All students are expected to:
- Evaluate the suitability of three common detectors (FID, TCD, and ECD) for different analytes
- Explain the operation principle of these detectors
- Differentiate these detectors in terms of selectivity and other properties (destructive, bulk, concentration/ mass depending) with regard to their suitability for different application
Quiz GC Detectors
Provide handwritten answers and bring them to the class
- Define the limit of detection, dynamic range, linear range and also significance of these parameters when selecting a detector
- Describe how FID works, provide its significant characteristics and optimization parameters
- Describe how ECD works, and describe its typical operation parameters
- Describe how TCD works, and describe its typical operation parameters
- Define the main classifications of common chromatographic detectors and give examples in terms of:
- Concentration vs. mass flow
- Selective vs. universal
- Destructive vs. nondestructive
A. Flame Ionization detector (FID)
- Fill the missing labels for the FID detector diagram below.
- Explain the purpose of using each gas.
- Explain the operational principle of FID.
- Which analytes can be analyzed on an FID and which cannot?
B. Thermal conductivity detector (TCD)
- Sketch the flow of the molecules in a single cell TCD for the 2 scenarios shown below
- a reference gas passing through the filament
- an analyte in a carrier gas passing through the filament
- Why is a valve switching required for the application shown below?
Hint: Consider thermal conductivities listed.
C. Electron Capture detector (ECD)
- Sketch fast β- and thermal electrons e-, makeup gas and carrier gases, analyte species CX in the following three scenarios for ECD
- Only the carrier gas is passing through the ECD
- Both carrier and makeup gases are passing through the ECD
- The carrier gas with an analyte and makeup gas are passing through the ECD
- Write three reactions, which occur in an ECD.
- Which analytes can be analyzed using an ECD?
D. GC detector characteristics
- List all possible detectors for the analytes in the following samples:
- Total petroleum hydrocarbons (TPH) in gasoline
- Nitrated polycyclic aromatic hydrocarbons (N-PAHs) extracted from air particulate matter
- Alcohol content in wine
- Chlorinated disinfectant products in water
- Polychlorinated biphenyls (PCBs) extracted from soil
- Hydrogen, CO2, methane, ethane and propane from biofuel production
- Considering their sensitivity, highlight the detector of choice for the analytes listed above in those samples.
- What solvents used for extraction would be detrimental to the detectors proposed in response to Q2?
- Which detector is universal and would be suitable for all analytes and why is it not the detector of choice?
- For which application would it be suitable to use two detectors in series and what would be the benefits of such a setup?