Biochemical instrumental analysis-14 Dr. Maha Al-Sedik

Automation

During the past few year, there has been a considerable increase in clinical demand for laboratory investigations. When the volume of work increased, there must be a need for work simplification.

Definition Laboratory automation: is the use of instrument and specimen processing equipment to perform clinical assay with only minimal involvement of the technologist. Another definition is mechanization of the laboratory work.

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Why automation? 4 decrease 2 increase 1 funny Decrease human error. Decrease liability to infection. Decrease laboratory costs. Decrease time needed for the test. increase productivity. Increase number of tests for the same sample.   Employ relatively less skilled laboratory technician. 

I-Continuous flow analysers In these systems, the samples and reagents are passed sequentially through the same analytical pathway and separated by means of air bubbles.

Samples were aspirated into tubing to introduce samples into a sample holder. Bring in reagent. Create a chemical reaction. Pump the chromogen solution into incubator then cuvette for spectrophotometric analysis.

Principle of detection: Detection is by measuring absorbance by spectrophotometer through a continuous flow cuvette (cell) at a certain wavelength. When there is no sample, the sample probe is placed in distilled water to avoid blockages, clogging and precipitation.

Disadvantages: 1-The machine does not allow test selection, all tests must be performed even if not requested. 2-The machine must run continuously even when there are no tests. 3-Because of the continuous flow, reagents must be drawn at all times even when there are no tests to perform.

4-The instrument must be closely monitored all the time for air bubbles uniformity; reagent availability and tubing integrity and most important of all carry over problems. 5-They are usually large in size and occupy large space.

II-Discrete analyzers Discrete analysis is the separation of each sample and accompanying reagents in a separate container. Discrete analyzers have the capability of running multiple tests on one sample at a time or multiple samples one test at a time. They are the most popular and versatile analyzers and have almost completely replaced continuous flow.

Sample reactions are kept discrete (separated) through the use of separate reaction cuvettes, cells, slides, or wells that are disposed of following chemical analysis. This keeps sample and reaction carryover to a minimum but increases the cost per test due to disposable products.

Hitachi 902 Analyzer

How it work? The Operator selects the test(s) he would like to run and enters the Sample IDs and any other information for the analysis. Sample test tubes and reagent bottles are loaded onto the system. The run is started.

The system uses its robotic arm, sample needle and syringe to mix samples and reagents in the reaction cuvettes.  Once the end point of the reaction is completed, the photometer measures the resultant absorbance.

The data is collected by the software. The data can be printed. Discrete analyzers have the capability to run multiple tests one sample at a time or multiple samples one test at a time. They are the most common analyzers.

Discrete analyzer Batch analysers Stat analysers

(A) Batch analysers: These are convenient to analyse specimen in batches ( groups ) such as of sugar, urea or creatinine etc. state testing may not be conveniently carried out on these analysers. The batch analysers can be further differentiated as semi automated. fully automated.

(B) Stat Analysers: In the case of these analysers many reagents (8 to 20 or more) can be pipetted one after another, so that various biochemical determinations can be performed on one specimen, according to the number of tests ordered for the patient.

Sample 1 glucose, urea, creatinine and electrolytes. Each sample is treated differently according to the tests requested and programmed by the operator. E.g. Sample 1 glucose, urea, creatinine and electrolytes. Sample 2 total protein, albumin, calcium. Sample 3 triglycerides, cholesterol. Sample 4 bilirubin, ALT, AST, ALP.

III-Centrifugal Analyzer Samples and reagents are added in a specially designed centrifugal type cuvette that has three main compartments. Sample is added from the sample cup by auto-sampler into the sample compartment of the centrifugal cuvette. The reagent probe into the reagent compartment of the centrifugal cuvette adds Reagent.

Both sample and reagents are allowed to equilibrate to the reaction temperature. Mixing of sample and reagent occurs when the rotor holding the cuvette is spun at high speed (4000 rpm) and then sudden stop. The spinning causes the sample to be added to the reagent while the turbulence caused by sudden stop results in mixing of sample and reagent.

After mixing, the rotor is spun at 1000 rpm After mixing, the rotor is spun at 1000 rpm. The reaction mixture is pushed horizontally to the bottom of the cuvette. Principle of detection: It has clear transparent sides for spectrophotometric measurement.

Advantages: Rapid test performance analyzing multiple samples. Batch analysis is a major advantage because reactions in all cuvettes are read simultaneously.