B.Pharmacy 7th Semester Instrumental Method of Analysis Important Question Answer

B.Pharm 7th Semester Instrumental Method of Analysis Important Question Answer

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Instrumental Method of Analysis Important Question Answer

Instrumental Method of Analysis Very Short Question Answer [2 marks]

1. Define chromophores and auxochromes.
Chromophores are part of a molecule responsible for color by absorbing UV/visible light (e.g., –C=C–, –C=O).
Auxochromes are groups that do not absorb light but shift absorption when attached to chromophores (e.g., –OH, –NH₂).

2. What is absorptivity?
Absorptivity (also called molar absorptivity or molar extinction coefficient, ε) is a constant that indicates how strongly a chemical species absorbs light at a given wavelength, expressed in L·mol⁻¹·cm⁻¹. It is used in Beer-Lambert's Law to relate absorbance with concentration.

3. What are different types of vibrational modes observed in IR spectroscopy?
Vibrational modes include:

Stretching (Symmetric & Asymmetric)

Bending (Scissoring, Rocking, Wagging, and Twisting)
These motions arise due to changes in bond lengths or angles in molecules absorbing IR radiation.

4. Write about hollow cathode lamp.
A hollow cathode lamp is a light source used in Atomic Absorption Spectroscopy (AAS). It contains a cathode made of the target element, an anode, and a filler gas like neon or argon. It emits sharp spectral lines specific to the element being analyzed.

5. What is the difference between normal phase and reverse phase chromatography?

Normal Phase: Polar stationary phase and non-polar mobile phase.

Reverse Phase: Non-polar stationary phase (e.g., C-18 silica) and polar mobile phase (e.g., water, methanol).
In reverse phase, polar compounds elute first.

6. What is electrophoretic mobility?
Electrophoretic mobility is the velocity of a charged particle under an electric field per unit field strength. It depends on the charge, size, and shape of the molecule and the viscosity of the medium.

7. What is HETP? Give its significance.
HETP (Height Equivalent to a Theoretical Plate) measures column efficiency in chromatography. Lower HETP means better separation. It is calculated using the Van Deemter equation and reflects how well a column separates components.

8. What is Eddy diffusion?
Eddy diffusion is the band broadening caused by multiple flow paths through a packed chromatography column. Molecules travel at different speeds, reducing resolution. It is one of the terms in the Van Deemter equation.

9. Write two examples each of cation and anion exchangers.

Cation exchangers: Carboxymethyl cellulose, Sulfonated polystyrene.

Anion exchangers: Diethylaminoethyl cellulose (DEAE), Quaternary ammonium resins.

10. Enlist the advantages and disadvantages of agarose and polyacrylamide gels.

Agarose: Easy to prepare, low resolution.

Polyacrylamide: High resolution, more complex and toxic during preparation.
Agarose suits large DNA fragments; polyacrylamide suits proteins and small DNA.

11. What do you understand by chromophores? Give examples.
Chromophores are molecular groups that absorb UV or visible light, causing electronic transitions. Examples include –C=C–, –C=O, –NO₂. These groups are responsible for the color of compounds.

12. How hydrogen bond affects the vibration pattern in IR spectroscopy?
Hydrogen bonding lowers the vibrational frequency of stretching modes (especially –OH and –NH) and broadens the IR peaks. This is due to weakening of the bond by hydrogen bonding interactions.

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13. Write a note on J-value.
J-value or coupling constant in NMR indicates the interaction between neighboring nuclei. It is measured in Hz and provides information on the number of adjacent protons and their spatial relationship.

14. What is chemical ionization technique?
Chemical ionization is a soft ionization method in mass spectrometry. It uses reagent gases (e.g., methane) to ionize sample molecules with minimal fragmentation, producing [M+H]+ ions for molecular weight determination.

15. Define quenching. Explain the factors for quenching.
Quenching is the decrease in fluorescence intensity due to collision or chemical interactions. Factors include temperature, pH, presence of quenchers (e.g., oxygen), and concentration of fluorophores.

16. What do you mean by agarose gel electrophoresis?
Agarose gel electrophoresis separates DNA or RNA fragments based on size. The negatively charged nucleic acids move through the gel matrix under an electric field; smaller fragments move faster.

17. Write a note on ISO 9001 series.
ISO 9001 is a set of international standards for quality management systems. It ensures consistent product/service quality, customer satisfaction, and continuous improvement in organizational processes.

18. Give principle of UV spectroscopy.
UV spectroscopy is based on the absorption of ultraviolet light causing electronic transitions (e.g., π→π*, n→π*) in molecules. The absorbance is proportional to concentration as per Beer-Lambert’s law.

19. Describe quenching with examples.
Quenching is a process that reduces fluorescence. Example: Oxygen quenches fluorescence of aromatic hydrocarbons. Heavy atoms and halides also cause quenching by increasing non-radiative decay.

20. Explain principle of Flame Photometry.
Flame photometry works on the principle that certain metal ions emit light at characteristic wavelengths when excited in a flame. The intensity of emitted light is proportional to the concentration.

21. What are various methods for preparation of TLC plates?

Pre-coated plates (commercially available)

Glass plate coating using slurry of adsorbent (e.g., silica gel) and binder (e.g., gypsum)
The plates are dried and activated by heating before use.

22. Give significance of Fermi Resonance.
Fermi resonance occurs when two vibrational modes have similar energy and interact, leading to splitting and shifting of IR bands. It enhances intensity and provides structural information.

23. Define Chromophores with examples.
Chromophores are functional groups that absorb UV-visible light due to electronic transitions. Examples: –C=C– (alkene), –C≡C– (alkyne), –NO₂ (nitro group), –C=O (carbonyl).

24. Give names of detectors used in HPLC.
Common HPLC detectors include:

UV-Visible detector

Refractive Index (RI) detector

Fluorescence detector

Conductivity detector

Mass spectrometric detector (LC-MS)

25. Describe principle of Affinity Chromatography.
Affinity chromatography is based on specific interactions between a ligand and its target molecule (e.g., antigen-antibody). The target binds to the immobilized ligand and is later eluted selectively.

26. Explain applications of Nephelometry.
Nephelometry measures the intensity of scattered light by suspended particles. Applications include:

Quantification of proteins (e.g., CRP, IgG)

Water turbidity analysis

Detection of immune complexes.

27. Discuss factors affecting Vibrational frequency in IR spectroscopy.
Factors include:

Bond strength: Stronger bonds vibrate at higher frequencies.

Atomic mass: Lighter atoms vibrate faster.

Hybridization: sp > sp² > sp³

Hydrogen bonding: Lowers and broadens peaks.

Conjugation: Lowers stretching frequency.

Instrumental Method of Analysis Short Question Answer [5 marks]

1. What is Lambert-Beer’s law? Explain its deviations along with quantitative applications.

Lambert-Beer’s Law relates the absorbance of light to the properties of the material. It states:

A = ε × c × l
Where,

A = Absorbance (unitless)

ε = Molar absorptivity (L·mol⁻¹·cm⁻¹)

c = Concentration (mol/L)

l = Path length (cm)

It is the basis of UV-Visible spectroscopy, allowing concentration determination of analytes.

Deviations from Beer’s Law:

Real Deviations: Occur at high concentrations due to changes in refractive index and solute-solvent interactions.

Chemical Deviations: Caused by association/dissociation or chemical reactions during measurement.

Instrumental Deviations: Caused by stray light, polychromatic radiation, or non-linear detector response.

Quantitative Applications:

Determination of drug concentration (e.g., paracetamol, aspirin)

Kinetics of photochemical reactions

Quality control in pharmaceutical formulations

Analysis of colored compounds and complexes

Beer’s law is reliable only in dilute solutions under ideal conditions. It enables rapid, non-destructive and accurate analysis.

2. Compare the working of dispersive IR and FTIR instruments. Explain working of FTIR in detail.

Dispersive IR Spectrometer:

Uses prism or grating to disperse IR light into components.

Scans one frequency at a time using monochromator.

Slower and less sensitive.

FTIR (Fourier Transform Infrared) Spectrometer:

Uses interferometer (Michelson type).

Collects all IR frequencies simultaneously (multiplex advantage).

High resolution, sensitivity, and speed.

FTIR Working:

Source: Emits IR radiation.

Interferometer: Splits light into two beams using beam splitter. One reflects off a moving mirror, other off fixed mirror.

Interference Pattern (Interferogram): Created due to beam recombination.

Sample Compartment: Interfered beam passes through the sample.

Detector: Measures intensity changes.

Fourier Transform: Converts time-domain signal (interferogram) into frequency-domain (IR spectrum).

Advantages of FTIR:

High signal-to-noise ratio

Rapid scanning

Accurate wavelength calibration

Applications:

Functional group identification

Polymer analysis

Drug quality control

3. Explain principle, instrumentation, and application of fluorimetry.

Principle:
Fluorimetry is based on fluorescence, where molecules absorb light at one wavelength and emit it at a longer wavelength. It measures the intensity of emitted light, which is proportional to analyte concentration.

Instrumentation:

Light Source: Mercury arc or xenon lamp.

Primary Filter/Monochromator: Selects excitation wavelength.

Sample Cell: Usually quartz cuvette.

Secondary Filter/Monochromator: Selects emitted wavelength.

Detector: Photomultiplier tube (PMT).

Readout: Displays emission intensity.

Applications:

Determination of vitamins (e.g., riboflavin)

Analysis of drugs (e.g., quinine, fluorescein)

Detection of contaminants in water

Clinical assays for hormones and proteins

Advantages:

Highly sensitive (detects ng levels)

Selective and non-destructive

Limitations:

Only fluorescent substances can be analyzed

Fluorescence quenching may affect results

4. Explain principle, methodology with applications of ion exchange chromatography.

Principle:
Ion exchange chromatography separates molecules based on their net charge by using charged resins (ion exchangers). Cation exchangers bind positively charged ions, while anion exchangers bind negatively charged ions. Elution is done by altering pH or ionic strength.

Methodology:

Column Packing: Ion exchange resin (e.g., sulfonated polystyrene for cations or DEAE cellulose for anions) is packed in a column.

Sample Application: Sample solution is introduced onto the column; ions bind to oppositely charged groups.

Washing: Unbound substances are washed away.

Elution: Bound ions are eluted by changing pH or using salt gradients.

Detection: Collected fractions are analyzed using suitable detectors (UV, conductivity).

Applications:

Separation of amino acids and proteins

Water softening (removal of Ca²⁺/Mg²⁺)

Purification of antibiotics

Analysis of nucleotides and peptides

Drug formulation analysis

Advantages:

High resolution and capacity

Applicable to biomolecules

Reusable columns

5. What is electrophoresis? Explain different types of electrophoresis techniques with their principle and applications.

Electrophoresis is the separation of charged particles under an electric field. Molecules migrate based on charge-to-mass ratio.

Types:

Paper Electrophoresis:

Uses paper (e.g., Whatman) as support.

For amino acids, peptides.

Agarose Gel Electrophoresis:

Separates nucleic acids.

Larger fragments move slower.

Polyacrylamide Gel Electrophoresis (PAGE):

For proteins and small nucleic acids.

SDS-PAGE separates by size.

Capillary Electrophoresis:

Uses narrow capillaries.

High efficiency and fast.

Isoelectric Focusing:

Separates proteins based on isoelectric point (pI).

Applications:

DNA fingerprinting

Protein profiling

Quality control of vaccines

Serum protein analysis

Advantages:

High resolution

Simple setup

Small sample size required

6. Write about principle, methods, and applications of TLC.

Principle:
TLC separates components based on differential adsorption on a stationary phase (silica gel or alumina) and solubility in mobile phase.

Methods:

Plate Preparation: Glass or plastic plates coated with adsorbent (precoated plates also available).

Sample Application: Small spots of solution are applied.

Development: Plate placed in a solvent chamber; mobile phase moves up by capillary action.

Visualization: Spots are visualized using UV light, iodine vapors, or chemical reagents.

Rf Value Calculation:
Rf=Distance travelled by soluteDistance travelled by solvent frontR_f = \frac{\text{Distance travelled by solute}}{\text{Distance travelled by solvent front}}Rf =Distance travelled by solvent frontDistance travelled by solute

Applications:

Identification of phytochemicals, alkaloids, steroids

Monitoring synthesis reactions

Checking purity of drugs

Separation of multi-component mixtures

Advantages:

Simple and inexpensive

Requires minimal sample

Multiple samples analyzed simultaneously

7. Write note on theory and working of gel electrophoresis.

Theory:
Gel electrophoresis separates charged biomolecules (DNA, RNA, proteins) through a gel matrix under an electric field. Molecules migrate based on size and charge. The gel acts as a molecular sieve — smaller molecules migrate faster.

Working:

Gel Preparation:

Gel is cast using agarose (for nucleic acids) or polyacrylamide (for proteins).

Buffer solution (e.g., TAE or TBE) maintains pH and conductivity.

Sample Loading:

Samples are mixed with loading dye and placed into wells.

Electrophoresis:

Electric field is applied; negatively charged molecules move towards the positive electrode.

Migration depends on size: smaller fragments travel faster.

Visualization:

DNA/RNA stained with ethidium bromide or SYBR Green, visualized under UV light.

Proteins visualized by Coomassie blue or silver staining.

Applications:

DNA fingerprinting

Protein purity analysis

Detection of genetic mutations

Monitoring PCR products

Advantages:

High resolution

Easy sample comparison

Qualitative and semi-quantitative analysis

8a. What is Woodward-Fieser rule? Give suitable example to explain the same.

Woodward-Fieser Rule is used to calculate λmax (maximum absorbance wavelength) of conjugated dienes and α,β-unsaturated carbonyl compounds.

Basic values:

Acyclic diene: 217 nm

α,β-unsaturated ketone: 215 nm
Additive Increments:

Each additional conjugated double bond: +30 nm

Alkyl substituent: +5 nm

Exocyclic double bond: +5 nm

Example:
For 2,4-hexadiene with one exocyclic bond and one alkyl group:
λmax = 217 + 5 (alkyl) + 5 (exocyclic) = 227 nm

8b. Define and derive Beer Lambert’s law. What is molar absorptivity?

Beer-Lambert’s Law:
A = ε × c × l

Where:

A = Absorbance

ε = Molar absorptivity (L·mol⁻¹·cm⁻¹)

c = Concentration (mol/L)

l = Path length (cm)

Derivation:
When monochromatic light passes through a solution, intensity decreases with concentration and path length:

dIdc∝−I⇒ln⁡I0I=εcl\frac{dI}{dc} \propto -I \Rightarrow \ln \frac{I_0}{I} = εcldcdI ∝−I⇒lnII0 =εcl

Convert ln to log:
A=log⁡(I0I)=εclA = \log \left( \frac{I_0}{I} \right) = εclA=log(II0 )=εcl

Molar Absorptivity (ε):
It is a measure of how strongly a compound absorbs light at a given wavelength. Units: L·mol⁻¹·cm⁻¹.

9a. Discuss the spin-spin coupling with example for any splitting of compound.

Spin-spin coupling (also called J-coupling) is an interaction between nuclear spins of neighboring atoms in NMR spectroscopy. It causes splitting of NMR signals into multiple peaks.

Key Points:

Occurs between non-equivalent protons on adjacent atoms.

Results in multiplet patterns (doublet, triplet, quartet, etc.)

Follows the n + 1 rule, where n is the number of adjacent equivalent protons.

Example:
In CH₃–CH₂–Br:

Methyl (CH₃) protons are adjacent to two CH₂ protons → triplet.

CH₂ protons are adjacent to three CH₃ protons → quartet.

Coupling Constant (J):

Measured in Hz, indicates the spacing between multiplet peaks.

Provides information about proton proximity and bonding.

9b. Write the principle of NMR. Enumerate the solvents and standards in NMR.

Principle of NMR:
NMR spectroscopy is based on the absorption of radiofrequency radiation by nuclei placed in a magnetic field. Nuclei with spin (e.g., ¹H, ¹³C) align with or against the magnetic field. The energy absorbed during flipping is measured as resonance frequency.

Solvents in NMR:

Deuterated solvents are used to avoid interference from solvent protons:

CDCl₃ (deuterated chloroform)

D₂O (deuterated water)

DMSO-d₆ (deuterated DMSO)

CD₃OD (deuterated methanol)

Standards in NMR:

TMS (Tetramethylsilane):

Chemical shift reference (δ = 0 ppm)

Inert, volatile, and soluble in organic solvents

NMR provides structural and conformational information about molecules and is essential in drug discovery and compound verification.

10a. Describe the instrumentation of mass spectrometer with neat sketch.

Mass Spectrometry (MS) determines molecular weight and structure by generating ions and separating them based on mass-to-charge ratio (m/z).

Instrumentation:

Sample Inlet: Introduces sample (solid, liquid, or gas).

Ion Source: Converts sample to ions (e.g., EI, CI).

Mass Analyzer: Separates ions by m/z (e.g., quadrupole, TOF).

Detector: Detects ions and amplifies signals.

Vacuum System: Maintains low pressure for ion travel.

Neat Sketch:
A simple diagram includes:
Sample inlet → Ion Source → Mass Analyzer → Detector → Data System

Applications:

Molecular weight determination

Structural elucidation

Drug metabolism studies

10b. Demonstrate MALDI technique with matrix preparation in detail.

MALDI (Matrix-Assisted Laser Desorption Ionization) is a soft ionization technique in mass spectrometry, ideal for large biomolecules like proteins, peptides, and polymers.

Principle:
The analyte is co-crystallized with a UV-absorbing matrix. A laser pulse vaporizes the matrix, carrying the analyte into the gas phase and ionizing it without fragmentation. Most ions formed are singly charged.

Matrix Preparation:

A matrix is a small organic compound that absorbs laser energy and aids desorption/ionization.

Common matrices include:

α-Cyano-4-hydroxycinnamic acid (CHCA) – for peptides

Sinapinic acid – for proteins

Dihydroxybenzoic acid (DHB) – for carbohydrates

Steps:

Matrix and analyte are dissolved in a suitable solvent (e.g., acetonitrile/water with TFA).

1:1 or 2:1 ratio of matrix:analyte solution is mixed.

A small drop is spotted onto a metal MALDI plate and dried to form crystals.

The laser hits the dried spot, causing desorption and ionization.

Advantages:

Minimal fragmentation

High sensitivity

Tolerates contaminants (e.g., salts)

Applications:

Protein identification (MALDI-TOF)

Microbial biotyping

Polymer analysis

11a. Write the principle of fluorescence with Jablonski energy diagram.

Fluorescence is the emission of light by a substance that has absorbed light. After absorbing high-energy UV light, molecules release excess energy as visible light.

Jablonski Diagram:

Illustrates electronic transitions:

S₀ → S₁/S₂ (Absorption)

S₂ → S₁ (Internal conversion)

S₁ → S₀ (Fluorescence emission)

Competes with non-radiative decay and intersystem crossing to triplet state (leads to phosphorescence).

Key Features:

Fluorescence occurs quickly (nanoseconds)

Emitted light is longer in wavelength than excitation light

Applications:

Fluorimetry in drug analysis

DNA/RNA labeling

Fluorescence microscopy

11b. Elaborate the principle of scanning electron microscopy with its working.

Principle:
SEM uses a focused electron beam to scan a specimen's surface. Secondary or backscattered electrons emitted from the surface are collected to form high-resolution images.

Working:

Electron Gun: Emits a beam of high-energy electrons.

Lenses: Focus the beam onto the sample.

Scanning Coils: Move the beam in a raster pattern over the surface.

Detectors: Collect secondary/backscattered electrons.

Signal Processing: Converts electron signals into digital images.

Sample Preparation:

Conductive coating (e.g., gold) is applied to non-conductive specimens to avoid charging.

Applications:

Surface morphology analysis

Pharmaceutical particle imaging

Quality control of coatings

12a. What is quality audit? Explain the types of Quality audits.

Quality Audit is a systematic and independent examination of a quality system to determine whether activities comply with planned arrangements and whether these arrangements are effective in achieving objectives.

Purpose:

Ensure compliance with regulatory standards (e.g., GMP, ISO 9001)

Identify areas for improvement

Maintain documentation and product quality

Types of Quality Audits:

Internal Audit (First-party audit):

Conducted by an organization on its own processes.

Helps prepare for external audits.

External Audit (Second-party audit):

Conducted by customers or regulatory agencies.

Ensures supplier or contractor compliance.

Third-party Audit:

Conducted by independent organizations (e.g., ISO certification bodies).

Leads to certifications like ISO 9001.

Product Audit:

Focuses on verifying a specific product against predefined specifications.

Process Audit:

Reviews procedures and workflows to evaluate efficiency and compliance.

Outcome:
A quality audit results in reports, corrective actions, and preventive measures to ensure continuous quality improvement.

12b. Write a detailed note on master formula record. What is TQM?

Master Formula Record (MFR):
MFR is a detailed, authorized document that contains instructions for manufacturing a specific product batch. It includes:

Name and strength of the product

Batch size

Raw material specifications

Equipment to be used

Manufacturing steps

In-process and final controls

Packaging and labeling instructions

Importance:

Ensures consistency in production

Aids in batch record preparation (BMR)

Helps maintain GMP compliance

TQM (Total Quality Management):
TQM is a management approach aimed at long-term success through customer satisfaction. It involves:

Continuous improvement

Employee involvement

Customer focus

Process-centered thinking

TQM tools include PDCA cycle, Six Sigma, and Kaizen. It integrates all organizational functions to achieve high-quality performance.

13. Give theory of Gel Electrophoresis. Explain factors affecting electrophoretic mobility.

Theory:
Gel electrophoresis separates biomolecules (DNA, RNA, proteins) using a gel matrix under an electric field. Charged molecules migrate based on size and charge; smaller molecules move faster through the gel’s pores.

Factors Affecting Electrophoretic Mobility:

Molecular Size:

Larger molecules experience more resistance, moving slower.

Charge:

Higher charge increases mobility.

Gel Concentration:

High % gel restricts movement; suitable for small molecules.

Voltage Applied:

High voltage increases speed but may distort bands.

Buffer System:

Maintains pH and ionic strength, affecting mobility.

Temperature:

High temperature reduces viscosity but may denature samples.

Applications include gene analysis, protein purity testing, and clinical diagnostics.

14. What is Finger Print region? Explain fundamental modes of vibrations in polyatomic molecules.

Fingerprint Region (IR Spectroscopy):
The fingerprint region is the area of an infrared spectrum ranging from 400–1500 cm⁻¹. It contains many absorption bands resulting from complex vibrational modes specific to the molecular structure.

Each compound has a unique pattern in this region.

Useful for identifying compounds by comparison with reference spectra.

Fundamental Modes of Vibration:
In polyatomic molecules, atoms vibrate in specific ways when they absorb IR radiation. The vibrational modes are classified into:

Stretching Vibrations:

Symmetric Stretching: Atoms move in or out together.

Asymmetric Stretching: One atom moves in while the other moves out.

Bending Vibrations:

Scissoring: Two atoms move toward and away from each other in the same plane.

Rocking: Atoms move back and forth in the same direction.

Wagging: Atoms move up and down together (out of plane).

Twisting: One atom moves up while the other moves down (out of plane).

Number of Modes:
For non-linear molecules: 3N–6
For linear molecules: 3N–5
Where N = number of atoms

These modes help in identifying functional groups and analyzing molecular structures using IR spectroscopy.

15. Explain applications of Spectrofluorometry.

Spectrofluorometry is a technique that measures the intensity of fluorescent light emitted by a substance after it absorbs excitation light.

Applications:

Pharmaceutical Analysis:

Quantification of drugs like quinine, fluorescein, tetracycline

Assay of vitamins (e.g., riboflavin, thiamine)

Clinical Diagnosis:

Detection of biomolecules (e.g., DNA, proteins)

Enzyme activity and immunoassays (fluorescent tags)

Environmental Monitoring:

Detection of pollutants (e.g., PAHs, pesticides) in water and air

Food Industry:

Analysis of food preservatives, vitamins, and quality control

Biotechnology:

Labeling and detection of nucleic acids/proteins

Real-time PCR (fluorescent probes)

Forensic Science:

Detection of body fluids (e.g., blood, semen) under UV light

Advantages:

High sensitivity (ng or pg levels)

Specificity due to selective excitation and emission

Non-destructive technique

Limitations:

Only applicable to fluorescent substances or fluorophore-labeled compounds

Quenching effects may reduce accuracy

16. Describe mechanism of ion exchange process in Ion Exchange Chromatography.

Ion Exchange Chromatography (IEC) separates ions and polar molecules based on their affinity to ion exchangers. It is widely used for separating proteins, peptides, amino acids, and nucleotides.

Mechanism:

Ion Exchange Resin:

Cation exchangers contain acidic groups (e.g., –SO₃H) and exchange positive ions.

Anion exchangers contain basic groups (e.g., –NH₃⁺) and exchange negative ions.

Sample Binding:

The column is equilibrated with a buffer.

The sample containing charged species is applied.

Oppositely charged analytes bind to the resin.

For example, in cation exchange, positively charged molecules bind to the negative groups on resin.

Washing:

Unbound or weakly bound molecules are washed off with buffer.

Elution:

Bound molecules are eluted by:

Increasing salt concentration (competes for binding)

Changing pH (alters analyte charge)

Detection:

Eluted fractions are collected and analyzed (UV detector commonly used).

Applications:

Protein purification

Water softening and deionization

Separation of amino acids

Analysis of ionic drugs and formulations

Advantages:

High resolution and reproducibility

Suitable for large biomolecules

Reusable columns

17. Explain Isocratic and Gradient Elution in HPLC.

In High-Performance Liquid Chromatography (HPLC), the mobile phase can be delivered using two elution modes:

1. Isocratic Elution:

The mobile phase composition remains constant throughout the run.

Simpler setup, reproducible.

Best for simple mixtures or when all components have similar retention.

Advantages:

Easy method development

Stable baseline

Lower chance of equipment wear

Limitations:

Poor separation for complex mixtures

Long retention time for some analytes

2. Gradient Elution:

The composition of the mobile phase is gradually changed during the run (e.g., increasing % of organic solvent).

Helps elute compounds with varying polarities.

Advantages:

Better separation of complex mixtures

Shorter run time

Sharper peaks and improved sensitivity

Limitations:

More complex instrumentation

May require re-equilibration after each run

Applications:

Isocratic: routine QC, simple drug analysis

Gradient: analysis of plant extracts, multi-component formulations, peptides, and proteins

18. Discuss significance of derivatisation in Gas Chromatography.

Derivatisation is the process of chemically modifying a compound to improve its properties for Gas Chromatography (GC) analysis.

Need for Derivatisation:
Many analytes (e.g., sugars, amino acids, steroids) are:

Non-volatile

Thermally unstable

Polar or have poor detectability

These properties hinder GC analysis. Derivatisation enhances:

Volatility

Thermal stability

Chromatographic behavior

Detector response

Types of Derivatisation:

Silylation:

Converts polar –OH, –COOH, –NH₂ groups to trimethylsilyl (TMS) ethers or esters.

Reagents: BSTFA, MSTFA

Common for sugars, steroids.

Acylation:

Introduces acyl groups (e.g., acetyl, trifluoroacetyl) to reduce polarity.

Reagents: Acetic anhydride, TFAA

Alkylation:

Replaces active hydrogens with alkyl groups (e.g., methyl).

Reagents: Diazomethane (to convert –COOH to methyl esters)

Applications:

Drug metabolites analysis

Environmental contaminants (e.g., phenols, pesticides)

Amino acid and carbohydrate profiling

Advantages:

Improved peak shape and resolution

Enables GC of otherwise non-volatile compounds

Increases detection sensitivity (e.g., in FID or MS)

19. Describe spectral shifts and solvent effect on absorption spectra in UV Spectroscopy.

Spectral Shifts:
Spectral shifts refer to changes in the λmax (wavelength of maximum absorbance) due to structural or environmental changes.

Types:

Bathochromic shift (Red shift):

Shift to longer wavelength

Caused by conjugation, auxochromes, or polar solvents

Example: –OH group on benzene causes shift from 256 nm to ~270 nm

Hypsochromic shift (Blue shift):

Shift to shorter wavelength

Caused by removal of conjugation or change in solvent

Solvent Effects:
Solvents can influence electronic transitions due to polarity:

Polar solvents stabilize the excited state more than the ground state (n → π* transitions), causing red shift.

In π → π* transitions, non-polar solvents stabilize both states equally → minimal shift.

Examples:

Acetone in hexane vs. water shows red shift due to n → π* transition

Benzene in alcohols shows bathochromic shift due to hydrogen bonding

Applications:

Structural elucidation

Solvent selection for UV analysis

Understanding electronic environments in molecules

Instrumental Method of Analysis Long Question Answer [10 marks]

1. Enlist the different components of UV-visible spectrophotometer and explain the working of double beam spectrophotometer along with well-labeled diagram.

Components of UV-Visible Spectrophotometer:

Radiation Source:

Deuterium lamp (190–400 nm) for UV

Tungsten lamp (400–800 nm) for visible region

Monochromator:

Separates polychromatic light into individual wavelengths using prisms or diffraction gratings.

Sample Holder (Cuvette):

Typically quartz for UV and glass for visible; holds the sample and reference.

Beam Splitter (only in double beam):

Splits light into two beams: one passes through the sample, the other through reference.

Detector:

Converts light into electrical signals (e.g., photodiode, photomultiplier tube)

Amplifier and Recorder:

Amplifies signals and displays absorbance or transmittance values.

Working of Double Beam Spectrophotometer:

In a double beam spectrophotometer, the monochromatic light from the source is split into two equal intensity beams using a beam splitter:

Reference Beam: Passes through a cuvette containing solvent or blank

Sample Beam: Passes through a cuvette containing the sample solution

Both beams reach the detector alternately, and the ratio of their intensities is used to calculate absorbance. This eliminates baseline noise and compensates for any fluctuations in light source intensity or solvent absorbance.

Diagram:

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[Light Source]
     ↓
[Monochromator]
     ↓
[Beam Splitter] → [Reference Cuvette] → ↓
                     ↓                    [Detector] → [Readout]
               [Sample Cuvette]    → ↓

Advantages of Double Beam:

Greater stability and accuracy

Compensates for solvent and instrument fluctuations

Suitable for kinetic studies and continuous monitoring

Applications:

Quantitative analysis of drugs

Detection of impurities

Kinetic studies of reactions

Estimation of metal complexes and colored compounds

Conclusion:
UV-Vis spectrophotometry, especially with a double beam configuration, is a powerful analytical tool widely used in pharmaceutical quality control and research due to its precision, simplicity, and speed.

2. Explain principle, instrumentation, and application of flame photometry.

Principle:

Flame photometry, also known as flame atomic emission spectrometry, is based on the measurement of light emitted by metal atoms when they are excited in a flame. When a sample containing metal ions is introduced into a flame, the atoms become excited and emit radiation at characteristic wavelengths as they return to the ground state. The intensity of the emitted light is directly proportional to the concentration of the metal ion in the sample.

Instrumentation:

Flame/Burner System:

Uses a fuel (like propane or acetylene) and oxidant (like air or oxygen) to produce a stable flame.

Atomizes the sample and excites atoms.

Nebulizer:

Converts liquid sample into a fine mist and transports it into the flame.

Monochromator:

Isolates the specific wavelength of interest for the element being analyzed.

Detector:

Usually a photomultiplier tube; converts emitted light into an electrical signal.

Readout Device:

Displays the intensity of emitted radiation, which is proportional to concentration.

Filters (in simpler instruments):

Used instead of monochromators to select specific wavelengths.

Procedure:

Prepare standard solutions of the target metal ion.

Aspirate standards and unknown sample into the flame.

Measure and record emission intensity.

Construct a calibration curve and use it to determine unknown concentration.

Applications:

Quantitative estimation of alkali and alkaline earth metals like Na⁺, K⁺, Ca²⁺, and Li⁺.

Electrolyte analysis in biological fluids (e.g., serum sodium, potassium).

Soil testing in agriculture.

Cement and glass industry for detecting metal content.

Water quality monitoring.

Advantages:

Simple, rapid, and cost-effective

High sensitivity for group IA and IIA metals

Minimal sample preparation

Limitations:

Only suitable for metals that can be excited in a flame

Interferences due to ionization, spectral overlap, or flame instability

Conclusion:
Flame photometry is a robust and straightforward technique for detecting and quantifying certain metal ions. Its accuracy and simplicity make it a valuable tool in pharmaceutical, clinical, agricultural, and industrial fields.

3. Discuss the principle and instrumentation of HPLC.

Principle of HPLC (High-Performance Liquid Chromatography):
HPLC is a chromatographic technique used to separate, identify, and quantify components in a mixture. It works based on the principle of partitioning between a stationary phase (solid or liquid coated on solid support) and a liquid mobile phase under high pressure.

Compounds are separated due to differences in their interaction (adsorption/partition) with the stationary phase. More strongly retained compounds elute later, while weakly retained ones elute earlier.

Types of HPLC Based on Stationary Phase:

Normal Phase HPLC:

Polar stationary phase (e.g., silica) and non-polar mobile phase (e.g., hexane).

Reverse Phase HPLC (RP-HPLC):

Non-polar stationary phase (e.g., C18 column) and polar mobile phase (e.g., water-methanol).

Most commonly used in pharmaceutical analysis.

Instrumentation of HPLC:

Solvent Reservoirs:

Contain mobile phase (single or mixture of solvents like water, methanol, acetonitrile).

Pump:

Delivers the mobile phase through the system at high pressure (typically 1000–4000 psi).

Types: Reciprocating piston, diaphragm pump.

Injector:

Introduces sample into the mobile phase stream.

Manual or automatic (loop injector).

Column:

Stainless steel column packed with stationary phase (e.g., C18 silica).

Column length typically 10–30 cm.

Detector:

Detects eluted compounds.

Common types: UV/Vis detector, PDA (Photodiode Array), Refractive Index (RI), Fluorescence.

Data Processor:

Converts detector signals into chromatograms and performs peak analysis.

Applications:

Quantitative and qualitative analysis of pharmaceuticals.

Stability studies and impurity profiling.

Drug formulations and bulk drug analysis.

Biological fluid analysis (plasma/urine).

Advantages:

High resolution, sensitivity, and speed.

Precise and reproducible results.

Suitable for thermolabile and non-volatile compounds.

Conclusion:
HPLC is a powerful and versatile tool in pharmaceutical analysis. Its ability to handle complex mixtures with high precision makes it indispensable in R&D, quality control, and regulatory compliance.

4. Discuss the FT-IR instrumentation and interferogram with a neat sketch.

FT-IR (Fourier Transform Infrared) Spectroscopy is an advanced IR technique that measures the absorption of infrared radiation by molecules to identify functional groups and molecular structure.

Principle:

FT-IR operates on the principle that molecular vibrations absorb specific IR wavelengths. It uses interferometry to collect all frequencies simultaneously and then applies Fourier Transform to convert time-domain data into frequency-domain spectra.

Instrumentation of FT-IR:

IR Source:

Typically Globar (silicon carbide) or Nernst glower.

Emits a broad spectrum of IR radiation.

Interferometer:

Heart of FT-IR, most commonly the Michelson Interferometer.

Consists of:

Beam splitter: Divides light into two paths.

Fixed mirror & Moving mirror: Create optical path differences.

Recombination of beams produces interference pattern (interferogram).

Sample Compartment:

Sample is placed as a thin film, pellet, or solution.

Attenuated Total Reflectance (ATR) is also used for solids/liquids.

Detector:

Converts IR radiation into electrical signals.

Common detectors: DTGS (Deuterated Triglycine Sulfate), MCT (Mercury Cadmium Telluride).

Computer with Fourier Transform Software:

Performs Fourier Transform on the interferogram to generate the IR spectrum.

Interferogram:

An interferogram is a time-domain signal obtained from the interferometer.

Contains information from all IR wavelengths.

Fourier Transform converts it into an absorbance vs. wavenumber spectrum.

Sketch (simple layout):

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[IR Source] → [Interferometer] → [Sample] → [Detector] → [Computer]

Advantages of FT-IR over Dispersive IR:

Faster data collection (entire spectrum in seconds)

Higher sensitivity and resolution

Better signal-to-noise ratio

Easy background subtraction

Applications:

Identification of functional groups

Purity analysis of drugs

Characterization of polymers and excipients

Analysis of degradation products and formulation studies

Conclusion:
FT-IR spectroscopy is an indispensable tool in pharmaceutical and chemical analysis due to its speed, accuracy, and broad applicability in identifying molecular structures.

5. What is chemical shift? Explain shielding and deshielding phenomena.

Chemical Shift (δ):
Chemical shift is the resonance frequency of a nucleus relative to a standard reference compound (usually TMS – tetramethylsilane) in a magnetic field, expressed in parts per million (ppm).

It is calculated as:

δ=(vsample−vreference)vspectrometer×106 ppm\delta = \frac{(v_{\text{sample}} - v_{\text{reference}})}{v_{\text{spectrometer}}} \times 10^6 \ \text{ppm}δ=vspectrometer (vsample −vreference ) ×106 ppm

Chemical shift provides information about the electronic environment of nuclei (usually protons or carbons in NMR).

Shielding and Deshielding:

Shielding:

When electron clouds surround a nucleus, they create a small magnetic field that opposes the external magnetic field.

This reduces the net magnetic field experienced by the nucleus, requiring lower energy (lower frequency) for resonance.

Shielded nuclei appear upfield (lower δ values).

Example: Protons in alkyl groups are more shielded (δ ≈ 0.5–2 ppm).

Deshielding:

When electron-withdrawing groups (like –NO₂, –OH, –Cl) pull electron density away from the nucleus, it experiences a higher effective magnetic field.

Thus, more energy (higher frequency) is needed for resonance.

Deshielded nuclei appear downfield (higher δ values).

Example: Protons near electronegative atoms (–OH, –COOH) show δ ≈ 3–13 ppm.

Factors Affecting Chemical Shift:

Electronegativity of nearby atoms: Increases deshielding.

Hybridization: sp² protons are more deshielded than sp³.

Hydrogen bonding: Shifts δ downfield (especially in alcohols, acids).

Aromaticity: Induces ring current effects leading to deshielding (aromatic protons δ ≈ 6–8 ppm).

Anisotropy: π-electron clouds in double/triple bonds cause magnetic anisotropy affecting δ values.

Applications of Chemical Shift:

Helps in identifying functional groups

Determines chemical environment of nuclei

Aids in structure elucidation of organic compounds

Differentiates isomers based on proton environments

Conclusion:
Chemical shift is a fundamental concept in NMR spectroscopy. Understanding shielding and deshielding phenomena helps chemists interpret NMR spectra, determine molecular structures, and analyze chemical environments of various atoms.

6. Discuss the molecular fragmentation pattern of molecule by mass spectrometry.

Mass Spectrometry (MS) is an analytical technique used to determine the molecular weight and structure of compounds. One of its key features is molecular fragmentation, which provides structural information by breaking molecules into smaller charged fragments.

Molecular Ion (M⁺):

When a molecule is bombarded with high-energy electrons (usually 70 eV), it loses an electron and forms a molecular ion (M⁺).

M⁺ gives the molecular weight of the compound.

Example: CH₃CH₂OH → [CH₃CH₂OH]⁺

Fragmentation Pattern:

The molecular ion is often unstable and undergoes fragmentation into smaller ions or neutral species. These fragments are detected based on their mass-to-charge ratio (m/z).

Common Fragmentation Mechanisms:

Alpha (α) Cleavage:

Involves breaking a bond adjacent to a heteroatom.

Example: In alcohols or amines, α-cleavage produces a stable cation.

McLafferty Rearrangement:

Common in carbonyl compounds with a γ-hydrogen.

Results in the formation of an enol and a neutral alkene.

Heterolytic vs. Homolytic Cleavage:

Homolytic: Equal bond breakage → radicals.

Heterolytic: Unequal bond breakage → ions.

Cleavage at Branching Points:

Branched chains often fragment at branch points due to increased stability of resulting carbocations.

Base Peak:

The most intense peak in the mass spectrum is called the base peak.

It is assigned a relative intensity of 100%.

Often corresponds to a particularly stable fragment.

Isotopic Peaks:

Presence of elements like Cl (³⁵Cl/³⁷Cl) or Br (⁷⁹Br/⁸¹Br) shows characteristic M+2 peaks, useful for identifying halogens.

Applications:

Molecular weight determination

Structural elucidation using fragmentation patterns

Identifying unknown compounds

Purity assessment in pharmaceutical analysis

Conclusion:
The fragmentation pattern in mass spectrometry is a powerful tool to deduce molecular structure. Each molecule has a unique fragmentation fingerprint, making MS essential for compound identification in both research and industry.

7. Describe the principle and instrumentation of Atomic Absorption Spectrometry (AAS).

Principle of AAS:

Atomic Absorption Spectrometry (AAS) is based on the absorption of light by free metallic ions in the ground state. When a sample is atomized (converted into free atoms) and exposed to light of a specific wavelength (characteristic of the metal of interest), these atoms absorb the light, reducing its intensity. The amount of light absorbed is directly proportional to the concentration of the metal in the sample.

Absorbance∝Concentration of atoms\text{Absorbance} \propto \text{Concentration of atoms}Absorbance∝Concentration of atoms

Instrumentation of AAS:

Radiation Source (Hollow Cathode Lamp - HCL):

Emits light specific to the element being analyzed.

The cathode is made of the metal of interest (e.g., Na, K, Ca, Fe).

Ensures selectivity by providing a narrow bandwidth emission.

Atomizer:

Converts liquid sample into free atoms.

Two types:

Flame Atomizer: Sample is aspirated into a flame (Air–Acetylene or N₂O–Acetylene).

Graphite Furnace Atomizer (GFAAS): Electrically heated graphite tube; more sensitive and suited for trace analysis.

Monochromator:

Isolates the desired wavelength of radiation emitted from HCL.

Eliminates stray light and ensures accurate readings.

Detector:

Usually a photomultiplier tube that measures the intensity of transmitted light.

Converts light intensity into electrical signal.

Amplifier and Recorder:

Amplifies signal and displays absorbance readings or concentration directly.

Applications of AAS:

Pharmaceuticals: Trace metal analysis in raw materials and formulations.

Clinical: Measurement of metals like Ca, Fe, Zn in blood or serum.

Environmental: Water quality analysis (e.g., Pb, Hg, Cd).

Food Industry: Nutrient and contaminant detection.

Advantages:

High selectivity and sensitivity (ppm to ppb levels).

Applicable to a wide range of metals.

Accurate and reproducible results.

Limitations:

Cannot detect non-metals.

Interference from matrix effects and flame instability.

Requires separate lamp for each element.

Conclusion:
Atomic Absorption Spectroscopy is a robust and highly specific method for metal analysis, extensively used in pharmaceutical, environmental, clinical, and food testing laboratories.

8. Describe the types of validation with their salient features.

Validation is the documented process of demonstrating that a method, process, or system consistently produces results within predetermined specifications and quality attributes.

In pharmaceutical analysis, validation ensures accuracy, precision, reliability, and reproducibility of analytical methods or manufacturing processes.

Types of Validation:

1. Analytical Method Validation:

Used to validate analytical procedures in quality control and R&D.

Parameters include:

Accuracy: Closeness of test results to true value.

Precision: Repeatability and reproducibility.

Specificity: Ability to measure target analyte in presence of others.

Linearity & Range: Ability to obtain test results that are directly proportional to concentration.

LOD & LOQ: Minimum detectable and quantifiable limits.

Robustness: Resistance to small variations in method conditions.

2. Process Validation:

Ensures manufacturing processes produce consistent quality products.

Types:

Prospective Validation: Done before production (new process).

Concurrent Validation: Done during routine production.

Retrospective Validation: Based on past production data.

Revalidation: Done after significant change in process or equipment.

3. Cleaning Validation:

Confirms that cleaning procedures remove product residues and contaminants to acceptable levels.

Salient Features:

Use of worst-case product

Acceptable residue limit (MAC: Maximum Allowable Carryover)

Validated sampling and analytical methods

4. Equipment Validation:

Ensures equipment functions as intended.

Stages:

DQ (Design Qualification): Equipment meets design requirements.

IQ (Installation Qualification): Proper installation.

OQ (Operational Qualification): Operates correctly under specified conditions.

PQ (Performance Qualification): Performs effectively and reproducibly in actual operation.

5. Computer System Validation (CSV):

Validation of software and computerized systems (e.g., LIMS, HPLC software) to ensure data integrity.

Importance of Validation:

Required by regulatory bodies (e.g., USFDA, WHO, ICH).

Assures product quality and patient safety.

Reduces batch failure and recalls.

Facilitates compliance with GMP guidelines.

Conclusion:
Validation is a critical part of pharmaceutical quality assurance. By validating analytical methods, equipment, cleaning procedures, and processes, manufacturers ensure consistent product quality, safety, and compliance with regulatory standards.

Q9(a). Discuss theory involved in IR Spectroscopy. Explain instrumentation of IR spectrophotometer with applications.

Theory of IR Spectroscopy:

Infrared (IR) spectroscopy is based on the absorption of infrared radiation by molecules, which causes changes in their vibrational and rotational energy levels. When the frequency of IR radiation matches the natural vibrational frequency of a bond, absorption occurs.

Only bonds with a dipole moment change during vibration are IR-active.

Vibrational Modes:

Stretching: Symmetric and asymmetric

Bending: Scissoring, rocking, wagging, twisting

The region from 4000–400 cm⁻¹ is typically analyzed in IR.

Instrumentation of IR Spectrophotometer:

IR Source:

Globar (silicon carbide) or Nernst glower emits IR radiation.

Sample Holder:

KBr pellet, liquid film between salt plates, or ATR setup.

Monochromator:

Uses prisms or gratings to isolate specific IR wavelengths.

Detector:

Thermocouples, bolometers, or pyroelectric detectors convert IR radiation to electrical signals.

Recorder:

Plots absorbance or transmittance vs. wavenumber.

Applications:

Identification of functional groups

Structural elucidation of organic compounds

Purity testing and detection of polymorphs

Analysis of excipients and polymer blends

Q9(b). Describe theory, principle, instrumentation, and applications of Gas Chromatography (GC).

Theory & Principle:
GC separates volatile compounds based on their distribution between a stationary phase (in the column) and a mobile phase (inert gas). Separation depends on boiling point, polarity, and interaction with the stationary phase.

Instrumentation:

Carrier Gas:

Helium, nitrogen, or hydrogen used to carry analyte through the column.

Injector:

Vaporizes sample into the mobile phase.

Column:

Packed or capillary column containing stationary phase (e.g., silicone oil).

Oven:

Maintains temperature for effective separation.

Detector:

FID (Flame Ionization Detector), TCD (Thermal Conductivity Detector), or ECD (Electron Capture Detector).

Data System:

Generates chromatograms for quantitative and qualitative analysis.

Applications:

Analysis of volatile oils and organic solvents

Quality control of drugs and formulations

Residual solvent testing (ICH Q3C)

Pesticide and pollutant detection

Q9(c). Differentiate between Atomic Absorption and Atomic Emission. Describe various interferences in AAS.

Atomic Absorption vs. Atomic Emission:

Feature	Atomic Absorption (AAS)	Atomic Emission (AES)
Principle	Measures light absorbed by atoms	Measures light emitted by excited atoms
Energy Source	Hollow cathode lamp	Flame or plasma
Sensitivity	Higher for trace analysis	Lower than AAS
Quantification	Absorbance is directly proportional	Emission intensity is directly proportional
Used for	Trace metal analysis	Group I and II metals

Interferences in AAS:

Spectral Interference:

Overlapping absorption lines from other elements or flame components.

Chemical Interference:

Formation of refractory compounds (e.g., phosphate with calcium) that don't atomize easily.

Ionization Interference:

At high flame temperatures, atoms may ionize, reducing absorbance.

Matrix Effects:

Viscosity or surface tension differences affect nebulization and atomization.

Background Absorption:

Due to solvent or flame gases; corrected by deuterium lamp or Zeeman correction.

Conclusion:
This combined question covers essential techniques—IR for functional groups, GC for volatile analysis, and AAS for trace metals. Understanding their principles and limitations is vital in modern pharmaceutical analysis.