Category: Biomedical Analysis & Related Instrumentation
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Confocal Laser Scanning Microscopy (CLSM)
Confocal Microscopy Technique In conventional microscopy, the specimen is usually mounted on a glass slide and then a coverslip placed to sandwich the specimen between it and the slide. For biological samples, the tissue is often stained to visualize specific cell components and then embedded in paraffin wax. This destroys cell function; nevertheless, there are…
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Polarographic Clark Electrodes
Polarographic electrodes differ from the typical pH and ion specific cells in that a polarographic cell is run at a constant potential in order to force two electrochemical reactions to take place. The current which flows in the cell is determined by and is proportional to the limiting concentration of one reactant. A Clark cell…
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Dispersive Spectrophotometry Chemical Analysis Technique
Dispersive spectrometry (DS) methods make up a large number of ultraviolet, visible light and infrared spectroscopy systems. DS refers to the fact that the light or electromagnetic radiation passed through the sample (analyte) must pass through a monochromator either before or after the analyte, to describe the analyte’s absorption/transmission characteristic spectrum. A simplest monochromator is…
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Flame Atomic Absorption Spectrometry
When a sample is introduced into a flame, only a small fraction of the atoms are in an excited or high energy state [as per the Boltzmann equation] and most atoms of the element remain in the unexcited or ground state and are capable of absorbing energy. If light energy is supplied as a continuous…
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Principle for Measurement of Partial Pressure of Carbon Dioxide
The electrodes used for measurement of partial pressure of CO2 in blood are based on measuring the pH as demonstrated in the figure below: The measurement is based on the fact that when CO2 is dissolved in water, it forms a weakly dissociated carbonic acid (H2CO3) that subsequently forms free hydrogen and bicarbonate ions per…
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How Spectrofluorimeters are used in Biomedical Measurements
After absorption of light energy, all compounds release some energy as heat; fluorescent compounds represent a special case in which some energy is also given off as light. Spectrofluorimeters are optical devices that measure the amount of light that is emitted by fluorescent compounds. Basic Principle of Spectrofluorimeter When light is directed at a fluorescent…
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Principle of Operation of a Medical Mass Spectrometer
A mass spectrometer is an instrument that produces a stream of charged particles (ions) from a substance being analyzed, separates the ions into a spectrum according to their mass-to-charge ratios, and ascertains the relative abundance of each type of ion present. The figure below shows a medical mass spectrometer system: The above medical mass spectrometer…
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How Gas-Liquid Chromatograph (GLC) is used in Clinical Measurements
In chromatography, differences in the rate of movement of components of a mixture in the mobile phase, caused by interaction of these components with the stationery phase, are used to separate the components. In clinical laboratory instrumentation, chromatographic methods are used mainly for the detection of complex substances such as drugs and hormones. The operation…
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The Principle of Measurement of pH
A pH meter is an instrument that determines the acidity or basicity of aqueous solutions. The measurement of pH is achieved by utilizing a glass electrode that generates an electric potential when solutions of differing pH are placed on the two sides of its membrane. The glass electrode is a member of the class of…
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How Estimation of Oxygen and Carbon dioxide is Carried out in Biological Solutions
Estimating Oxygen in Biological Solutions Oxygen concentration in solution is usually estimated electrolytically. The basic principle is that, if a bright platinum electrode is placed in a solution, and +0.7 V is applied to it with respect to a reversible (silver-silver chloride in biological systems), oxygen will be reduced at it, and the current flowing…