What is the automatic analyzer and principle

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The AutoAnalyzer is an automated analyzer using a flow technique called continuous flow analysis (CFA),The first applications were for clinical analysis,but methods for industrial analysis soon followed.The design is based on separating a continuously flowing stream with air bubbles.

Operating principle
In continuous flow analysis (CFA) a continuous stream of material is divided by air bubbles into discrete segments in which chemical reactions occur,The continuous stream of liquid samples and reagents are combined and transported in tubing and mixing coils,The tubing passes the samples from one apparatus to the other with each apparatus performing different functions,such as distillation,dialysis,extraction,ion exchange,heating,incubation,and subsequent recording of a signal,An essential principle of the system is the introduction of air bubbles,The air bubbles segment each sample into discrete packets and act as a barrier between packets to prevent cross contamination as they travel down the length of the tubing,The air bubbles also assist mixing by creating turbulent flow (bolus flow),and provide operators with a quick and easy check of the flow characteristics of the liquid,Samples and standards are treated in an exactly identical manner as they travel the length of the tubing,eliminating the necessity of a steady state signal,however,since the presence of bubbles create an almost square wave profile,bringing the system to steady state does not significantly decrease throughput ( third generation CFA analyzers average 90 or more samples per hour) and is desirable in that steady state signals (chemical equilibrium) are more accurate and reproducible.

A continuous flow analyzer (CFA) consists of different modules including a sampler,pump,mixing coils,optional sample treatments (dialysis,distillation,heating,etc.),a detector,and data generator,Most continuous flow analyzers depend on color reactions using a flow through photometer,however,also methods have been developed that use ISE,flame photometry,ICAP,fluorometry,and so forth.

Flow injection analyzer
Flow injection analysis (FIA),was introduced in 1975 by Ruzicka and Hansen,The first generation of FIA technology,termed flow injection (FI),was inspired by the AutoAnalyzer technique invented by Skeggs in early 1950s.[citation needed] While Skeggs' AutoAnalyzer uses air segmentation to separate a flowing stream into numerous discrete segments to establish a long train of individual samples moving through a flow channel,FIA systems separate each sample from subsequent sample with a carrier reagent,While the AutoAnalyzer mixes sample homogeneously with reagents,in all FIA techniques sample and reagents are merged to form a concentration gradient that yields analysis results.

FIA methods can be used for both fast reactions as well as slow reactions,For slow reactions,a heater is often utilized,The reaction does not need to reach completion since all samples and standards are given the same period to react,For typical assays commonly measured with FIA (e.g.,nitrite,nitrate,ammonia,phosphate) it is not uncommon to have a throughput of 60-120 samples per hour.

FIA methods are limited by the amount of time necessary to obtain a measurable signal since travel time through the tubing tends to broaden peaks to the point where samples can merge with each other,As a general rule,FIA methods should not be used if an adequate signal cannot be obtained within two minutes,and preferably less than one.[citation needed] Reactions that need longer reaction times should be segmented,However,considering the number of FIA publications and wide variety of uses of FIA for serial assays,the "one minute" time limitation does not seem to be a serious limitation for most real life assays.[citation needed] Yet,assays based on slow chemical reactions have to be carried either in stopped flow mode ( SIA) or by segmenting the flow.

OI Analytical,in its gas diffusion amperometric total cyanide method,uses a segmented flow injection analysis technique that allows reaction times of up to 10 minutes by flow injection analysis.

Technicon experimented with FIA long before it was championed by Ruzicka and Hansen,Andres Ferrari reported that analysis was possible without bubbles if flow rates were increased and tubing diameters decreased.In fact,Skegg's first attempts at the auto analyzer did not segment,Technicon chose to not pursue FIA because it increased reagent consumption and the cost of analysis.

The second generation of the FIA technique,called sequential injection analysis (SIA),was conceived in 1990 by Ruzicka and Marshal,and has been further developed and miniaturized over the course of the following decade.[citation needed] It uses flow programming instead of the continuous flow regime (as used by CFA and FIA),that allows the flow rate and flow direction to be tailored to the need of individual steps of analytical protocol,Reactants are mixed by flow reversals and a measurement is carried out while the reaction mixture is arrested within the detector by stepping the flow,Microminiaturized chromatography is carried out on microcolumns that are automatically renewed by microfluidic manipulations,The discrete pumping and metering of microliter sample and reagent volumes used in SI only generates waste per each sample injection,The enormous volume of FI and SI literature documents the versatility of FI and SI and their usefulness for routine assays (in soil,water,environmental,biochemical and biotechnological assays) has demonstrated their potential to be used as a versatile research tool.

Dialyzer module
In medical testing applications and industrial samples with high concentrations or interfering material,there is often a dialyzer module in the instrument in which the analyte permeates through a dialysis membrane into a separate flow path going on to further analysis,The purpose of a dialyzer is to separate the analyte from interfering substances such as protein,whose large molecules do not go through the dialysis membrane but go to a separate waste stream,The reagents,sample and reagent volumes,flow rates,and other aspects of the instrument analysis depend on which analyte is being measured,The autoanalyzer is also a very small machine

Recording of results
Previously a chart recorder and more recently a data logger or personal computer records the detector output as a function of time so that each sample output appears as a peak whose height depends on the analyte level in the sample.

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