Gas Chromatography Mass Spectrometry (GC-MS) Quiz & Flashcards

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Questions and Answers

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?

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?

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?

To separate the ions by their mass-to-charge ratio Signup and view all the answers

Which of the following is a quantitative application of GC-MS?

Analysis of a diverse array of samples Signup and view all the answers

What is typically used to determine the peak area in a chromatogram?

All of the above Signup and view all the answers

Which detector type is selective for compounds containing phosphorus and sulfur?

Flame photometric detector Signup and view all the answers

What is the primary advantage of using GC-MS with continuous total ion scan?

Ability to identify a mixture's components using mass spectra Signup and view all the answers

Which of the following detectors is not typically used for analyte identification?

Flame ionization detector (FID) Signup and view all the answers

What is the primary purpose of selective-ion monitoring in GC-MS?

To achieve some degree of selectivity for specific analytes Signup and view all the answers

What is the typical range of the limit of detection (LOD) for GC-MS?

25 fg to 100 pg Signup and view all the answers

Which of the following is a benefit of using GC-MS with continuous recording of the mass spectrum?

Ability to examine the mass spectrum for any time increment Signup and view all the answers

What is the primary advantage of using fluorescence detection in HPLC?

It provides higher sensitivity and selectivity compared to UV detection Signup and view all the answers

In reversed-phase HPLC, what is the primary factor that determines the retention of organic molecules in the column?

Their degree of hydrophobicity Signup and view all the answers

In ion-exchange chromatography, what is the primary factor that determines the elution order of organic acids and bases?

Their pKa or pKb values Signup and view all the answers

What is the primary mechanism of separation in gel filtration chromatography?

Size exclusion of analytes based on their molecular size and shape Signup and view all the answers

What is the primary advantage of using mass spectrometry in detection?

It allows for the specific identification of compounds based on their mass-to-charge ratio Signup and view all the answers

What is the primary purpose of using a flow cell in HPLC detection?

To allow for the measurement of differential light output Signup and view all the answers

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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Description

Understand the principles of Gas Chromatography-Mass Spectrometry (GC-MS) instrumentation, including the ionization chamber, mass analyzer, and detector. Learn about the applications of GC and GC-MS in various fields.