Top 31 Gas chromatography interview questions and answers

Gas chromatography interview questions and answers are somewhere that kept us on the backfoot while interviewing. In this article, we will try to cover such Gas chromatography interview questions.

Gas Chromatography Interview Questions And Answers:

Question 1: What is GC full form?

Answer: GC full form is Gas Chromatography.

Question 2: What are the types of Gas Chromatography?

Answer: There are two types of Gas chromatography;

  1. Gas-Solid chromatography (GSC)
  2. Gas-liquid chromatography (GLC)

Question 3: What is gas-solid chromatography?

Answer: In gas-solid chromatography, Gas acts as a mobile phase and solid as a stationary phase hence called gas-solid chromatography.

Question 4: What is USP General Chapter for Gas Chromatography?

Answer: USP general chapter no. <621> Chromatography.

Question 5: What is the gas chromatography principle?

Answer: It is a separation technique based on the principle of adsorption of gases or vapors of liquid by an adsorbent.

Question 6: What is Gas Chromatography instrumentation?


  1. Gas Chamber
  2. Injection port
  3. Column compartment
  4. Detector
  5. Recorder

Question 7: What is the Stationary phase in Gas Chromatography?

Answer: Stationary phase may be a solid adsorbent called Gas Solid Chromatography (GSC) or can be liquid inert support called Gas Liquid Chromatography (GLC).

Question 8: What types of gas are used in Gas Chromatography?

Answer: Inert type of gas is used as a mobile phase in GC.

Question 9: What are the gases used as mobile phase in Gas Chromatography?

Answer: Helium, Nitrogen, and Hydrogen are used as a mobile phase in GC.

Question 10: What are the Gas chromatography detectors?


  1. Flame Ionization Detector (FID)
  2. Thermal Conductivity Detector (TCD)
  3. Nitrogen Phosphorous Detector (NPD)
  4. Electron Capture Detector (ECD)
  5. Flame Photometric Detector (FPD)
  6. Photo Ionization Detector (PID)
  7. Electrolytic Conductivity Detector (ELCD)
  8. Mass Spectrometer (MS)

Question 11: Which is the most common detector used in GC?

Answer: Flame Ionization Detector (FID detector)

Question 12: FID detector used to detect what type of compound?

Answer: FID detector is useful to detect organic types of compounds.

Question 13: What is the difference between FID and TCD?

Answer: FID is a flame ionization of an organic compound by burning the compound in hydrogen-air flame.

TCD is based on the difference in thermal conductivity properties between carrier gas and the target being detected.

Question 14: How do identify the peaks in gas chromatography?

Answer: This question could be tricky but let’s understand it in a simple way, gas chromatography works on different factors such as temperature, gas flow, and column length. Because of factors affecting retention time, it is important that, If the gas chromatography is having a specified method then it will be easy to identify the peaks in gas chromatography and understand the elution pattern of peaks.

In another way, peaks can be identified in gas chromatography by using the GCMS method. In GCMS, the mass spectrometer is used and on the basis of the mass, the peak can be identified.

These all Gas chromatography interview questions and answers will help to crack the interview for Quality control in the pharmaceutical or in chemical industry.

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Question 15: Why is makeup gas used in Gas Chromatography?

Answer: Make-up gas is used in GC to sweep the components through the detector and minimizes the band broadening.

Question 16: How does Gas Chromatography work?

Answer: When the sample solution is injected through the injection port, the sample is entered into a column. Due to the high temperature in the column, the sample gets evaporated and travels through the column with the mobile phase. The temperature (Temperature Program) is set in such a way that the component should get a response at its Boiling point only. The components which are having a lower boiling point will elute first as compared to high boiling point components.

Question 17: What is the difference between ALS and Headspace?

Answer: ALS is used to inject liquid samples and evaporates into the column and headspace is used to convert liquid/solid samples into vapor form and inject in to the column.

Question 18: What are the 3 types of autosamplers?


  1. Headspace Autosampler
  2. Liquid Autosampler
  3. Solid Phase Micro Extraction (SPME)

Question 19: What is the split ratio in Gas Chromatography?

Answer: When the sample is injected it is split into two parts, the minimum part goes into the column and the maximum parts vent out.

Question 20: Explain an example of a split ratio?

Answer: Suppose the split ratio is 1:5, then 1 part of the sample solution goes into the column, and 4 parts of the sample solution vent out.

Question 21: Which is the best practice, split injection or splitless injection?

Answer: Split injection is the best practice.

Question 22: Why is temperature programming required in GC?

Answer: To elute high boiling point molecules fast and easy.

Question 23: What type of molecules elute first in GC?

Answer: Low boiling points are eluted first in GC.

Question 24: What are gas chromatography applications?


There are multiple applications of GC some are listed out;

  1. Quality Control in pharmaceutical
  2. Chemical Industry
  3. Research & Development
  4. Forensic science lab
  5. Food industry
  6. Petroleum & Petrochemical
  7. Air pollution measurement
  8. Wine Industry
  9. Alcohol analysis in Blood

Question 25: What are the GC make and model do you handled?


  1. Agilent GC 6890
  2. Agilent GC 7890b
  3. Agilent 8860
  4. Agilent GC 8890

Question 26: What is the GC Column stationary phase?

Answer: It is a solid phase that absorbs the components from the sample and releases them as per molecular weight in a sequential manner.

Question 27: What are the types of GC columns?

Answer: Generally three column are used,

  1. Capillary Column
  2. Glass column and
  3. Packed column

Question 28: What is a capillary column in GC?

Answer: A fused silica capillary column that holds a liquid adsorbent (stationary phase) in the tube on its wall.

Question 29: What is a packed column in GC?

Answer: A steel or glass tube round in shape as a coil that holds a stationary phase.

Question 30: If the boiling point is the same which one elute first?

Answer: If boiling point of components is the same then a low size molecule will elute first and a high size molecule elutes later.

Question 31: What is the Full form of GC-MS?

Answer: Gas Chromatography Mass Spectroscopy is the full form of GC-MS.

I hope you enjoyed the Gas Chromatography interview questions and answers.

Gas Chromatography Interview questions and answers
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