Today modern laboratories are equipped with latest sophisticated instrumental analytical techniques which are capable of delivering results of highest precision and accuracy. Automation of analysis with same if not better precision and accuracy is the key requirement of most laboratories.
Flow injection analysis (FIAS) offers an ideal solution which provides the following key advantages :
- Saving of time which is a major consideration for process quality control and commercial testing laboratories
- Improve precision over manual operations involved in sample preparation and detection
- Reduction in analysis costs due to reduced sample and reagent consumption
- Lowering limits of detection thereby offering ready solutions for ultra trace analysis
- Reduced burden on disposal of waste
The flow injection analysis system was developed in 1975 by Hansen and Ruzicka. It uses only a fraction of volume of samples and reagents in comparison to conventional analysis.
Small volume of sample is injected as a slug into the continuous uninterrupted stream of carrier solution. Reagent stream moves separately and mixing takes place in the chemifold. The reaction product is then driven to the detection cell.
Application Areas of Flow Injection Analysis
Flow injection analysis has been applied to several analysis techniques and main applications areas are mentioned in this article.
Atomic Absorption Spectroscopy
FIAS has been adapted to AAS mainly for analysis of volatile hydride forming elements and mercury. A stream of argon gas drives the volatile hydrides to the quartz cell which is in the beam path of AAS. Detection limits of some elements like arsenic and antimony are improved around 100 times.
Analysis is carried out either by direct absorption by the absorbing species or by the product of reaction with a reagent. Commercial UV- VIS systems with flow through detector or HPLC detector are commonly used. Direct and indirect determininations by complexation with metal chelation agents are generally adopted.
Majority of applications are in the mid-and far- IR regions. Flow cells have been used with KBr windows or Zn Se windows for aqueous samples. Gaseous compounds have been analysed using gas cells.
Turbidimetric detection is based on principle of light scattering by solutions containing solid suspensions. Majority of applications have been developed around measurement of light scattering by insoluble precipitates such as barium or lead sulphates.
Luminescence methods show a wider response and better selectivity than absorption methods. Fluorescence agents or dyes have also been used to enhance the fluorescence on complexation.
Flow injection systems have been developed along with biosensors for online monitoring of glucose and enzyme induced processes online.
Flow injection analysis is finding its way into numerous application areas. It makes possible analysis of samples containing high levels of dissolved solids. Sample pre-concentration or matrix removal is achieved by adding a pre-columnl in the solvent flow path. This extends scope to speciation studies for elements like Cr (III) and Cr (VI).
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