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Field Research Project. Anne Powers MT(ASCP), CLS(NCA) COM 545 February 17, 2005. What is a Clinical Laboratory Scientist?. Baccalaureate prepared Strong science education Anatomy & Physiology Chemistry Hematology Immunohematology Immunology Microbiology. How is a CLS/MT Credentialed?.

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field research project

Field Research Project

Anne Powers MT(ASCP), CLS(NCA)

COM 545

February 17, 2005

what is a clinical laboratory scientist
What is a Clinical Laboratory Scientist?
  • Baccalaureate prepared
  • Strong science education
    • Anatomy & Physiology
    • Chemistry
    • Hematology
    • Immunohematology
    • Immunology
    • Microbiology
how is a cls mt credentialed
How is a CLS/MT Credentialed?
  • National Credentialing Agency for Laboratory Personnel (NCA)(CLS)
  • American Society for Clinical Pathology (ASCP)(MT)
  • Some states in the US also require state licensure. At the present time Illinois does not require licensure
where do they work
Where do they work?
  • Employed in hospital laboratories
  • Employed in physician’s clinic laboratories
  • Employed as managers for hospital/physicians office laboratories
  • Employed as educators
  • Employed in businesses needing individuals with science background
what do they do
What do they do?
  • Analyze blood and body fluids for abnormalities in:
    • Chemical constituents
    • Hematological constituents
    • Immunohematological constituents (blood typing, compatibility testing)
    • Microbiological organisms
vampires
Vampires?
  • Some of our patients refer to us as vampires because we draw blood. This procedure is known as phlebotomy
professional affiliations
Professional Affiliations
  • American Society for Clinical Pathology
  • National Credentialing Agency for Laboratory Personnel
  • American Society for Clinical Laboratory Science
  • Illinois Society for Clinical Laboratory Science
what are all those different colored blood collection tubes used for
What are all those different colored blood collection tubes used for?
  • Red or Yellow top tubes
    • Do not contain any anti-coagulants in the tube so that the blood is allowed to clot
    • Normally, these tubes are centrifuged to separate the serum (liquid portion) from the cells (RBC, WBC, Platelets)
    • Chemistry and Immunology are the departments that use this type of specimen most often
what are all those different colored blood collection tubes used for9
What are all those different colored blood collection tubes used for?
  • Purple top tube
    • Contains an anticoagulant, EDTA
    • This is allows a whole blood analysis in which we may need to count the cells
    • If this tube is centrifuged, the liquid portion is referred to as plasma
    • This tube is used most often in the hematology department
what are all those different colored blood collection tubes used for10
What are all those different colored blood collection tubes used for?
  • Blue top tube
    • Contains an anticoagulant,citrate
    • Used most often for coagulation studies such as when a patient is taking “blood thinners”
    • Coagulation studies are often performed in the hematology department
what are all those different colored blood collection tubes used for11
What are all those different colored blood collection tubes used for?
  • Green top tube
    • Contains an anticoagulant, heparin
    • Often used as a substitute for red top in chemistry
    • Specimen can be centrifuged immediately upon receipt
    • May decrease the turn-around-time for results
common laboratory tests
Common Laboratory Tests
  • CBC (Complete Blood Count)
  • Glucose (Blood Sugar)
  • Cholesterol
  • BMP (Basic Metabolic Panel)
  • Urinalysis
  • Protime/PTT (coagulation tests)
  • Cultures (urine, throat, other body fluids)
field research project16
Field Research Project
  • How can the use of multimedia enhance a current lecture on Spectroscopy?
  • This lecture is currently presented to students as a text document and transparencies of diagrams from reference textbooks.
field interview
Field Interview
  • Contact: Shannon Heisler
  • Company: Levi, Ray, and Shoup
  • Job Title: Marketing Manager
  • Educational Background: BA in English Communications from Illinois College
field interview18
Field Interview
  • Work Experience:
    • Public Affairs at Illinois College while a student
    • Public Affairs with US Navy Reserves
    • Focus on Marketing, Web Development
    • In 9th year at LRS
suggestions project
Suggestions Project
  • Use PowerPoint hover feature that would describe each component of the spectrophotometer
    • This would require that each component be separated and graphically redesigned
suggestions for project
Suggestions for Project
  • Use HTML for web
    • Again, hover feature
suggestions for project21
Suggestions for Project
  • Flash
    • Lots of possibilities here but requires quite a bit of expertise
    • Would be more of a visual product
    • Students may learn more from an interactive product
st john s hospital school of clinical laboratory science

St. John’s HospitalSchool of Clinical Laboratory Science

Chemistry Lecture

Molecular Absorption Spectroscopy

i introduction
I. Introduction
  • Most methods based on the measurements of radiant energy transmitted or absorbed under controlled conditions
  • Spectrophotometer
    • Device capable of detecting transmitted or absorbed light
    • Commonly used in the clinical laboratory
ii components of spectrophotometers
II. Components of Spectrophotometers
  • A. Exciter Lamp
    • Must furnish intense, reasonably cool constant beam of light
    • Easily aligned
    • Highly reproducible
    • Tungsten and halogen work well for near infrared and visible light range
    • Quartz preferred
      • Provide more intense beam of light
      • Better source of white light in the near ultraviolet region
b collimating lenses
B. Collimating Lenses
  • Inserted between the exciter lamp and the monochromator
  • Serve to collect light rays emitted from the source lamp and focus them so that the light passing into the monochromator will be an organized beam of parallel light
  • Sometimes a heat filter is placed in the light beam close to the source lamp to protect the monochromator from radiant heat
c monochromator
C. Monochromator
  • Produces light of a single color from an impure source
  • Monochromatic light in its true form is of one specific wavelength
  • Light of one specific wavelength is difficult to isolate and normally, there is a range of wavelengths that are allowed in a monochromator
c monochromator27
C. Monochromator
  • For example, light of green color would be about 550 nm but wavelengths of 525-575 nm may also be present
  • This “range” (525-575nm) is the band pass which is 50nm
  • The narrower the band pass, the more monochromatic the light
types of monochromators
Types of Monochromators
  • A. Single Glass Filter
    • Simplest monochromator
    • Band pass is wide and not truly monochromatic
    • Made by suspending a coloring agent in molten glass
    • Thickness of glass determines how much light is absorbed
    • Filters are often identified by (1) peak absorbance, (2) band pass, (3) thickness and/or opacity
types of monochromators29
Types of Monochromators
  • B. Double Glass Filter
    • Two glass filters of different colors are cemented together
    • Achieves a narrower band pass
    • Only wavelengths that are passed in common by both filters will be part of the band pass
    • Are used for transmitting visible and near visible light
    • Are not precise but are simple, inexpensive, and useful
types of monochromators30
Types of Monochromators
  • C. Interference Filters
    • Produce monochromatic light based on the principle of constructive interference of waves
    • Two pieces of glass each mirrored on one side are separated by a transparent spacer that is precisely one-half the desired wavelength
    • Light waves enter one side of the filter and are reflected at the second surface
types of monochromators31
Types of Monochromators
  • Interference filters
    • Wavelengths that are twice the space between the two glass surfaces will reflect back and forth, reinforcing others of the same wavelength, and finally pass on through
    • Other wavelengths will cancel out (destructive interference)
    • These filters produce a very narrow range of wavelengths
types of monochromators32
Types of Monochromators
  • D. Prisms
    • A narrow beam of light focused on a prism is refracted as it enters the more dense glass
    • Short wavelengths are refracted more than long wavelengths, resulting in the dispersion of white light into a continuous spectrum
    • Prism can be rotated, allowing only the desired wavelength to pass through an exit slit
types of monochromators33
Types of Monochromators
  • E. Diffraction Gratings
    • Most common monochromator
    • Consists of many parallel grooves (15,000 to 30,000 per inch) etched onto a polished surface
    • Light is diffracted (separated) into component wavelengths as the wavelengths of light are bent when they pass a sharp corner
    • This results in a complete spectra
    • Gratings with very fine line ruling produce a widely dispersed spectrum
d sample cell
D. Sample Cell
  • Known as a cuvet
  • Can be round or square
  • Light path must be constant and have absorbance proportional to concentration
  • Must be optically clear
  • Scratches or buildup can compromise optical integrity
    • Glass cuvets can be used in the visible range but Quartz is better suited for the ultraviolet range since glass absorbs ultraviolet light
e photodetectors
E. Photodetectors
  • Convert transmitted radiant energy into an equivalent amount of electrical energy
e photodetectors36
E. Photodetectors
  • A. Photocell
    • Also known as a barrier-layer cell
    • Composed of film of light-sensitive material such as selenium on a plate of iron
    • A transparent layer of silver is place over the light-sensitive layer
    • When exposed to light, electrons in the light-sensitive material are excited and released to flow to the highly conductive silver
photodetectors
Photodetectors
  • A. Photocell
    • In comparison with the silver, a moderate resistance opposes the electron flow in that direction
    • This causes the cell to generate its own electromotive force, which can then be measured
    • The produced current is proportional to the incident radiation
photodetectors38
Photodetectors
  • A. Photocell
    • Do not require external voltage source
    • Rely on internal electron transfer to produce a current in an external circuit
    • Electrical energy is not easily amplified
    • Used mostly in photometers with wide band passes
    • Is inexpensive and durable
    • Temperature-sensitive and nonlinear at very low and very high levels of illumination
e photodetectors39
E. Photodetectors
  • B. Phototube
    • Similar to a photocell but requires an outside voltage source
    • Contains a negatively charged cathode and a positively charged anode enclosed in a glass case
    • Cathode is composed of rubidium or lithium that will act as a resistor in the dark but will emit electrons when exposed to light
e photodetectors40
E. Photodetectors
  • B. Phototube
    • Emitted electrons jump over to the positively charge anode, where they are collected and return an external, measurable circuit
photodetectors41
Photodetectors
  • C. Photomultiplier Tube
    • Detects and amplifies radiant energy
    • Incident light strikes the coated cathode, emitting electrons
    • The electrons are attracted to a series of anodes (dynodes)
    • Each dynode has a successively higher positive voltage
    • Dynodes are made of a material that will give off many secondary electrons when hit by single electrons
e photodetectors42
E. Photodetectors
  • C. Photomultiplier Tube
    • Initial electron emission at the cathode triggers a multiple cascade of electrons within the photomultiplier tube
    • Is 200 times more sensitive than the phototube
    • Are generally used in instruments designed to detect extremely low levels of light
e photodetectors43
E. Photodetectors
  • Photodiode
    • Absorption of radiant energy by a reversed-biased pn-junction diode produces a photocurrent that is proportional to the incident radiant energy
    • Are not as sensitive as the photomultiplier tube
    • Have excellent linearity and are quite fast
    • Each photodiode responds to a specific wavelength
f readout device
F. Readout Device
  • Historically these devices consisted of ammeters or galvanometers
  • Newer devices consist of digital displays and printers
g single beam spectrophotometer
G. Single Beam Spectrophotometer
  • Can be useful in certain circumstances
  • Voltage fluctuations and changes in light source present a problem
    • When a heavy load is placed on the electric power system, lights dim and later brighten
    • If measurements are being taken on the spectrophotometer at the same time, the readings will be unreliable
g single beam spectrophotometer46
G. Single Beam Spectrophotometer
  • Aging lamp source may momentarily flicker and cause the readings to be unstable and erroneous
use of two photocells
Use of two photocells
  • Two photocells are positioned at equal distances from the lamp source and are attached to the same meter so that they oppose each other
  • This cancels the instability of the lamp source
use of a beam splitter
Use of a beam splitter
  • A device that ‘splits’ the path of light
  • The device is can be a half-silver mirror (dichroid mirror)
  • Is placed in the light path between the monochromator and the sample
  • The light is split and goes to the sample and reference detectors
use of beam splitter
Use of Beam Splitter
  • Since the light is being split between the sample and a reference cell simultaneously, any fluctuations will affect the sample and the reference cell equally and thus will cancel itself out
h double beam spectrophotometer
H. Double Beam Spectrophotometer
  • Monochromatic light is focused through both a reference cell and a sample compartment
  • The intensity of these two beams of light is measured by a detector and the sample beam is compared to the reference beam as a ratio
h double beam spectrophotometer52
H. Double Beam Spectrophotometer
  • This ratio fed into a meter or directly into a ratio-recording instrument
  • Any fluctuations are cancelled out via the ratio
double beam in space
Double Beam in Space
  • Light is split with half mirror
  • Half the beam passes through the sample
  • Half the beam passes through the reference
  • Two separate detectors measure radiant power of each beam
  • Any fluctuations of power affect sample and reference equally
double beam in time
Double Beam in Time
  • Light beam is split with a rotating chopper
  • Split beams through sample and reference are recombined to strike a single detector
  • Power fluctuation to either lamp or detector will affect both beams equally
i beer s law
I. Beer’s Law
  • Basic law of all absorption spectroscopy
  • Concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light
equation
Equation
  • A = -logP/Po - ∑bC Where
  • A = absorbance
  • P = transmitted light
  • Po = incident light
  • ∑ = molar absorbtivity
  • B = length of light path through solution
  • C = concentration of absorbing molecules
more beer s law
More Beer’s Law
  • If Beer’s law is true then,
  • Cu = Au x Cs
  • As
  • Cu = concentration of the unknown
  • Cs = concentration of the standard
  • Au = absorbance of the unknown
  • As = absorbance of the standard
j absorbance vs transmittance
J. Absorbance vs. Transmittance
  • Percent transmittance is the ratio of the radiant energy transmitted T divided by the radiant energy incident on the sample I (%T = T/I x 100)
  • 0% T occurs when all light is absorbed
  • 100% T occurs when no light is absorbed
j absorbance vs transmittance59
J. Absorbance vs. Transmittance
  • Absorbance A is the amount of light absorbed
  • Cannot be measured directly on spectrophotometer but is mathematically derived from %T as follows:
  • %T = P0 x 100
  • P
references
References
  • Clinical Chemistry Principles, Procedures, Correlations, by Michael L. Bishop, Janet L. Duben-Engelkirk, Edward P. Fody, Fourth Edition (2000)
  • Principles of Chemical Instrumentation, by Gary T. Bender (1987)
  • Principles of Laboratory Instruments, by Larry E. Schoeff & Robert H. Williams (1993)
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