Podcast
Questions and Answers
What is the primary purpose of the ion source in a GC-MS instrument?
What is the primary purpose of the ion source in a GC-MS instrument?
- To detect the ions and display the mass spectrum
- To separate the ions by their mass-to-charge ratio
- To eliminate the majority of the carrier gas
- To ionize and fragment the remaining molecules (correct)
Which of the following applications is NOT typically associated with GC-MS analysis?
Which of the following applications is NOT typically associated with GC-MS analysis?
- Food science
- Purity of solvents
- Clinical analysis
- Astronomy (correct)
What is the relationship between the area under a peak in a chromatogram and the amount of analyte injected?
What is the relationship between the area under a peak in a chromatogram and the amount of analyte injected?
- The area under the peak is proportional to the square of the amount of analyte
- The area under the peak is unrelated to the amount of analyte
- The area under the peak is inversely proportional to the amount of analyte
- The area under the peak is directly proportional to the amount of analyte (correct)
What is the primary function of the mass analyzer in a GC-MS instrument?
What is the primary function of the mass analyzer in a GC-MS instrument?
Which of the following is a quantitative application of GC-MS?
Which of the following is a quantitative application of GC-MS?
What is typically used to determine the peak area in a chromatogram?
What is typically used to determine the peak area in a chromatogram?
Which detector type is selective for compounds containing phosphorus and sulfur?
Which detector type is selective for compounds containing phosphorus and sulfur?
What is the primary advantage of using GC-MS with continuous total ion scan?
What is the primary advantage of using GC-MS with continuous total ion scan?
Which of the following detectors is not typically used for analyte identification?
Which of the following detectors is not typically used for analyte identification?
What is the primary purpose of selective-ion monitoring in GC-MS?
What is the primary purpose of selective-ion monitoring in GC-MS?
What is the typical range of the limit of detection (LOD) for GC-MS?
What is the typical range of the limit of detection (LOD) for GC-MS?
Which of the following is a benefit of using GC-MS with continuous recording of the mass spectrum?
Which of the following is a benefit of using GC-MS with continuous recording of the mass spectrum?
What is the primary advantage of using fluorescence detection in HPLC?
What is the primary advantage of using fluorescence detection in HPLC?
In reversed-phase HPLC, what is the primary factor that determines the retention of organic molecules in the column?
In reversed-phase HPLC, what is the primary factor that determines the retention of organic molecules in the column?
In ion-exchange chromatography, what is the primary factor that determines the elution order of organic acids and bases?
In ion-exchange chromatography, what is the primary factor that determines the elution order of organic acids and bases?
What is the primary mechanism of separation in gel filtration chromatography?
What is the primary mechanism of separation in gel filtration chromatography?
What is the primary advantage of using mass spectrometry in detection?
What is the primary advantage of using mass spectrometry in detection?
What is the primary purpose of using a flow cell in HPLC detection?
What is the primary purpose of using a flow cell in HPLC detection?
Flashcards
Flame Photometric Detector (FPD)
Flame Photometric Detector (FPD)
A type of detector in gas chromatography that detects compounds containing phosphorus and sulfur through optical emission.
Thermionic Detector (TID)
Thermionic Detector (TID)
A type of detector in gas chromatography that responds to compounds containing nitrogen or phosphorus.
Fourier Transform Infrared Spectrophotometer (FT-IR)
Fourier Transform Infrared Spectrophotometer (FT-IR)
A detector used in Gas Chromatography that identifies compounds by their unique infrared absorption patterns.
Total Ion Scan (TIS)
Total Ion Scan (TIS)
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Selective Ion Monitoring (SIM)
Selective Ion Monitoring (SIM)
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Limit of Detection (LOD)
Limit of Detection (LOD)
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Mass Analyzer
Mass Analyzer
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Ionization Chamber
Ionization Chamber
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Ionization
Ionization
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Fragmentation
Fragmentation
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Mass Spectrometry
Mass Spectrometry
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Mass-to-Charge Ratio (m/z)
Mass-to-Charge Ratio (m/z)
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Quantitative Applications of GC-MS
Quantitative Applications of GC-MS
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UV Detector
UV Detector
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Refractive Index (RI) Detector
Refractive Index (RI) Detector
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Fluorescence (FD) Detector
Fluorescence (FD) Detector
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Analyte Concentration
Analyte Concentration
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Integration
Integration
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Study Notes
Detectors in Gas Chromatography
- Flame photometric detector: detects compounds containing phosphorus and sulfur through optical emission
- Thermionic detector: responds to compounds containing nitrogen or phosphorus
- Fourier transform infrared spectrophotometer (FT-IR): detects and examines IR spectrum for any time increment
Gas Chromatography-Mass Spectrometry (GC-MS)
- Total ion scan: provides universal detection for all analytes by continuously scanning the entire mass spectrum
- Selective-ion monitoring: achieves selectivity by monitoring specific mass-to-charge ratios
- Limit of detection (LOD): 25 fg to 100 pg, with a linear range of 10 orders of magnitude
- Advantage: uses mass spectrum to help identify a mixture's components
GC-MS Instrumentation
- Effluent from the column enters the mass spectrometer's ion source, eliminating most of the carrier gas
- Ionization chamber: molecules undergo ionization and fragmentation
- Mass analyzer: separates ions by their mass-to-charge ratio, and a detector counts the ions and displays the mass spectrum
GC-MS Applications
- Environmental analysis: GHGs in air, pesticides in water and soil, vehicle emissions, and trihalomethanes in drinking water
- Clinical analysis: drugs and blood alcohols
- Forensic analysis: analysis of arson accelerants, detection of explosives, and consumer products
- Petrochemical and chemical industry: purity of solvents, refinery gas, and composition of gasoline
Quantitative Applications
- Analysis of a diverse array of samples in methods for determining areas in environmental, clinical, pharmaceutical, biochemical, forensic, food science, and petrochemical laboratories
- Peak area is proportional to the amount of analyte injected onto the column and is determined by integration
Detection Methods
- UV light: most popular, uses a lamp, grating/lens, flow cell, and photo diode to measure differential light output
- Refractive index (RI): universal analyte indicator, but solvent must remain the same throughout separation and is very temperature sensitive
- Fluorescence (FD): greater sensitivity, but analytes must have a fluorophore group and is not very common
- Mass spectrometry: uses mass-to-charge ratio (m/z) for specific compound identification
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