Auto analyser
- 1. AUTO ANALYSER By, A. Michael nickson BIOMEDICAL INSTRUMENTTION
- 2. An Auto analyzer is used for clinical analysis (e.g. to measure blood chemistry) and display that on a graphic recorder. It was invented in 1957 by Leonard Skeggs and commercialized by Jack Whitehead’s Technicon Corporation It works on the principle of Continuous flow analysis (CFA) which comprises of both segmented flow analysis (SFA) and flow injection analysis (FIA) AUTO ANALYSER:
- 3. The basic principle of the SFA is the introduction of air bubbles. In SFA a continuous stream of material is divided by air bubbles into discrete segments 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 SFA is the introduction of air bubbles. The act as a barrier between packets to prevent cross contamination as they travel down the length of the glass tubing. Segmented Flow Analysis (SFA):
- 4. Flow Injection Analysis (FIA): SFA 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 while FIA systems separate each sample from subsequent sample with a carrier reagent. In all FIA techniques sample and reagents are merged to form a concentration gradient that yields analysis results.
- 5. COMPONENTS : Sampler Proportioning pump Dialyzer Heating bath Colorimeter Graphic recorder
- 6. SAMPLER: This module holds the batch of samples awaiting analysis in separate cups on a circular tray which is rotated at intervals. A probe connected by plastic tubing to the proportionating pump enters each sample serially. The volume of sample aspirated is determined by the pumping rate and the adjustable dwell time of the probe in the sample.
- 7. PROPOTIONING PUMP: This module determines the relative flow rates of sample and all reagents and replaces the use of different sizes of pipettes in manual methods. The pumping technique involves the peristaltic action produced by a series of rollers passing along an array of parallel plastic “Pump tubes”. Each roller compresses all tubes so that the rate flow in each tube is proportional to the square of the pump tube diameter.
- 8. DIALYSER: This module achieves the separation of small and large molecules by allowing the former to pass through a semipermeable membrane from the donor (sample) stream of liquid and air bubbles to a recipient , stream of liquid again segmented by air bubbles. The dialysis rate depends on the temperature but complete passage of small molecules into the recipient stream is rarely achieved and may be only a few percent of the total.
- 9. HEATING BATH: It is to maintain the reaction mixture at a constant temperature for a defined time to bring about the required chemical change under controlled conditions. The incubator bath consists of a glass delay coil mounted in a thermostatically controlled oil bath. This is sealed and stirred constantly. Most baths are set at 37°C or 95°C but some have adjustable thermo- regulators which allow operation up to 120°C or even higher.
- 10. COLORIMETER: The colorimeter is to measure the intensity of colour produced in the reaction and to provide a graphical display of change in colour with time. The use of double beam spectrophotometer is costly and is rarely justified by analytical requirements. The single beam colorimeters have insufficient stability to operate reliably over the long period required. The Auto-analyser MKI colorimeter combines double beam operation with interference filters to select the wavelength.
- 11. RECORDER: 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.