The Electromagnetic Spectrum

Questions and Answers

What is the primary purpose of the electric sector analyzer (ESA) in mass spectrometry?

To separate ions based on their charge-to-mass ratio.

To fragment ions into smaller molecules.

To detect ions by collecting their charge.

To accelerate ions to a uniform velocity. (correct)

What is the relationship between the radius of curvature (Re) of an ion's trajectory in the electric sector analyzer and the accelerating voltage (v) and electrostatic field (E)?

Re is directly proportional to v and inversely proportional to E. (correct)

Re is inversely proportional to v and directly proportional to E.

Re is inversely proportional to both v and E.

Re is directly proportional to both v and E.

Why do ions exiting the electric sector analyzer have different kinetic energies, despite having the same velocity?

The ions have different initial kinetic energies.

The ions have different masses. (correct)

The ions are subjected to different electric fields in the ESA.

The ions have different charges.

What is the function of the magnetic sector analyzer (MSA) in mass spectrometry?

To separate ions based on their mass-to-charge ratio. Signup and view all the answers

What is the advantage of using a double focusing mass spectrometer (electrostatic + magnetic fields) for mass analysis?

It can distinguish between compounds with the same nominal mass but different accurate mass. Signup and view all the answers

Which of the following is NOT a characteristic of ion detectors used in mass spectrometry?

They must be able to accelerate ions to a high velocity. Signup and view all the answers

What is the main reason for using a stainless steel plate in the electric sector analyzer?

All of the above. Signup and view all the answers

Which of the following is a key advantage of using an electric sector analyzer (ESA) for energy analysis in mass spectrometry?

It can accelerate ions to a uniform velocity. Signup and view all the answers

What happens to absorbance values when the concentration of a substance is too high?

They exceed the linear range. Signup and view all the answers

To measure low concentrations of non-colored substances, which method is appropriate?

Using a cell with a larger path length. Signup and view all the answers

What is the maximum absorbance wavelength for proteins due to the presence of specific amino acids?

280 nm Signup and view all the answers

Which of the following components is NOT typically found in a spectrophotometer?

Chromatography column Signup and view all the answers

What modification might be made to experimental parameters when the absorption is too high?

Diluting the sample or reducing path length. Signup and view all the answers

Which of the following reactions can help generate a measurable substance with absorption in the visible or UV range?

Dehydration and condensation reaction. Signup and view all the answers

Which of the following wavelengths corresponds to the absorption of nucleic acids?

255-260 nm Signup and view all the answers

What role does a monochromator play in a spectrophotometer?

It separates light into different wavelengths. Signup and view all the answers

What is the key principle underlying the use of tables compiled for fragmentation patterns in the GNPS platform?

To identify unknown compounds by comparing their fragmentation patterns to those in the database. Signup and view all the answers

Which of the following is NOT a requirement for obtaining a mass spectrum?

Simultaneous detection of all ions in the sample. Signup and view all the answers

Why is the accurate determination of the molecular ion to four decimal places important for chemical structure elucidation?

It helps to distinguish between isomers with similar fragmentation patterns. Signup and view all the answers

What is the significance of the base peak in a mass spectrum?

It represents the most abundant ion in the spectrum, providing information about the most stable fragment. Signup and view all the answers

What is the primary purpose of the resolving power of a mass spectrometer?

To accurately determine the mass-to-charge ratio of ions. Signup and view all the answers

How does the height of a peak in a mass spectrum relate to the abundance of ions?

The height is directly proportional to the abundance, with taller peaks indicating higher abundance. Signup and view all the answers

What is the primary advantage of using mass spectrometry for chemical structure elucidation?

It is a highly sensitive technique that can analyze small amounts of complex samples. Signup and view all the answers

Which of these statements is TRUE regarding the parent peak/molecular ion peak (M+) in a mass spectrum?

It represents the analyte molecule that has not undergone fragmentation. Signup and view all the answers

What is the wavelength range for the ultraviolet (UV) region of electromagnetic radiation?

200-400 nm Signup and view all the answers

Which color of light corresponds to the lowest wavelength in the visible (VI) region?

Violet Signup and view all the answers

If a substance absorbs light at a wavelength of 500-520 nm, which color will it appear?

Red Signup and view all the answers

What is the relationship between wavelength (λ), speed of light (c), and frequency (v) as defined in the equation λ = c/v?

Wavelength is inversely proportional to frequency. Signup and view all the answers

When white light is passed through a colored substance and absorbs a specific wavelength, what color will it appear?

It appears complementary to the absorbed wavelength. Signup and view all the answers

Which of the following statements about infrared (IR) radiation is true?

It has longer wavelengths than ultraviolet light. Signup and view all the answers

What is the wavelength range for the radio-wave (RW) region of the electromagnetic spectrum?

1-5 m Signup and view all the answers

If a solution appears blue, what color of light is being absorbed?

Reddish-orange Signup and view all the answers

Which of the following statements accurately describes the process of ion formation in mass spectrometry?

The removal or addition of a proton (H+) to a molecule results in the formation of an ion, with the mass of the resultant ion differing by ± 1 from the original entity. Signup and view all the answers

Why is positive ion electron impact (EI) mass spectrometry more common than negative ion EI mass spectrometry?

The ionization process produces a significantly larger number of cations than anions. Signup and view all the answers

What is the difference in mass between the original entity and the resultant ion when a proton (H+) is added to a molecule?

The mass of the resultant ion will be 1 unit more than the original entity. Signup and view all the answers

In chemical ionization, which of the following ions are commonly used to form adducts with molecules?

NH4+ and CH5+ Signup and view all the answers

Which of the following statements accurately describes the behavior of cations in a mass spectrometer?

Cations are attracted to a negative electrode and repelled from a positive electrode. Signup and view all the answers

How does the efficiency of electron capture to form an anion compare to the efficiency of removing an electron to form a cation?

Electron capture is less efficient than removing an electron. Signup and view all the answers

Study Notes

Electromagnetic Radiation

Includes radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays.
Regions divided based on wavelength (λ):
- Ultraviolet (UV): 200-400 nm
- Visible (VI): 400-700 nm
- Infrared (IR): 700 nm-500 µm
- Radio waves (RW): 1-5 m
Visible light colors vary by wavelength:
- Violet and blue correspond to lower λ
- Orange and red relate to higher λ

Wavelength Definition

Wavelength (λ) is the distance between adjacent wave peaks.
Calculated using the formula: λ = c/v
- c = speed of light
- v = frequency of light

Color Perception and Absorption

When white light interacts with colored substances:
- Specific wavelengths are absorbed, giving rise to complementary colors in the transmitted light.
- Example: Absorption of 420-430 nm appears yellow; 500-520 nm appears red.

Absorption and Concentration

Blue-colored substances absorb reddish-orange light and transmit blue light.
High molar absorptivity (ɛ) corresponds to higher absorbance at equivalent concentrations.

Extinction Coefficient Determination

Excessively high concentrations can lead to absorbance values outside the linear range.
Solutions include:
- Diluting the sample
- Modifying path length using spacers in sample holders.
Low concentrations may require longer path lengths to increase measurable absorbance.

Non-Colored Substances in Spectrophotometry

Organic substances often do not absorb visible light but can absorb in the UV region.
Key absorption points:
- Proteins: λmax at 280 nm (due to tyrosine and tryptophan)
- Nucleic acids: absorb around 255-260 nm
- Coenzyme NADH: absorbs at 340 nm.

Chemical Reactions and Absorption

Chemical reactions can produce substances measurable in UV/visible regions.
Techniques may involve using indicators or undergoing redox reactions.

Spectrophotometer and Colorimeter Components

Measure light absorption through:
- Light source
- Monochromator or filter (selects wavelength)
- Variable slit
- Sample holder
- Photo-detector
- Meter

Ionization Process in Mass Spectrometry

Ions are produced through the removal or addition of electrons.
Cations are generally produced more efficiently than anions, explaining the prevalence of positive ion mass spectrometry techniques.

Ionization Chamber Function

Ions created in the source chamber can be from removing protons (H+) or through adduct formation.
Ions vary in momentum and kinetic energy upon emerging from the chamber.

Analyzers in Mass Spectrometry

Electric sector analyzer helps in energy analysis of ions, utilizing two stainless steel plates.
The radius of ion trajectory is determined by the equation: Re = 2v/E.

Magnetic Sector Analyzer

Further analyzes ions with appropriate velocities for mass differentiation.
Double focusing mass spectrometers distinguish compounds of the same nominal mass.

Detection Mechanisms

Most detectors are impact types, requiring a surface for ion collection.
Detectors neutralize charge through electron collection or donation.

Mass Spectrometry Key Features

Mass spectra display peaks corresponding to m/z values of ions.
Peak height indicates relative abundance, with the parent peak representing the original analyte.

Resolving Power

Defined as the ability to separate ions of similar mass.
Influenced by slits width and requires producing ions in a gaseous phase, accelerating them through electric fields, and detecting them sequentially.

Applications of Mass Spectrometry

Useful for identifying chemical structures and qualitative analysis of organic molecules.
Accurate molecular ion measurement assists in determining unique molecular formulas.

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Description

This quiz covers the different regions of the electromagnetic spectrum, including radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays, classified by their wavelengths.