Flashcards in Spectrometry Deck (31)
1. What is the identity or properties of the drug or substance?
2. Separation, isolation, or purification required in most cases, but not all
1. How much substance is present
Major identification technique involves the interaction of the molecules of interest with ____________________
Electromagnetic energy has properties of ________ and has ____________ and wavelengths
1. Properties of waves
2. Has frequency
1. Hertz (hz) (1 cycle/second), kilohertz (1,000 cycles/sec)
2. Think of it as how quickly it gets to you
2. Think of a typical wave going up and down
Example: standing on beach- every time waves hits you that's the frequency. Distance between the peaks and trophy is the wavelength
1 micron (u)
1 nanometer (nm)
10-9 meters (1 mu)
Most frequently seen in chemistry
1 angstrom (A)
The Electromagnetic Spectrum: Radio, tv, radar VS x rays and gamma rays?
1. Radio, tv, radar: lower frequency, long wavelengths
2. X rays and gamma rays: high frequency, short wavelengths
Wavelengths of the visible part of the spectrum in nanometers and in angstroms:
1. 390 nm-750 nm
2. 4300 A (violet)- 7000 (red)
The shorter the wavelength, the ____________ the frequency and the ___________ the energy
1. The greater the frequency
2. Higher the energy
Angstrom length (m)
As molecules are exposed to light (or other energy) they can absorb energy by:
1. Electromagnetic excitation: electrons in the molecule goes from low energy state to a higher energy state
2. Molecular vibrations: each compound has a natural vibration frequency
After a molecule is excited it can release the energy in various forms: (3)
1. Heat **** most common result
2. Rupture of molecule
3. Re-emission of energy as altered electromagnetic energy (fluorescence)
The useful parts of the spectrum are UV, visible, and ________ radiation?
1. Infrared radiation
UV and visible absorption:
1. Electronic absorption (electrons in molecules are excited to a higher energy state). Then they relax and emit energy
Infrared absorption is due to:
1. Vibrational energies of a molecule: bending, stretching, and rotation. (lower energy radiation)
Most molecules have chromophores that do what?
1. Absorb light.
2. Chromophores may be certain molecular groups, such as phenyl groups or double bonds
Basic instrument components: (4)
1. Energy source to produce radiation, usually UV or visible light by deuterium (UV) or tungsten lamp (visible)
2. A system to select limited part of spectrum (prism or grating)
3. Sample chamber
4. Detector (photomultiplier tube-converts light energy to electrical energy)
For any compound, absorbency is proportional to: (2)
1. The thickness of the cuvette (or light path)--- thicker=more absorption
2. Concentration of the compound
Absorption is dependent on the probability of radiation causing an electron being ___________ in the substance?
1. Electron being excited.
2. If coefficient is small, substance poorly absorbs light
Light intensity across a cell is exponential decay equation?
Log 10= IO/I = K X L / 2.303
I= emergent light
IO= incident light
K= constant for any pure compound
L= length of light path
Therefore, absorbance is proportional to the thickness of the cell (L)
Absorbance, extinction and optical density?
1. All mean the same thing, that light is being absorbed