Instrumental Analysis Flashcards

Flashcards based on chromatography, polarimetry, polarography, coloumetry, refractometry, specific gravity and density, radioactivity, spectrometry notes.

What is the mobile phase in chromatography?

Solvent moving through the column

What is the stationary phase in chromatography?

Adsorbent substance that stays fixed inside the column

What is elution in chromatography?

Process of washing out adsorbed substances by passing a suitable solvent (eluent) through the column

What is an analyte?

Mixture whose individual components are to be separated and analyzed

What is the principle behind chromatography?

The principle behind chromatography lies in the differential affinities of the various components of the analyte toward the stationary and mobile phases, resulting in their separation

What is adsorption in chromatography?

How well a component sticks to the stationary phase

What is solubility in chromatography?

How well a component dissolves in the mobile phase

Who is Mikhail Tswett?

He first developed chromatography in 1903

How does separation occur in adsorption chromatography?

Separation occurs through a competitive process where mobile phase molecules compete with analyte molecules for polar adsorption sites on the absorbent

What is partition chromatography?

Separation is based on the differences in partition coefficients of substances between two immiscible liquids

What is ascending chromatography?

Mobile phase rises upward on the paper by capillary attraction

What is cation exchange chromatography?

Positively charged molecules are attracted to a negatively charged solid support

What is molecular exclusion chromatography?

Separation is based on molecular size; operative for solutes with distribution coefficient between 0 and 1

Column Chromatography

Based on the differential adsorption of substances by the adsorbent.

What are the advantages of gas chromatography?

Fast analysis, efficient, sensitive, non-destructive, highly accurate.

What are the disadvantages of gas chromatography?

Limited to volatile samples, not suitable for thermally labile samples, difficult for large, preparative samples

What is retention time in gas chromatography?

The time required for a molecule to pass through the column to the detector

What is retention volume in gas chromatography?

Volume of carrier gas needed to carry a molecule from injection point to the detector

What is HPLC?

Depends on adsorption, partition, ion exchange, and molecular exclusion processes

For what type of substances is HPLC suitable?

Suitable for non-volatile, high polarity, ionic, high molecular weight, or thermally unstable substances

What is Silica Gel in HPLC?

Straight-phase packing, retardation via absorption of polar groups.

What is ODS-Coated Silica Gel in HPLC?

Reversed-phase packing, retardation via partitioning of the molecule into the stationary phase.

What does Polarimetry measure?

Measures the rotation of polarized light as it passes through an optically active compound

What is dextrorotatory?

Rotates light to the right (clockwise), designated by (+)

What is levorotatory?

Rotates light to the left (counterclockwise), designated by (-)

What is Specific Rotation?

The rotary power of a given solution

What is a quantitative application of polarimetry?

If the specific rotation of a sample is known, its concentration can be estimated

What is a qualitative application of polarimetry?

Optical activity is the only parameter available for distinguishing between D and L isomeric forms

What is saccharimetry?

Determination of high concentration of sugars using visual saccharimeters called polaroscopes

What is polarography?

Measures the current resulting from electrolysis of an electroactive species at a given electrode potential under controlled conditions

Determination of inorganic compounds in polarography

Cations and anions in the presence of interfering ions can be determined using it

What pharmaceutical applications use polarography?

Tetracycline antibiotics and sulfonamides can be analyzed

What is Coloumetry?

An electroanalytical method in which the quantity of electricity consumed during an electrolysis reaction measures the quantity of electro-active species being analyzed

What is Karl Fischer Titration reagent?

Reacts with the water in a sample and converts the water into a non-conductive metal

What is refractometry?

Method of measuring a substance's refractive index to assess its composition or purity

What is Refractive Index?

Ratio of the speed of light in a vacuum to the speed of light in another substance

What is Specific Gravity?

Ratio of the apparent weight of a substance in air at 25°C to that of an equal volume of distilled water at the same temperature

What is Density?

Mass per unit volume of a substance, typically measured in g/mL

What is Archimedes Principle?

A body immersed in a liquid displaces an amount of the liquid equal to its own volume and suffers an apparent loss in weight equal to the weight of the displaced liquid

Clinical Applications of specific gravity

A low specific gravity indicates that the urine is dilute, which may result from Diabetes insipidus

What is a nuclide?

A species of atom characterized by the number of protons and neutrons in its nucleus

What are isotopes?

Nuclides having the same atomic number but different atomic mass numbers

What is a radioactive nuclide?

Unstable nuclides whose nuclei spontaneously undergo change toward a more stable configuration, emitting radiation

What is Half-life?

Time interval required for a given activity of a radionuclide to decay to one-half of its initial value

What is Spectrometry?

Methods of analysis that deal with the measurement of spectra

What is Spectrophotometry?

Measures the absorption, by chemical species, of radiant energy of a definite and narrow wavelength

What is a chromophore?

Functional group that absorbs radiant energy in the UV or VIS region

What is Lambert's Law?

The power of a transmitted radiant beam decreases exponentially as the thickness of the solution increases arithmetically

What is Beer's Law?

The power of a transmitted radiant beam decreases exponentially as the concentration of the solution increases arithmetically

Luminescence

Emission of light by a substance when an electron returns to the electronic ground state from an excited state