AutoAnalyzer
From Wikipedia, the free encyclopedia
AutoAnalyzer is an automated analyzer using a special flow technique named "continuous flow analysis (CFA)" first made by the Technicon Corporation. The instrument was invented 1957 by Leonard Skeggs, PhD and commercialized by Jack Whitehead's Technicon Corporation. The first applications were for clinical analysis, but methods for industrial analysis soon followed, and by the time Technicon sold its business to separate clinical (Bayer) and industrial (Bran+Luebbe) buyers in 1987 industrial applications accounted for about 20% of CFA machines sold.
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[edit] Instruments
The best known of Technicon's CFA machines are the AutoAnalyzer II (introduced 1970), the Sequential Multiple Analyzer (SMA, 1969), and the Sequential Multiple Analyzer with Computer (SMAC, 1974). After Technicon was dissolved in 1987 Bayer did not manufacture any new CFA instruments, but Bran+Luebbe continued to manufacture the AutoAnalyzer II and TRAACS, a micro-flow analyzer for environmental and other samples, and went on to develop the AutoAnalyzer 3 in 1997 and the QuAAtro in 2004.
Today there are other manufacturers of CFA instruments. Astoria-Pacific International, for example, was founded in 1990 by Raymond Pavitt, who owned another CFA manufacturing company in the past. Based in Clackamas, Oregon, U.S.A., Astoria-Pacific manufactures its own micro-flow systems. Its products include the Astoria Analyzer lines for Environmental and Industrial applications; the SPOTCHECK Analyzer for Neonatal screening; and FASPac (Flow Analysis Software Package) for data acquisition and computer interface.
[edit] Clinical analysis
AutoAnalyzers were used mainly for routine repetitive medical laboratory analyses, but they had been replaced during the last years more and more by discrete working systems which allow lower reagent consumption. These machines typically determine levels of albumin, alkaline phosphatase, aspartate transaminase (AST), blood urea nitrogen, bilirubin, calcium, cholesterol, creatinine, glucose, inorganic phosphorus, proteins, and uric acid in blood serum or other bodily samples. AutoAnalyzers automate repetitive sample analysis steps which would otherwise be done manually by a technician, for such medical tests as the ones mentioned previously. This way, an AutoAnalyzer can analyze hundreds of samples every day with one operating technician. Early AutoAnalyzer instruments each tested multiple samples sequentially for individual analytes. Later model AutoAnalyzers such as the SMAC tested for multiple analytes simultaneously in the samples.
[edit] Industrial analysis
The first industrial applications - mainly for water, soil extracts and fertilizer - used the same hardware and techniques as clinical methods, but from the mid 1970s special techniques and modules were developed so that by 1990 it was possible to perform solvent extraction, distillation, on-line filtration and UV digestion in the continuously flowing stream. In 2005 about two thirds of systems sold world-wide were for water analysis of all kinds, ranging from sub-ppb levels of nutrients in seawater to much higher levels in waste water; other common applications are for soil, plant, tobacco, food, fertilizer and wine analysis.
[edit] Operating Principle
In a continuous flow analyzer, a peristaltic pump contains several tubes including one for the sample, one or more for various reagents and one or more to generate air bubbles. The pump tubes deliver into the "manifold" of junctions, coils and tubing where the reactions take place. In Segmented Flow Analyzers (SFA), the sample is mixed with small reproducible volumes of the required reagents and air bubbles are introduced into the flow, creating about 20 - 100 segments of liquid for each sample, keeping them separated as they flow sequentially through the tubing. The inlet side of the sample pump tube is connected to the sample probe in an autosampler. The sample probe moves between the small cups holding liquid samples and a reservoir of wash solution, normally pure water, which also serves to generate a baseline response. The sample / reagent mixture flows through mixing coils, and depending on the method a heated coil for elevated reaction temperature or other modules to develop a color proportional to the amount of analyte in each sample. The samples with developed color flow through a colorimeter to measure the color. Other detectors such as a flame photometer, a fluorometer or an ISE module are used for some applications.
Flow Injection Analyzers (FIA) operate similarly to SFA, but without the air segmentation. A flow injection analyzer introduces sample into a flowing stream of reagents using an injection valve. The reagents and sample are mixed together while passing through tightly coiled narrow bore teflon tubing and other modules to develop a product that is measurable by a detector. Normally the same chemistries possible by SFA are possible by FIA. SFA methods have a clear advantage at obtaining lower detection limits, and the ability to bring all chemical reactions to completion prior to measurement.
Previously a chart recorder and more recently a PC 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. 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 the diaphragm 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.
AutoAnalyzers are still used for a few clinical applications such as neonatal screening or Anti-D, but the majority of instruments are now used for industrial work. There exist standard methods published by the American Society of Testing Materials (ASTM), the US Environmental Protection Agency (EPA) as well as ISO for parameters in environmental analysis such as nitrite, nitrate, ammonia, cyanide, and phenol, and also for vegetable and tobacco leaf analysis. The main reasons for using an AutoAnalyzer for these applications are the convenience of integrating difficult sample preparation and cleaning steps like distillation or ultrafiltration (dialysis); the low detection limits, which make CFA still the most widely used technique for the determination of nutrients in seawater; and the high analysis rate, typically between 30 and 100 samples per hour.
