Exam 5 Electrochemistry & Chromatography Essay

question

What are the 3 types of Electrochemistry?
answer

Ion selective electrodes & pH meters
Gas Sensing Electrodes
Electrophoresis
question

What are the 4 types of Chromatography?
answer

TLC – thin layer chrom
HPLC – high performance liquid chrom
GC – gas chromatography
MS – mass spec
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Define Electrochemistry
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Chemical reactions that occur due to the flow or presence of electrons
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Define Current
answer

Number of electrons traveling through a substance, measured in amperes
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Define Potential
answer

For electrons to flow, force must be applied to the system. Measured in volts
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True or False:
You can’t measure the potential of one electrode; only the potential difference between two electrodes
answer

True
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What does the Ion-Selective Electrodes measure?
answer

Potential
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What does ISE stand for?
answer

Ion-Selective Electrodes
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What is the potential (V) measured by ISE proportional to?
answer

Level of ion in the patient’s sample
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Describe a Reference Electrode
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known potential and generates a reproducible, constant V
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Describe an Indicator Electrode
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The V will vary depending on the
level of patient ion
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What are commonly used Reference Electrodes
answer

Mercury/mercurous chloride (calomel) and Ag/AgCl
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What do ISEs selectively allow?
answer

Only 1 Ion to pass through a membrane to the tip of the electrode
question

When the 1 ion passes through the membrane to the tip of the electrode, what is generated?
answer

V (Potential)
question

What are 2 Commonly used Glass Sample Membranes
answer

pH meters
Sodium
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What is the commonly used Liquid membrane?
answer

Calcium
question

What is the commonly used Liquid membrane antibiotic?
answer

Potassium (uses valinomycin)
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What does Direct ISE use?
answer

Whole Blood
question

What does Indirect ISE use?
answer

Pre-diluted plasma or serum
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Indirect ISE – High TP or lipid can cause Sodium to be what?
answer

Falsely Decreased
question

What is another name for the pCO2 Electrode?
answer

Severinghaus Electrode
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What is another name for the Severinghaus Electrode?
answer

pCO2
question

pCO2 – CO2 diffuses through and mixes with bicarbonate buffer, causing the release of ________
answer

H+ ions
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pCO2 Electrode – The H+ ions then diffuse thru a H+-permeable membrane, what is this membrane associated with?
answer

ISE
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Ammonia Gas Electrode – NH3 mixes with Ammonium Chloride, causing the release of _______
answer

OH- ions
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Ammonia Gas Electrode –
The amount of OH- ions is proportional to what?
answer

Level of NH3 in the sample
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What is another name for the pO2 Electrode?
answer

Clark Electrode
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What is another name for the Clark Electrode?
answer

pO2 Electrode
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True or False:
Current will not be conducted without O2 in the system
answer

True
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pO2 Electrode – The amount of current generated is proportional to what?
answer

Level of pO2 in the sample
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What is Chromatrography used for?
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Separate mixtures into individual components based on different physical characteristics such as size, solubility, or charge
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What are the major applications for Chromatrography?
answer

Drug screens
Drug Confirmation
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Define the following component of the chromatography system:
Mobile Phase
answer

A liquid or gas that carries the patient sample through the system
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Define the following component of the chromatography system:
Stationary Phase
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A solid or liquid through which the mobile phase flows; housed in a column
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Define the following component of the chromatography system:
Eluate
answer

separated components
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True or False:
Chromatography –
Compounds interacting more strongly with the stationary phase spend a longer time in the column than those with less affinity
answer

True
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What are the 4 Chromatography Modes of Separation?
answer

Adsorption
Partition
Steric Exclusion
Ion-Exchange
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Describe Adsorption
answer

Competition between the sample and the mobile phase for adsorptive sites on a solid stationary phase
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What type of Chromatography is Adsorption?
answer

Liquid-Solid
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What type of Chromatography is Partition?
answer

Liquid-Liquid
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What type of Chromatography is Steric Exclusion
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Liquid-Solid
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Partition is based on what?
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Solubility patterns in an organic (nonpolar) solvent and an aqueous (polar) solvent
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Partition – Polar molecules remain where?
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Aqueous Layer
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Partition – Nonpolar molecules are what?
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Extracted into the organic solvent
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What is Steric Exclusion based on?
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Size & Shape of molecules
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With Steric Exclusion which molecules pass through rapidly:
Larger or smaller?
answer

Larger Molecules
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With Steric Exclusion which molecules pass through more slowly because they become trapped in the pores:
Larger or smaller?
answer

Small molecules
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With Ion-Exchange, the Stationary phase (resin) has what on its surface?
answer

Charged functional groups
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Ion Exchange – What do Cation-exchange resins remove?
answer

Na+ and other cations
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Ion Exchange – What do Anion-exchange resins remove?
answer

Cl- and other anions
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Which system is used to deionize water?
answer

Ion-Exchange
–Anion & Cation columns combined
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How do sample molecules move in Thin Layer Chromatography?
answer

Solvent migrates up by capillary action, dissolving & carrying sample molecules
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Define Retention Factor (Rf)
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The distance a compound migrates, compared to the distance the solvent front moves
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What is the Mathematical formula for the Retention Factor
answer

Distance leading edge unknown component moves / total distance solvent front moves
question

What is TLC mainly used for?
answer

Drug Screens
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What does HPLC use to force a sample through the system?
answer

Pressure
question

What does HPLC reduce?
answer

Test Time
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With HPLC what stage is the mobile phase?
answer

Liquid
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What does the following do in the HPLC:
Pump
answer

forces the mobile phase through the column
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What does the following do in the HPLC:
Sample injector or syringe
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Shoots the sample into the path of the mobile phase
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Describe the following in the HPLC:
Column or Stationary Phase
answer

Packed into long stainless steel tubes
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What does the following do in the HPLC:
Detector
answer

generates an electronic signal as compounds are eluted
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What does the following do in the HPLC:
Recorder
answer

generates a peak as each compound elutes out
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What in the HPLC pump provides constant flow?
answer

Pistons
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HPLC Detector – The signal is proportional to what?
answer

Concentration of each separated component
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What is the print-out of a HPLC called?
answer

Chromatograph
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Define HPLC Retention Time
answer

The time it takes for a compound to elute (after sample injection)
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What is retention time used to determine?
answer

Compound identity when compared to standards
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True or False:
HPLC – Height/Area of the component peak is proportional to quantity
answer

True
question

What is HPLC most commonly used to screen for & ID?
answer

Drugs of abuse
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What does Gas Chromatography do?
answer

Separates mixtures of compounds that are volatile or can be made volatile.
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What is the mobile phase of Gas Chromatography?
answer

carrier gas (N, helium, argon)
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Gas Chromatography – Which compounds move more slowly?
answer

Higher Boiling Points
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Gas Chromatography – Which compounds move most quickly?
answer

Compounds that most easily become gaseous
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What do Thermal conductors or flame ionization detectors produce?
answer

Electric signal proportional to
the concentration of the volatile components
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A chromatogram will ID compounds by what?
answer

Retention Time
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Mass Spectrometry – Ions and Fragments are separated according to what?
answer

Mass-to-charge ratio
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What is the most specific method for drug confirmation?
answer

GC/Mass Spec
question

True or False:
GC/Mass Spec – Fragmentation is
reliable, allowing for published reference library of compounds
answer

True
question

What is the mobile phase for the following:
TLC
answer

Organic Solvent
question

What is the mobile phase for the following:
HPLC
answer

Liquid
question

What is the mobile phase for the following:
GC
answer

Inert Gas
question

What is the stationary phase for the following:
TLC
answer

Silica/cellulose on flat support
question

What is the stationary phase for the following:
HPLC
answer

Solid (silica gel or column)
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What is the stationary phase for the following:
GC
answer

Polymer or glass filled with inert liquid
question

What is the stationary phase for the following:
Mass Spec
answer

Electron bombardment after leaving HPLC or GC
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What is the application for/of the following:
TLC
answer

L/S ratios; Drug Screens
question

What is the application for/of the following:
HPLC
answer

Screen & quantitative drugs
question

What is the application for/of the following:
GC
answer

Screen & quantitative drugs
question

What is the application for/of the following:
Mass Spec
answer

Drug confirmation and quantitation

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