Introduction: Instrumental Methods of Analysis are essential in pharmaceutical analysis, providing precise, sensitive and rapid determination of drugs, impurities and excipients. This introduction covers core techniques—UV-Vis spectroscopy, FTIR, NMR, mass spectrometry, AAS, HPLC, GC-MS and electrochemical methods—and explains principles, detectors, sample preparation, calibration and validation parameters like LOD, LOQ, accuracy and precision. Emphasis is on interpretation of spectra, chromatograms, ionization modes, and coupling techniques (LC-MS, GC-MS) commonly used in B.Pharm labs for quantitation and structural elucidation. Mastery of these methods improves drug quality control, stability testing and formulation analysis. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the fundamental principle of UV-Vis spectroscopy used in drug quantitation?
- Scattering of light by particles in solution
- Absorption of ultraviolet or visible light by electronic transitions
- Emission of light after thermal excitation
- Resonance absorption of microwave radiation
Correct Answer: Absorption of ultraviolet or visible light by electronic transitions
Q2. According to Beer–Lambert law, absorbance is directly proportional to which of the following?
- Wavelength and refractive index
- Concentration and path length
- Detector sensitivity and noise
- Temperature and pressure
Correct Answer: Concentration and path length
Q3. Which detector is most commonly used in HPLC for UV-absorbing pharmaceutical compounds?
- Flame ionization detector
- Refractive index detector
- UV-Visible diode array detector (DAD)
- Thermal conductivity detector
Correct Answer: UV-Visible diode array detector (DAD)
Q4. In gas chromatography, retention time primarily depends on which factor?
- Ionization energy of analyte
- Partitioning between mobile gas phase and stationary liquid film
- Electron capture cross-section
- Absorbance at 254 nm
Correct Answer: Partitioning between mobile gas phase and stationary liquid film
Q5. Which ionization technique is most suitable for coupling liquid chromatography with mass spectrometry for polar pharmaceuticals?
- Electron ionization (EI)
- Electrospray ionization (ESI)
- MALDI (matrix-assisted laser desorption/ionization)
- Fast atom bombardment (FAB)
Correct Answer: Electrospray ionization (ESI)
Q6. Which parameter describes the lowest concentration of analyte that can be reliably detected but not necessarily quantified?
- Limit of Quantitation (LOQ)
- Signal-to-noise ratio (S/N)
- Limit of Detection (LOD)
- Linearity range
Correct Answer: Limit of Detection (LOD)
Q7. Fourier-transform infrared (FTIR) spectroscopy is especially useful for identifying which functional groups in drug molecules?
- Alkali metal cations
- Vibrational modes of bonds like O–H, C=O, N–H
- Isotopic abundance of carbon
- Proton coupling constants
Correct Answer: Vibrational modes of bonds like O–H, C=O, N–H
Q8. Which chromatographic mode is most appropriate for separating ionic drug molecules?
- Normal-phase chromatography with nonpolar mobile phase
- Ion-exchange chromatography
- Size-exclusion chromatography
- Gas chromatography
Correct Answer: Ion-exchange chromatography
Q9. In atomic absorption spectroscopy (AAS), what is the main role of the flame or furnace?
- To produce ions for mass analysis
- To atomize the sample into free atoms for absorption
- To emit light for background correction
- To separate isotopes based on mass
Correct Answer: To atomize the sample into free atoms for absorption
Q10. Which mass spectrometric fragmentation pattern is most informative for structural elucidation of organic drug molecules?
- Isotopic peak spacing only
- Characteristic fragment ions and neutral losses
- Baseline noise patterns
- Retention index values
Correct Answer: Characteristic fragment ions and neutral losses
Q11. What advantage does LC-MS/MS provide in pharmaceutical analysis?
- Only qualitative information without quantitation
- High selectivity and sensitivity with tandem mass transitions for quantitation
- Better separation than GC for volatile compounds
- Replaces need for sample preparation entirely
Correct Answer: High selectivity and sensitivity with tandem mass transitions for quantitation
Q12. Which parameter is assessed during method validation to ensure results are consistently close to true values?
- Precision
- Linearity
- Accuracy
- Resolution
Correct Answer: Accuracy
Q13. In UV spectroscopy, hypochromic shift refers to which phenomenon?
- Increase in absorbance with bathochromic shift
- Decrease in absorbance (reduced intensity) of a band
- Shift of absorption to longer wavelengths
- Appearance of new vibrational fine structure
Correct Answer: Decrease in absorbance (reduced intensity) of a band
Q14. Which detector in GC is most universal and sensitive for organic compounds containing carbon?
- Flame ionization detector (FID)
- Electron capture detector (ECD)
- Thermal conductivity detector (TCD)
- Refractive index detector (RID)
Correct Answer: Flame ionization detector (FID)
Q15. What is the main purpose of using an internal standard in quantitative instrumental analysis?
- To increase the resolution between peaks
- To correct for sample loss and instrument variability during analysis
- To serve as a blank for baseline correction
- To degrade interfering substances
Correct Answer: To correct for sample loss and instrument variability during analysis
Q16. Which technique provides information about crystalline structure and polymorphism in pharmaceuticals?
- NMR spectroscopy
- X-ray diffraction (XRD)
- UV-Vis spectroscopy
- Atomic absorption spectroscopy
Correct Answer: X-ray diffraction (XRD)
Q17. In NMR spectroscopy, chemical shift primarily reflects which molecular property?
- Molecular weight
- Electronic environment of nuclei
- Vibrational frequency of bonds
- Retention time in chromatography
Correct Answer: Electronic environment of nuclei
Q18. Which sample preparation technique is commonly used to concentrate analytes and remove interferences before LC-MS analysis?
- Solid-phase extraction (SPE)
- Direct injection without cleanup
- Freeze-drying without solvents
- Molecular distillation
Correct Answer: Solid-phase extraction (SPE)
Q19. What is the significance of resolution (Rs) in chromatography?
- It represents detector sensitivity
- It quantifies separation between two adjacent peaks
- It measures the mobile phase flow rate
- It indicates column temperature stability
Correct Answer: It quantifies separation between two adjacent peaks
Q20. Which electrochemical method measures the potential difference of an electrochemical cell without passing significant current?
- Voltammetry
- Chronoamperometry
- Potentiometry
- Coulometry
Correct Answer: Potentiometry
Q21. In mass spectrometry, the m/z value stands for what?
- Magnetic susceptibility over charge
- Mass-to-charge ratio
- Molarity times charge
- Mean ionization potential
Correct Answer: Mass-to-charge ratio
Q22. Which statement best describes limit of quantitation (LOQ)?
- Lowest concentration that produces any detectable signal
- Highest concentration that can be measured linearly
- Lowest concentration that can be quantitatively measured with acceptable precision and accuracy
- Concentration at which detector saturates
Correct Answer: Lowest concentration that can be quantitatively measured with acceptable precision and accuracy
Q23. Which type of chromatography separates molecules primarily based on size exclusion?
- Reverse-phase HPLC
- Size-exclusion chromatography (SEC)
- Ion-pair chromatography
- Chiral chromatography
Correct Answer: Size-exclusion chromatography (SEC)
Q24. Derivatization in analytical chemistry is performed mainly to:
- Lower the boiling point of solvents
- Improve detectability, volatility or chromatographic behavior of analytes
- Remove impurities selectively
- Change the isotopic composition of the analyte
Correct Answer: Improve detectability, volatility or chromatographic behavior of analytes
Q25. Diode array detector (DAD) advantage over single-wavelength UV detector is:
- Lower cost and simpler maintenance
- Ability to obtain full absorbance spectrum across wavelengths for peak identification
- Exclusive use for fluorescence measurements
- No need for wavelength selection because it is a mass detector
Correct Answer: Ability to obtain full absorbance spectrum across wavelengths for peak identification
Q26. Which parameter indicates how close repeated measurements are to each other?
- Accuracy
- Specificity
- Precision
- Robustness
Correct Answer: Precision
Q27. Which of the following is a non-destructive technique widely used for stability-indicating assays and structural analysis?
- Destructive gravimetric titration
- Nuclear magnetic resonance (NMR) spectroscopy
- Bomb calorimetry
- Combustion analysis
Correct Answer: Nuclear magnetic resonance (NMR) spectroscopy
Q28. In fluorescence spectroscopy, which factor greatly enhances sensitivity compared to UV-Vis absorbance?
- Fluorescence measures emitted light with low background, increasing signal-to-noise
- It uses ionization of analytes to generate current
- It depends solely on mass-to-charge ratio
- It measures refractive index changes
Correct Answer: Fluorescence measures emitted light with low background, increasing signal-to-noise
Q29. Which LC mobile phase modifier is commonly used to improve peak shape for basic pharmaceuticals in reversed-phase HPLC?
- Trifluoroacetic acid or formic acid to control pH and suppress ionization
- High concentration of sodium chloride to increase ionic strength
- Pure water with no additives
- Strong oxidizing agents to break down analytes
Correct Answer: Trifluoroacetic acid or formic acid to control pH and suppress ionization
Q30. Which noise reduction technique improves signal-to-noise ratio in instrumental analysis?
- Using lower sample concentration
- Increasing detector bandwidth to maximum
- Averaging multiple scans and smoothing data carefully
- Removing calibration standards
Correct Answer: Averaging multiple scans and smoothing data carefully
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com