ANALYTICAL METHODS AND INSTRMENTATION Flashcards
what is the 4 basic discipline of analytical chemistry
Spectrometry
Luminescence
Electroanalytic methods
Chromatography
what is under the spectrometry
spectrophotometry
atomic absorption spectrometry
mass spectrometry
what is under the luminescence
fluorescence
chemiluminescence
nephelometry
what is under the electroanalytic methods
electrophoresis
potentiometry
amperometry
what is under the chromatography
gas, liquid, and thin-layer
both spectrometry and luminescence is similar in using radiant energy, but what is the difference, how do we differentiate them both?
the light produced by S will then be converted into electrical energy for the signaling of the result while L is focused on the detection of the light as a potential marker of the analyte.
what are the 2 primary considerations in colorimetry analysis
Quality of color
Intensity of color
QUALITY AND INTENSITY
In spectro, light is either __ or ___
absorbed and transmitted
what is the similarity of spectrometry and luminescence
both uses radiant energy or light
relationship of the color of the result experimentation and the amount of analyte
directly proportional
is spectrophotometry a colorimetry method analysis?
yes
a type of method associated with the color produced in the experimentation.
colorimetry
- most commonly used light source in the near uv, near visible, and near infrared
tungsten filament
a kind of colorimetry that uses the eyes in determining the end point
Visual Colorimetry
solutions were able to get a colored reaction is because of the addition of
chromogen
one of the photoelectric colorimetry type which is about the
measurement of
light intensity in a much narrower wavelength. It
uses a device (prisms and/or gratings) to disperse
the source of light into a continuous spectrum
SPECTROPHOTOMETRY/ spectrophotometric measurements
photoelectric colometry used two instrument such as the
Spectrophotometry and filter photometry
a kind of colorimetry that uses equipment or electricity
Photoelectric Colorimetry
photoelectric colorimetry uses instrument such as the spectrophotometry and the filter photometry in order to ____
isolate the discrete portion of the spectrum for the purpose of measurement
one of the type of photoelectric colorimetry that is about the
measurement of light intensity of MULTIPLE WAVELENTH. It uses filter to
isolate part of the spectrum
FILTER PHOTOMETRY/ photometric measurement
monochromators used in spectrophotometry?
prism and diffraction grating
example of visual colorimetry
reagent strip
monochromators used in filter photometry or photometric measurement
filters
2 types of photoelectric colorimetry
spectrophotometric measurement
photometric measurement
They are PHOTONS of energy traveling in a wavelike manner.
Electromagnetic energy
The shorter the wavelength, the ____ the
electromagnetic energy.
lighter or heavier?
lighter
how photons are being transmitted?
Via electromagnetic waves
electromagnetic waves are characterized by the two named
frequency and wavelength
distance between peaks as light is envisioned to travel in
wavelike manner.
wavelength
number of vibrations of wave motion per
second
frequency
range of visible spectrum in nanometers
400 -700 nanometers
the relationship between wavelength and energy is described as/with
PLANCK’S FORMULA E=hv
what is the h and v in the plank’s formula?
h - constant (6.62 x 1027 erg sec)
v → frequency
wha is the relationship of the wavelength and the frequency at each other
they are inversely proportional to each other
represents the wavelength in nanometers at peak transmittance
nominal wavelength
a slight error in wavelength adjustments can introduce a ___
significant error in absorbance readings
wavelength accuracy is the wavelength indicated on the ___ is the actual wavelength of light passed by the monochromator
control dial
is used to check wavelength accuracy (wavelength calibration)
didymium or holmium oxide filter
for quality control what is the one we used to calibrate wavelength?
didymium or holmium oxide filter
it involved measurement of the light transmitted by a solution to determine the concentration of the light-absorbing substances in the solution
spectrophotometry
States that the concentration of a substance is directly
proportional to the amount of the light absorbed or
inversely proportional to the logarithm of transmitted
light.
Beer’s law or Beer Lambert’s law
this law Deals with the concentrations of a substance
beer’s law
ratio of the radiant energy transmitted, divided by
the radiant energy incident on the sample.
transmittance
what is the formula for the transmittance
%T = It/Iox100
It = light transmitted
Io = incident light
The amount of light absorbed by the molecule
absorbance
what are the 6 basic components of spctrophotometer
Light source
Device to isolate light of a desired wavelength
Cuvet
Photodetector
Read-out device
Data system
Provides radiant energy in the form of
visible or non-visible light that may pass through the
monochromator.
light source
2 types of spectrophotometer
single beam spectrophotometer
double beam spectrophotometer
It is the simplest type of absorption spectrometer.
Single beam spectrophotometer
It is designed to make one measurement at a time at one specified
wavelength
Single beam spectrophotometer
type of spectrophotometer
The absorption maximum of the analyte must be known in advance
when a ___ is used.
single-beam instrument
a type of spectrophotometer that only has 1 cuvette holder
single beam spectrophotometer
a type of spectrophotometer that Splits monochromatic light into two components
double beam spectrophotometer
double beam spectrophotometer has 2 beam,
the first beam is for __
and the second beam is for ___
1st - sample
2nd - blank solution
in the double beam spectrophotometer, we can add the additional beam which it can __
which it can corrects the variation of the light source intensity
in this type of spectrophotometry, the absorbance of the sample can be recorded directly as the electrical output of the sample beam
double-beam spectrophotometer
2 types of double beam spectrophotomeer
double beam in space
double beam in time
a type of double-beam spectrophotometer that has 2 photodetectors
for the sample and the reference beam
double beam in space
a type of double beam spectrophotometer that uses one photodetector
and alternately passes the monochromatic light
through the sample cuvet and then reference
cuvet using a chopper Sample
double beam in time
7 basic components of single or double-
beam configuration spectrophotometer:
- Stable source of radiant energy
- Filter that isolates a specific region of the electromagnetic spectrum
- Cuvets
- Sample holder
- Radiation detector
- Signal processor and
- Readout device
first part of the spectrophotometer
radiant or light source
It provides polychromatic light and must generate sufficient
radiant energy or power to measure the analyte of interest.
light/radiant source
An intense beam of light is directed through the
monochromator and the sample.
light/radiant source
To give accurate absorbance measurements throughout its
absorbance range, its response to change in light intensity
must be ____.
LINEAR
the ability to absorb energy n a particular wavelength is called
linear or line spectrum
what are the 2 types of light source
continuum and line source
a type of light source that emits radiation that CHANGES IN INTENSITY
continuum
example of continuum light source
tungsten, deuterium, and xenon lamps
this type of continuum light source is routinely used to provide UV radiation in analytic spectrometers
deuterium lamp
this type of continuum light source produces a continuous source of radiation which covers both UV and visible range
xenon discharge lamp
another type of light source that emits LIMITED RADIATION and
wavelength; uses an intense beam of light directed through the monochromator and the sample
line source
example of lamp under line source
mercury and sodium vapor lamps in spectrophotometer (UV and visible regions)
hollow cathode lamp (AAS - atomic absorption spectro)
last example we can use for line source
LASER (LightAmplification by Stimulated Emission of Radiation)l
a light source we can use for AAS - atomic absorption spectro
hollow cathode lamp
what are the factors we need to consider for choosing a light source
o Range
o Spectral distribution
o Source of radiant production
o Stability for the radiant energy
o temperature
what are the alternatives for tungsten bulb
+ Mercury arc (visible and UV)
+ Deuterium lamp (165nm) - UV
+ Hydrogen lamp - UV
+ Xenon lamp - UV
+ Merst glower -IR
+ Globar (silicone carbide) - IR
minimizes UNWANTED or stray light and
prevents the entrance of scattered light into the monochromator system
entrance slit
Stray light causes systematic error; causes loss of linearity
true or false
true
Isolate specific wavelength of light
monochromator
light radiation of a single wavelength
monochromator light
a monochromator of spectro
wedge-shaped pieces of glass, quartz, NaCl, or some
other material that allows transmission of light.
prism
Disperses white light into a continuous spectrum of
colors based on variation of refractive index for different
wavelength.
prism
the width of the spectral
transmittance curve at a point equal to ½ the peak
transmittance (spectral purity)
spectral bandwidth
the most commonly used type of monochromator
diffraction grating
has small grooves cut at such as angle that each groove
behave like a very small prism.
diffraction grating
wavelength are bent as they pass a sharp corner
diffraction grating
Advantage of gratings over prisms
Produces LINEAR SPECTRUM and therefore maintaining a
constant and pass which is simple.
Can be used in the regions of spectrum where light energy is absorbed by glass prism.
the 3rd type of monochromator used for filter protometry
filter
These are simple, least expensive, not precise but useful.
filters
These are made by placing semi-transparent silver films on
both sides of a dielectric such as magnesium fluoride.
filters
light waves enter
one side of the filter and are reflected at the second
surface
constructive interference
a type of monochromator that usually pass a wide band of radiant energy and have a
low transmittance of the selected wavelength.
Filters
It controls the width of light beam (bandpass)
exit slit
allows only a
narrow fraction of the spectrum to reach the sample cuvette.
exit slit
__ is the total range of wavelengths transmitted
bandpass
Accurate absorbance measurement requires a bandpass less than
___ the natural bandpass of the spectrophotometer.
1/2
EXPLAIN THE RELATIONSHIP OF THE BANDPASS AND THE RESOLUTION
narrower the bandpass, the greater the
resolution.
___ of the spectrophotometer is reflected by the
bandpass,
Spectral purity
It is also called absorption cell/analytical cell/sample cell.
Cuvet
It holds the solution whose concentration is to be
measured
CUVET
what are the kinds of cuvets
+ Alumina silica glass-
+ Quartz/plastic
+ Borosilicate
+ Soft glass
a type of cuvet that is most commonly used (can be used
in 350-2000m)
alumina silica glass
a type of cuvet that is used for measurement of solution
requiring visible and ultraviolet spectra
quartz/plastic
a type of cuvet that do not etch
borosilicate glass
this cuvette is used for acidic solution
borosilicate glass
cuvette used for basic or alkalin
soft glass cuvette
Cuvets with ___ on their optical surface scatter light and should be
discarded.
scratches
Silica cuvettes transmit light effectively at wavelengths ___.
220mm
Alkaline solutions should not be left standing in cuvets for prolonged
periods because alkali slowly dissolves glass producing etching.
true or false
true
the path length of cuvets is ___cm, although much smaller path lengths
are used in automated systems.
1
To increase sensitivity, some cuvets are designed to have path lengths of
___cm, increasing the absorbance for a given solution by a factor of 10.
10
It detects and converts transmitted light into
photoelectric energy.
photodetectors
It detects the amount of light that passes through the
sample in the cuvet.
photodetector
It is the simplest detector; least expensive; temperature-sensitive
Barrier layer cell/Photocell/Photovoltaic cell
a type of detector used in filter photometers with a wide bandpass
Barrier layer cell/Photocell/Photovoltaic cell
it is a basic phototransducer that is used for detecting and measuring
radiation in the visible region
Barrier layer cell/Photocell/Photovoltaic cell
It is composed of selenium on a plate of iron covered with transparent
layer of silver, it requires external voltage source but utilized internal
electron transfer for current production - low internal resistance.
Barrier layer cell/Photocell/Photovoltaic cell
This cell typically has a maximum sensitivity at about 550 m and the
response falls off to about 10% of the maximum at 350 and 750 nm.
Barrier layer cell/Photocell/Photovoltaic cell
a photodetector that contains cathode and anode enclosed in a glass case.
phototube
a photodetector that has a photosensitive material that gives off electron
when light energy strikes it.
phototube
a photodetector that requires an external voltage for operation
phototube
the most common photodetector is the - measures visible and UV
regions.
photomultiplier tube
a detector that has excellent sensitivity and has a rapid response - detects very low
levels of light
Photomultiplier tube
a photodetector that should never be exposed to a room light because it will burn out.
photomultiplier tube
a detector that is not as sensitive as PMT but with excellent linearity
photodiode
a photodetector that measures light at a multitude of wavelengths - detects less
amount of light
photodiode
a photodetector that has a lower dynamic range and higher noise compared to PMT.
photodiode
a photodetector that is most useful as a simultaneous multichannel detector
photodiode
It displays output of the detection system
Meter or read-out device
example of the read out device
galvanometer
ammeter
LED Display
a technique that sets the reading to 0 or zero
blanking technique
means the blank contains serum but without the reagent to
complete the assay.
blanking technique
corrects absorbance caused by the COLOR OF THE REAGENTS - the
absorbance of reagents is automatically subtracted from each of unknown reading.
reagent blank
measures absorbance of the sample and reagent in the absence of the
end product, and corrects the measurement for optical interference (like
hemoglobin) absorbing the wavelength of measurement.
sample blank
a biomolecule that can interfere by increasing light blocked turbidity
Lipids
turbidity readings on a spectrophotometer are greater in the ____ region than in
the ___region of the spectrum
blue; red
