Structure and application of fully automatic biochemical analyzer

The fully automatic biochemical analyzer wraps the main components of the spectrophotometer: light source, monochromator (F dispersion device) colorimetric cell, detector, etc.; in addition, it also wraps the unique parts required for biochemical analysis, such as the sampling system, Cleaning system, temperature control system, software system, etc. It is mostly used for routine biochemistry, special protein and drug monitoring and other testing, with diversified program selection and microcomputer control. It can be freely programmed and can perform statistical processing. Some analyzers use chemically inert "capsule chemistry technogy" to strictly isolate analysis specimens or test items (sampling probes, reagent probes, and colorimetric cups are kept clean) to prevent cross-infection.
(1) Classification:
According to the structure of the reaction device, automatic biochemical analyzers are mainly divided into two categories: flow system and discrete system.
1. Flow type means that the chemical reaction of each sample to be tested and the reagents with the same measurement items are mixed and completed in the process of flowing in the same pipeline. This was the first generation of automated biochemical analyzers.
2. Discrete type means that the chemical reactions after the samples to be tested and the reagents are mixed are completed in their own reaction cups. There are several types of branches.
(1) Typical discrete automatic biochemical analyzer. This type of instrument is the most widely used.
(2) Centrifugal automatic biochemical analyzer. Each sample to be tested is mixed with reagents in its own reaction tank under the action of centrifugal force to complete the chemical reaction and measure. Since mixing, reaction and detection are completed almost simultaneously, its analysis efficiency is high.
3. The bag-type automatic biochemical analyzer uses reagent bags instead of reaction cups and cuvettes. Each sample to be tested is reacted and measured in its own reagent bag.
4. Solid-phase reagent self-customized biochemical analyzer (also known as dry chemical formula automatic analyzer) is to put the reagent solid phase on a carrier such as film or filter paper, and each sample to be tested is dropped on the corresponding test paper strip for reaction and measurement. Its advantages are quick operation and easy portability.
(2) Basic structure of a typical discrete automatic biochemical analyzer
1. Sample system
Samples include calibrators, controls, and patient samples. The system generally consists of sample loading, transportation and distribution devices.
Common types of sample loading and transport devices are:
(1) Sample disk, that is, the turntable on which the sample is placed has a single turn or multiple inner and outer turns. It is placed alone or combined with the reagent turntable or reaction turntable, and rotates in conjunction with the sample distribution arm during operation. Some use replaceable sample trays, which are divided into working and standby areas, in which multiple arc-shaped sample racks (sectors) are placed as transfer platforms. The instrument is automatically placed and replaced during the measurement, and the height of the sample cup or test tube placed on the sample tray is adjusted. , diameter and depth have certain requirements, some require special sample cups, and some can directly use blood collection test tubes. The number of sample trays loaded, as well as the number of calibrators, controls, routine samples, and emergency samples, is generally fixed. These should be selected based on job needs.
(2) Drive belt or orbital sampling, that is, the test tube racks (Rack) are discontinuous, usually 10 racks, and the conveyor belt is driven by a stepper motor to move the test tube racks forward in sequence, and then the racks are moved laterally to a fixed position one by one. position, sampled by the sample distribution arm.
(3) The chain-type sampling test tubes are fixedly arranged on the circulating transmission chain and moved horizontally to the sampling position. Some instruments can then clean the test tubes.
Distribution and sample addition devices are mostly composed of syringes, stepper motors or transmission pumps, sample addition arms, and sample probes.
① Syringe unit. According to the diameter of the syringe and the movement distance of the piston, the sample or reagent is quantitatively aspirated. Its accuracy determines the accuracy of sample addition, which can generally be accurate to 1 microliter. When the syringe leaks, first consider whether the probe is clogged, and secondly whether the syringe piston is worn. Some liquid adding systems use volumetric syringe pumps and numerically controlled pulse stepper motors to improve accuracy.
②The sample probe (Probe) is connected to the sample arm to directly absorb the sample. The probes are equipped with liquid level sensors to prevent probe damage and reduce carrying pollution. Some are equipped with a blockage detection alarm system: when blood clots and other substances in the probe sample are blocked, the instrument will automatically alarm to flush the probe, skip the current sample, and add the next sample. Some also have intelligent anti-collision devices: the probe immediately stops moving and alarms when encountering obstacles. Even so, it is still a wearing part during irregular operation. In order to protect the probe, in addition to setting the height of the sample container, the minimum liquid level, etc. in advance, the specifications, placement, liquid level, and other setting conditions of the sample container must not be changed at will. On some instruments, the sampler and liquid doser are combined, and adding sample and reagent or diluent to one probe are completed at one time.
③Sampling arm. Connect the probe and move between the sample cup (reagent bottle) and reaction cup to complete sampling and loading (adding reagents). Its movement method has a certain relationship with the working efficiency and working life of the instrument.
④The valve is used to determine the direction of liquid flow.
⑤Dilution system. Pre-dilute, post-dilute or double the sample, serially dilute the standard stock solution, etc. The dilution methods of different instruments are different, so pay attention to identification. The reagent system also has a dilution function:
2. Reagent system:
It generally consists of reagent storage and distribution and liquid adding devices.
(1) The reagent compartment is often combined with the reagent turntable. Most instruments set the reagent compartment as a cold storage room to improve the stability of online reagents.
(2) Dispense unit. Similar to the sample system. , the reagent probe can often pre-warm the reagent. The starting amount of the reagent 2 (R2) probe of the dual-reagent system should be lower to accommodate reagents with different R1/R2 ratios.
(3) Reagent bottle (Bottle). Available in different shapes and sizes. For example, COBAS MIRA PLUS instruments are available in 4, 10, 15, 35ml and other specifications, and the bottom of the bottle is concave; OLYMPUS Au600 instruments are available in 30 and 60ml; Hitachi 7060 instruments are available in 20, 50, 100ml and other specifications. Should be based on workload and reagent specifications. Consider the remaining volume of the reagent bottle and replacement frequency to make a reasonable selection. The uniquely designed cassette kit is small in size, prevents evaporation, and is easy to store.
(4) Supporting reagents often have barcodes, and the instrument is equipped with a barcode inspection system, which can check and verify the type, batch number, inventory, expiration date, calibration curve, etc. of the reagent, such as BeckmanCX7, etc.
(5) The automatic opening and closing system of reagent bottle caps is more conducive to reagent storage. Some instruments can add and replace reagents during operation, while others must do so in a paused state.
3. Barcode (Barcode) reading system
It generally consists of three parts: scanning system, signal shaping and decoder. The scanning system uses a light source to scan the barcode symbols with alternating black bars and white spaces. Due to the different reflections of light by the bars and spaces, and the different durations of reflected light from bars of different widths, reflected light with different intensities is produced. Then it is received and converted into an electrical signal of corresponding intensity through the photoelectric conversion element, and finally the signal is shaped and interpreted by the decoder. The system automatically identifies the sample rack and sample number, identifies reagents, calibrators, their batch numbers, expiration dates, and some can also identify calibration curves and other information.
Commonly used barcode types in laboratories include CODE 39, CODE 128, 2 of 5 Standard, Interleaved2of 5, etc. To self-program sample barcodes, a barcode input device is required, and the barcode reading system must match the barcode. There is a fully automatic test tube distribution and barcode pasting preparation system.
4.Reaction system
(1) The reaction plate is loaded with a series of reaction cuvettes (Cuvettes), mostly in the form of a turntable. During the reaction measurement process, the sample arm, liquid adding arm, stirring rod, light path and cleaning device are rotated according to a fixed procedure. Some instruments complete the reaction in the reaction cup and then inhale the cuvette for colorimetry. Nowadays, it is more common for the reaction and detection to be performed in the cuvette at the same time, which is more efficient and is especially suitable for continuous monitoring methods. Colorimetric cups are mostly made of hard quartz glass, hard glass, acrylic plastic without UV light absorption, etc., and their service life varies. The Dimension series cuvettes are automatically manufactured in the machine, automatically sealed, rinse-free, and pollution-free. The flow cell type is mainly used in small analyzers. The volume is generally tens of microliters, but the liquid extraction pipeline takes up more reaction liquid, and multiple samples are used continuously, which increases the chance of cross-contamination.
Peristaltic pump (Pump). The semi-automatic biochemical instrument requires a peristaltic pump to pump the reaction solution into the flow colorimetric cell for measurement. It is required to calibrate the peristaltic pump regularly, that is, to check whether the pump's liquid suction volume is accurate by sucking in a certain amount of water. Generally, there is a pump calibration function.
(2) Mixing unit (Mixing unit) For example, a multi-head rotating stirring rod (two-head double cleaning mixing system) is used. Stirring rods often have a Teflon non-stick coating to prevent liquids from sticking.
(3) Temperature control device The biochemical analyzer uses a constant temperature control device to maintain the regulation and stability of the incubation temperature, which is also controlled by a computer. The ideal incubation temperature fluctuation should be less than ±01°C.
There are three ways to maintain a constant temperature.
①Air bath constant temperature: there is air between the cuvette and the heater. The characteristics of air bath constant temperature are that it is convenient, fast and does not require special materials, but its stability and uniformity are slightly worse than that of water bath. Roche's cobas and 0lympus Au2700 systems use the air bath constant temperature mode.
②Water bath circulation type: that is, the cuvette is filled with water, and the heater controls the temperature of the water. The characteristic of constant heat water bath is that the temperature is constant, but special preservatives are required to ensure the cleanliness of the water quality, and the circulating water must be replaced regularly. The Hitachi system biochemical analyzer uses a water bath circulation constant temperature device.
③ Constant temperature liquid circulation indirect heating type: The structural principle is that a special constant temperature liquid flows around the cuvette (it has the characteristics of odorless, non-polluting, inert, non-evaporating, etc.). There is a very small air slit between the cuvette and the constant-temperature liquid. The constant-temperature liquid reaches a constant temperature by heating the air in the slit. Its temperature stability is better than that of the dry type. Compared with the water bath circulation type, it does not require special maintenance.
5. Wash system
The probe and stirrer are automatically flushed using torrent and other methods. The cleaning device generally consists of a suction needle, a liquid spitting needle and a wiping brush. The cleaning workflow is as follows: suction reaction, suction, injection of pure water, suction and drying. There are two types of cleaning fluids: alkaline and acidic. Generally speaking, after sucking out the reaction solution, the instrument is first rinsed with alkaline solution, then acidic solution, and finally rinsed three times with deionized water. The function of the wiping brush is to suck away the water hanging on the wall of the cup. There is a negative suction device inside the brush body. Pay attention to whether the wiping brush is worn during use.
It is worth noting that experiments in which cross-contamination (carry-over) cannot be removed by conventional flushing must be specially processed to reduce cross-contamination or carry-over contamination. For example, cholates in cholesterol measurement reagents interfere with the measurement of serum total bile acids. In the program to eliminate cross-contamination, a program can be entered to instruct total bile acids not to be measured in the colorimetric cup used to test cholesterol. If this cannot be avoided, When turned on, the instrument performs special flushing of the color comparison cup to prevent cross-contamination.
The temperature of the flushing water is automatically controlled to be close to the temperature of the constant temperature reaction tank to ensure the constant temperature of the reaction system and increase the detergency. Targeted cleaning after emergency assays appears to be more efficient and cost-effective than a fixed comprehensive cleaning program. Water consumption varies greatly between instruments.
Systems such as the ABBOTT AEROSET automatic biochemical analyzer have automatic cleaning functions (smart wash) and optimal specimen sequence selection functions (OSS). That is, the instrument automatically changes the detection sequence according to the combination of cross-contamination items between reagents or samples to avoid analysis items that affect each other; when it is truly unavoidable, a selected special cleaning agent is used for automatic cleaning.
6． colorimetric system
(1) Most light sources use halogen lamps with working wavelengths of 325 to 800nm. Halogen lamps have a short service life, generally only 1,000 to 1,500 hours. When the luminous intensity of the lamp is not enough, the instrument will automatically alarm and should be replaced in time. Some biochemical analyzers use long-life xenon lamps, which can work for several years on 24-hour standby, and the operating wavelength is 285-750nm.
(2) Colorimetric cup. The colorimetric cup of the automatic biochemical analyzer is also a reaction cup. The light diameter of the cuvette ranges from 0.5 to 0.7 cm, and is usually made of quartz or high-quality plastic. The small light path saves reagents. When the radius of the cuvette is less than 1 cm, some instruments can automatically calibrate to 1 cm. The automatic flushing device of the cuvette of the biochemical analyzer performs automatic repeated flushing and drying actions after the instrument completes the colorimetric analysis. The cuvette continues to be recycled after passing the automatic inspection. Unqualified cuvettes should be replaced promptly. If a quartz cuvette is used, the cuvette must be inspected and cleaned regularly.
(3) Monochromator and detector Various types of automatic biochemical analyzers use visible-ultraviolet absorption spectrometry, which monitors changes in the absorbance of chromophores at a specific wavelength in the 200-700nm optical region, supplemented by microcomputer software systems calculation to complete the determination. The basis of visible-ultraviolet absorption spectrum quantification is Lamber-Beer's law.
Traditional spectrophotometry generally uses front spectroscopy, that is, a filter, prism or grating is first used to split the light between the light source lamp and the sample cup. After passing through the adjustable slit, the monochromatic light that is "complementary" to the sample is obtained. Irradiate the sample cup, and then use a photocell or photoelectric tube as a detector to measure the absorption of monochromatic light (absorbance) by the sample.
Most modern biochemical analyzers use post-spectroscopic measurement technology. Post-spectroscopic measurement: first illuminate a beam of white light (mixed light) into the sample cup, and then use a grating to separate the light. At the same time, a row of light-emitting diodes is arranged behind the grating as a detector. The advantage of post-spectrometry is that there is no need to move any components in the colorimetric system of the instrument, and dual or multiple wavelengths can be selected for measurement at the same time. This can reduce colorimetric noise, improve analysis accuracy and reduce failure rates.
The monochromator of the biochemical instrument is the spectroscopic device, which has two types: interference filter and grating spectrometer. Interference filters are available in insert type and rotatable disc type. The plug-in type means that the required filter is inserted into the filter slot. The disc type means that all the filters equipped with the instrument are installed in the disc, and can be rotated to the required filter during use. Interference filters are cheap, but they are prone to moisture and mildew, which affects the accuracy of test results. Semi-automatic biochemical analyzers often use this type of filter.
Grating light splitting can be divided into two types: holographic reflection grating and etched concave grating. The former is made by covering the glass with a metal film, which has a certain degree of phase difference and is easily corroded; the latter is where the selected wavelength is fixedly engraved on the concave glass, which is wear-resistant, corrosion-resistant, and has no phase difference. Fully automatic biochemical analyzers mostly use grating spectroscopy.
7. program control system
The computer is the brain of the automatic biochemical analyzer. The filling and identification of specimens and reagents, bar code identification, constant temperature control, flushing control, result printing, quality control monitoring, and alarms for various instrument failures are all controlled by the computer. Each generation of instruments is getting better and better, and the degree of automation is getting higher and higher. Some instruments can even complete some daily maintenance procedures. The data processing functions of automatic biochemical analyzers are becoming more and more perfect, such as: absorbance during the reaction process, statistics of various measurement methods, indoor quality control results of various calibration methods, etc., the biochemical analyzer can all be processed. The computer can also check patient data, instrument performance indicators, instrument operating status, etc. The quality control and patient results in the automatic biochemistry instrument can also be network managed through the connection between the instrument computer and the laboratory information system (LIS).
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