Exam 5 Electrochemistry & Chromatography

What are the 3 types of Electrochemistry?
Ion selective electrodes & pH meters
Gas Sensing Electrodes
Electrophoresis
What are the 4 types of Chromatography?
TLC – thin layer chrom
HPLC – high performance liquid chrom
GC – gas chromatography
MS – mass spec
Define Electrochemistry
Chemical reactions that occur due to the flow or presence of electrons
Define Current
Number of electrons traveling through a substance, measured in amperes
Define Potential
For electrons to flow, force must be applied to the system. Measured in volts
True or False:
You can’t measure the potential of one electrode; only the potential difference between two electrodes
True
What does the Ion-Selective Electrodes measure?
Potential
What does ISE stand for?
Ion-Selective Electrodes
What is the potential (V) measured by ISE proportional to?
Level of ion in the patient’s sample
Describe a Reference Electrode
known potential and generates a reproducible, constant V
Describe an Indicator Electrode
The V will vary depending on the
level of patient ion
What are commonly used Reference Electrodes
Mercury/mercurous chloride (calomel) and Ag/AgCl
What do ISEs selectively allow?
Only 1 Ion to pass through a membrane to the tip of the electrode
When the 1 ion passes through the membrane to the tip of the electrode, what is generated?
V (Potential)
What are 2 Commonly used Glass Sample Membranes
pH meters
Sodium
What is the commonly used Liquid membrane?
Calcium
What is the commonly used Liquid membrane antibiotic?
Potassium (uses valinomycin)
What does Direct ISE use?
Whole Blood
What does Indirect ISE use?
Pre-diluted plasma or serum
Indirect ISE – High TP or lipid can cause Sodium to be what?
Falsely Decreased
What is another name for the pCO2 Electrode?
Severinghaus Electrode
What is another name for the Severinghaus Electrode?
pCO2
pCO2 – CO2 diffuses through and mixes with bicarbonate buffer, causing the release of ________
H+ ions
pCO2 Electrode – The H+ ions then diffuse thru a H+-permeable membrane, what is this membrane associated with?
ISE
Ammonia Gas Electrode – NH3 mixes with Ammonium Chloride, causing the release of _______
OH- ions
Ammonia Gas Electrode –
The amount of OH- ions is proportional to what?
Level of NH3 in the sample
What is another name for the pO2 Electrode?
Clark Electrode
What is another name for the Clark Electrode?
pO2 Electrode
True or False:
Current will not be conducted without O2 in the system
True
pO2 Electrode – The amount of current generated is proportional to what?
Level of pO2 in the sample
What is Chromatrography used for?
Separate mixtures into individual components based on different physical characteristics such as size, solubility, or charge
What are the major applications for Chromatrography?
Drug screens
Drug Confirmation
Define the following component of the chromatography system:
Mobile Phase
A liquid or gas that carries the patient sample through the system
Define the following component of the chromatography system:
Stationary Phase
A solid or liquid through which the mobile phase flows; housed in a column
Define the following component of the chromatography system:
Eluate
separated components
True or False:
Chromatography –
Compounds interacting more strongly with the stationary phase spend a longer time in the column than those with less affinity
True
What are the 4 Chromatography Modes of Separation?
Adsorption
Partition
Steric Exclusion
Ion-Exchange
Describe Adsorption
Competition between the sample and the mobile phase for adsorptive sites on a solid stationary phase
What type of Chromatography is Adsorption?
Liquid-Solid
What type of Chromatography is Partition?
Liquid-Liquid
What type of Chromatography is Steric Exclusion
Liquid-Solid
Partition is based on what?
Solubility patterns in an organic (nonpolar) solvent and an aqueous (polar) solvent
Partition – Polar molecules remain where?
Aqueous Layer
Partition – Nonpolar molecules are what?
Extracted into the organic solvent
What is Steric Exclusion based on?
Size & Shape of molecules
With Steric Exclusion which molecules pass through rapidly:
Larger or smaller?
Larger Molecules
With Steric Exclusion which molecules pass through more slowly because they become trapped in the pores:
Larger or smaller?
Small molecules
With Ion-Exchange, the Stationary phase (resin) has what on its surface?
Charged functional groups
Ion Exchange – What do Cation-exchange resins remove?
Na+ and other cations
Ion Exchange – What do Anion-exchange resins remove?
Cl- and other anions
Which system is used to deionize water?
Ion-Exchange
–Anion & Cation columns combined
How do sample molecules move in Thin Layer Chromatography?
Solvent migrates up by capillary action, dissolving & carrying sample molecules
Define Retention Factor (Rf)
The distance a compound migrates, compared to the distance the solvent front moves
What is the Mathematical formula for the Retention Factor
Distance leading edge unknown component moves / total distance solvent front moves
What is TLC mainly used for?
Drug Screens
What does HPLC use to force a sample through the system?
Pressure
What does HPLC reduce?
Test Time
With HPLC what stage is the mobile phase?
Liquid
What does the following do in the HPLC:
Pump
forces the mobile phase through the column
What does the following do in the HPLC:
Sample injector or syringe
Shoots the sample into the path of the mobile phase
Describe the following in the HPLC:
Column or Stationary Phase
Packed into long stainless steel tubes
What does the following do in the HPLC:
Detector
generates an electronic signal as compounds are eluted
What does the following do in the HPLC:
Recorder
generates a peak as each compound elutes out
What in the HPLC pump provides constant flow?
Pistons
HPLC Detector – The signal is proportional to what?
Concentration of each separated component
What is the print-out of a HPLC called?
Chromatograph
Define HPLC Retention Time
The time it takes for a compound to elute (after sample injection)
What is retention time used to determine?
Compound identity when compared to standards
True or False:
HPLC – Height/Area of the component peak is proportional to quantity
True
What is HPLC most commonly used to screen for & ID?
Drugs of abuse
What does Gas Chromatography do?
Separates mixtures of compounds that are volatile or can be made volatile.
What is the mobile phase of Gas Chromatography?
carrier gas (N, helium, argon)
Gas Chromatography – Which compounds move more slowly?
Higher Boiling Points
Gas Chromatography – Which compounds move most quickly?
Compounds that most easily become gaseous
What do Thermal conductors or flame ionization detectors produce?
Electric signal proportional to
the concentration of the volatile components
A chromatogram will ID compounds by what?
Retention Time
Mass Spectrometry – Ions and Fragments are separated according to what?
Mass-to-charge ratio
What is the most specific method for drug confirmation?
GC/Mass Spec
True or False:
GC/Mass Spec – Fragmentation is
reliable, allowing for published reference library of compounds
True
What is the mobile phase for the following:
TLC
Organic Solvent
What is the mobile phase for the following:
HPLC
Liquid
What is the mobile phase for the following:
GC
Inert Gas
What is the stationary phase for the following:
TLC
Silica/cellulose on flat support
What is the stationary phase for the following:
HPLC
Solid (silica gel or column)
What is the stationary phase for the following:
GC
Polymer or glass filled with inert liquid
What is the stationary phase for the following:
Mass Spec
Electron bombardment after leaving HPLC or GC
What is the application for/of the following:
TLC
L/S ratios; Drug Screens
What is the application for/of the following:
HPLC
Screen & quantitative drugs
What is the application for/of the following:
GC
Screen & quantitative drugs
What is the application for/of the following:
Mass Spec
Drug confirmation and quantitation