bus flashacrds Flashcards
bus (13 cards)
what was another way to measure oxygen without a ship?
The clarks cell- oxygen is reduced- the use of a platinum electrode- A platinum white where oxygen is reduced
O2+ 4e- + 4H+ goes to 2 h2o
The current measured is proportional to the oxygen concentration
The electron flow between the anode and cathode (via an external circuit) creates a current- rate of reduction is related to the amount of oxygen
Advantages - small and cheap but it requires calibration and consumes the oxygen.
Minimum of 2 electrodes.
what is the optode
Requires blue light and a fluorophore
The blue fluorophore activates a fluorescence layer- its response changes to the amount of oxygen that is present. - requires a photodiode.
Oxygen quenches the fluorescence signal
Measuring the decrease in fluorescence
the amount that the samples spread out does what in terms of standard deviation?
the amount that they spread out increases with the square root of the coulum
what is H?
spatial or temporal resolution
what value for H is good?
a small H is better
how much is the accuracy’s for the gas chromatography?
1-5%
the measurement of the sample through the detector is- what
tr; = tr-tm
what does the thermal conductivity detector do?
A hot wire sits in a flow of gas (usually helium).
Helium cools the wire well because it has high thermal conductivity.
When a sample comes out of the GC column, it mixes with the helium.
Most samples don’t cool the wire as well as helium does → the wire gets a bit hotter.
A hotter wire has higher resistance, and the detector picks up this change.
So, when something comes out of the column, the detector sees a change in resistance- universal
Flame Ionization Detector (FID)
Mixes with H2/air and is burned.
Leads to flame rich in electrons and
cations. Universal detector for
organic compounds.
Electron Capture detector (ECD)
the amount of beta electrons that flows through how much it.
what was the limitations of the wrinkler method?
multistep, time consumeing, tested quickly as bacteria that consume oxygen can act quilckly, other ozides can interfer.
the wrinkler method
Fixation: Add manganese(II) sulfate and alkaline iodide – oxygen oxidizes Mn²⁺ to Mn(IV) hydroxide.
Acidification: Add acid to dissolve the Mn(IV) complex, which releases iodine (I₂) proportional to O₂.( acid is sulfuric acid )
Titration: Titrate the liberated I₂ with sodium thiosulfate until the solution becomes colorless (starch indicator turns blue → colorless).
