Fia Lecture 7

7/30/2019 Fia Lecture 7

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Chemistry concept on FIA

Lecture #7


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Chemistry on FIA

Play important role in FIA

Converting the analyte into a detectablespecies compatible with the used detector

Initially colorimetric reactions dominated thechemistry of FIA, however other reactions hasalso been applied to FIA

One of the most important points to keep inmind in adapting a manual method to FIA is thatmanual methods are generally equilibrium basedwhile FIA methods are non-equilibrium based.


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Available method

Searching internet based database:

http://www.fia.unf.edu/

Searching FIA reference books

Searching for a conventionalanalytical method which can be

adapted to FIA/SIA


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Single stream FIA

A stream containing reagent is pumped through the system.A volume of sample is injected into the stream anddispersion causes mixing of the reagent with the samplezone leading to chemical reaction between analyte andreagent as the zone passes through the reactor and

detector.


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Single stage chem. reactionin two stream FIA

The sample is injected into a reagentless carrier, and thereagent stream is merged with it downstream. This

provides a uniform mixing of the reagent with sampleover the length of the sample zone, and often providesbetter sensitivity and performance compared to thesingle-steam approach. For this reason, the two-streammanifold is often preferred over the single-stream

manifold for simple chemistries.


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Two stage chem. reaction intwo stream FIA

The sample is injected into the first streamcontaining reagent 1. The analyte reacts with

the reagent, generating an intermediate. Onmerging with stream two downstream, theintermediate reacts with reagent 2, forming theproduct that is measured by the detector.


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Analysing cyanide based onthe Knig reaction

The first stream contains the reagent, chloramine-T.On injecting the sample into this stream, the cyanide

reacts with the chloramine-T to form cyanogenchloride. The second stream contains a mixture ofsodium isonicotinate (INA) and 3-methyl-1-phenyl-2-pyrazollin-5-one (PZ). On merging with thisstream, the cyanogen chloride reacts with the PZ to

form a highly colored purple product.


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Three stream FIA

Three stream manifolds are generally used for twostage or three stage chemistries. When used for two

stage chemistries, the sample is injected into areagentless carrier, and merges downstream withthe first reagent. Further downstream, it mergeswith the second reagent.


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Multi-determinations in

FIA

whether the sample is injected once or

many times (simultaneously orsequentially); and

the number of detectors used (a single

multi-channel detector or severaldetectors arranged in series or inparallel).


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Two examples of FIA assemblies for multi-determinations, (a) Schematic diagram of an FIA manifold formulti-determinations on the basis of a reverse FIA procedure with sequential injection of reagents. R1 ,R2 and R3 are different reagents inserted into the sample solution, S. (b) Schematic diagram of an FIAmanifold with simultaneous double injection of sample and an asymmetric merging configuration. Eachinjected sample aliquot is submitted to a different chemical reaction; R (reagents) and C (carrier) can bedifferent. Both sample plugs arrive separately to the detector flow-cell due to the asymmetricconfiguration. D, detector; Rc, recorder; Iv, injection valve; P, propulsion unit


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Spliting the sample into two boluses with different ways (and lengths) to detector.The chemical treatments are different for both sample parts. S, sample; C,carrier; R, reagent; Iv, injection valve


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Configurations with a Single Detector

Multi-determinations by changing the composition of the carrier-reagent. P2 isthe pump for changing the rotating speed to produce a mixture (C1 and C2) of

variable pH. S, sample; R, derivatizing reagent; Iv, injection valve


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FIA Configurations using Several Detectors

(a) Schematic diagram of an F1A manifold with several detectors in serial configuration; (b)schematic diagram of FIA manifolds for simultaneous determinations with several detectors in

parallel configuration. P, pump; S, sample; C, carrier; R, reagent; Iv, injection valve; Rc,recorder; D, detector; W, waste


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Reversed FIA

Reverse FIA manifold (on top) compared with the normal FIA mode. Nodifferences are observed in manifolds. Differences are in how the method is

operated. P, pump; R, reagent; S, sample; C, carrier; D, detector; W, waste; Iv,njection valve


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Monitoring Industrial Processes

Continuous monitoring without injecting samples (no FIA). The system is alternately workingwith the sample and with the standard solutions. The calibration can be periodicallyrepeated. Types of signal are depicted in the bottom part of the figure. Stn, standard

solution; Br, branch stream; R, reagents; W, waste; D, detector;P, pump; Sk, selecting key

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Fia Lecture 7