Hi Arisa,

In chronoamperometry graphs, setting a desired voltage value, you see the current response with respect to time. To have several "detection range" for an electrochemical sensor would require you to run several potential steps for which you predict your analyte to be in.

This will give you the current-time response at some fixed time (ensure a steady-state value for accuracy) into each of these step experiments. You can further make your sampled-current voltammetry plots from those.

I hope this helps.

Arisa Ueda Chronoamprometry is a technique where current is measured at constant potential as a function of time

Where as in Cyclic voltammetry potential is varied as a function of time at a fixed scan rate.

For in chronoamperometry

Direct fomat-analyte promote activity of enzyme which catalyze the formation of measurable product.

Ex: First generation biosensor

Second generation enzymatic glucose sensor works on above principle

Glucose oxidase which catalyze the oxidation of glucose contains FAD as cofactor, initially FAD act as a electron acceptor and converts glucose to glucono lactone and FAD converted in to FADH2.

In the presence of artificial electron mediator SUCH AS FERRI CYANIDE

FADH2 converts back to FAD and the electron is accepted by oxidized form of mediator (for ex, Fe3+) and get reduced to Fe2+ in the presence of applied potential (oxidation) Fe2+ converts back to Fe3+.

In the above case glucose concentration is directly proportional to current produced by electrochemical mediator, i.e if more glucose is present in sample more current will be produced and vice versa

Indirect format : Analyte inhibit the activity and results in reduced rates of measurable product,

In the case of non enzymatic sensing analyte of our interest analyte bind with electrochemical active redox mediator. its based on the specific interaction between analyte and electrochemical mediator if X- CONC- of analyte is present it will bind with X amount of mediator and we and we measure remaining left over current produced by electrochemical mediator,

i.e more analyte less current and lees analyte more current. In such case concentration of analyte is inversely proportional to the current measured.

Conclusion its based on the reaction between analyte and electrochemical active species present on in our system current either increase or decrease not on the potential applied

Arisa Ueda In amperometry we can measure either oxidation or reduction at a time as it potential is fixed and resulting current is measured with time.it based on the interaction of analyte with electrochemically active mediator or reaction mechanism of analyte and mediator, current will increase or it decrease.

We can select either oxidation or reduction potential based on our experimental requirement. For ex in amperometry determination of hydrogen peroxide mostly reduction potential is applied to overcome anodic interference.

When we measure hydrogen peroxide amperometrically in negative (reduction) potential current increases with increase in the concentration of hydrogen peroxide.