Module 5 Flashcards
(29 cards)
What is the purpose of calibration curves/standard graphs?
To determine the concentration of unknowns.
What info is required on a calibration curve?
Analyte name
Name of analysis method (reagent)
Instrument name/number
Date
Wavelength
Tech ID
How are samples with readings above the linear range read?
They must be diluted, the absorption reread and calculated from the calibration curve and multiplied by the dilution factor.
What else is the linear range known as?
Analytical or reportable range.
When do instruments need to have new calibration curves made?
If a component is changed.
If new/different reagents are used.
What are standards?
Pure solutions of analyze with known or predetermined concentrations.
AKA calibrators
What is stock standard?
Concentrated standard used to make working standards.
Allows for longer storage.
Dilutions are easier to prepare.
What are working standards?
Dilutions of the standard stock prepared in smaller volumes to create a calibration curve.
Why is light transmitted less than incident light?
Loss of radiation due to:
Absorption of the substance to measured
Scattering of light
Reflection of the cuvette wall
Absorption by the solvent or reagent
Interfering substances
What is a reagent blank?
Contains reagent and diluent instead of sample.
What is the purpose of the reagent blank?
Accounts for the colour of the reagent.
Used as zero concentration standards.
Set as 0A
What is a sample blank?
Contains the sample but diluent instead of reagent.
What is the purpose of a sample blank?
Accounts for the colour of the sample.
When are sample blanks required?
Coloured samples that contain interfering substances.
What are controls?
Commercially prepared samples with known concentrations of various analytes.
What is the purpose of controls?
Carried through procedure as a patient sample to detect procedural errors.
If a control result falls outside the control range it indicates a problem.
When are controls used?
For every procedure performed.
What is the matrix of the control?
The same as the patient samples.
What is slope?
The direction and steepness of the curve.
Slope=rise/run or change in y/change in x
What is the intercept?
Where the curve intercepts the x or y axis.
y = mx + b
What is the intercept of the reagent blank?
The origin
What is sensitivity?
The ability to detect or measure small changes in concentration.
How does sensitivity affect the absorbance measured?
Small changes in concentration cause big changes in the signal measured (absorbance).
Steeper slopes- better sensitivity
Max A gives the max sensitivity
What is a calibration curve?
Plot of the absorption of at least three standards against their known concentration.
X- axis- concentration
Y-axis- absorbance
