" (NATIBO, 2001)
The method of operation of a "bubbler or impinger" is through "drawing aerosols through a current inlet tube and jet. Usually the jet is submerged in the liquid contained in the sampler." (NATIBO, 2001) the aerosol particles become capture din the base of the jet by the surface of the liquid as the air moves through the liquid. Collection of the smallest of the particles is enabled by a "small critical orifice causing the flow to become sonic." (NATIBO, 2001)There are designs that also form bubbles in the liquid as air leaves the jet which is fitted. The Variable Particle-Size Impactors are stated to generally have."..multiple stages" in which "each stage contains a number of precision-drilled orifices that are appropriate for the size of the participle to be collected in that stage and orifice sizes decrease with each succeeding impactor state." (NATIBO, 2001) as particles in the air are collected in the instrument, they are forced toward the surface collector by the orifices of the jet. Particles uncollected at that stage follow the air stream around the collection surfaces edge to the next stage.
Two Types of Triggers in Bio-Sensing Technologies
Technologies used in detection and triggering include: (1) a simple trigger; and (2) a complex trigger. The simple trigger is stated to "...respond to an increase in the atmospheric particulate background count or concentration. Once the threshold is breached, it activates the more complex and precise detector element to determine the nature of the suspected agent." (NATIBO, 2001)
Flow Cytometry
Cytometry is stated to refer "to the measurement of both the physical and chemical characteristics of cells. Flow cytometry refers to this same technique in which the characteristic measurements are made as the cells or other participles, which are present in a moving fluid stream, pass through an interrogation point." (NATIBO, 2001) This technology is a "hybrid technology" in which development in computer processing, optoelectronics, monoclonal antibody production, flurochrome chemistry and laser technology are all combined to make provision of a method that is automated in making analysis of bio-chemical properties. (NATIBO, 2001; paraphrased) This technique is one which "permits characterization and identification of biochemical species within a heterogeneous mixture of organic and inorganic material." (NATIBO, 2001) Flow Cytometry enables the measurement of the "physical and chemical characteristics of cells or particles." The following table shows the structural characteristic so biological cells measurable by flow cytometry.
Structural Characteristics of Biological Cells Measurable by Flow Cytometry
Source: (NATIBO, 2001)
Stated as advantages of using flow cytometry for biological sensing are the advantages as follows:
1) Fast sample preparation and analysis;
2) Single particle analysis;
3) Detection and identification in one instrument;
4) Significant multiplexing advantages;
5) Easily quantifiable results;
6) Adaptability to high, automated throughput;
7) Simple to operate; and 8) Compact instrumentation. (NATIBO, 2001)
Mass Spectrometry (MS)
Mass spectrometers separate ionized atoms and molecules from each other through using the mass-to-charge ratio differential. Mass Spectrometry is useful for "quantification of atoms or molecules and also for determining chemical and structural information about molecules." (NATIBO, 2001) Mass spectroscopy is a process that re-assembles fragments and then works in a fashion of backing up to bring about a generation of the original molecule. Stated to be the general operation of a mass spectrometer is the creation of "gas-phase ions" and then separation of the ions in space or in time "based upon their mass-to-charge ratio. The process known as resolution is one in which the mass spectrometers power is used in a process of separating ions dependent on their mass-to-charge ratio. Resolutions is defined as follows:
m/m where m is the ion mass and m is the difference in mass between two resolvable peaks in a mass spectrum." (NATIBO, 2001)
The ionization techniques used by mass spectrometers are varied with the various techniques producing different degrees of "fragmentation and organic compounds and therefore producing varying results for analysis." (NATIBO, 2001) Some of the various mass spectrometry techniques include the following:
1) Electron Impact Ionization;
2) Chemical Ionization;
3) Fast Atom Bombardment (FAB);
4) Electrospray Ionization (ESI); and 5) in MALDI in which the analyte is diluted in a solid or liquid matrix which strongly absorbs laser light. (NATIBO, 2001)
The analyzer that mass spectrometers use to quantify the ions by their mass-to-charge ratios are calibrated and there are several types of these analyzers which include the following:
1) Fourier-transform mass spectrometers;
2) Ion-trap mass spectrometers;
3) Time-of-Flight mass spectrometer; and 4) Quadrupole mass filter consisting of four rods. (NATIBO, 2001)
Hand Held Immunochromatographic Assays (HHA)
The Hand Held Immunochromatrographic Assays (HHA)...
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