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Which application is associated with laser technology?
A reference electrode always has a fluctuating voltage.
False
What equation is used to determine the concentration of ions in potentiometry?
Nernst equation
The two types of Ion-Selective Electrodes are Direct ISE and ______.
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Match the following types of electrodes with their characteristics:
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Which of the following is NOT an example of a read-out device?
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A double-beam spectrophotometer uses one photodetector to compare the sample and reference cuvet.
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What purpose do optical filters serve in quality assurance for spectrophotometry?
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The device that modulates the light beam in atomic absorption spectrophotometry is called a ______.
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Match the following components with their functions in atomic absorption spectrophotometry:
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Which component is used in flameless atomic absorption spectrophotometry?
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Stray light in a spectrophotometric system refers to light that originates from the desired light source.
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What is the primary application of atomic absorption spectrophotometry?
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What does Beer’s law state about the concentration of a substance?
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The visible region of the electromagnetic spectrum ranges from 100 to 400 nm.
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What is the formula for the relationship between wavelength and energy?
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The unit used to measure wavelength in the visible spectrum is __________.
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Which component of a spectrophotometer is responsible for providing light?
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Match the types of light sources with their respective regions:
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The frequency of a wave is measured in nanometers.
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What is the range of the ultraviolet region of the electromagnetic spectrum?
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Which electrode is commonly used as an internal reference electrode in pH measurements?
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Amperometry is used exclusively for detecting chloride ions in serum and plasma.
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What is the primary application of enzyme electrodes?
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The __________ electrode is specifically designed to detect carbon dioxide levels.
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Which method is used to measure heavy metals like lead?
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Match the following staining methods with their corresponding uses:
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Electrophoresis separates compounds based on their electrical charge.
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List one component necessary for an electrophoresis setup.
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Which technique is considered the most useful for alkaline phosphatase (ALP) isoenzyme analysis?
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Osmometry can only measure the osmolality of blood plasma.
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What is the principle of chromatography?
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The measure of freezing point depression in osmometers is expressed in milliosmolal per kilogram (___).
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Match the following chromatography types with their applications:
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Which of the following is an example of osmotically active particles?
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Freezing point depression is proportional to the number of solute particles present in a solution.
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What type of chromatography is noted for its use in analyzing organic molecules, including many drugs?
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Study Notes
Spectrophotometry
- Electromagnetic radiation is described as photons of energy traveling in waves.
- Other forms of electromagnetic radiation include gamma rays, x-rays, microwaves, radiofrequency radiation, and ultraviolet radiation.
- Wavelength is the linear distance between any two equivalent points on a successive wave.
- The relationship between wavelength (λ) and energy (E) is described by Planck’s formula: E = hv, where h is Planck’s constant (6.62 X 10 -27 erg sec) and v is frequency.
- Frequency is the number of oscillations of the waveform in a second.
- The visible region of the electromagnetic spectrum is from 400 - 700 nm.
- The ultraviolet region is less than 400 nm.
- The infrared region is greater than 700 nm.
- Beer’s law states that the concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light.
- A spectrophotometer is used to measure the light transmitted by a solution to determine the concentration of the light-absorbing substance in the solution.
- Components of a spectrophotometer are: a light source, a monochromator, a sample cell or cuvet, a photodetector, and a meter or read-out device.
- Light sources provide polychromatic light.
- Incandescent tungsten or tungsten-iodide lamps are used for visible and near-infrared regions.
- Deuterium lamps and mercury arc lamps are used for the UV region.
- Two types of spectrophotometers are single-beam and double-beam.
- A double-beam spectrophotometer uses two photodetectors.
- A double-beam in time spectrophotometer uses one photodetector and a chopper to pass the monochromatic radiation through the sample cuvet and then to the reference cuvet.
- Quality assurance in spectrophotometry includes wavelength or photometric accuracy, absorbance check, linearity, and stray light.
- Wavelength or photometric accuracy implies that a photometer is measuring at the wavelength that it is set to.
- Absorbance checks are done using known absorbance values for glass filters or solutions at a specific wavelength.
- Linearity is the ability of a photometric system to yield a linear relationship between the radiant power incident upon its detector and the concentration.
- Stray light is any light that impinges upon the detector that does not originate from a polychromatic light source.
- Atomic absorption spectrophotometry (AAS) measures concentration by detecting the absorption of electromagnetic radiation by atoms rather than by molecules.
- The light source for AAS is a hollow-cathode lamp.
- A chopper modulates the light beam for AAS.
- The photodetector for AAS is a PM tube.
- AAS is sensitive and precise and measures concentrations of trace metals.
- Flameless AAS uses an electric furnace to break chemical bonds.
- Fluorometry measures the concentrations of solutions that contain fluorescing molecules.
- Laser applications are based on the interaction of radiant energy with excited atoms or molecules and can serve as a source of incident energy in a spectrometer or nephelometer.
- Laser applications are used in hematology and flow cytometer analyzers for differential analysis of white blood cells.
Electrochemistry
- Electrochemistry involves the measurement of the current or voltage generated by the activity of specific ions.
- Potentiometry is the measurement of potential (voltage) between two electrodes in a solution.
- Reference electrodes have a constant voltage.
- Indicator electrodes are measuring electrodes.
- The concentration of ions is determined by the difference between two electrodes, represented by the Nernst equation.
- Ion-selective electrodes (ISE) are very sensitive and selective for the ion they measure, consisting of a membrane separating a reference solution and a reference electrode from the solution to be analyzed.
- ISEs are used in direct and indirect methods.
- pH electrodes are used to measure hydrogen ion activity.
- Buffer samples have known hydrogen ion concentrations.
- Internal reference electrodes are silver/silver chloride.
- External reference electrodes are calomel electrodes.
- Gas-sensing electrodes are designed to detect specific gases.
- Enzyme electrodes are used for enzymatic methods to measure concentrations of substances like urea and glucose.
- Coulometry measures the quantity of electricity (in coulombs) needed to convert an analyte to a different oxidation state.
- Coulometric titration is used to determine sweat chloride concentration.
- Amperometry is the measurement of the current flow produced by an oxidation–reduction reaction.
- Amperometry is used to determine chloride ion concentration in serum, plasma, CSF, and sweat samples as well as for measuring pO2 in blood gas analyzers.
- Voltammetry involves applying a potential to an electrochemical cell and measuring the resulting current.
- Anodic stripping voltammetry is used to measure heavy metals like lead.
Electrophoresis
- Electrophoresis is the separation of charged compounds based on their electrical charge.
- Cations (+) move toward the cathode (-), and anions (-) toward the anode (+).
- Support media is paper, cellulose acetate, agarose gel, polyacrylamide gel, and starch gel.
- Electrophoresis is used to separate proteins in serum, urine, CSF, and other body fluids.
- Electroendosmosis or endosmosis is the movement of buffer ions and solvent relative to the fixed support.
- Iontophoresis is the migration of small charged ions.
- Zone electrophoresis is the migration of charged macromolecules.
- An electrophoretogram is the result of zone electrophoresis and consists of sharply separated zones of macromolecule.
- Components of an electrophoresis system are: a power supply, a buffer, a support medium, a sample, and a detecting system.
- Stains for visualization of fractions include Amido Black, Ponceau S, Oil Red O, Sudan Black B, Fat Red 7B, Coomassie Blue, and gold/silver stain.
- Electrophoresis is considered the most useful single technique for ALP (alkaline phosphatase) and CK (creatine kinase) isoenzyme analysis.
- Intestinal ALP is located at the origin, with placental, bone, and liver located towards the anode.
Osmometry
- Osmometry is the measurement of the osmolality of an aqueous solution such as serum, plasma, or urine.
- Osmotically active particles include glucose, urea nitrogen, and sodium.
- Osmometers measure freezing point depression or vapor pressure depression.
- The freezing point osmometer uses freezing point depression which is proportional to the number of solute particles.
Chromatography
- Chromatography is a separation method based on different interactions of specimen compounds with the mobile and stationary phases as the compounds travel through a support medium.
- Components of a chromatography system are: a mobile phase (gas or liquid) which carries the sample, a stationary phase (solid or liquid) which the mobile phase flows through, a column which holds the stationary phase, and an eluate comprised of the separated components.
- Paper chromatography separates sugars and amino acids.
- Thin layer chromatography is used for semi-quantitative drug screening tests.
- Gas chromatography is used for compounds that are naturally volatile or can be easily converted into a volatile form, such as various organic molecules, including many drugs.
- Liquid Chromatography uses high-performance liquid chromatography (HPLC), the most widely used liquid chromatography technique.
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Description
This quiz covers the essential concepts of spectrophotometry, including the nature of electromagnetic radiation, its different forms, and the key principles such as wavelength, frequency, and Beer’s law. Understanding these topics is crucial for applying spectrophotometry in various scientific fields. Test your knowledge and comprehension of these foundational ideas!
