Author Archives: David Harvey

Peristaltic Pump

A propelling unit moves the carrier stream through the flow injection analyzer. Although several different propelling units have been used, the most common is a peristaltic pump. As illustrated here, a peristaltic pump consists of a set of rollers attached … Continue reading

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Instrumentation for Flow Injection Analysis

The basic components of a flow injection analyzer are shown below and include a pump for propelling the carrier stream and reagent streams, a means for injecting the sample into the carrier stream, and a detector for monitoring the composition … Continue reading

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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 contribute to the sample’s dispersion. Also shown on … Continue reading

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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 zone and reaction zone, the width of its … Continue reading

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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 by the transfer disk’s size, FIA allows for … Continue reading

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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 this example, B reacts more slowly (kB = … Continue reading

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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 we decrease the inhibitor’s concentration. A reversible inhibitor … Continue reading

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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, P, and to release the enzyme to react … Continue reading

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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 to choline and acetic acid. Many enzyme–substrate reactions … Continue reading

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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 in a few seconds, or even a few … Continue reading

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