Calibration of UV-Visible spectrophotometer MCQs With Answer

Calibration of UV-Visible spectrophotometer MCQs With Answer is an essential topic for B.Pharm students preparing for laboratory work and regulatory compliance. This introduction covers UV-Visible spectrophotometer calibration fundamentals, including wavelength accuracy, photometric accuracy, stray light, spectral bandwidth, baseline stability, and validation using standards like holmium oxide and neutral density filters. Understanding instrument qualification (IQ/OQ/PQ), routine checks, detector and lamp types, and impact on pharmaceutical assays ensures reliable assay results, dissolution testing, and content uniformity analysis. These MCQs emphasize practical calibration steps, troubleshooting, and quality assurance concepts vital for pharmaceutical analysis. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which standard is commonly used to check wavelength accuracy of a UV-Visible spectrophotometer?

• Potassium dichromate solution
• Neutral density filter
• Holmium oxide glass filter
• Quartz cuvette blank

Correct Answer: Holmium oxide glass filter

Q2. Which material is typically used for checking photometric accuracy in the UV range?

• Didymium glass filter
• Potassium dichromate solution
• Holmium oxide filter
• Sample drug solution

Correct Answer: Potassium dichromate solution

Q3. Which test is mainly used to evaluate stray light in a spectrophotometer?

• Baseline noise test
• Cutoff filter test (using sharp cutoff filters)
• Photometric linearity using serial dilutions
• Wavelength repeatability test

Correct Answer: Cutoff filter test (using sharp cutoff filters)

Q4. How is photometric linearity most commonly verified?

• Measuring lamp intensity over time
• Comparing peak wavelengths of holmium oxide
• Preparing serial dilutions and plotting absorbance vs concentration
• Measuring baseline drift at zero absorbance

Correct Answer: Preparing serial dilutions and plotting absorbance vs concentration

Q5. Wavelength repeatability is best expressed in which unit?

• Absorbance units (AU)
• Percent transmittance (%)
• Nanometers (nm)
• Counts per second

Correct Answer: Nanometers (nm)

Q6. Which sequence describes instrument qualification phases?

• PQ → OQ → IQ
• IQ → OQ → PQ
• OQ → PQ → IQ
• IQ → PQ → OQ

Correct Answer: IQ → OQ → PQ

Q7. Which lamp is commonly used as the UV light source in UV-Visible spectrophotometers?

• Tungsten-halogen lamp
• Deuterium lamp
• LED white lamp
• Mercury vapor lamp

Correct Answer: Deuterium lamp

Q8. Which lamp is typically used for the visible region in a UV-Visible spectrophotometer?

• Deuterium lamp
• Tungsten-halogen lamp
• Sodium lamp
• Xenon flash lamp only

Correct Answer: Tungsten-halogen lamp

Q9. Which detector type offers high sensitivity for low-light UV measurements?

• Charge-coupled device (CCD)
• Photodiode array (PDA)
• Photomultiplier tube (PMT)
• Thermistor detector

Correct Answer: Photomultiplier tube (PMT)

Q10. What does spectral bandwidth (bandpass) refer to in a spectrophotometer?

• The physical width of the cuvette
• The width of wavelengths transmitted by the monochromator (FWHM)
• The maximum absorbance measurable
• The height of the light source intensity

Correct Answer: The width of wavelengths transmitted by the monochromator (FWHM)

Q11. Increased stray light primarily affects measurements at which condition?

• Low absorbance (high transmittance)
• High absorbance (low transmittance)
• Medium absorbance only
• It has no effect on measurements

Correct Answer: High absorbance (low transmittance)

Q12. Baseline noise and drift most directly impact which performance characteristic?

• Wavelength accuracy
• Photometric sensitivity and detection limit
• Slit width
• Monochromator groove density

Correct Answer: Photometric sensitivity and detection limit

Q13. For routine pharmaceutical assays, how often should quick performance checks (wavelength and photometric) be performed?

• Annually
• Monthly
• Daily or before critical assays
• Never, only after repairs

Correct Answer: Daily or before critical assays

Q14. Why are NIST-traceable standards used for instrument calibration?

• They are cheaper than other standards
• They provide traceability to national measurement standards
• They eliminate the need for maintenance
• They increase stray light

Correct Answer: They provide traceability to national measurement standards

Q15. Which maintenance action helps reduce stray light in a spectrophotometer?

• Using wider slit widths
• Cleaning optical surfaces and replacing damaged gratings
• Removing the monochromator entirely
• Increasing lamp current beyond recommended settings

Correct Answer: Cleaning optical surfaces and replacing damaged gratings

Q16. Spectral resolution describes the instrument’s ability to:

• Measure very high absorbance values only
• Separate two closely spaced spectral peaks
• Increase lamp life
• Automatically correct baseline drift

Correct Answer: Separate two closely spaced spectral peaks

Q17. Photometric accuracy is commonly checked at which absorbance values?

• 0.0, 0.3, and 1.0 absorbance units
• Only at 2.0 absorbance units
• 10%, 50%, and 100% transmittance
• At arbitrary absorbance values chosen by operator

Correct Answer: 0.0, 0.3, and 1.0 absorbance units

Q18. What does photometric accuracy refer to?

• The accuracy of reported wavelength positions
• The ability to measure absorbance values correctly against known standards
• The physical cleanliness of cuvettes
• The speed of spectral scans

Correct Answer: The ability to measure absorbance values correctly against known standards

Q19. If the instrument bandpass is larger than a narrow spectral feature, the observed peak will:

• Appear taller and narrower
• Be unchanged
• Decrease in height and broaden
• Shift wavelength by several nm

Correct Answer: Decrease in height and broaden

Q20. Baseline drift during a run is most commonly caused by:

• Stable lamp output and constant temperature
• Lamp instability and temperature fluctuations
• Using certified reference materials
• Proper blanking with solvent

Correct Answer: Lamp instability and temperature fluctuations

Q21. To set 100% transmittance (zero absorbance) before measuring samples, you should:

• Use an empty sample compartment
• Place the sample directly without blanking
• Use the solvent blank in the reference beam or reference cell
• Measure distilled water even if solvent differs

Correct Answer: Use the solvent blank in the reference beam or reference cell

Q22. Which qualification stage verifies the instrument performs consistently for the intended analytical methods?

• Installation Qualification (IQ)
• Operational Qualification (OQ)
• Performance Qualification (PQ)
• Design Qualification (DQ)

Correct Answer: Performance Qualification (PQ)

Q23. A practical method to verify wavelength accuracy is to:

• Measure absorbance of an unknown drug sample
• Scan holmium oxide and compare observed peak positions with reference values
• Use a neutral density filter for wavelength check
• Change slit width and record lamp current

Correct Answer: Scan holmium oxide and compare observed peak positions with reference values

Q24. Stray light causes what systematic error in high-absorbance samples?

• Apparent absorbance increases falsely
• Measured absorbance is lower than true value
• No impact on measured absorbance
• Wavelength shifts to higher nm

Correct Answer: Measured absorbance is lower than true value

Q25. Which parameter most directly limits detection of low-concentration analytes?

• Photometric noise and baseline stability
• Wavelength calibration only
• Cuvette color
• Detector mount type

Correct Answer: Photometric noise and baseline stability

Q26. Adjusting the spectral slit width primarily affects:

• Monochromator mechanical stability
• The trade-off between spectral resolution and signal intensity
• The chemical stability of standards
• The shape of volumetric flasks

Correct Answer: The trade-off between spectral resolution and signal intensity

Q27. Which practice is essential when preparing calibration standards for UV-Visible assays?

• Using approximate reagent masses to save time
• Accurate weighing, high-purity reagents, and calibrated volumetric glassware
• Using any available solvent regardless of solubility
• Preparing standards only once per instrument lifetime

Correct Answer: Accurate weighing, high-purity reagents, and calibrated volumetric glassware

Q28. Linearity testing in UV-Visible calibration examines:

• Whether absorbance is directly proportional to concentration over a given range
• Only the lamp intensity variation
• The wavelength repeatability over time
• The chemical decomposition of the analyte

Correct Answer: Whether absorbance is directly proportional to concentration over a given range

Q29. Which filter is commonly used for wavelength calibration in the visible region?

• Holmium oxide glass
• Neutral density filter
• Didymium glass filter
• Potassium dichromate solution

Correct Answer: Didymium glass filter

Q30. Why is instrument qualification and periodic calibration critical in pharmaceutical analysis?

• It reduces the need for trained analysts
• It ensures accurate results, method validity, and regulatory compliance
• It eliminates the need for reagents
• It allows arbitrary changes to method acceptance criteria

Correct Answer: It ensures accurate results, method validity, and regulatory compliance

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