Sample interview questions: Describe your knowledge of different extraction techniques for sample preparation in analytical chemistry.
Sample answer:
- Solid-phase extraction (SPE):
- Involves passing a liquid or gaseous sample through a solid sorbent material that selectively retains the analytes of interest.
- Common sorbents include silica, alumina, and activated carbon.
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SPE is widely used for sample cleanup, concentration, and fractionation.
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Liquid-liquid extraction (LLE):
- Involves shaking a sample with two immiscible liquids, causing the analytes to partition between the two phases.
- The choice of solvents and their relative volumes determines the selectivity of the extraction.
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LLE is often used for extracting organic compounds from aqueous samples.
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Gas chromatography-mass spectrometry (GC-MS):
- Involves separating analytes in a gaseous sample by chromatography and then ionizing and detecting them using mass spectrometry.
- GC-MS is a powerful technique for identifying and quantifying volatile and semi-volatile organic compounds.
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It is widely used in environmental analysis, food safety, and pharmaceutical analysis.
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High-performance liquid chromatography (HPLC):
- Involves separating analytes in a liquid sample by chromatography and then detecting them using a variety of detectors, such as UV-Vis, fluorescence, or evaporative light scattering.
- HPLC is a versatile technique that can be used to analyze a wide range of compounds, including organic and inorganic compounds, pharmaceuticals, and biomolecules.
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It is widely used in pharmaceutical analysis, environmental analysis, and food safety.
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