Assignment Code: MEV-013/TMA-01/January 2023 to July 2024 session

Course Code: MEV-013

Assignment Name: Environmental Chemistry

Year: 2023-2024

Verification Status: Verified by Professor

Q1) Explain modern methods of separation and Electrical methods of analysis with suitable examples?

Ans) Modern Methods of Separation: An example of an advanced technique is the process of isolating and purifying substances that have been extracted from mixtures by utilising the cutting-edge separation technology available today. In the course of their work, they make use of fundamental techniques such as chromatography, electrophoresis, and membrane processes. Here are a few examples:

a) Chromatography:

1) High-Performance Liquid Chromatography (HPLC): HPLC separates compounds based on their interaction with a high-pressure liquid mobile phase and a stationary phase inside a column. It is widely used in pharmaceuticals to analyse drug purity and in food science to detect additives and contaminants.

2) Gas Chromatography (GC): GC separates volatile compounds by vaporizing them and passing them through a column. It's used in forensic analysis for drug and toxicology testing, environmental analysis, and in the flavour and fragrance industry for quality control.

b) Electrophoresis:

1) Polyacrylamide Gel Electrophoresis (PAGE): PAGE separates proteins or nucleic acids based on size and charge. It is crucial in molecular biology for DNA and protein analysis.

2) Capillary Electrophoresis (CE): CE employs a narrow-bore capillary tube to separate ions based on their electrophoretic mobility. CE is used in forensic analysis and biotechnology for DNA sequencing and genotyping.

c) Membrane Processes:

1) Reverse Osmosis (RO): RO is used to purify water by separating solutes from water through a semi-permeable membrane. It's essential in desalination, water treatment, and the food and beverage industry.

2) Ultrafiltration (UF): UF separates particles, colloids, and macromolecules from a solvent. It's applied in the dairy industry for milk and whey protein concentration.

Electrical Methods of Analysis: Different electrical methods of inspection, such as measuring electric currents, voltages, or impedance, are utilised in order to ascertain a wide range of characteristics associated with the substances being investigated. Examples include:

a) Potentiometry:

1) Ion-Selective Electrodes (ISE): ISEs measure the activity of specific ions in a solution. A pH electrode is a common example used for pH measurement.

b) Conductometry:

1) Conductivity Meters: These devices measure the ability of a solution to conduct an electric current. They are used to determine the concentration of ions or the purity of water.

c) Voltammetry:

1) Cyclic Voltammetry: This technique measures the current response as a function of applied potential. It is widely used in electrochemistry for studying redox reactions and analyzing trace metals.

d) Electrochemical Impedance Spectroscopy (EIS): EIS measures the impedance response of an electrochemical system as a function of frequency. It is used in materials science and electrochemistry for corrosion analysis and battery characterization.

e) Capacitance and Dielectric Spectroscopy: These methods analyse the dielectric properties of materials, which are sensitive to factors like moisture content, composition, and phase transitions. They are used in food science, pharmaceuticals, and materials science.

Q2) Differentiate between the following

Q2a) Accuracy and Precision

Ans) Comparison between Accuracy and Precision:

Q2b) Determinate and Indeterminate Errors

Ans) Comparison between Determinate and Indeterminate Errors:

Q3) What are the applications of chromatography technique in environmental monitoring?

Ans) In the field of environmental monitoring, chromatography techniques are used extensively to investigate and identify a wide variety of pollutants, contaminants, and chemicals that can be found in air, water, soil, and sediments. These pollutants and chemicals can be found in all of these different mediums. These methods are incredibly helpful tools for evaluating the quality of the environment and detecting whether or not regulatory standards are being met. Their great sensitivity, precision, and selectivity make them particularly effective instruments in this regard.

Here are some key applications of chromatography in environmental monitoring:

a) Water Quality Analysis:

1) Detection of Organic Pollutants: Gas chromatography (GC) and liquid chromatography (LC) are used to identify and quantify organic compounds in water, such as pesticides, herbicides, industrial chemicals, and disinfection byproducts.

2) Identification of Microbial Contaminants: Liquid chromatography-mass spectrometry (LC-MS) helps detect and quantify microbial toxins and byproducts in water, including cyanotoxins and endotoxins.

b) Air Quality Monitoring:

1) Analysis of Volatile Organic Compounds (VOCs): GC is employed to analyse VOC emissions from industrial processes, transportation, and indoor air quality assessments.

2) Determination of Particulate Matter (PM): Chromatography can identify and quantify pollutants such as polycyclic aromatic hydrocarbons (PAHs) associated with airborne particulate matter.

c) Soil and Sediment Analysis:

1) Detection of Pesticides and Herbicides: GC and LC are used to assess the presence and concentrations of pesticide residues and herbicides in soil and sediments.

2) Heavy Metal Analysis: Ion chromatography (IC) can determine the levels of heavy metals like lead, cadmium, and mercury in soil and sediment samples.

d) Waste Characterization:

1) Identification of Hazardous Waste Constituents: GC and LC are used to analyse the chemical composition of hazardous waste materials to ensure proper disposal and compliance with regulations.

e) Biomonitoring:

1) Analysis of Bioaccumulation: Chromatography can determine the bioaccumulation of contaminants in aquatic organisms, providing insights into the environmental impact of pollutants.

2) Identification of Endocrine-Disrupting Compounds: LC-MS is used to detect endocrine-disrupting compounds like pharmaceuticals and personal care products in aquatic ecosystems.

f) Wastewater Treatment Monitoring:

1) Effluent Monitoring: Chromatography techniques help assess the efficiency of wastewater treatment processes and determine the presence of contaminants in treated effluents.

2) Identification of Emerging Contaminants: LC-MS is instrumental in detecting emerging pollutants, including pharmaceuticals, hormones, and personal care products in wastewater.

g) Environmental Forensics:

1) Source Identification: GC and LC are used in environmental forensics to trace the origin of contaminants and pollutants, aiding in pollution source identification and remediation efforts.

h) Regulatory Compliance:

Chromatography methods are essential for monitoring compliance with environmental regulations and standards, ensuring that pollutants and contaminants do not exceed permissible levels.

Q4) Give a note on scintillation process and working mechanism of scintillation counter?

Ans) Scintillation Process:

There is a phenomenon known as the scintillation process that takes place when particular chemicals, which are known as scintillators, are subjected to ionising radiation, such as alpha, beta, or gamma radiation. Scintillations are the flashes of light that are produced by the scintillators as a result of this process. The radiation can be identified and quantified through the detection and analysis of these scintillations, which are possible to be detected and assessed. Due to the fact that it is a fundamental component in the field of radiation detection, scintillation detectors, which are sometimes referred to as scintillation counters, make substantial use of the process.

Working Mechanism of a Scintillation Counter

Utilizing the scintillation process, a scintillation counter is a piece of equipment that is utilised for the purpose of detecting and measuring ionising radiation. An explanation of the operation of a scintillation counter is as follows, simplified slightly:

a) Scintillator Material: A crystal or liquid that is a scintillator serves as the central component of the scintillation counter. Because of its capacity to generate scintillations when subjected to ionising radiation, this material has been selected with great caution after thorough consideration. Sodium iodide (NaI), cesium iodide (CsI), and organic scintillators are examples of those that are commonly used as scintillators.

b) Interaction with Ionizing Radiation: When ionising radiation, such as gamma photons or beta particles, interacts with the scintillator material, it transfers energy to the atoms or molecules that are contained within the material. Higher energy levels are achieved by the electrons in the atoms as a result of this energy.

c) De-Excitation and Light Emission: After the contact with the radiation, the excited electrons return to their ground state, releasing the excess energy in the form of scintillations, which are bursts of light that are either visible or ultraviolet in wavelength. There is just one interaction event that corresponds to each scintillation occurring.

d) Photon Detection: Following this, a photosensitive component of the scintillation counter is responsible for detecting the scintillation light that has been emitted. This component is often a photomultiplier tube (PMT) or a photodiode, both of which are capable of converting the scintillation photons into electrical signals.

e) Amplification and Counting: The photosensitive component is responsible for the generation of electrical impulses, which are then amplified and processed using counting electronics technology. Every single scintillation flash is considered to be one instance of ionising radiation that has been detected. During a certain time period, the counter documents the total number of scintillations that have occurred.

f) Calibration and Analysis: To determine the relationship between the number of scintillations and the radiation dose or activity, the scintillation counter is frequently calibrated by utilising known radiation sources. This is done in order to create a relationship. The equipment is able to quantify the radiation intensity using measures such as counts per minute (CPM) or becquerels as a result of this calibration (Bq).

Q5) Explain basic instrumentation for IR Spectrometry and its environmental applications?

Ans) Basic Instrumentation for Infrared (IR) Spectrometry

Infrared spectrometry is a versatile analytical technique that is used to identify and quantify chemical compounds based on their interaction with infrared radiation. The basic instrumentation for IR spectrometry includes the following components:

a) IR Light Source: An IR spectrometer typically uses a light source that emits infrared radiation. Common sources include nichrome wire or a global, which emits a broadband spectrum of IR radiation. In some modern instruments, a more stable and efficient source, such as a silicon carbide (SiC) or ceramic source, is used.

b) Sample Compartment: This is where the sample to be analysed is placed. The sample can be in the form of a gas, liquid, or solid, depending on the instrument's configuration. For liquids and solutions, a transmission cell is often used.

c) Monochromator: The monochromator is responsible for isolating a narrow range of IR wavelengths (frequencies) from the broadband IR source. It consists of mirrors and a diffraction grating or interferometer and allows the selection of specific wavelengths for analysis.

d) Sample Holder: A sample holder or sample cell holds the sample in the path of the IR beam. It is typically made of a material that is transparent to IR radiation, such as potassium bromide (KBr) or sodium chloride (NaCl) for solid samples, or a suitable material for liquid samples.

e) Detector: The detector is responsible for converting the selected IR radiation into an electrical signal. Common detectors include photodetectors like thermocouples, pyroelectric detectors, or more modern detectors like deuterated triglycine sulphate (DTGS) or mercury cadmium telluride (MCT) detectors.

f) Signal Processor and Data Display: The electrical signal from the detector is processed and converted into a spectrum that represents the absorbance of IR radiation at different wavelengths. This spectrum is then displayed on a computer screen or as a printout.

g) Data Analysis Software: Specialized software is used to process and analyse the IR spectra. It helps in identifying functional groups and chemical bonds in the sample by comparing the spectrum to reference libraries.

Environmental Applications of IR Spectrometry

IR spectrometry has several environmental applications, making it a valuable tool for analyzing and monitoring environmental samples. Some key applications include:

a) Air Quality Monitoring: IR spectrometry is used to detect and quantify various air pollutants, including volatile organic compounds (VOCs), greenhouse gases (e.g., CO2, CH4), and particulate matter. It plays a crucial role in assessing air quality and identifying pollution sources.

b) Water Quality Analysis: IR spectrometry can be applied to assess water quality by detecting and quantifying contaminants in natural waters, industrial effluents, and drinking water. It is used for monitoring organic and inorganic pollutants, as well as determining parameters like chemical oxygen demand (COD) and biological oxygen demand (BOD).

c) Soil Analysis: IR spectrometry is used for soil analysis to determine soil composition, organic matter content, and contamination levels. It assists in assessing soil fertility and identifying potential soil pollutants.

d) Waste Characterization: It is employed to characterize and classify hazardous waste materials, which helps in proper disposal and compliance with waste management regulations.

e) Environmental Forensics: IR spectrometry is used in environmental forensics to investigate contamination sources and identify the origin of pollutants in soil, water, and air.

f) Monitoring of Greenhouse Gases: IR spectrometry is essential for monitoring greenhouse gases, which contribute to climate change. It is used to measure and track the concentrations of CO2, CH4, and other greenhouse gases in the atmosphere.

g) Remote Sensing: In remote sensing applications, IR spectrometry can be used to analyse environmental conditions from a distance, such as studying atmospheric composition, vegetation health, and land cover.