What is the definition of Spectrophotometry?
measurement of the intensity of light at selected wavelengths (absorption, emission)
What does "c"=
velocity - speed of light in a vacuum ( 3 x 1010 cm/s)
What does "v"=
frequency of light cycles/sec
What does "λ"=
wavelength in cm
What is the definition of wavelength?
It is the distance that a wave propagates in one period or the distance between wave crests.
What is the definition of frequency?
is the measurement of the number of occurrences of a repeated event per unit of time.
What does "c"=
speed of light 3 x 1010 cm/s
What does "λ"=
wavelength (nm)
What does "h"=
Planck’s constant 6.62 x 10-34 Joules•s
What does "E"=
Energy (joules)
What is absorbance?
It is the capacity of a substance to absorb radiation.
What is transmittance?
Fraction of the incident light reaching the detector.
Formula for calculating absorbance.
A=2-log%T
What is Lambert’s Law?
The fraction of light absorbed is proportional to the thickness of the absorber or the path length
What is Beer’s Law?
the concentration of a substance is directly proportional to the
amount of light
absorbed.
What does "A"=
absorbance
What does "ε"=
molar absorptivity; the absorbance of 1 M solution of pure substance through a 1 cm light path at a given wavelength;
What does "b"=
light path in cm
What does "c"=
concentration of absorbing compound (mol/L)
Formula for calculating concertation using Beer=Lambert equation?
C = A/(L x Ɛ)
What does "Cu"=
concentration of unknown compound
What does "Cs"=
concentration of standard
What does "Au"=
absorbance of unknown compound
What does "As"=
absorbance of standard
What are the function of prisms?
separates light into a continuous spectrum and provides optical efficiency
What are the function of Monochromators?
isolate light of a desired wavelength and exclude other wavelengths
What is the function of diffraction gratings?
has low light scatter and is accurate at selecting the correct λ
What are the function of Lenses and slits?
used to adjust the amount of light and the λ that reaches the detector
What is bandpass?
Range of wavelengths that passes through the exit slit of the monochromator or filter
What is stray light?
Light reaching the detector that is outside the band of wavelengths
transmitted by
the monochromator.
What is chemiluminescence?
light emitted when an electron returns from a higher energy level to a lower energy level. Caused by a chemical reaction when the product is formed from the oxidation of an organic compound
What is Electrochemiluminescence?
emission of light produced during electrochemical reactions in solution
What is turbidity?
Undissolved particles that are suspended in solution can make the solution cloudy
Nephelometry has the following characteristics.
- More sensitive at low concentration of Ag-Ab complexes
- Special instrumentation required to have detectors at a 30° and 90° angle
- directly proportional to the concentration of the analyte
Turbidimetry has the following characteristics.
- Difficult to measure small changes in absorbance
- Performed easily on photometers or spectrophotometers
- Require little optimization
- inversely proportional to the concentration of the analyte
Atomic Absorption Spectrometry has the following characteristics.
- Detects light absorption
- Requires light source
- Temperature in the atomizer is adjusted to atomize atoms when electrons are in the ground state
Atomic Emission Spectrometry has the following characteristics.
- Detects light emission
- Doesn’t require a light source
- Temperature in the atomizer is adjusted to atomize atoms and excite electrons to higher energy levels
Tungsten light bulb is used for measurements in...
the visible light spectrum
Hydrogen & deuterium is used for measurements in...
UV region (200 – 400 nm)
A photodiode is....
Is a type of photodetector capable of converting light into either current or voltage.
What is the definition of atomic absorption spectroscopy?
A technique in which the absorption of light by free gaseous atoms or ions in a flame, furnace, or plasma is used to measure concentration
What is the definition of atomic emission spectroscopy?
A technique in which the emission of light by thermally excited atoms or ions in a flame, furnace, or plasma is used to measure concentration.
What is the definition of atomization?
The process in which a compound is decomposed into atoms at high temperature.
What is the definition of background correction?
In atomic spectroscopy, a means of distinguishing signal due to analyte from signal due to absorption, emission, or scattering by the flame, furnace, plasma, or sample matrix.
What is the definition of Boltzmann distribution?
The relative population of two states at thermal equilibrium:
What is the definition of a chemical interference?
In atomic spectroscopy, any chemical reaction that decreases the efficiency of atomization.
What is the definition of a graphite furnace?
graphite tube that can be heated electrically to about 2 500 K to atomize a sample for atomic spectroscopy.
What is the definition of an hollow-cathode lamp?
One that emits sharp atomic lines characteristic of the cathode material.
What is the definition of an inductively coupled plasma?
A high-temperature plasma that derives its energy from an oscillating radio-frequency field. It is used to atomize a sample for atomic emission spectroscopy.
What is the definition of ionization interference?
In atomic spectroscopy, loss of signal as a result of ionization of analyte atoms
What is the definition of isobaric interference?
In mass spectrometry, overlap of two peaks with nearly the same mass. For example, 41K+ and 40ArH+ differ by 0.01 atomic mass unit and appear as a single peak unless the spectrometer resolution is great enough to separate them
What is the definition of a matrix?
The medium containing analyte (that is, everything in a sample other than the analyte). For many analyses, it is important that standards be prepared in the same matrix as the unknown.
What is the definition of a spectral interference?
In atomic spectroscopy, any physical process that affects light intensity at the analytical wavelength. Created by substances that absorb, scatter, or emit light at the analytical wavelength
What is Zeeman background correction?
Amplifier is used to subtract out the light from lamp and background flame light to detect atomic absorption.
What are the 3 options of returning to the ground state?
1. Quenching
2. Fluorescence
3. Phosphorescence