Analytical Techniques in Clinical Chemistry

Vocabulary flashcards generated from lecture notes covering analytical techniques, colorimetry, spectrophotometry, scatter analysis, electrochemistry, and electrophoresis.

Spectrophotometric measurement

The measurement of light intensity in a narrower wavelength.

Photometric measurement

The measurement of light intensity using a specific wavelength.

Molecular Absorption Spectrophotometry (MAS)

A technique involving the measurement of light transmitted by a solution to determine the concentration of light-absorbing substances in that solution.

Wavelength

The linear distance between any two equivalent points on a successive wave, expressed in nanometers ($\text{nm}$).

Visible spectrum

The wavelength region of electromagnetic radiation spanning $400\text{--}700\text{ nm}$.

Ultraviolet region (UV)

The wavelength region of electromagnetic radiation that is $<400\text{ nm}$.

Infrared region (IR)

The wavelength region of electromagnetic radiation that is $>700\text{ nm}$.

Frequency

The number of vibrations of wave motion per second.

Planck’s formula

The relationship $E = hv$, where $E$ is energy of a photon in Joules, $h$ is Planck’s constant ($6.626 \times 10^{-34}\text{ J s}$), and $v$ is frequency in Hertz.

Rayleigh scattering

Scattering by molecules or aggregates of molecules with dimensions significantly smaller than the wavelength of the radiation.

Tyndall effect

Scattering that occurs with particles of colloidal dimensions and can be seen with the naked eye.

Raman scattering

Scattering that involves absorption of photons producing vibrational excitation.

Single-beam Spectrophotometer

A spectrophotometer designed to make one measurement at a time at one specified wavelength.

Double-beam Spectrophotometer

A spectrophotometer that splits monochromatic light into two beams: one passing through the sample and the other through a reference solution or blank to correct for light source intensity variations.

Continuum source

A radiant energy source that emits radiation changing in intensity very slowly as a function of wavelength, such as tungsten, deuterium, and Xenon lamps.

Line source

A radiant energy source that emits a limited number of discrete lines or bands of radiation, each spanning a limited range of wavelengths.

Stray light

Any wavelengths outside the band transmitted by the monochromator that do not originate from the polychromatic light source, causing absorbance error and loss of linearity.

Monochromator

A component used to isolate specific wavelengths of light or select the amount of light that passes through the cuvet.

Diffraction grating

The most commonly used monochromator, consisting of many parallel grooves ($15{,}000$ or $30{,}000\text{ per inch}$) etched onto a polished surface to bend wavelengths as they pass sharp corners.

Photomultiplier Tube (PMT)

The most common photon detector that detects and amplifies radiant energy, being $200$ times more sensitive than a standard phototube.

Didymium or Holmium oxide filter

Filters used to check the wavelength accuracy or photometric calibration of a spectrophotometer.

Linearity

The ability of a photometric system to yield a linear relationship between the radiant power incident upon its detector and the concentration.

Beer’s Law

States that the concentration of an unknown substance is directly proportional to absorbed light and inversely proportional to the logarithm of transmitted light ($A = abc = 2 - \text{log}(\text{\%T})$).

Complementary color

The observed color formed by light that is not absorbed by a solution and passes through to the eyes.

Reagent blank

A blank containing only reagent without sample, used to correct for absorbance readings due to background materials in the reagent.

Sample blank

A blank containing only sample without reagent, used to correct for non-specific absorbance from interfering substances like hemoglobin, bilirubin, and lipids.

Flame Emission Photometry

A method for quantitative analysis of serum electrolytes involving electron excitation by the heat energy of a flame.

Atomic Absorption Spectrophotometry (AAS)

A technique measuring the concentration of trace metals in their neutral ground state by measuring their absorption of light radiation without prior electron thermal excitation.

Turbidimetry

A technique that determines the amount of light blocked by suspending particles in a sample as light passes through a cuvet.

Nephelometry

A technique measuring the amount of light scattered by suspending particles in a solution at an angle, typically $15\text{--}90^\text{o}$ to the incident light beam.

Fluorometry

A technique determining the amount of light emitted by a molecule after excitation by electromagnetic radiation, measured over a zero background.

Fluorescence

Light emission resulting from a single excited state.

Phosphorescence

Light emission resulting from an excited triplet state.

Quenching

Any decrease in fluorescence caused by environmental changes, pH, temperature, chemical contaminants, or excitation light.

Chemiluminescence

A process where a chemical reaction yields an electronically excited compound that emits light as it returns to its ground state without requiring excitation radiation.

Osmometry

The measurement of changes in the colligative properties of solutions (such as osmotic pressure, boiling point, freezing point, and vapor pressure) due to variations in particle concentration.

Electrophoresis

The migration of charged particles or solutes in an electric field to separate proteins based on their electric charge densities.

Ampholyte

A molecule, such as a protein, whose net charge can be either positive or negative depending on the pH of the surrounding buffer relative to its isoelectric point.

Densitometry

The measurement of the absorbance of a stain on a support medium, serving as the standard method for quantitating separated protein bands.

Isoelectric Focusing

A modification of electrophoresis where charged proteins migrate through a continuous pH gradient until reaching a pH equal to their isoelectric point ($pI$), where migration ceases.

Capillary Electrophoresis

A separation method performed in narrow-bore fused silica capillaries with inner diameters of $25\text{--}75\text{ }\frac{1}{1000}\text{mm}$ (\text{\mu m}).

Two-Dimensional Electrophoresis

A procedure combining isoelectric points in the first dimension and relative molecular weight via SDS-PAGE in the second dimension to separate complex protein mixtures.

Saturated calomel electrode

A reference electrode consisting of mercury in contact with a solution saturated with mercurous chloride (calomel) and a known concentration of potassium chloride.

Silver-silver chloride electrode

A reference electrode consisting of a silver electrode immersed in potassium chloride solution saturated with silver chloride, suitable for temperatures higher than $60^\text{o}\text{C}$.

Ion Selective Electrode

An electrochemical transducer capable of selectively responding to and measuring the activity of a specific single ion depending on membrane composition.