Different techniques of pharmaceutical analysis MCQs With Answer

Different techniques of pharmaceutical analysis MCQs With Answer

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Pharmaceutical analysis covers a wide range of analytical techniques—spectroscopy, chromatography, titrimetry, electrochemical methods and mass spectrometry—used to ensure drug quality, potency and safety. This concise, keyword-rich guide focuses on Different techniques of pharmaceutical analysis MCQs With Answer tailored for B. Pharm students, emphasizing method principles, sample preparation, instrument parameters, method validation (accuracy, precision, LOD/LOQ), and troubleshooting during HPLC, GC, UV-Vis, IR, NMR and MS analyses. Questions are designed to deepen understanding of theory, instrumentation, data interpretation and regulatory requirements, preparing you for exams and practical labs. Model answers reinforce concepts and practical troubleshooting tips. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. The primary separation mechanism in reversed-phase high performance liquid chromatography (HPLC) is:

  • Differential partitioning between mobile and stationary phases
  • Size exclusion based on molecular size
  • Ion exchange between charged groups
  • Gas–liquid partitioning

Correct Answer: Differential partitioning between mobile and stationary phases

Q2. The capacity factor (k’) in chromatography is defined by which expression?

  • k’ = (t0 / tR)
  • k’ = (tR – t0) / t0
  • k’ = tR × t0
  • k’ = tR / (t0 + tR)

Correct Answer: k’ = (tR – t0) / t0

Q3. Which parameter is most commonly used to describe column efficiency in chromatography?

  • Resolution (Rs)
  • Tailing factor
  • Theoretical plates (N)
  • Retention time (tR)

Correct Answer: Theoretical plates (N)

Q4. According to Beer–Lambert law, absorbance (A) is directly proportional to:

  • Molar absorptivity × path length × concentration (A = ε b c)
  • Wavelength squared
  • Detector voltage
  • Temperature only

Correct Answer: Molar absorptivity × path length × concentration (A = ε b c)

Q5. The limit of detection (LOD) of an analytical method is best described as:

  • The lowest concentration that can be measured with acceptable precision
  • The lowest concentration that can be reliably detected but not necessarily quantified
  • The concentration at which the method is perfectly accurate
  • The highest concentration that gives a linear response

Correct Answer: The lowest concentration that can be reliably detected but not necessarily quantified

Q6. Using an internal standard in quantitative chromatography primarily helps to:

  • Eliminate the need for calibration
  • Compensate for sample preparation and injection variability
  • Change retention times of analytes
  • Increase detector sensitivity

Correct Answer: Compensate for sample preparation and injection variability

Q7. For trace-level cleanup and concentration of drug residues from biological matrices, which technique is most suitable?

  • Simple dilution
  • Solid-phase extraction (SPE)
  • Recrystallization
  • Direct injection without cleanup

Correct Answer: Solid-phase extraction (SPE)

Q8. How does mobile phase pH affect the retention of ionizable analytes in reversed-phase HPLC?

  • pH has no effect on retention of ionizable analytes
  • Alters ionization state of the analyte, changing its retention
  • Only affects column temperature, not retention
  • Makes the stationary phase charged and always increases retention

Correct Answer: Alters ionization state of the analyte, changing its retention

Q9. A C18 column in reversed-phase HPLC is best characterized as having what stationary phase chemistry?

  • Highly polar silica surface
  • Nonpolar octadecyl (C18) bonded phase
  • Ion-exchange sulfonic groups
  • Hydrophilic interaction (HILIC) phase

Correct Answer: Nonpolar octadecyl (C18) bonded phase

Q10. Gas chromatography (GC) is generally unsuitable for which type of analyte?

  • Volatile and thermally stable small molecules
  • Very high molecular weight, thermally labile compounds
  • Small hydrocarbons
  • Volatile organic solvents

Correct Answer: Very high molecular weight, thermally labile compounds

Q11. Which ionization technique is most appropriate for coupling liquid chromatography to mass spectrometry for large polar molecules?

  • Electron ionization (EI)
  • Electrospray ionization (ESI)
  • Field ionization (FI)
  • Matrix-assisted laser desorption (MALDI)

Correct Answer: Electrospray ionization (ESI)

Q12. Which NMR nucleus is most commonly used for routine structural elucidation of organic pharmaceuticals?

  • 31P
  • 19F
  • 1H (proton)
  • 15N

Correct Answer: 1H (proton)

Q13. In infrared (IR) spectroscopy, the fingerprint region is typically located at:

  • 4000–2500 cm⁻¹
  • 2500–2000 cm⁻¹
  • 2000–1500 cm⁻¹
  • Below 1500 cm⁻¹

Correct Answer: Below 1500 cm⁻¹

Q14. Which electrode is commonly used in potentiometric pH measurements?

  • Platinum electrode
  • Glass electrode
  • Silver nitrate electrode
  • Calomel electrode only

Correct Answer: Glass electrode

Q15. Coulometric titration determines the amount of analyte by measuring:

  • Color change at the endpoint
  • Total charge (current × time) passed during electrolysis
  • Change in solution temperature
  • Change in refractive index

Correct Answer: Total charge (current × time) passed during electrolysis

Q16. Which reagent is a key component of Karl Fischer titration for water determination?

  • Potassium permanganate
  • Iodine
  • Sodium hydroxide
  • Silver nitrate

Correct Answer: Iodine

Q17. In method validation, accuracy is commonly expressed as:

  • Standard deviation of measurements
  • Percent relative standard deviation (%RSD)
  • Percent recovery compared to true value
  • Resolution between peaks

Correct Answer: Percent recovery compared to true value

Q18. Repeatability in analytical precision refers to which condition?

  • Different labs, different analysts, over months
  • Same analyst, same equipment, short time interval
  • Different instruments, same day
  • Same lab but different analysts across weeks

Correct Answer: Same analyst, same equipment, short time interval

Q19. A commonly accepted signal-to-noise ratio used to estimate LOD is approximately:

  • 100:1
  • 10:1
  • 3:1
  • 0.5:1

Correct Answer: 3:1

Q20. Derivative UV spectroscopy is especially useful to:

  • Increase baseline noise only
  • Resolve overlapping absorption bands and enhance small features
  • Reduce the number of analytes in a mixture
  • Measure non-absorbing compounds directly

Correct Answer: Resolve overlapping absorption bands and enhance small features

Q21. In thin-layer chromatography (TLC), the Rf value is defined as:

  • Distance solvent front traveled divided by distance compound traveled
  • Distance compound traveled divided by distance solvent front traveled
  • Time taken to elute the compound
  • Ratio of mobile phase components

Correct Answer: Distance compound traveled divided by distance solvent front traveled

Q22. A practical rule for selecting mobile phase pH for ionizable compounds is to:

  • Choose pH equal to the compound pKa
  • Keep pH at least 2 units away from the pKa to suppress ionization
  • Always use neutral pH 7 regardless of pKa
  • Adjust pH to 14 for best retention

Correct Answer: Keep pH at least 2 units away from the pKa to suppress ionization

Q23. The most commonly used detector in HPLC for pharmaceutical assays is:

  • Flame ionization detector (FID)
  • Thermal conductivity detector (TCD)
  • UV-Visible absorbance detector
  • Refractive index detector only

Correct Answer: UV-Visible absorbance detector

Q24. Which common HPLC solvent has the lowest UV cutoff wavelength and is often preferred for low-wavelength UV detection?

  • Methanol
  • Acetonitrile
  • Water
  • Tetrahydrofuran (THF)

Correct Answer: Acetonitrile

Q25. In gravimetric analysis, the precipitate is typically washed with which solvent to remove soluble impurities without dissolving the analyte?

  • Hot concentrated acid
  • Cold deionized water
  • Strong organic solvent that dissolves the precipitate
  • Dilute oxidizing agent

Correct Answer: Cold deionized water

Q26. The key difference between “assay” and “content uniformity” tests for tablets is that assay measures:

  • Variability between individual units only
  • Amount of active pharmaceutical ingredient in an average unit or bulk sample
  • Microbial contamination levels
  • Dissolution rate exclusively

Correct Answer: Amount of active pharmaceutical ingredient in an average unit or bulk sample

Q27. Chromatographic resolution (Rs) is influenced by which three primary factors?

  • Detector type, pump pressure, and injection volume
  • Selectivity (α), column efficiency (N), and retention factor (k)
  • Buffer color, mobile phase odor, and room lighting
  • Column length, detector wavelength, and sample pH only

Correct Answer: Selectivity (α), column efficiency (N), and retention factor (k)

Q28. The standard addition method is primarily used to:

  • Reduce the number of calibration standards required
  • Correct for matrix effects in quantitative analysis
  • Replace internal standards in all assays
  • Increase sample throughput

Correct Answer: Correct for matrix effects in quantitative analysis

Q29. A common cause of carryover between HPLC injections is:

  • Insufficient autosampler/needle wash between injections
  • Using high-quality solvents only
  • Excessive column equilibration
  • Too low injection volumes

Correct Answer: Insufficient autosampler/needle wash between injections

Q30. When calibration data show increasing variance at higher concentrations (heteroscedasticity), the recommended approach is to:

  • Use unweighted linear regression always
  • Discard high concentration points
  • Apply weighted linear regression to account for heteroscedasticity
  • Use only a single-point calibration

Correct Answer: Apply weighted linear regression to account for heteroscedasticity

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