Sample interview questions: Describe the principles behind laser-induced fluorescence spectroscopy and its applications.
Sample answer:
Principles of Laser-Induced Fluorescence Spectroscopy (LIFS):
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Excitation: A laser beam is focused onto the sample, exciting the atoms or molecules of interest. The laser wavelength is chosen to match the absorption wavelength of the target analyte. Upon absorption of a photon, the analyte undergoes an electronic transition to an excited state.
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Fluorescence: The excited analyte rapidly relaxes to a lower energy state, emitting a photon in the process. This emitted photon is called fluorescence, which is typically longer in wavelength (lower in energy) compared to the excitation photon.
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Detection: The emitted fluorescence is collected and detected using a photodetector, such as a photomultiplier tube or a CCD camera. The intensity of the fluorescence signal is proportional to the concentration of the analyte in the sample.
Applications of LIFS:
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Chemical Analysis: LIFS is used for the qualitative and quantitative analysis of various compounds in different matrices. It is widely employed in environmental monitoring, food safety, and pharmaceutical analysis to detect trace levels of contaminants, pollutants, and active ingredients.
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Medical Diagnostics: LIFS has applications in medical diagnostics, including disease detection, tissue characterization, and surgical guidance. It allows for non-invasive and real-time monitoring of biological processes.
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Environmental Monitoring: LIFS is used for the detection and quantification of pollutants in air, water, and soil. It helps assess environmental quality and monitor compliance with regulation… Read full answer