Chemical methods of sterilization MCQs With Answer

Chemical methods of sterilization MCQs With Answer

Chemical methods of sterilization are essential for B. Pharm students studying pharmaceutical sterilization, sterilant mechanisms, and sterility assurance of heat-sensitive products. This compact, SEO-friendly introduction focuses on key chemical sterilants—ethylene oxide, glutaraldehyde, formaldehyde, hydrogen peroxide (vapor), peracetic acid, and ozone—covering mechanisms, parameters (concentration, temperature, humidity, contact time), material compatibility, safety, residues, and validation. These topics help pharmacy students prepare for exams and practical lab work while improving understanding of regulatory and environmental considerations. Clear, targeted MCQs will reinforce learning and application in pharmaceutical manufacturing and hospital sterilization practices. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which chemical sterilant inactivates microorganisms primarily by alkylation of nucleic acids and proteins?

• Glutaraldehyde
• Ethylene oxide
• Hydrogen peroxide
• Peracetic acid

Correct Answer: Ethylene oxide

Q2. Which biological indicator organism is commonly used to validate ethylene oxide sterilization?

• Geobacillus stearothermophilus
• Bacillus atrophaeus
• Escherichia coli
• Staphylococcus aureus

Correct Answer: Bacillus atrophaeus

Q3. Which chemical sterilant is a liquid aldehyde widely used for high-level disinfection of heat-sensitive medical equipment?

• Peracetic acid
• Formaldehyde
• Glutaraldehyde
• Hydrogen peroxide

Correct Answer: Glutaraldehyde

Q4. Vaporized hydrogen peroxide (VHP) sterilization is particularly advantageous because it:

• Leaves toxic residues requiring long aeration
• Requires high process temperatures above 150°C
• Produces water and oxygen as breakdown products
• Is ineffective against spores

Correct Answer: Produces water and oxygen as breakdown products

Q5. Peracetic acid is preferred for sterilizing flexible endoscopes primarily due to:

• Its ability to penetrate deep packaging without aeration
• Strong sporicidal activity at low temperatures and short contact time
• Its non-corrosive nature to all metals
• Lack of toxicity to operators

Correct Answer: Strong sporicidal activity at low temperatures and short contact time

Q6. Which factor most increases the efficacy of ethylene oxide sterilization?

• Decreased humidity
• Higher relative humidity within the chamber
• Lower temperature
• Reduced exposure time

Correct Answer: Higher relative humidity within the chamber

Q7. Formaldehyde gas sterilization is limited in pharmaceutical settings mainly because it:

• Is ineffective against viruses
• Produces pungent odors but no residues
• Is a known carcinogen and requires careful control
• Cannot sterilize porous materials

Correct Answer: Is a known carcinogen and requires careful control

Q8. Which sterilant is most appropriate for sterilizing heat-sensitive, moisture-sensitive electronic medical devices?

• Autoclave steam
• Ethylene oxide
• Peracetic acid immersion
• Dry heat at 160°C

Correct Answer: Ethylene oxide

Q9. The primary disadvantage of ethylene oxide sterilization is:

• High-temperature requirement
• Long aeration time required to remove residues
• Ineffectiveness against spores
• Leaves only benign water as residue

Correct Answer: Long aeration time required to remove residues

Q10. Which chemical sterilant acts through generation of free radicals that damage cell components?

• Glutaraldehyde
• Ethylene oxide
• Hydrogen peroxide
• Formaldehyde

Correct Answer: Hydrogen peroxide

Q11. Which sterilization indicator would you use to monitor a peracetic acid sterilization cycle?

• Geobacillus stearothermophilus biological indicator
• Pseudomonas aeruginosa culture swab
• Ethylene oxide chemical indicator
• ATP bioluminescence assay only

Correct Answer: Geobacillus stearothermophilus biological indicator

Q12. Glutaraldehyde requires activation and is typically used at which approximate concentration for high-level disinfection?

• 0.1%
• 2%
• 50%
• 100%

Correct Answer: 2%

Q13. Which sterilant is effective at room temperature and often used in whole-room decontamination with plasma or vapor systems?

• Autoclave steam
• Vaporized hydrogen peroxide
• Dry heat
• Chlorine bleach

Correct Answer: Vaporized hydrogen peroxide

Q14. What is a common validation parameter for chemical sterilization cycles in pharmaceutical manufacturing?

• Number of operators present
• Bioburden reduction and biological indicator kill results
• Color of the sterilant
• Room height

Correct Answer: Bioburden reduction and biological indicator kill results

Q15. Which chemical sterilant is commonly used as a cold sterilant but requires subsequent neutralization to minimize toxicity?

• Peracetic acid
• Ethylene oxide
• Glutaraldehyde
• Vaporized hydrogen peroxide

Correct Answer: Glutaraldehyde

Q16. Ozone sterilization kills microorganisms primarily by:

• Alkylation of DNA
• Oxidation of cell components and membrane disruption
• Cross-linking proteins with aldehydes
• Heat denaturation

Correct Answer: Oxidation of cell components and membrane disruption

Q17. A major concern when using peracetic acid in pharmaceutical instrument processing is:

• Formation of radioactive residues
• Corrosive effects on some metals and rubber
• Excessive heat generation
• Inability to kill gram-positive bacteria

Correct Answer: Corrosive effects on some metals and rubber

Q18. Which statement about vaporized hydrogen peroxide (VHP) sterilization is true?

• VHP requires temperatures above 121°C to be effective
• VHP leaves long-term toxic residues in materials
• VHP is non‑corrosive to all polymers
• VHP is a low-temperature, residue-minimizing sterilization method

Correct Answer: VHP is a low-temperature, residue-minimizing sterilization method

Q19. Which chemical is commonly used as a fumigant for whole-room sterilization of cleanrooms and equipment?

• Ethylene oxide
• Hydrogen peroxide vapor
• Sterile water vapor
• Isopropyl alcohol spray

Correct Answer: Hydrogen peroxide vapor

Q20. Chemical sterilization effectiveness is least affected by which of the following?

• Organic load and biofilms
• Temperature and humidity
• Type and concentration of sterilant
• Color of the instrument

Correct Answer: Color of the instrument

Q21. Which agent is most suitable for sterilizing heat-sensitive, water-sensitive pharmaceutical packaging?

• Steam autoclave
• Peracetic acid immersion
• Ethylene oxide
• Boiling water

Correct Answer: Ethylene oxide

Q22. For ethylene oxide sterilization, which post-process step removes residual EtO from products?

• Immediate packaging and shipping
• Aeration (outgassing) at controlled temperature and ventilation
• Immersion in sterile saline
• Microwave treatment

Correct Answer: Aeration (outgassing) at controlled temperature and ventilation

Q23. Which factor most reduces the activity of glutaraldehyde solutions over time?

• Storage in airtight amber containers
• Repeated exposure to organic matter and dilution
• Maintenance at recommended pH and concentration
• Refrigeration

Correct Answer: Repeated exposure to organic matter and dilution

Q24. Which sterilant would be inappropriate for use on cellulose-based materials (paper) due to degradation?

• Hydrogen peroxide vapor
• Ethylene oxide
• Peracetic acid
• Dry heat

Correct Answer: Hydrogen peroxide vapor

Q25. In the context of sterilization, the term ‘sterility assurance level (SAL)’ refers to:

• The pH of the sterilant solution
• The probability of a single viable microorganism occurring on an item after sterilization
• The time required to sterilize an item
• The concentration of the sterilant used

Correct Answer: The probability of a single viable microorganism occurring on an item after sterilization

Q26. Which chemical sterilant is commonly used in combination with hydrogen peroxide to broaden microbicidal spectrum and reduce dwell time?

• Sodium hypochlorite
• Peracetic acid
• Formaldehyde
• Isopropyl alcohol

Correct Answer: Peracetic acid

Q27. Which is the main safety concern for workers handling ethylene oxide sterilization chambers?

• Risk of electric shock
• Toxicity and carcinogenicity of ethylene oxide gas
• Noise exposure
• Risk of heat burns from autoclave steam

Correct Answer: Toxicity and carcinogenicity of ethylene oxide gas

Q28. Chemical indicators for sterilization cycles primarily provide information about:

• Microbial kill achieved
• Exposure to at least one critical process parameter such as temperature or presence of sterilant
• Exact sterility assurance level
• Operator competence

Correct Answer: Exposure to at least one critical process parameter such as temperature or presence of sterilant

Q29. Which sterilant is effective in the presence of organic matter compared to others?

• Hydrogen peroxide
• Peracetic acid
• Glutaraldehyde
• Chlorine-based agents (e.g., sodium hypochlorite)

Correct Answer: Chlorine-based agents (e.g., sodium hypochlorite)

Q30. For sterilization of prefilled syringes with thermolabile drug solutions, the recommended chemical method is often:

• Steam sterilization at 121°C
• Ethylene oxide sterilization with controlled aeration
• Dry heat at 160°C
• Boiling for 30 minutes

Correct Answer: Ethylene oxide sterilization with controlled aeration

Q31. Which chemical sterilant is characterized by rapid action, broad spectrum, and decomposition into non-toxic residues, but can be corrosive?

• Ethylene oxide
• Peracetic acid
• Formaldehyde
• Glutaraldehyde

Correct Answer: Peracetic acid

Q32. The primary mechanism of action of glutaraldehyde is:

• Oxidation of membrane lipids
• Alkylation and cross-linking of proteins
• Generation of free radicals
• Denaturation by heat

Correct Answer: Alkylation and cross-linking of proteins

Q33. Which parameter is NOT critical when validating ethylene oxide sterilization cycles?

• Gas concentration
• Exposure time
• Humidity level
• Room paint color

Correct Answer: Room paint color

Q34. During chemical sterilization, a high organic load can cause:

• Increased sterilant efficacy
• Inactivation or neutralization of the sterilant leading to reduced efficacy
• No effect on sterilization
• Sterilant to become more volatile

Correct Answer: Inactivation or neutralization of the sterilant leading to reduced efficacy

Q35. Which sterilant is generally favored for sterilizing implantable medical devices that tolerate low-temperature processing and require minimal residue?

• Ethylene oxide
• Vaporized hydrogen peroxide
• Glutaraldehyde immersion
• Formaldehyde fumigation

Correct Answer: Vaporized hydrogen peroxide

Q36. Which chemical sterilization method requires careful control of relative humidity because it directly influences antimicrobial activity?

• Dry heat sterilization
• Ethylene oxide sterilization
• Autoclave steam sterilization
• Gamma irradiation

Correct Answer: Ethylene oxide sterilization

Q37. Which disinfectant is unsuitable as a sterilant because it does not reliably inactivate bacterial spores at practical exposure times?

• Glutaraldehyde at high concentration and long exposure
• Ethylene oxide
• 70% isopropyl alcohol
• Peracetic acid under validated conditions

Correct Answer: 70% isopropyl alcohol

Q38. A disadvantage of peracetic acid sterilization systems is:

• Long-term toxic residues remaining on instruments
• Requirement for high temperatures above 200°C
• Potential corrosiveness to some metals and rubber components
• Inability to inactivate vegetative bacteria

Correct Answer: Potential corrosiveness to some metals and rubber components

Q39. Which sterilant requires the longest validated aeration time for safe use with medical devices?

• Vaporized hydrogen peroxide
• Ethylene oxide
• Peracetic acid
• Bleach (sodium hypochlorite)

Correct Answer: Ethylene oxide

Q40. Which chemical sterilization method is most easily integrated into isolators and restricted-access barrier systems for aseptic processing?

• Hot air at 180°C
• Ethylene oxide fumigation
• Vaporized hydrogen peroxide decontamination
• Immersion in boiling water

Correct Answer: Vaporized hydrogen peroxide decontamination

Q41. Which of the following is a correct statement about formaldehyde sterilization?

• It is non-toxic and requires no PPE
• It is highly reactive and can cross-link nucleic acids and proteins
• It leaves only water as a breakdown product
• It is ineffective against spores

Correct Answer: It is highly reactive and can cross-link nucleic acids and proteins

Q42. When selecting a chemical sterilant for a polymeric device, the main compatibility concern is:

• Sterilant odor
• Potential for chemical degradation, embrittlement, or discoloration of the polymer
• Packaging color
• Operator preference

Correct Answer: Potential for chemical degradation, embrittlement, or discoloration of the polymer

Q43. Which monitoring method provides the most conclusive evidence that a sterilization process achieved microbial inactivation?

• Chemical indicator color change
• Biological indicator showing no growth after incubation
• Visual inspection of chamber conditions
• Operator logbook entry

Correct Answer: Biological indicator showing no growth after incubation

Q44. Which chemical sterilant can be neutralized by catalase-producing materials or residual organic load, reducing its effectiveness?

• Hydrogen peroxide
• Ethylene oxide
• Formaldehyde
• Glutaraldehyde

Correct Answer: Hydrogen peroxide

Q45. For validation of a new chemical sterilization process, one key step is to determine the D-value. The D-value represents:

• The dose of sterilant at which the sterilant decomposes
• The time required to reduce the microbial population by one log (90%) under specified conditions
• The concentration of sterilant needed for sterilization
• The number of biological indicators to place in a chamber

Correct Answer: The time required to reduce the microbial population by one log (90%) under specified conditions

Q46. Which sterilant is most likely to penetrate complex lumens of flexible endoscopes when used in validated automated systems?

• Ethylene oxide gas
• Peracetic acid automated immersion systems
• Dry heat
• Boiling water

Correct Answer: Peracetic acid automated immersion systems

Q47. Which of the following statements about chemical residues after sterilization is correct?

• All chemical sterilants leave no residues on any materials
• Residues can be toxic and require validated removal or aeration steps
• Residues are always beneficial for long-term sterility
• Residue testing is unnecessary for pharmaceutical products

Correct Answer: Residues can be toxic and require validated removal or aeration steps

Q48. When choosing between ethylene oxide and vaporized hydrogen peroxide for sterilizing a batch of mixed materials, which consideration is most important?

• Whether the operator prefers gas or vapor
• Material compatibility, residues, cycle time, and regulatory requirements
• Room decor
• Color of packaging labels

Correct Answer: Material compatibility, residues, cycle time, and regulatory requirements

Q49. Which of the following is a correct environmental consideration for chemical sterilization processes in pharmaceutical plants?

• Emissions are always negligible and unregulated
• Proper capture, neutralization, and monitoring of fugitive emissions are required
• Disposal of used sterilants in regular drains is acceptable
• No worker protection is needed for chemical sterilants

Correct Answer: Proper capture, neutralization, and monitoring of fugitive emissions are required

Q50. In a risk assessment for selecting a chemical sterilization method, which factor should be weighed most heavily?

• Brand popularity of sterilization equipment
• Compatibility with product materials, sterility assurance requirements, and patient safety
• Ease of advertising the method
• Color of the sterilant container

Correct Answer: Compatibility with product materials, sterility assurance requirements, and patient safety

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