IR Spectroscopy Quiz: Sampling Techniques and Liquid Gas Methods

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Questions and Answers

What is the primary purpose of the pressure regulator and flow meter in a flame photometer?

To adjust the temperature of the flame

To filter out unwanted wavelengths of light

To monitor the intensity of the emitted light

To control the flow and pressure of the gases used in the instrument (correct)

What is the role of the atomizer in a flame photometer?

To filter out unwanted wavelengths of light

To introduce the liquid sample into the flame at a stable and reproducible rate (correct)

To measure the intensity of the emitted light

To ignite the flame

What is the primary function of the optical system in a flame atomic absorption spectroscopy instrument?

To ignite the flame

To measure the temperature of the flame

To collect and focus the light emitted from the flame onto the photosensitive detector (correct)

To amplify the signal from the photosensitive detector

Why is a narrow slit necessary for the monochromator in a flame atomic absorption spectroscopy instrument?

To improve the resolution of the instrument, allowing it to isolate the characteristic wavelengths of the analyte Signup and view all the answers

Why are photosensitive detectors not useful in flame atomic emission spectroscopy instrumentation?

Their response is not amplifiable Signup and view all the answers

What is the purpose of using a deep metal grid across the mouth of the burner in a flame photometer?

To prevent the flame from striking back Signup and view all the answers

What is the primary function of the sample handling system in a mass spectrometer?

To introduce the sample into the ion source at low and reproducible pressure Signup and view all the answers

Why is it essential to maintain low pressure in the mass spectrometer?

To allow all the components to travel to the detector Signup and view all the answers

What is the function of the mass analyzer in a mass spectrometer?

To resolve ions with different mass-to-charge ratios Signup and view all the answers

How is the sample introduced into the ion source for less volatile samples?

By using a sample inlet system with a heater Signup and view all the answers

What is the purpose of the chemical ionization chamber in a mass spectrometer?

To introduce methane into the electron beam source at a pressure of 1 torr Signup and view all the answers

What is the purpose of the vacuum system in a mass spectrometer?

To maintain low pressure in the instrument Signup and view all the answers

What type of spectroscopy is used to determine functional groups in organic and inorganic molecules based on the vibrations of atoms?

Infrared Spectroscopy Signup and view all the answers

Which region of the electromagnetic spectrum is mainly used in Fourier Transform Infrared (FTIR) Spectroscopy?

Infrared Light Signup and view all the answers

What environmental application involves using Infrared Spectroscopy to identify pollutants from poorly maintained vehicles?

Measuring air quality Signup and view all the answers

Which technique involves splitting infrared radiation into two beams, one static and one moving, for analysis?

Fourier Transform Infrared (FTIR) Spectrometry Signup and view all the answers

What is the frequency range of the mid-IR region used in Fourier Transform Infrared (FTIR) Spectrometers?

$5000 \text{ to } 400 , \text{cm}^{-1}$ Signup and view all the answers

Apart from determining functional groups, what other application of Infrared Spectroscopy is mentioned in the text?

Measuring blood alcohol content Signup and view all the answers

Which of the following is not a common window material used in IR spectroscopy?

Aluminum oxide Signup and view all the answers

Which of the following organic solvents is useful in the region of 2222-1540 cm$^{-1}$?

CS$_2$ Signup and view all the answers

Which of the following is the most common detector used in IR spectroscopy?

Bolometer Signup and view all the answers

What is the long wavelength sensitivity limit for the PbTeO$_3$ cell used in IR detectors?

6 $ {mu}$m Signup and view all the answers

Which of the following prisms is typically used for measurements in the range of 400 cm$^{-1}$?

Potassium bromide prism Signup and view all the answers

What is the primary purpose of a recorder in IR spectroscopy?

To record the spectrum obtained from analyzed substances Signup and view all the answers

What is the primary advantage of combining gas chromatography (GC) with mass spectrometry (MS) in analytical chemistry?

It enables the separation and analysis of complex mixtures with high sensitivity and resolution. Signup and view all the answers

Which of the following is NOT a common application of mass spectrometry in forensic investigations?

Paternity testing Signup and view all the answers

What is the purpose of shielding the collector electrode in a mass spectrometer?

To prevent interference from stray ions and ensure accurate peak recording. Signup and view all the answers

Which of the following is NOT a common application of mass spectrometry in the field of healthcare?

Gene sequencing Signup and view all the answers

What is the term used to describe the combination of gas chromatography and mass spectrometry?

Hyphenated technique Signup and view all the answers

Which type of mass spectrometer is commonly used in combination with gas chromatography for sample analysis?

Quadrupole Signup and view all the answers

Study Notes

Atomic Emission Spectroscopy

Uses flame and argon plasma sources to analyze samples
Flame transforms solid or liquid samples into a vapor state and decomposes them into simpler molecules or atoms

Components of Flame Photometer

Pressure regulator and flow meter: for proper adjustment of pressure and flow gases
Atomizer: introduces liquid sample into the flame at stable and reproducible rates
Burner: e.g. Maker burner, used for working at low temperatures
Optical system: collects and monochromates light, focusing on a photosensitive detector
Photosensitive detector: not amplifiable, so a filter flame photometer is used instead
Amplifier: amplifies the signal to boost the output

Mass Spectrometry

Sampling device: includes all optics and equipment needed to deliver the excitation beam to the sample, collect the emission, and hold the sample in place
Ionization chamber: converts molecules into gaseous ions
Ion separator: resolves ions with different mass-to-charge ratios
Mass analyzer: similar to a prism or monochromator in spectrophotometry, essential to maintain low pressure
Detector: detects the ions
Signal processor unit: processes the signal

Infrared Spectroscopy

Uses the infrared spectrum to identify structures of organic and inorganic molecules
Functional groups give rise to characteristic bands in terms of intensity and frequency or wavelength
Uses: determining functional groups, catalytic research, forensic science, food industry, and environmental analysis

Fourier Transform Infrared (FTIR) Spectroscopy

Technique used for recording infrared spectra from analyzed solid, liquid, and gaseous samples
FTIR spectrometers collect high spectral resolution data in the mid and near-IR regions
Mid-IR region: 5000-400 cm⁻¹, near-IR region: 10,000-4,000 cm⁻¹

Sample Handling in FTIR Spectroscopy

Liquid samples: use alkali metal halide cells, e.g. sodium chloride, potassium bromide, and cesium iodide
Solid samples: dissolve in organic solvents, e.g. CCl₄ and CS₂, to prepare the solution
Gas samples: similar to liquid sampling technique

Monochromators in IR Spectroscopy

Prisms and windows made of glass, fused silica, lithium fluoride, calcium fluoride, sodium chloride, silver chloride, potassium bromide, etc.
Sodium chloride prism: used for measurements at 4000-650 cm⁻¹, potassium bromide prism: used for measurements at 400 cm⁻¹

Detectors in IR Spectroscopy

Bolometer: most common detector, provides an electric signal by a change in resistance of the metallic conductor with temperature
PbS or PbTeO₃ layer: used as coating material, with a long wavelength sensitivity limit of 3.5μ and 6μ, respectively

Recorder in IR Spectroscopy

Records the spectrum obtained from analyzed substances
Collector electrode: well shielded from stray ions, records peaks of all sizes

Applications of Mass Spectrometry

Analysis of proteins and protein complexes, sequencing of peptides
Environmental analysis, drug discovery, pharmacokinetic and pharmacodynamics analysis, metabolite screening
Forensic applications, disease screening, drug therapy monitoring, cancer screening, and diagnosis
Combines with gas chromatography (GC) for sample analysis, called the hyphenated technique

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Description

Learn about the sampling techniques used in IR spectroscopy for liquid and gas samples, as well as the use of alkali metal halide cells and organic solvents like CCl4 and CS2. Discover the specific regions in which CCl4 and CS2 are useful in spectroscopy.

IR Spectroscopy: Liquid and Gas Sampling Techniques

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