Lecture 27 Clinical Chemistry

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Lecture 27ClinicalChemistry
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Outline

• Helicopter visit
• Eye Clinic visit
• Ph Meter
• CO2 sensor
• Oxygen Sensor Clark Electrode
• Ion Detectors
• Blood analysis
• Antibody test for disease history
• Coagulation tests
• Genetic marker tests
• DNA tests

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Helicopter Notes

• Helicopters do not make money but bring in
  patients who then are money makers
• Helicopter are mini ERs
• Ventilators and respiration monitors
• Drug pack to treat patients
• Blood gas measurement
• Transport services special neonatal infant
  units

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Eye Clinic devices

• Refractory automated test
• Ocular pressure measurements
• Retinal Scan devices
• Laser surgery
• Corneal implants

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Ph Meters
Properties of glass at different Ph values
Note special glass membrane that allows only H
to pass. This causes small voltage across
membrane which is directly related to Ph
Left electrode has special glass. Right
electrode is GND reference
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Carbon Dioxide Meters

• Carbon dioxide sensors are examples of dual
  membrane probes
• Carbon dioxide water yields carbonic acid H2CO3
• This is soluble in water forming H and HCO3-
• The first membrane is passes Carbon Dioxide only
• Then the second membrane is a Ph sensor with
  measure the Hydrogen concentration of carbonic
  acid reaction
• This electrode system is VERY slow due to the two
  stages of diffusion

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Carbon Dioxide - Capniograph

• Carbon dioxide also has an color spectrum when it
  absorbs radiant energy at 10 microns
• By using a capniograph, the absorption is
  measured and the concentration of carbon dioxide
  (in gas) can be measured

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Mass Spec

• Mass spectrophotometers can be used to measure
  the concentration of various elements in a gas.
• The elements in the gas are ionized and then
  accelerated past a magnet.
• Mass of the element with bend in the magnetic
  field and strike a detection surface at different
  position
• Oxygen, Carbon dioxide, Nitrogen etc are detected
  in this way

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Clark Oxygen sensor
On left is diagram of apparatus. The calomel
electrode is the reference ground. Both the
current I and voltage V are monitored
On right is the voltage/current plot. Note that
for particular V/I plots the curve depends on the
oxygen concentrate. Measuring the curve gives the
Oxygen concentration in fluid.
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Sensor to measure oxygen concentration
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Glucose enzyme monitors (for diabetes patients)

• Glucose in combination with oxygen will form
  gluconic acid hydrogen peroxide.
• If a small sample of blood in contact with oxygen
  is place next to a membrane permeable to oxygen
  then on the other side of the membrane an oxygen
  sensor (clark electrode) can monitor the oxygen
  level and infer the glucose concentration
• Other methods are used as well

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Liquid Ion-exchange Microelectrodes

• Intracellular microelectrode to monitor Calcium,
  Magnesium, Chloride and Potassium can be build by
  having a special membrane that passes only that
  ion.
• Then the electrode on the other side of the
  membrane will measure a small voltage
  proportional to the concentration of that ion

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Blood Coagulation

• This is important to determine proper dose of
  blood thiner. Too much can lead to internal
  bleeding. Too little can lead to clots.
• Blood is exposed to air and agitated. The time
  needed to clot is measured. One method uses a
  magnetic stirring process
• Several parameters of clotting are measured

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Antibody detection

• Needed to determine if patient has been exposed
  to different diseases and has developed
  antibodies to that disease
• Blood samples are mixed with special test
  compounds that change color if a particular
  antibody is present.
• Small changes can be detected optically

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Genetic tests

• DNA tests using TLC this measure the sizes of
  different genes as they migrate across a gel.
  The genes (which are charges) are expose to a
  high, pulsing voltage.
• Specific gene patterns are made into keys with
  a fluorescent tag. When these key are exposed to
  DNA strings and a match is found, the fluorescent
  tag can be detected

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The end

• Final exams will be available on May 2 - optional
  date May 4
• Project reports and late homeworks are due last
  day of finals May 9