Lecture 1 - chemical techniques Flashcards
what is an analyte
the chemical/substance of interest to be detected in the test
what measurable characteristics must analytes have
light emission
light absorbance
charge
what must there be for a quantification of an analyte
predicatable relationship between the measureable effect and the amount of analyte
what is accuracy
closeness of a results to the true value
what is precision
closeness of repeated results
what is sensitivity
smallest amount that can be accurately measured
what is specificity
ability to measure only the analyte of interest
what are the qualities of an analytical test
robustness - no interferences
ruggedness - consistency w small changes
time - how many can happen at the same time
cost - machines
what is robustness
consistency in the presence of interferences
what is ruggedness
consistency throughout small changes in conditions
what is an immune complex
the specific reaction between an antibody and an antigen
antigen-antibody complex
what does the amount of immune complex indicate in immunoassay
the amount of analyte in the sample
what is a tracer
a radioactive isotope label on an assay component
what are radioactive isotopes
unstable variants of atoms that spontaneously transform to a more stable state emitting energy
what can radioactive isotopes be measured by
using a Geiger counter or scintillation counter
what are common isotopes
iodine: I125, I131
tritium: 3H
what does enzyme labes use
catalytic properties of enzymes to generate coloured, fluorescent
or luminescent compounds from the substrate
what can single enzyme labels produce
many detectable product molecules which enhances assay sensitivity
what are common enzyme labels
alkaline phosphatase
horseradish peroxidase
why are coloured dyes used in lateral flow and pregnancy test
labels the specific antibody for the analyte
what are colorimetric assays detected by
spectrophotometer
what does a fluorphore do
absorbs light at one wavelength and reemits light at a longer wavelength
what do lanthide chelates do
absorb light and then use that energy to emit fluorescence - can be detected with a fluorimeter
what can break down a chemiluminescent substrate
enzymes such as adamantyl phosphate
what detects light emission
luminometer
why are immunoassays useful in a clinical lab
highly specific
sensitive
can be manufactured on a large scale
can be automated
what do labs use immunoassay for
hormones
antibodies
pregnancy
urine albumin
what is optical density measured by
passing a beam of white light through the mixture and measuring the amount of absorbance
what happens in photometric assay
a reagent is added to the sample, resulting in a reaction that causes the mixture to undergo an optical change, which can be measured
what is an example of photometric assays
bradford essay to measure protein concentration
whats the difference between a photometer and a spectrophotometer
spectro uses light of a single wavelength, rather than white account
why is absorbance an idea method in the lab
quick and easy
cheap
reproducible
readily integrated into automation
what is turbidimetry
measure of the cloudiness of a sample
how is turbidimetry measured
light is passed through a sample and scattered or absorbed by solid particles in the suspension
what does the amount of scattering in turbidimetry depend on
concentration of particles
size of particles
distribution of particles
wavelength of light source
does turbidimetry follow the Beer-Lamber Law
No
what does ion selective electrodes compare
the electric potential generated across a membrane by specific ions (Eise) to a reference electrode (Eref)
what is the principal of potentiometry
The strength of this net charge (ECell) is directly proportional to the concentration of the selected ion.
