medical lab instrument

8/7/2019 medical lab instrument

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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

sujith.m,lecturer/eee,9600286256


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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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