Methods for standardization of vitamins MCQs With Answer

Methods for standardization of vitamins MCQs With Answer — For B. Pharm students this introduction summarizes key analytical approaches used to standardize vitamins in pharmaceutical formulations. Covering titrimetric assays, UV-Vis and derivative spectrophotometry, HPLC, LC-MS/MS, microbiological assays and fluorescence methods, these techniques ensure accurate potency, purity and stability measurement. Emphasis is placed on sample preparation, derivatization, calibration curves, validation parameters (accuracy, precision, LOD/LOQ, specificity) and pharmacopoeial requirements (USP, BP, IP). Understanding appropriate detectors, columns, solvents and common interferences helps in method selection and troubleshooting. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which titrimetric reagent is commonly used for the determination of vitamin C (ascorbic acid) in pharmaceutical formulations?

• Potassium permanganate in acidic medium
• 2,6-Dichlorophenolindophenol (DCPIP)
• Sodium hydroxide
• Silver nitrate

Correct Answer: 2,6-Dichlorophenolindophenol (DCPIP)

Q2. Which chromatographic technique is most widely used for simultaneous assay of multiple vitamins in a multivitamin tablet?

• Gas chromatography (GC)
• Thin layer chromatography (TLC)
• High performance liquid chromatography (HPLC)
• Paper chromatography

Correct Answer: High performance liquid chromatography (HPLC)

Q3. For fat‑soluble vitamins (A, D, E, K), which sample preparation step is critical before chromatographic analysis?

• Direct dissolution in water
• Acid hydrolysis without extraction
• Lipophilic solvent extraction and defatting
• Protein precipitation with saline

Correct Answer: Lipophilic solvent extraction and defatting

Q4. Which detector is preferred for tocopherols (vitamin E) in HPLC due to sensitivity and selectivity?

• UV detector at 254 nm
• Fluorescence detector
• Refractive index detector
• Evaporative light scattering detector

Correct Answer: Fluorescence detector

Q5. Which method is a classical microbiological assay used for vitamin B12 potency determination?

• Plate count using E. coli
• Microbial growth response using Lactobacillus leichmannii
• Enzyme-linked immunosorbent assay (ELISA)
• UV spectrophotometry at 280 nm

Correct Answer: Microbial growth response using Lactobacillus leichmannii

Q6. Which parameter describes the lowest concentration of vitamin that can be detected but not necessarily quantified accurately?

• Linearity
• Limit of quantitation (LOQ)
• Limit of detection (LOD)
• Accuracy

Correct Answer: Limit of detection (LOD)

Q7. In HPLC method development for vitamins, which stationary phase is most commonly used for reversed-phase separations?

• Silica gel normal phase
• Cation exchange resin
• C18 (octadecyl) bonded silica column
• Anion exchange column

Correct Answer: C18 (octadecyl) bonded silica column

Q8. Which derivatization is commonly used to convert thiamine (vitamin B1) to a fluorescent derivative for HPLC or spectrofluorimetric detection?

• Formation of thiochrome by oxidation with potassium ferricyanide
• Acetylation with acetic anhydride
• Silylation with BSTFA
• Nitrosation with nitrous acid

Correct Answer: Formation of thiochrome by oxidation with potassium ferricyanide

Q9. Which mobile phase modifier is commonly used to improve peak shape for polar B‑vitamins in reversed-phase HPLC?

• Triethylamine or formic acid as ion-pairing/ pH modifier
• Pure hexane
• Concentrated sulfuric acid
• Glycerin

Correct Answer: Triethylamine or formic acid as ion-pairing/ pH modifier

Q10. Which instrumental technique provides the highest specificity for vitamin D metabolites in complex matrices?

• UV-Vis spectrophotometry
• LC-MS/MS (tandem mass spectrometry)
• Fluorimetry
• Potentiometry

Correct Answer: LC-MS/MS (tandem mass spectrometry)

Q11. Which pharmacopoeial sources commonly describe standardized procedures for vitamin assays?

• USP, BP, IP
• WHO Essential Medicines only
• Only manufacturer SOPs
• European Pharmacopoeia exclusively

Correct Answer: USP, BP, IP

Q12. In spectrophotometric assays, what is the main reason for using derivative spectrophotometry for vitamins?

• To increase solvent volatility
• To resolve overlapping absorption peaks and improve specificity
• To change molar absorptivity drastically
• To avoid calibration

Correct Answer: To resolve overlapping absorption peaks and improve specificity

Q13. Which titrimetric method can be used for determination of vitamin B2 (riboflavin)?

• Redox titration with dichromate
• Colorimetric titration with iodine
• None; riboflavin is commonly measured by fluorescence or HPLC
• Complexometric titration with EDTA

Correct Answer: None; riboflavin is commonly measured by fluorescence or HPLC

Q14. What does system suitability testing in HPLC typically assess before sample analysis?

• Column particle size distribution
• Parameters like theoretical plates, tailing factor and resolution
• Sample pH only
• Detector warranty validity

Correct Answer: Parameters like theoretical plates, tailing factor and resolution

Q15. Which internal standard practice improves accuracy in vitamin assays by compensating for sample loss?

• Using an unrelated drug compound as a marker
• Adding a structurally similar labelled or stable isotope internal standard
• Adding distilled water as control
• Using the drug itself as standard only

Correct Answer: Adding a structurally similar labelled or stable isotope internal standard

Q16. Which solvent is typically used to extract fat‑soluble vitamins from oil‑based formulations?

• Methanol–water (1:1)
• n‑Hexane or hexane–isopropanol mixtures
• Saturated saline solution
• Acetic acid

Correct Answer: n‑Hexane or hexane–isopropanol mixtures

Q17. Which calibration approach helps to correct matrix effects in vitamin assays?

• Use of external calibration in pure solvent only
• Standard addition method
• No calibration required for vitamins
• Random calibration points

Correct Answer: Standard addition method

Q18. For ascorbic acid determination by titration with DCPIP, which condition must be maintained to avoid oxidation losses?

• High temperature (above 60°C)
• Acidic medium and protection from air/light
• Strongly alkaline pH
• Continuous exposure to sunlight

Correct Answer: Acidic medium and protection from air/light

Q19. What is the principal advantage of LC-MS/MS over HPLC-UV for vitamin quantitation?

• Lower instrument cost
• Greater specificity and sensitivity, especially in complex matrices
• No sample preparation needed
• Does not require calibration

Correct Answer: Greater specificity and sensitivity, especially in complex matrices

Q20. Which validation parameter measures closeness of measured value to true value in vitamin assays?

• Precision
• Robustness
• Accuracy (recovery)
• System suitability

Correct Answer: Accuracy (recovery)

Q21. Which vitamin commonly requires derivatization to improve detectability in GC analysis?

• Vitamin C (ascorbic acid)
• Vitamin B12 (cyanocobalamin)
• Many B vitamins or vitamin D metabolites often require silylation for GC
• Vitamin E as native molecule

Correct Answer: Many B vitamins or vitamin D metabolites often require silylation for GC

Q22. Which pH control is important when analyzing vitamin B6 (pyridoxine) due to pH-dependent speciation?

• Strongly basic (pH >12)
• Near neutral to slightly acidic pH depending on method
• Always pH 14
• pH control is unnecessary

Correct Answer: Near neutral to slightly acidic pH depending on method

Q23. In spectrophotometric assays, what is molar absorptivity (ε) used for?

• To calculate retention time in HPLC
• To relate absorbance to concentration via Beer–Lambert law
• To measure detector noise only
• To adjust column temperature

Correct Answer: To relate absorbance to concentration via Beer–Lambert law

Q24. Which stability concern is most relevant for vitamin A (retinol) during storage and analysis?

• Hydrolysis at neutral pH
• Oxidation and photodegradation
• Polymerization in water
• Becomes ionic at low temperatures

Correct Answer: Oxidation and photodegradation

Q25. What is the main purpose of using buffer in HPLC mobile phase for vitamin assays?

• To increase detector temperature
• To control pH and improve reproducibility and peak shape
• To reduce solvent polarity only
• To avoid using organic solvents

Correct Answer: To control pH and improve reproducibility and peak shape

Q26. Which technique is suitable for simultaneous determination of niacin (B3) and nicotinamide in formulations?

• Gravimetric analysis
• HPLC with UV detection
• Flame photometry
• Conductometric titration

Correct Answer: HPLC with UV detection

Q27. For method validation, what does precision assess?

• Closeness to true value
• Repeatability and reproducibility of measurements
• Ability to separate peaks
• Stability under light

Correct Answer: Repeatability and reproducibility of measurements

Q28. Which reagent is used to oxidize vitamin C to dehydroascorbic acid in some analytical schemes?

• Sodium chloride
• Potassium permanganate or iodine under controlled conditions
• Calcium carbonate
• Formaldehyde

Correct Answer: Potassium permanganate or iodine under controlled conditions

Q29. Which analytical characteristic ensures the method measures only the analyte of interest in presence of excipients?

• Precision
• Specificity/selectivity
• Robustness
• LOD

Correct Answer: Specificity/selectivity

Q30. What is an appropriate approach to quantify low concentration vitamins near LOQ in presence of matrix effects?

• Ignore matrix and use solvent calibration
• Use matrix-matched calibration or isotope-labeled internal standard
• Reduce sample cleanup to save time
• Use only visual color comparison

Correct Answer: Use matrix-matched calibration or isotope-labeled internal standard

Q31. Which mobile phase component can be adjusted to control retention of polar vitamins in reversed-phase HPLC?

• Column length only
• Organic solvent proportion and aqueous buffer pH
• Only detector settings
• Ambient room lighting

Correct Answer: Organic solvent proportion and aqueous buffer pH

Q32. Which analytical method is described as a primary method for vitamin C when using a primary standard for titration?

• UV spectrophotometry
• Direct titration with iodometric or DCPIP using standard procedures
• HPLC without standards
• Microbiological assay only

Correct Answer: Direct titration with iodometric or DCPIP using standard procedures

Q33. Which detector is least suitable for non‑chromophoric water‑soluble vitamins by HPLC without derivatization?

• Mass spectrometer
• Refractive index detector
• UV detector
• Fluorescence detector with derivatization

Correct Answer: Refractive index detector

Q34. In standardization, what is an assay “potency” usually expressed as for vitamins?

• Only percentage w/w
• Units such as IU (international units) or mg per dosage form
• Colony forming units
• pH units

Correct Answer: Units such as IU (international units) or mg per dosage form

Q35. Which parameter indicates the consistency of peak area for repeated injections of a standard solution?

• Resolution
• Repeatability (percent RSD of peak area)
• Theoretical plates only
• Baseline drift

Correct Answer: Repeatability (percent RSD of peak area)

Q36. For vitamin K analysis, which detection mode can improve sensitivity after HPLC separation?

• UV at 700 nm
• Fluorescence after post‑column derivatization or MS detection
• Gas detector
• Refractometric index at low wavelength

Correct Answer: Fluorescence after post‑column derivatization or MS detection

Q37. Which extraction technique reduces lipid interference when preparing samples for vitamin analysis in fish oil?

• Direct aqueous dilution
• Saponification followed by solvent extraction
• Simple filtration
• Heating to evaporate oil

Correct Answer: Saponification followed by solvent extraction

Q38. Which method is commonly used to standardize a titrant before performing vitamin titrations?

• Use of densitometry
• Titration against a primary standard of known purity
• Guessing concentration
• Measuring pH only

Correct Answer: Titration against a primary standard of known purity

Q39. Which parameter is examined under robustness testing for a vitamin HPLC method?

• Effect of small deliberate changes like pH, flow rate and mobile phase composition
• Long-term stability of stock standard over years only
• Operator’s handwriting quality
• Brand of glassware used

Correct Answer: Effect of small deliberate changes like pH, flow rate and mobile phase composition

Q40. Which analytical approach is best when vitamins have overlapping UV spectra in a combined dosage form?

• Use of derivative spectrophotometry or HPLC separation
• Ignore overlap and sum absorbances
• Use only visual color comparison
• Measure total absorbance at 400 nm only

Correct Answer: Use of derivative spectrophotometry or HPLC separation

Q41. What is the common role of antioxidants like BHT during analysis of fat‑soluble vitamins?

• They act as mobile phase buffers
• They prevent oxidation of analytes during extraction and storage
• They increase column pressure
• They induce fluorescence

Correct Answer: They prevent oxidation of analytes during extraction and storage

Q42. For quantifying riboflavin by fluorescence, which property makes it easy to detect?

• High UV absorbance but no fluorescence
• Intrinsic strong fluorescence without derivatization
• High volatility
• Strong refractive index

Correct Answer: Intrinsic strong fluorescence without derivatization

Q43. Which approach is appropriate to confirm identity of a vitamin peak in HPLC when retention times alone are insufficient?

• Change column temperature drastically
• Use retention time and spectral library match (PDA) or MS confirmation
• Assume identity based on color of solution
• Only rely on system suitability results

Correct Answer: Use retention time and spectral library match (PDA) or MS confirmation

Q44. What is the typical effect of light exposure on many vitamins during analytical work?

• Increases their potency
• Causes photodegradation and loss of assay value
• Makes them more soluble in water
• Has no effect

Correct Answer: Causes photodegradation and loss of assay value

Q45. Which technique is ideal for trace-level quantitation and structural confirmation of vitamin metabolites in biological fluids?

• TLC with UV lamp
• LC-MS/MS with appropriate sample cleanup
• Simple UV spectrophotometry
• Colorimetric dipstick

Correct Answer: LC-MS/MS with appropriate sample cleanup

Q46. During HPLC assay, what does tailing factor greater than 2 indicate?

• Excellent peak symmetry
• Peak tailing and potentially poor chromatography requiring optimization
• Column is perfectly packed
• Detector is off

Correct Answer: Peak tailing and potentially poor chromatography requiring optimization

Q47. Which sample treatment reduces protein binding and frees water‑soluble vitamins in biological samples prior to analysis?

• Protein precipitation with acetonitrile or methanol
• Direct freezing without treatment
• Adding oil to sample
• Evaporation to dryness only

Correct Answer: Protein precipitation with acetonitrile or methanol

Q48. Which quality attribute is tested by recovery experiments in vitamin assay validation?

• Specificity only
• Accuracy and effect of matrix on measured concentration
• Column life span
• Detector linearity only

Correct Answer: Accuracy and effect of matrix on measured concentration

Q49. For routine QC of vitamin tablets, which test is commonly performed besides assay?

• Disintegration and dissolution testing to confirm release
• Only visual inspection of color
• Checking pH of excipient alone
• Measuring boiling point

Correct Answer: Disintegration and dissolution testing to confirm release

Q50. When analyzing a multivitamin complex by HPLC, what is a practical strategy to handle vitamins with very different polarities?

• Use a single isocratic mobile phase without optimization
• Develop gradient elution method or use sample fractionation and different detectors
• Use only TLC
• Ignore polar vitamins

Correct Answer: Develop gradient elution method or use sample fractionation and different detectors

G S Sachin

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