Applications of UV–Visible spectroscopy MCQs With Answer

Applications of UV–Visible spectroscopy MCQs With Answer is designed to help M. Pharm students master how UV–Vis techniques are applied in modern pharmaceutical analytical practice. From routine assays and dissolution profiling to multi-component quantification, chemometric modeling, kinetic monitoring, and photostability studies, UV–Vis underpins rapid, cost-effective quality control and research workflows. These MCQs emphasize real-world method selection, validation, matrix handling, and data interpretation, including derivative and difference spectrophotometry, chromogenic complexation, and in situ fiber-optic measurements. Whether you are optimizing λmax, validating specificity per ICH, or selecting between simultaneous equation and absorbance ratio methods, this quiz will refine both conceptual understanding and decision-making for robust, regulatory-compliant UV–Vis applications in pharmaceutical analysis.

Q1. In pharmaceutical quality control, the most common application of UV–Visible spectroscopy is:

• Qualitative identification of unknown solids without any sample preparation
• Microbiological potency testing of antibiotics
• Thermal stability profiling of APIs and excipients
• Quantitative assay of drug substance or content in formulations using Beer–Lambert law

Correct Answer: Quantitative assay of drug substance or content in formulations using Beer–Lambert law

Q2. Choosing to measure absorbance at λmax for an analyte primarily:

• Minimizes stray light effects at all wavelengths
• Maximizes sensitivity and minimizes error from small wavelength shifts
• Eliminates the need for a blank solution
• Removes matrix interferences automatically

Correct Answer: Maximizes sensitivity and minimizes error from small wavelength shifts

Q3. For two APIs with overlapping spectra and known absorptivities at two wavelengths, the most appropriate UV–Vis approach is:

• First derivative spectrophotometry
• Simultaneous equation (Vierordt’s) method
• Standard addition calibration
• Dual-beam baseline correction

Correct Answer: Simultaneous equation (Vierordt’s) method

Q4. When a binary mixture exhibits an isosbestic point, a convenient method for simultaneous estimation is:

• Absorbance ratio (Q-analysis) using the isosbestic point and λmax
• Second-order derivative zero-crossing method only
• Gravimetric standardization followed by UV
• Polarographic pre-concentration before UV

Correct Answer: Absorbance ratio (Q-analysis) using the isosbestic point and λmax

Q5. For drugs showing pH-dependent spectra, improved selectivity in formulations can be achieved by:

• Measuring at any wavelength in deep UV
• Difference spectrophotometry using equimolar solutions at two pH values
• Using wider slit width to increase signal
• Shortening pathlength to 0.1 cm

Correct Answer: Difference spectrophotometry using equimolar solutions at two pH values

Q6. To compensate for matrix effects in colored syrups during UV assay, the best calibration strategy is:

• External calibration in water only
• Standard addition to the actual sample matrix
• Using a plastic cuvette instead of quartz
• Relying on higher lamp intensity

Correct Answer: Standard addition to the actual sample matrix

Q7. A key application advantage of derivative spectrophotometry in pharmaceutical analysis is:

• Eliminates the need for validation
• Enhances resolution of overlapped spectra and reduces baseline drift
• Works only for single-component samples
• Replaces proper sample preparation

Correct Answer: Enhances resolution of overlapped spectra and reduces baseline drift

Q8. In dissolution testing, UV measurements can be collected in real time without withdrawing samples by using:

• Handheld colorimeters
• In situ fiber-optic UV probes
• Flame atomic absorption
• Electrochemical detectors

Correct Answer: In situ fiber-optic UV probes

Q9. Monitoring photodegradation per ICH Q1B using UV–Vis typically involves:

• Single-point absorbance with no time-course
• Time-based spectral scans to calculate degradation kinetics
• Measuring only in the infrared region
• Relying solely on visual color changes

Correct Answer: Time-based spectral scans to calculate degradation kinetics

Q10. A weak UV absorber is often quantified after forming a colored complex measured in the visible region. This application illustrates:

• Matrix-matched blanking
• Chromogenic derivatization/complex formation to enhance sensitivity
• Baseline correction by dual-beam optics
• Isosbestic point normalization

Correct Answer: Chromogenic derivatization/complex formation to enhance sensitivity

Q11. In UV–Vis method validation for an assay, the parameter that directly demonstrates no interference from excipients or degradants is:

• Linearity
• Precision
• Specificity
• Ruggedness

Correct Answer: Specificity

Q12. For assessing chromatographic peak purity based on spectral homogeneity across a peak, the most suitable UV–Vis-based detector is:

• Single-wavelength UV detector
• Refractive index detector
• Photodiode array (PDA/DAD) detector
• Electrochemical amperometric detector

Correct Answer: Photodiode array (PDA/DAD) detector

Q13. Enzyme assays in biopharmaceuticals are often monitored by UV–Vis via the change in NADH absorbance. The relevant wavelength is:

• 210 nm
• 254 nm
• 280 nm
• 340 nm

Correct Answer: 340 nm

Q14. UV–Vis is used to characterize colloidal gold nanoparticles in formulations by tracking the surface plasmon band. A red shift of this band most commonly indicates:

• Decrease in particle size
• Increase in particle size or aggregation
• No change in colloidal state
• Complete dissolution of particles

Correct Answer: Increase in particle size or aggregation

Q15. When a sample is visibly turbid, the best UV–Vis practice to minimize scattering artifacts during assay is:

• Use a wider slit width
• Record spectra at random wavelengths
• Clarify by filtration/centrifugation and use a matched matrix blank
• Shorten integration time

Correct Answer: Clarify by filtration/centrifugation and use a matched matrix blank

Q16. Using a 1 mm (0.1 cm) pathlength microcuvette for concentrated samples, a practical way to compare results to 1 cm measurements is to:

• Ignore pathlength differences if absorbance is below 1.0
• Apply pathlength correction (A/ℓ) to report 1 cm-equivalent absorbance
• Always dilute samples tenfold regardless of result
• Switch to plastic cuvettes

Correct Answer: Apply pathlength correction (A/ℓ) to report 1 cm-equivalent absorbance

Q17. For assays performed at 210–220 nm, the appropriate cuvette material is:

• Plastic (polystyrene) cuvette
• Glass cuvette
• Quartz cuvette
• Ceramic cell

Correct Answer: Quartz cuvette

Q18. To quantify three or more APIs with highly overlapping UV spectra in a fixed-dose combination, a robust multivariate approach is:

• Manual baseline subtraction at one wavelength
• First-order derivative at λmax only
• Partial least squares (PLS) regression using full spectra
• Gravimetric recovery followed by single-wavelength readout

Correct Answer: Partial least squares (PLS) regression using full spectra

Q19. In UV-based dissolution testing, a critical check to ensure data integrity when using filters is:

• Verifying lamp warm-up time
• Filter compatibility study to confirm no analyte adsorption or leachables
• Using the highest possible scan speed
• Skipping blank measurements

Correct Answer: Filter compatibility study to confirm no analyte adsorption or leachables

Q20. In biopharmaceutical analysis, UV–Vis is used to assess nucleic acid purity. The commonly used metric and its implication are:

• A340/A260 ratio; indicates RNA integrity
• A280/A260 ratio; indicates carbohydrate content
• A260/A280 ratio; assesses protein contamination in nucleic acids
• A260/A230 ratio; assesses lipid purity

Correct Answer: A260/A280 ratio; assesses protein contamination in nucleic acids

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