Quantitative Analysis Flashcards
Quantitative/qualitative analysis
Any method used for determining the amount of a chemical in a sample.
Sample
The substance that is being tested, if collected from a patient it is also called a specimen.
Assay
The testing method used for measuring a specific analyte. There can be multiple assays for one analyte.
Analyte
The “thing” that is being measured (ex. bilirubin). Most tests are named after the analyte being tested, the main expectation being panel tests.
Standards
Substances that are used to set calibration of an instrument (“knowns”)
Controls
Substances that are used to ensure quality test results are being evaluated (“knowns”)
Calibration
The process that established a relation between a measurement tools output and the quantity that you are trying to measure with that tool.
Wavelength
The distance between two crests. Measured in nanometers for visible light (nm=1 x 10-9). When speaking about visible light this affects the lights colour.
Frequency
The number of peaks that pass through a given point in one second (more peaks = higher frequency).
Frequency and wavelength are inversely related.
Amplitude
The height of a crest from the centre line, the higher the amplitude the higher the energy. When speaking about visible light this affects the light intensity. (higher amplitude = higher intensity)
Photons
Bundles of energy that allow light to travel. Exhibit both particle and wave behaviour.
“In Phase”
When the troughs and peaks of two waves line up.
Describe the relationship between energy, velocity, wavelength, and frequency for an EM wave (Planck’s equation)
E=hv
h = Planck constant (6.63 x 1034 J/s)
v= Velocity
The energy of a lightwave is directly proportional to its frequency, and inversely proportional to its wavelength.
State the speed of EM radiation in a vacuum
c = 299,792,458 m/s.
List different types of EM radiation in order from lowest to highest energy
Radio
Microwave
Infrared
Visible
(Red, Orange, Yellow, Green, Blue, Violet)
Ultraviolet
X-Ray
Gamma Ray
State the range of wavelengths for visible light
380 nm - 780 nm
Violet, Blue, Green, Yellow, Orange, Red
State the approximate wavelengths for the different colours of visible light
Violet (380-450)
Blue (450-485)
Cyan (485-500)
Green (500-565)
Yellow (565-590)
Orange (580-625)
Red (625-750)
monochromatic
Containing only one colour
Polychromatic
Containing multiple colours (ex. White light)
Transmission
The light that travels straight through the matter, no change in direction or energy.
Absorption
Light that is taken into the medium. Light energy is transferred to the atoms, ions, and molecules in said medium.
Reflection
Light that is bounced back from a solid surface.
Scatter
Light that hits particles within the matter and is bounced in various directions.
Incident Light
Light Source
Discuss the absorption of EM radiation at the atomic level
When a chemical absorbs light, electrons take in the energy from the light source and enter an excited state. Only certain wavelengths are absorbed because electrons cannot absorb particle energy from photons, so the wavelengths that are absorbed are only the ones with the specific amount of energy that can move an electron from ground state up energy levels.
Describe absorption spectra and how they are used
Absorption Spectra are graphical representations of the relationship between absorbance and wavelength. It shows you the wavelengths absorbed the most and the least. This can be used to determine analyte concentration.
path length
How long light travels through a medium (ex. Cuvettes are 1 cm)
absorptivity and molar absorptivity
Refers to a substance’s ability to absorb light of a specific wavelength.
Describe the relationship between absorbance and transmittance
Absorbance refers to the amount of light a material absorbs, whereas transmittance is the amount of light allowed to pass through the material.
Calculate absorbance from transmittance values
A=-log T
A=2-log%T
State Lambert’s law
Absorption increases proportionally with the light path length. (solutions must be identical in order to use Lambert’s Law)
State Beer’s law
Absorbance increases proportionally as concentration increases.
State the combined Beer-Lambert law and define each of the variables
For a given material sample path length and concentration of the sample are directly proportional to the absorbance of light.
A=ebc or A= abc
A = Absorbance
e = molar absorptivity (L×mol-1×cm-1)
a = absorptivity (L×g-1×cm-1)
b = path length (cm)
c = concentration (mol/L or g/L)
Discuss the required conditions for using Beer’s law
Substances must be identical, and concentration must linearly increase.
Four methods for determining concentration of an unknown:
Graphical analysis
Regression analysis
Single standard formula
Beer’s Law equation
What is the Single Standard Equation
(Cu/Cs) = (Au/As)
Cu= Concentration unknown
Cs= Concentration standard
Au= Absorbance unknown
As= Absorbance standard
What are the restrictions of the single standard formula?
The single standard equation can only be used if:
1) The method is known to obey Beer’s Law. (concentration and absorbance must have a linear relationship.)
2) The concentration of the unknown does not exceed the linearity of the method.
What is a standard curve?
a specific type of graph that is used to determine concentrations of unknowns.
A standard curve is specific for the analyte being tested.
How do you create a standard curve?
To create a standard curve:
1) The absorbance values of standards are plotted against their known concentrations.
2) Measure the absorbance of the unknown sample.
3) Read the absorbance of the standard curve to determine the unknown concentrations.
What is regression analysis?
Using software to plot absorbance values of standards against their known concentrations. This is more accurate than plotting by hand.
What is graphical analysis?
When a graph is used to show a relationship between two or more variables.
How many decimal places should absorbance values have?
3
Ground state
The most comfortable energy level for an electron
Excited state
When an electron takes a higher level of energy than the ground state.
Ionizing Radiation
These radiation types have so much energy that they can remove electrons from molecules, essentially creating ions. (high UV waves, gamma rays, and X-ray)
All light waves can be described by three measurable properties:
Wavelength
Frequency
Amplitude
