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CHE EL 93

CHE EL 93 (Prelims)

QuestionAnswer
Weight of compound containing the species Direct Method
Loss of weight due to volatilization of species Indirect Method
Volume of solution that is chemically equivalent to the amount of species sought Titration Method
Volume of gaseous species produced or consumed Gas Analysis
Radiation emitted by species Emission Spectroscopy
Radiation absorbed by species Absorption Spectroscopy
Rotation of polarized light by species Polarimetry
Potential of the electrode in equilibrium with the species Potentiometry
Conductance of the solution of the species Conductimetry
Quantity of electricity equivalent to the species Coulometry
Current associated w/ reaction at polarized electrode Polarography
Capacitance of the solution of the species High Frequency Method
Mass-to-charge ration of the decomposition products of the species Mass Spectroscopy
Radioactive decay in species Radiochemical Method
Heat of reaction Enthalpy Titrations
Thermal conductance of species Thermal Conductivity
Isolation of different components of the sample Separation Technology
Identification and characterization of the chemical components of a sample Molecular Analysis Instrumentation
To identify and characterize the different elements in a sample Elemental Analysis
Produce analytical signals from the components of the sample SIGNAL GENERATORS
is a device that converts one type of signal to another INPUT TRANSDUCERS OR DETECTOR
Modifies the converted signal in such a way as to make it more convenient for operation of the readout device SIGNAL PROCESSOR
Classification of analytical method Radiant Energy Radioactivity Electrical Property Thermal Property Mechanical Property Miscellaneous Method
is that measured property that indicates presence of analyte in a sample. Qualitative instrumental analysis
is that magnitude of measured property that is proportional to concentration of analyte in a sample. Quantitative instrumental analysis
number of oscillations per second described by the electromagnetic wave. Frequency
Radiation travelling through vacuum Velocity of Propagation
The distance between wave in a beam adjacent crests of the of radiation Wavelength
The number of waves per centimeter Sometimes called as KAISER Wavenumber
the splitting up of white light to seven constituent colors on passing through a transparent medium Dispersion
is the bending of a wave when it enters a medium where it's speed is different. Refraction
the way in which the energy of a photon is taken up by matter, typically the electrons of an atom. Absorption
the reduction in intensity of a light wave propagating through a medium by absorption of a part of its photons is often called Attenuation
associated with the re-emission of radiation by entities of a system in all directions Scattering
type of scattering affected by media particles of colloidal dimensions Tyndall effect
scattering affected by molecules aggregates if dimensions are less than the wavelength of radiation Rayleigh Scattering
quantized scattering Raman Scattering
Light scattered in the opposite direction of incident light. Reflection
Light scattered in the forward direction combines with the incident beam to give rise to the phenomenon of refraction. Refraction
Superposition of scattered waves from individual atoms or molecules in the sample. Diffraction
light vibrating in all directions is made to vibrate in only one direction Polarization
is the range of all possible frequencies of electromagnetic radiation. Electromagnetic Spectrum
is the branch of science that deals with the study of interaction of electromagnetic radiation with matter SPECTROSCOPY
It is concerned with the interactions of electromagnetic radiation with atoms ATOMIC SPECTROSCOPY
It is concerned deals with the interaction of electromagnetic radiation with molecule MOLECULAR SPECTROSCOPY
The energy required is large for this transition. sigma- sigma transition
Compounds containing multiple bonds like alkenes , alkynes, carbonyl, nitriles, aromatic compounds, pi-pi transition
These transitions usually requires less energy n-sigma transition
require minimum energy and show absorption at longer wavelength around 300 nm. n- pi transition
To turn “light-absorbed” into “numbers we can interpret/use, Beer-Lambert Law
The instrument shines a broad spectrum of light Light Emission
specific wavelength is selected Selection
The light passes through the sample. Interaction
The instrument compares the light intensity going in Detection
The difference is converted into Absorbance or Transmittance and eventually to concentration if the path length and molar absorptivity are known. Calculation
Enumerate Instrumentation 1. Light Source 2. Filters and Monochromators 3. Sample Cell (Cuvette) 4. Detectors 5. Recording Device
Types of Light Source a. Hydrogen Discharge Lamp b. Deuterium Lamp c. Xenon Arc Lamp d. Tungsten Halogen Lamp
When current is passed through these electrodes maintained at high voltage, discharge of electrons occurs which excites hydrogen molecules which in turn cause emission of UV radiation. Hydrogen Discharge Lamp
It provides radiation in the range 185 – 380 nm. Deuterium Lamp
Emission of visible radiation also occurs along with the UV- radiation. Xenon Arc Lamp
The envelope is made up of quartz to tolerate higher lamp operating temperatures. Tungsten Halogen Lamp
is a device which converts a polychromatic light to monochromatic light. Monochromators
Types of Monochromators Prism Monochromators Grating Monochromators
These are usually made up of glass, quartz or fused silica. Prism Monochromators
Types of Prism Monochromators Refractive Type Reflective Type
Usually made up of glass, quartz or alkyl halides like KBr and NaBr. Back surface of the gratings are coated with aluminum to make them reflective. Grating Monochromators
Types of Grating Monochromators Diffraction Gratings Transmission Gratings
It works on the mechanism of reinforcement (strengthening). Diffraction Gratings
In this type of grating, the refracted rays produce reinforcement. Transmission Gratings
a device which allows only the light of required wavelength to pass through and absorbs the unwanted radiation. Filters
Types of Filters Absorption filters Interference filters
used to hold the sample solutions Sample Cell
(335 – 2500 nm) Optical glass
(320 – 2500 nm) Special Optical Glass
(220 – 3800 nm) Quartz (Infrared)
(170 – 2700 nm) Quartz (Far UV)
devices which convert light energy into electrical energy signals (transducers) that are displayed on the readout device. Detectors
Types of Detectors Photomultipliers tube Photovoltaic cell Photo tubes
It works on the principle of multiplication of the photo electrons by secondary emission of electrons. Photomultipliers tube
When light rays falls on the selenium layer, electrons are generated and taken by the photocathode. Photovoltaic cell
When light falls on the photocathode, electrons are produced that travel towards the collector anode and generate current. Photo tubes
Electronic instruments, displays, or microprocessors that capture ,process, and display signals or data from sensors/detectors. Readout Devices
Types of UV Spectophotometers Single-Beam UV-Visible Spectophotometer DOUBLE BEAM UV-VISIBLE SPECTROPHOTOMETER
Advantages of Single Beam Less expensive compared to double beam Higher sensitivity
Disadvantages of Single Beam The reference and sample must be put in light pathway alternately The reference must be run at each wavelength (in case of multiple wavelength)
Advantages of Double Beam Compensates for fluctuations •Very stable. Can continuously record spectra(absorbance and transmittance)
Disadvantages of Double Beam More expensive compared to single beam Lower sensitivity
The solvent must have low absorbance in the region of interest. UV Cut-off wavelength
Polar solvents can cause red shifts (bathochromic), while non- polar solvents may lead to blue shifts (hypsochromic). Solvent – Solute Interactions
The solvent must completely dissolve the analyte. Solubility
High-purity, spectroscopic-grade solvents are required to avoid impurities interfering with the spectrum. Purity
Commonly used UV-Vis Solvents water ethanol/ methanol hexane/ isooctane acteronitrile
Used to determine the concentration of known analytes, such as determining dissolved organic carbon (DOC), nutrients, or metals in environmental water samples. Quantitative Chemical Analysis
Essential for assessing the purity of compounds, identifying drug substances, and determining the potency of pharmaceutical products. Pharmaceutical Analysis
Identifies functional groups (chromophores), detects conjugation (e.g., double bonds, benzene rings), and determines tautomeric preferences or molecular weights. Structure Elucidation (Organic Compounds)
Detects heavy metals, dyes, and other contaminants in wastewater and natural water sources. Environmental Monitoring
Measures nutrient components, assesses color intensity in products like wine, oils, and juices, and checks for food adulteration. Food and Beverage Industry
DNA/RNA quantification at 260 nm, protein analysis, and characterizing the optical properties of nanoparticles or coatings. Biological & Materials Science
Quantifies substances such as hemoglobin in cancer research. Clinical Diagnostics
Monitors chemical reactions, analyzes the color index of industrial materials like oil, and verifies the absorbance of specialized materials like sunglasses. Industrial Process Control
Application of UV-Vis Spectroscopy Quantitative Chemical Analysis Pharmaceutical Analysis Structure Elucidation (Organic Compounds) Environmental Monitoring Food and Beverage Industry Biological & Materials Science Clinical Diagnostics Industrial Process Control
Limitation of UV-Vis Spectroscopy Sample Type Molecular Requirements Low Sensitivity/ Selectivity Spectral Overlap light Scattering Environmental Sensitivity Calibration Requirement Instrumental Factors
Common Causes of Errors Solvent Interference Cuvette Quality Non-monochromatic Light
one of the most common laboratory instruments, but the science behind it is a brilliant application of electrochemistry. pH Meter
Created by: oishieeeee
 

 



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