(P) Lec 5: Analytical Techniques in CC Flashcards
The 4 analytical techniques MAINLY used in the laboratory, except:
A. Electrophoresis
B. Osmometry
C. Turbidity
D. Nephlometry
E. NOTA
B
colorimetry, volumetric, turbidimetry, nephelometry, and electrophoresis
Transmitted via EM waves characterized by its frequency and wavelength
Energy
Analytes when placed in a machine are converted into?
energy
Wavelength
The distance between 2 successive peaks and is expressed in?
nanometer (nm)
TOF. Some analytes require specific wavelengths for their measurement.
T
3 regions where measurements are done
UV, Visible and Infrared region
Wavelength
less than 400 nm
UV Region
Wavelength
400 nm to 700 nm; majority of the analytes are measured here
Visible Region
Wavelength
TOF. Infrared (IR) Region has more than 800 nm.
F (700)
The Relationship Between Wavelength and Energy is Described by what formula?
E = hv
No. of vibrations of waves per second created during analysis
Frequency
TOF. Frequency is DIRECTLY proportional to wavelength and energy.
F.
Frequency is inversely proportional to wavelength and energy
Frequency
TOF. The lower the wave frequency, the longer the wavelength and energy.
T
Frequency
TOF. Wavelength and energy are directly proportional with each other.
T
Represent the wavelength in nm at peak transmittance of the analyt
Nominal Wavelength
Light that completely passed through the sample is called?
Peak transmittance
TOF. A slight error in adjustment can introduce significant errors in absorbance readings.
T
wavelength indicated on the control dial being the actual wavelength of light that has passed through (transmittance) the monochromator
Wavelength Accuracy
Wv accuracy
wavelength indicated on the control dial being the actual wavelength of light that has passed through (transmittance) the?
monochromator
Used to check for wavelength accuracy and proper calibration (quality control)
Didymium or Holmium Oxide Filter
- Verifies the absorbance accuracy on linearity
- Ensures correct readings on the samples in machines
Neutral Density Filters and Dichromate Solution
→ the color of the solution has an effect on the reading of the results
Colorimetry
This instruments measure light intensity without considering the wavelength (simple)
Photoelectric Colorimetry
this uses the isolation of discreet portions of the spectrum or wavelength for measurement purposes
spectrophotometry or filter photometry
photoelectric Colorimetry
Photoelectric Colorimetry
Two types of measurement:
- Spectrophotometric Measurment
- Photometric measurement
- The measurement of light intensity in a narrower wavelength (narrow range)
- May be on the UV, visible, or IR region
Spectrophotometric Measurement
methods of measurement
Measurement of light intensity
Photometric measurement
it’s also actually applicable to spectro also
TOF. Photoelectric measures the amount of light transmitted by a solution to determine the concentration of the light-absorbing substance in the solution
F (Spectrophotometry)
Spectrophotometry
The light that passes through the sample
Light transmitted
Spectrophotometry
Follows what principle?
principle of Beer’s Law
Beer’s Law
TOF. The concentration of an unknown substance is Directly proportional to the absorbed light (absorbance or optical density.
T
Spectrophotometry
TOF. The concentration of the unkown substance is directly proportional to the amount of transmitted light (transmittance)
F (indirectly)
TOF. Beer’s law mathematically established the relationship between CONCENTRATION and ABSORBANCE.
T
Spectro
TOF. a sample that is darkly colored/turbid, has higher concentration
T
Spectrophotometry:
TOF. If you introduce the light on it, the lightt absorbance is also?
increased
TOF. As light absorbance is increased, the transmitted light is low.
T
If majority of the light is already absorbed, the amount of light that passes through it will be much lower
TOF. A sample that is lightly colored/clear has a high concentration and high light transmittance.
F (low concentration; high light transmisttance.
→ aka optical density
→ amount of light absorbed by the solution
→ proportional to the inverse logarithm of transmittance (reflected light)
Absorabnce A
TOF. Absorbance (A) is proportional to the DIRECT log of transmittance (reflected light)
F (inverse)
Absorbance (A)
mathematically derived from?
%T (Percent transmittance)
Absorbance
FORMULAE (3)
A = abc
A = 2 - log%T
A = -logT
A - absorbance
a - molar absorptivity (compound absorptivity under standard conditions)
b - length of light through the solution
c - concentration of absorbing molecules or solutions
Formula for the concentration of the unknown
Cu = Au/As x Cs
TOF. The absorbance portion is provided by the machine using the abc formula.
T
Absorbance standard; ang need lang natin hanapin is Cu, la ka na pake sa iba
TOF. In the laboratory, we receive the concentration of the known derived from the absorbance formula.
F (unknown)
Formula of Percent Transmittance (%T)
%T = It/Io x 100
ratio of the radiant energy transmitted (T) divided by the radiant energy incident in the sample (I)
kahit ‘wag na kabisa kasi sabi galing lang rin naman sa machine ‘to makukuha
Percent Transmittance (%T)
It
transmittance of light through the sample
Percent Transmittance (%T)
Io
transmittance of light striking the sample
TOF. if the sample is blank/clear, light can pass through it completely, assuring a 90% transmittance.
F (100%)
Single Beam
A. the simplest type of absorption spectrometer
B. designed to make one measurement at a time at one specified wavelength
C. absorption maximum or wavelength of the analyte must be known in advance when used
D. AOTA
correct where
D
Double beam spectrophotometer
- An instrument that splits the monochromatic light into 2 components: beam for a sample and a beam for a reference solution
- the sample absorbance can be recorded directly as the electrical output of the sample beam
Regular double beam
Regular Double Beams
This beam corrects for the variation in the light source intensity
The second beam (that passes through the reference solution or blank)
→ uses 2 photodetectors for the sample beam and reference beam
Double Beam in Space
→ uses 1 photodetector and alternately passes the monochromatic light through the sample cuvette and then through the reference cuvette using a chopper or rotating sector mirror
Double Beam in Time
THE 6 COMPONENTS OF A SINGLE OR DOUBLE BEAM CONFIGURATION SPECTROPHOTOMETER
Stable source of radiant energy (light source)
Filter that will isolate a specific region of the EM spectrum
Sample holder
Radiation detector
Signal processor
Read-out device
PARTS OF THE SPECTROPHOTOMETER
→ provides polychromatic light and must generate sufficient power to measure the analyte of interest
→ an intense beam of light is directed through the monochromator in the sample
Light/Radiant Energy
Light/Radiant Energy
to give accurate absorbance measurements throughout its absorbance range, the response to a change in light intensity should always be?
linear
Light/Radiant Energy
TOF. If the light changes and the intensity continuously increase, it should decrease after some time.
F (kapag increase, increase lang, same for decreasing)
Light/Radiant Energy
→ emits radiation that **changes in intensity (is flexible) **which should be linear
→ the most widely used in the laboratory
Continuum Source