetic field, absorbing radio frequency energy and producing jumps in nuclear spin energy levels.

Representation of the spectrum: variation of absorbed light energy with chemical shift.

Information provided: chemical shifts, intensities, cleavage fractions and coupling constants of the peaks, providing information on the number of nuclei, the chemical environment in which they are located and their geometric configuration.

4. Fluorescence spectrometer, FS.

Principle of analysis: emission of fluorescence after excitation by electromagnetic radiation, from the *low single-line excited state back to the single-line ground state.

Representation of the spectrum: variation of the fluorescence energy emitted with the wavelength of the light.

Information provided: fluorescence efficiency and lifetime, providing information on the different electronic structures in the molecule.

5. Raman spectrometer, Ram.

Principle of analysis: absorption of light energy causes vibrations of molecules with a change in polarization rate, producing Raman scattering.

Representation of the spectrum: variation of the scattered light energy with the Raman shift.

Information provided: location, intensity and shape of the peaks, providing the characteristic vibrational frequencies of functional groups or chemical bonds.

6. Mass spectrometry analyzer, MS.

Analytical principle: molecules are bombarded with electrons in a vacuum, forming ions, which are separated by electromagnetic fields at different m/e.

Representation of the spectrum: the relative kurtosis of ions as a bar graph with m/e.

Information provided: mass number of molecular ions and fragment ions and their relative kurtosis, providing information on molecular weight, elemental composition and structure.

7. Gas chromatography, GC.

Principle of analysis: separation of the components of the sample between the mobile and stationary phases, due to different partition coefficients.

Representation of the spectrum: variation of the post-column effluent concentration with the retention value.

Information provided: retention value of the peak is related to the thermodynamic parameters of the components and is the qualitative basis; peak area is related to the component content.

8. electron paramagnetic resonance spectrometry, ESR.

Analytical principle: absorption of RF energy by unpaired electrons in molecules in an external magnetic field, resulting in electron spin energy level jumps.

Representation of the spectrum: variation of absorbed light energy or differential energy with magnetic field strength.

Information provided: spectral line positions, intensities, number of cleavages and hyperfine splitting constants, providing information on unpaired electron densities, molecular bonding properties and geometric configurations.

9. Cleavage gas chromatograph, PGC.

Analytical principle: instantaneous cleavage of polymeric materials under certain conditions to obtain fragments with certain characteristics.

Representation of the spectrum: variation of the post-column effluent concentration with the retention value.

Information provided: fingerprinting of the spectrum or characteristic fragmentation peaks, characterizing the chemical structure and geometric configuration of the polymer.

10 . Gel chromatography, GPC.

Principle of analysis: separation of the sample through the gel column according to the hydrodynamic volume of the molecules, with the larger molecules flowing out first.

Representation of the spectrum: variation of the post-column effluent concentration with the retention value.

Information provided: the average molecular weight of the polymers and their distribution.

11. Inverse gas chromatography, IGC.

Analytical principle: variation of the retention value of the probe molecule depending on the interaction forces between it and the polymer sample as stationary phase.

Representation of the spectrum: curve of the variation of the logarithm of the specific retention volume of the probe molecule with the inverse of the column temperature.

Information provided: the retention value of the probe molecule versus temperature provides the thermodynamic parameters of the polymer.

12. Thermogravimetry, TG.

Principle of analysis: variation of sample weight with temperature or time in a temperature-controlled environment.

Representation of the spectrum: curve of the weight fraction of the sample with temperature or time.

Information provided: the steep drop of the curve is the weight loss zone of the sample, and the plateau zone is the thermal stability zone of the sample.

13. static thermal-force analyzer, TMA.

Principle of analysis: deformation of the sample under the action of a constant force as a function of temperature or time.

Representation of the spectrum: curve of deformation values of the sample with temperature or time.

Information provided: thermal transition temperature and mechanical state.

14. Differential Thermal Analyzer, DTA.

Analytical principle: the sample and the reference are in the same temperature-controlled environment, and the temperature difference is generated due to the different thermal conductivity of the two, and the change in temperature with ambient temperature or time is recorded.

Representation of the spectrum: curve of temperature difference with ambient temperature or time.

Information provided: provide information on the thermal transition temperature of the polymer and various thermal effects.

15. Differential scanning calorimetry analyzer, DSC.

Analytical principle: the sample and the reference are in the same temperature-controlled environment and the variation of energy required to maintain the temperature difference at zero is recorded with ambient temperature or time.

Representation of the spectrum: curve of the heat or its rate of change with ambient temperature or time.

Information provided: provide information on the thermal transition temperature of the polymer and various thermal effects

16. dynamic thermal-force analyzer, DMA.

Principle of analysis: variation of the deformation of the sample with temperature under the action of a periodically varying external force.

Representation of the spectrum: curve of modulus or tanδ with temperature.

Information provided: thermal transition temperature modulus and tanδ.

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