Fiagrams
An FIA curve, or fiagram, is a plot of the detector’s signal as a function of time. The illustration below shows a typical fiagram for conditions in which both convection and diffusion […]
Image and Video Exchange
Get a look at images, photos, videos, and animations that encompass many facets of teaching and learning about analytical chemistry.
Flow Profile in Flow-Injection Analysis
When we first inject a sample into an FIA’s carrier stream it has the rectangular flow profile of width w as shown below in (a). As the sample moves through the mixing […]
Flow-Injection Analysis
Flow injection analysis (FIA) was developed in the mid-1970s as a highly efficient technique for the automated analyses of samples. Unlike a centrifugal analyzer, in which the number of samples is limited […]
Kinetic Analysis of a Mixture
The figure below illustrates how we can use a kinetic analysis to determine the concentration of two analytes, A and B, provided that there is a difference in their reaction rates. In […]
Elucidating Mechanisms for the Inhibition of Enzyme Catalysis
When an inhibitor interacts with an enzyme it decreases the enzyme’s catalytic efficiency. An irreversible inhibitor covalently binds to the enzyme’s active site, producing a permanent loss in catalytic efficiency even if […]
Lineweaver-Burk Plots
For an enzyme–substrate reaction following a simple mechanism E + S ↔ E–S ↔ E + P consisting of the initial formation of an enzyme–substrate complex, ES, and its subsequent decomposition to form the product, […]
Enzyme Kinetics
Enzymes are highly specific catalysts for biochemical reactions, with each enzyme showing a selectivity for a single reactant, or substrate. For example, the enzyme acetylcholinesterase catalyzes the decomposition of the neurotransmitter acetylcholine […]
Instrumentation for Kinetic Methods of Analysis
A significant experimental problem when the reaction’s kinetics are fast is ensuring that we rapidly and reproducibly mix the sample and the reagents. For a fast reaction we need to make measurements […]
Quenching a Kinetic Reaction
Monitoring a kinetic reaction is straight-forward, provided that the reaction does not proceed to a appreciable extent during the time it takes to make an individual measurement. As you might expect, this […]
Direct-Computation Rate Method
In a rate method we use the differential form of the rate law to determine the analyte’s concentration. As shown here, the rate of a reaction at time t, (rate)t, is the […]
Taxonomy of Chemical Kinetic Methods of Analysis
Shown here is one useful scheme for classifying chemical kinetic methods of analysis. Methods are divided into two main categories: direct-computation methods and curve-fitting methods. In a direct-computation method we calculate the […]
Capillary Electrochromatography
Another approach to separating neutral species is capillary electrochromatography, CEC. In CEC the capillary tubing is packed with 1.5–3 μm particles coated with a bonded stationary phase. Neutral species separate based on […]