Biochemical instrumental analysis-14

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.

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.

Definition

Sure

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. 

Why automation?

4 decrease2 increase

1 funny

I-Continuous flow analysersIn 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.

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.

II-Discrete analyzers

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

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.

How it work?

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

(1)semi automated.

(2)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.

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. 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.