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Medical LaboratoryInstrument
UNIT-3
BIO-CHEMICAL INSTRUMENT
SUJITH.M, LECTURER/EEE, VIDYAA VIKAS ENGG COLLEGE Ph.No. 9600286256
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Equipment
y Spectrophotometer
Is optical device that measure light absorption at various
wavelengths for a given liquid sample.
y Blood cell analyzer
Is a device to measures the number of red and white blood cells
per scaled volume.
The aperture impedance and flow cytometery
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Equipment
y Ph/ blood gas analyzer
Is a device which measure blood Ph, Po2, Pco2
y Chromatograph and Autoanalyzer
Is a electromechanical device used to separate, identify, andmeasure the concentration of substances in a liquid medium.
y Computer based record and operation system
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Electrophoresis
y Electrophoresis is the motion of dispersed particle
relative to a fluid under the influence of a spatially
uniform electric field
y This electro-kinetic phenomenon was observed for the
first time in 1807 by Reuss
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Principles of Gel Electrophoresis
y Electrophoresis is a techniqueused to separate and sometimespurify macromolecules -especially proteins and nucleicacids - that differ in size, chargeor conformation
y When charged molecules are
placed in an electric field, theymigrate toward either the positiveor negative pole according totheir charge. In contrast toproteins, which can have either anet positive or net negativecharge, nucleic acids have aconsistent negative chargeimparted by their phosphatebackbone, and migrate toward theanode.
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Definition
y Separation of DNA fragments according to
size, based on movement through a gel
medium when an electric field is applied.
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DNA negatively charged
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DNA cut up using restriction
endonucleases
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Make up the gel which the DNA will be
put into
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Dye added to the DNA
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Buffer solution added to the tank
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DNA samples loaded into wells
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Electrical current applied to the
chamber
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DNA is stained using ethidium bromide
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Colorimeter
The colorimeter is a filter photometer that measures the
color concentration of a substance in solution, this is
accomplished electronically by detecting the color light
intensity passing through a sample containing the reaction
products of the original substance and reagent
Eg: urine test
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Basic colorimeter analysisy Involves the precise measurement of light intensity.
y Transmittance is defined as:T= (I1/I0) x 100%
I2= T I1
I2=T2 I0
I0 is initial light intensity
I1 is first attenuated light intensity
I2
is second attenuated light intensity
T is the transmittance in percent
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Basic colorimeter analysis
y Absorbance is defined as:
A= log(I0/I1)=log 1/T
y Beers law
A= aCLL is cuvette path length
C is concentration of absorbing substance
a is absorbtivity (~ substance)
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Basic colorimeter analysis
y Concentration of unknown solution
C= Cs A/As
C is unknown concentrationCs standard concentration
A is unknown absorbance
As is standard absorbance
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Calibration
1. Ground the amplifier input V1 and adjust potentiometer
R4 and adjust potentiometer R4 for 0V 5mV at the
amplifier output.
2. Remove the ground and place reference concentration in
cuvettes 1 and 2
3. Adjust potentiometer (R1) for 0V 10mv at the
amplifier output.
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Calibration
4. Leave the reference concentration in cuvette 1 and replace
cuvette 2 with a cuvette containing the sample.
5. Read the unbalanced voltage on the meter in percentage
of transmittance or absorbance units.
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Calibration
y Example: if V1 = +1 mV with reference cuvettes and V1= +25 mV with reference and sample cuvette, R2 = 2k, R3 = 1 k
Calculate the voltage read on the meter display for bothconditions of V1.
Solution: Av = 1+ R2/R3 = 1+ 2/1 = 3
Av = Vm/V1
Condition 1: Vm = Av * V1 = 3 * 1mV = 3mVCondition 2: Vm = Av * V1 = 3 * 25 mV = 75 mV
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Maintenance
y Calibration
y Adjustment
y Replacement of burned-out lamp and photo detector
yElectronic problems are rare
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Medical Laboratory Instrumentation
Spectrophotometer
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Definition, Purpose, Use
y Spectrophotometer measures light absorption by a liquid
substance at various wavelengths.
y The Components of unknown material can be determined,
or the concentration of a number of known substances can be
measured.
y Eg: blood cell resistivity
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Operation, Calibration
y A monochromator uses a diffraction grating or prism to
disperse the light from the lamp (slit S1).y The light is broken into its spectral components as it arises
from slit S2 and falls on the sample in the cuvette.
y Narrower slits give rise to shorter wavelenghts.
y The angle of the diffraction grating determines light wavelength
if all other parameter are fixed.
y The mirror reduces equipment size
y Light output, Photodetector sensitivity, and sample substance
absorption change with wavelengths measurement
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Schematic
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Maintenance
y Calibration
y Adjustment
y Replacement of light source bulbs
yReplacement of the Photodetector
y Mechanically rotating assemblies (mirrors,)
y Electronics faulty
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Flame photometer
y It is measure the color intensity of a flame that
is supported by oxygen and a specific
substances
y The basic schematic shows that a reference
gas containing a lithium salt causes a red light
to shine on the reference photodetector
through the optical filtery A yellow or violet light from sample sodium
or potassium falls on the sample photodetector
y
It is similar to colorimetersujith.m,lecturer/eee,9600286256
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y Continuous calibration can be accomplished by
inspiration of air( oxygen to supportcombustion) and lithium.
y The output read in units of sodium or potassium
concentration
y Maintenance
y Adjustment of bulbs & photo detectors
y Aspiration device and flame chambers
occasionally cleaning
y Electronics failure usually frequent
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Auto analyzer
Purpose of A
utoanalyzer
y The autoanalyzer is sequentially measures
y blood chemistry and displays this on a graphic readout
This is accomplished by
y Mixing
y reagent
y
Reactiony Colorimetric measurement in continuous stream
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Elements of Autoanalyzer
y Sampler
y Proportioning pump and manifold
y Dialyzer
y Heating bath
y Colorimeter
y Record
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Sampler
Aspirates samples, standards, and wash solutions to the autoanalyzer
system
Proportioning pump
y Introduces samples with reagents to effect the proper chemical color
reaction to be read by the colorimeter.y Pumps fluids at precise flow rates to other modules, as proper color
development depends on reaction time and temperature
Dialyzer
y Separates interfacing substances from the sample material by
permitting selective passage of sample components through a
semipermeable membranesujith.m,lecturer/eee,9600286256
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Heating bath
y Heats fluids continuously to exact temperature (37 degree).
Colorimetery Monitors the changes in optical density of the fluid stream flowing
through a tubular flow cell.
y Color intensities proportional to substance concentrations
y Colorimeter convert the color intensity to equivalent electricalvoltages
Recorder
y Converts the electrical signal from the colorimeter into a graphic
display on moving chart
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Maintenance
y Calibration and adjustment
y MechanicalTubing
Moving pump parts
y Electrical
Switches
Motors
Electronic failures are few Problems
yIdentification of samples
y Sterilization for sample and glassware and
y equipment parts
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