Instrumentation

Question 1

spectrophotometry

Answer 1

Spectrophotometry is a method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution.

Question 2

atomic absorption

Answer 2

used to measure concentration by detecting absorption of electromagnetic radiation by atoms rather than by molecules; used to measure heavy metals

Question 3

chemiluminescence

Answer 3

the emission of light during a chemical reaction which does not produce significant quantities of heat.

Question 4

electrophoresis

Answer 4

migration of charged solutes or particles in an electrical field. Iontophoresis is migration of small molecules; zone electrophoresis is migration of charged macromolecules in a porous support

Question 5

fluorometry

Answer 5

excitation (absorption of energy by a molecule) followed by emission (fluorescence) as energy.

Question 6

ion-selective electrodes

Answer 6

potentiometric method of analysis for direct measurement of electrical potential due to activity of free ions. designed to be sensitive to individual ions.

Question 7

isoelectric focusing

Answer 7

modification of electrophoresis where charged proteins migrate through a support medium the has a continuous pH gradient. individual proteins migrate in the electric field until they reach a pH equal to their isoelectric point, at which point they have no charge.

Question 8

capillary electrophoresis

Answer 8

separation is performed in a narrow bore fused silica capillary tube (ID = 25-75 micrometer)

Question 9

2D electrophoresis

Answer 9

a form of gel electrophoresis commonly used to analyze proteins. Mixtures of proteins are separated by two properties in two dimensions on 2D gels.

Question 10

Electroendosmosis

Answer 10

the movement of liquid in a porous material due to an applied electric field

Question 11

Beer law

Answer 11

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=abc; A=2-log%T; Cu=Au/As x Cs (where u = unknown and c = standard)

Question 12

Spectrophotometer components

Answer 12

light source (tungsten, deuterium, mercury); monochromator (isolation of individual wavelengths of light); sample cell (cuvette; quartz for UV); photodetector (conversion of transmitted radiant energy into an equivalent amount of electrical energy; photocell, phototube; photomultiplier)

Question 13

Flame photometry

Answer 13

flame emission photometer, which measures light emitted by excited atoms. have been replaced by ion-selective electrodes.

Question 14

turbidity

Answer 14

the amount of light blocked by a suspension of particles depends on concentration and size of particles; sample handling critical due to tendency of particles to aggregate and settle.

Question 15

nephelometry

Answer 15

light is scattered by small particles and is measured as an angle to the beam incident on the cuvette

Question 16

laser applications

Answer 16

based on the interaction of radiant energy with suitably excited atoms or molecules. Leads to stimulated emission of radiation; 3-6 times more sensitive that conventional spectrophotometers

Question 17

galvanic cells

Answer 17

also known as voltaic cells, are electrochemical cells in which spontaneous oxidation-reduction reactions produce electrical energy.

Question 18

electrolytic cells

Answer 18

are composed of two half-cells–one is a reduction half-cell, the other is an oxidation half-cell. The direction of electron flow in electrolytic cells, however, may be reversed from the direction of spontaneous electron flow in galvanic cells, but the definition of both cathode and anode remain the same, where reduction takes place at the cathode and oxidation occurs at the anode. Because the directions of both half-reactions have been reversed, the sign, but not the magnitude, of the cell potential has been reversed.

Question 19

half-cells

Answer 19

A half-cell is half of an electrolytic or voltaic cell, where either oxidation or reduction occurs.

Question 20

pH electrodes

Answer 20

The most widely used ion-selective electrode is the glass pH electrode, which utilizes a thin glass membrane that is responsive to changes in H+ activity.

Question 21

Gas-sensing electrodes

Answer 21

A sensor composed of an indicator and a reference electrode in contact with a thin film of solution which is separated from the bulk of the sample solution by a gas-permeable membrane or an air gap. Designed to detect specific gas species (i.e. CO2 and NH3); used in clinical labs to for measuring serum electrolytes and blood gases.

Question 22

Enzyme electrodes

Answer 22

ion selective electrode covered by immobilized enzymes that can catalyze a specific chemical reaction. (i.e. urease to detect urea; glucose oxidase to detect glucose)

Question 23

Coulometric chloridometers

Answer 23

historically used to detect chloride

Question 24

anodic stripping coltammetry

Answer 24

historically used to detect lead

Question 25

osmometry

Answer 25

used to measure the concentration of solute particles in solution.

Question 26

surface plasmon resonance (SPR)

Answer 26

he resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light. Used to study the binding of ligands to surface receptors (i.e. membrane proteins) in real time.

Question 27

Osmolality

Answer 27

osmotic coefficient x number of dissociable particles (ions) x concentration in mol/kg of solvent (mOsmol/kg of H2O); 1.86 [Na+] + GLU/18 +BUN/2.8

Question 28

Osmolar Gap

Answer 28

difference between the calculated and measured osmolality of a solution (measured - calculated)

Question 29

Osmolar Gap

Answer 29

difference between the calculated and measured osmolality of a solution (measured - calculated)

Question 30

Rate of mobility of a molecule (u)

Answer 30

net charge (Q)/constant (K) ionic radius (r) viscosity (n); thus rate of migration is directly proportional to the net charge and inversely proportion to its size and the viscosity of the buffer

Question 31

electro osmotic flow (EOF)

Answer 31

bulk flow of the liquid toward the cathode upon application of an electric field and it is superimposed on electrophoretic migration. Controls amount of time solutes remain in the capillary; cations migrate the fastest