SCH 2450: Molecular Spectroscopy Quiz

SCH 2450: MOLECULAR SPECTROSCOPY

• Course Objectives: Demonstrate knowledge of various molecular spectroscopic techniques and competence in real sample analysis using these techniques.
• Course Description: Covers molecular electronic & vibrational energy levels, Raman effects, lasers, UV-Vis and visible absorption analysis, instrumentation, quantitative methods (differential, difference, derivative), turbidimetry & nephelometry, fluorescence, phosphorescence, and chemiluminescence spectroscopy. Practicals include applications of various techniques.
• Learning Outcomes: Learners will be able to describe molecular energy levels, explain spectroscopic techniques (UV-Vis, Raman, turbidimetry, nephelometry, fluorescence, phosphorescence, chemiluminescence), differentiate between spectroscopic methods, and detail the instrumentation of various spectroscopic techniques.
• Teaching Methodology: Lectures, tutorials, and practical sessions.
• Instructional Materials: Whiteboard/smart board, markers, computer, projector, course notes, duster.
• Course Assessment: Written CATS (15%), assignments (5%), practicals (10%), final examination (70%).
• Reference Journals: Journal of Analytical Sciences, Methods and Instrumentation, International Journal of Analytical Chemistry, Journal of Chromatography A, Talanta, Annual Review of Analytical Chemistry, Trends in Analytical Chemistry.
• Energy of Electromagnetic Radiation: Radiation can be described as an electromagnetic wave or as a photon, and every atom, ion, and molecule has a unique relationship with electromagnetic radiation.
• Photoelectric Effect: When sufficiently energetic radiation strikes a metal surface, electrons are emitted, the energy of the emitted electrons is related to the frequency of the incident radiation by E = hv - w, where ‘w’ is the work function.
• Molecular Electronic Energy Levels: Shows rotational and vibrational energy levels, electronic transitions, and a schematic representation of molecular, electronic, vibrational, and rotational energy levels. 
• Electromagnetic Spectrum: A diagram displays the different types of electromagnetic radiation from gamma rays to radio waves, including their approximate wavelengths and common regions.
• UV-Vis Spectroscopy: Absorption, emission, or scattering of electromagnetic radiation by molecules, in the ultraviolet and visible regions, where each species has characteristic energy states
• Beer-Lambert's Law: The relationship between absorbance, concentration, and path length. A = εbc, where A is absorbance, ε is molar absorptivity, b is path length, and c is concentration.
• Deviation from Beer-Lambert's Law: The relationship between absorbance and concentration is linear only at low concentrations. Higher concentrations may result in deviations due to factors like real, instrumental, and chemical.
• Instrumental Calibration Graph: Shows a hypothetical graph of absorbance versus concentration, where a linear relationship is assumed between the two variables.
• Regression Analysis: Statistics-based techniques to find the best line of fit and define uncertainties in linear plots of absorbance versus concentration.
• Components of Instruments (UV-visible Spectroscopy): Includes light sources, wavelength selectors (filters or monochromators), sample containers, detectors, and readout devices.
• Sources (UV-Vis Spectroscopy): Deuterium lamps and tungsten/halogen lamps provide continuous radiation over specific wavelength ranges.
• Sample Containers (UV-Vis Spectroscopy): Quartz or fused silica.
• Detectors (UV-Vis Spectroscopy): Photodiodes, photomultiplier tubes, or other appropriate devices.
• Components of Instruments (Fluorometry & Spectrofluorometry): Similarities and differences compared to UV-Vis instruments, including light sources, wavelength selectors, sample containers, detectors, readout devices.
• Applications of Photoluminescence Methods: Methods useful in various analytical fields, including organic and inorganic species, as well as for determining components in liquid chromatography, different types of chemiluminescence, and various aspects of the practical use of photoluminescent.
• Photoluminescence (Fluorescence and Phosphorescence): Two processes where a molecule absorbs light, enters an excited state, and then re-emit light of a different energy.
• Chemiluminescence: Light emission from a chemical reaction without initial excitation.
• Differential Spectroscopy: Techniques that improve precision and sensitivity in spectral measurements like the high-absorbance method, the trace analysis method, and the maximum precision method.
• Difference Spectroscopy: Comparing the spectra of two samples to isolate differences.
• Derivative Spectroscopy: Taking the derivative of the absorbance spectrum to accentuate narrow spectral features that might be obscured by broader features.
• Standard Addition Method: This method is used in UV and Visible absorption spectrophotometry and involves adding known amounts of a standard to sample aliquots, diluting to a fixed volume, and measuring absorbance, allowing for the determination of the analyte concentration in the original sample.

Nephelometry and Turbidimetry

• Nephelometry and Turbidimetry: Optical techniques based on the scattering of light by particles in solution, useful for determining clarity and concentration of dispersed particulate matter.
• Theoretical Basis: Intensity of scattered radiation depends on particle number, size, shape, refractive index, medium, and wavelength.
• Applications: Water quality analysis, turbidity measurements, controlling treatment processes, determining concentrations of various ions using specific precipitating reagents.