ANALYTICAL TECHNIQUES: ELECTROCHEMISTRY AND MASS SPECTROMETRY

ELECTROCHEMISTRY

It is the study of electron movement in an oxidation or reduction reaction at a polarized electrode surface.

• can be measured with an electrode-containing instrument.

electrode

anode

cathode

IN ELECTROCHEMISTRY,

Each ____________ is characterized by a half- cell reaction and a half-cell potential (voltage). The electrode from which electrons flow is called the __________. The electrode accepting the electrons is the ___________.

activity of selected ions

• reference electrode

• analytical electrode

• reference electrode

reference electrode

Electrode with a constant voltage

half cells

Serve as reference potential against unknown voltage.

Silver-silver chloride

Calomel (Hg2Cl2) electrode

• Concentration of ions in a test solution is calculated from the measured potential difference between the 2 electrodes.

analytical electrode

Measuring electrode

blood gas instruments

pH electrode

pCO2 Electrode

Severing haus electrode

pO2 Electrode

Clark electrode

pH electrode

Measure hydrogen ion activity

pCO2 Electrode

- pH electrode with a CO2-permeable membrane and bicarbonate buffer

pO2 Electrode

Measures current flow produced from loss or gain of electrons. ½ O2 + H2O + 2e- →2OH- Ag → Ag+ + e

Clark electrode

Ion-Selective Electrodes

Ion-Selective Electrodes

Composed of an electrochemical half-cell and an ionspecific membrane

• Sodium electrode

• Potassium electrode with valinomycin

• Calcium electrode 

300x

1000x

does not

IN ion selective electrodes,

Sodium electrode - _________ sensitive than potassium

Potassium electrode with valinomycin - ___________ sensitive than sodium

calcum electrode - _________ have specific value

MASS SPECTROMETRY

It is the definitive identification and quantitation of samples or compounds eluting from GC or HPLC columns.

Application of MASS SPECTROMETRY

- Measuring drugs of abuse in urine.

- Measuring low-level and mixed- polarity analytes.

- Vitamin D, testosterone and immunosuppressant drugs

PROTEOMICS

Study of proteomes and their functions

“Complete set of proteins expressed by a genome, cell, tissue, or organism at a specific time”

protein expression, matrices

- Investigation of the protein products encoded by genes

- Proteins are separated in ________ (resolved) using SDS-PAGE, visualized by colorimetric dyes, and analyze in MALDI-TOF.

SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis)

is a fundamental laboratory technique used to separate proteins based on their size (molecular weight)

MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization - Time-of-Flight)

powerful mass spectrometry technique used to identify and characterize molecules, especially large biomolecules like proteins and peptides