Prof. of Clinical Chemistry, Mansoura University
Implies a self – regulating process with
an element of feed-back which detect any
tendency to malfunction and readjusts
the equipment so that it continues to
function correctly.
Definitions and processing concepts:
Continuous flow analyser:
The reagent are pumped continuously by
syring pump
The samples are introduced at regular
intervals
The flow is segmented to separate one
specimen from anothor
This type is used as batch analyzer e.g
technicon .
Two types :
a) single channel continuous flow: analyse one
constituent in each specimen .
b) Multichannel continuous flow: determination
of several components in each sample
Discrete analyser:
Samples
are
processed
in
separate
reaction tubes.
The instrument contain a variety of
receptacle in which the sample and
reagents are mixed.
The reaction occurs: cuvettes, dry film
slides.
Some containers contain the reagents
and only the specimen need to be added.
Others add both reagents and specimen.
Reaction vessels and cuvets in discretes:
Reused or discarded
Used as cuvet or just reaction tube, aspirated in
tube then to
another tube for measurement
For wash reused reaction vesseles or cuvets
aspiration of the reaction mixture
a detergent ,alkaline or acid wash soln . is then
dispensed into and aspirated out of the cuvets
Parallel analysis:
All specimens are subjected to a series of
analytical processes at the same time in a
parallel fashion:

Discretionary multiple – channel analysis.

The specimen can be analyzed by any one
or by more than one of the available
processes (methods, channels).

Batch analyzer.
- A number of specimens are processed in the same
analytical session , or run:
The components steps in automated system
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Specimen identification.
Specimen preparation.
Specimen handling, transport and delivery.
Specimen processing.
Sample transport and delivery.
Reagent handling and storage.
Reagent delivery.
Chemical reaction phase.
Measurement approach.
Signal processing data handling and process
control.
These operations are usually performed sequentially but in some
instrument, they may be combined and occur in parallel.
Specimen identification:
Specimen Preparation:
Specimen Handling, Transport and Delivery:
Specimen processing:
Sample transport and delivery:
In continuous – flow system: the sample is
aspirated through the sample probe into
continuous reagent stream
In Discrete analyzers: the sample is
aspirated into sample probe and delivered,
with reagent into reaction tube or cup .
Carry over:
Carry over occurs when a previous sample
or reagent contaminates successive tests
in a run causing the next sample to have
an aberrantly higher or lower results .
Carry over occurs when anlytes occur in
extremely high levels e.g. enzyme or h CG
in pregnancy
Carry over also occurs in systems that
reuse cuvettes that are insufficiently
washed after each testing cycle.
In discrete systems with disposable reaction vessels and measuring
cuvettes carry over is caused by the pipeting system
Disadv: one analyte per rotor but now recent
models allow multiple analysis 24 rotors can be
loaded at one time.
In Continuous flow: by glass coils passing
through the samples and reagents.
Measurement approaches:
Spectrophotometry
Fluorimetry e.g. IMX
Chemiluminescenc e.g. IMMULITE
Electrochemical for electrolytes
Examples:
Automated immunoassay systems differ from
chemical analyzers in that they require the use
of:
1. solid – phase reagents to separate bound
and unbound
2. More sensitive detection methods e.g
fluorescence and chemiluminescence
3. Special handling of the reagents:
e.g. 1. Thermal conditioning to keep chemilum substrate stable.
2. Constant agitation to keep microparticles suspended.
Automated immunoassay
4-Multiple Calibrators: (upto 6)
• Calibration usually nonlinear
Example : ACS : 180
• benchtop
• R-A
• Imm . AS.S ay
IMMULITE :
• bench – top
• R-A
• Imm. Assay
Selection of instruments
Role of an automated system in the workflow of the
laboratory.
Identification of candidate system (RA or batch).
Cost effectiveness of the system.
User-friendiness (interface between the machine and
the human operator).
Analytical performance.
Advantages of automation:
Large number of samples may be processed
with minimal technician.
Two or more methods may be performed
simultaneously.
precision is superior to that of manual
performance.
calculations may not be required.
Disadvantages of automation:
limitation of the methodology "closed
system".
Expensive.
Many systems, are impractical to use for
small numbers of samples. Therefore, back
up manual methods may be required for
individual emergency analysis. Back up
methods must also be available in the
event of instrumental failures.