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What is a biochemical analyser?

Jul. 03, 2024



Fully automatic biochemical analyzer is a biochemical analysis instrument that automates the steps of sampling, adding reagents, mixing, heat preservation reaction, detection, result calculation and display, and cleaning in the analysis process. Due to the high degree of automation and calibration and automatic correction functions, the subjective error and system error are relatively small and easy to use.



Working principle


Spectrophotometry, its basic measurement principle is based on Beer's law.



Structure and application


It contains the main components of the spectrophotometer: light source, monochromator (F dispersion device), colorimetric cell, detector, etc.; in addition, it also contains the special parts required for biochemical analysis, such as sample addition system, cleaning system, temperature control system, software system, etc. It is mostly used for routine biochemistry, special protein and drug monitoring detection, with diversified program selection and microcomputer control. It can be freely programmed and statistically processed. Some analyzers use chemically inert "capsule chemistry technology" to strictly isolate the analysis specimens or test items (sample probes, reagent probes, and colorimetric cups are kept clean) to prevent cross infection.


(I) 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 system: refers to the chemical reaction of each sample to be tested and the reagent mixed together in the same pipeline. This is the first generation of automatic biochemical analyzers.


2. Discrete system: refers to the chemical reaction of each sample to be tested and the reagent mixed together in their respective reaction cups. There are several 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 the reagent in its own reaction tank under the action of centrifugal force to complete the chemical reaction and determination. Since mixing, reaction and detection are completed almost simultaneously, its analysis efficiency is relatively high.


3. Bag-type automatic biochemical analyzer uses reagent bags to replace reaction cups and colorimetric cups. Each sample to be tested reacts and is measured in its own reagent bag.


4. Solid-phase reagent automatic biochemical analyzer (also known as dry chemical automatic analyzer) solidifies the reagent on a carrier such as film or filter paper. Each sample to be tested is dripped onto the corresponding test strip for reaction and measurement. Its advantages are quick operation and easy portability.


(II) Basic structure of typical discrete automatic biochemical analyzer


1. Sample system


Samples include calibration products, quality control products and patient samples. The system is generally composed of sample loading, transportation and distribution devices.


Common types of sample loading and transportation devices are:


(1) Sample disk, that is, the turntable for placing samples has a single circle or multiple inner and outer circles, which is placed alone or fits with the reagent turntable or reaction turntable, and rotates with the sample distribution arm during operation. Some use a replaceable sample tray, which is divided into working and standby areas. Multiple arc-shaped sample racks (Sectors) are placed as transfer tables. The instrument automatically places and replaces them during the measurement. There are certain requirements for the height, diameter and depth of the sample cups or test tubes placed on the sample tray.


(2) Belt-type or track-type sampling, that is, the test tube rack (Rack) is discontinuous, usually 10 racks, and the conveyor belt is driven by a stepper motor to move the test tube rack forward in sequence, and then the single rack is moved horizontally to a fixed position for sampling by the sample distribution arm.


(3) Chain-type sampling test tubes are fixedly arranged on a circulating transmission chain and moved horizontally to the sampling position. Some instruments can then clean the test tubes.


2. Reagent system:


Generally composed of reagent storage and distribution and liquid addition devices.


(1) The reagent bin is often combined with the reagent turntable. Most instruments use the reagent bin as a cold storage room to increase the stability of online reagents.


(2) Dispense unit. Similar to the sample system. The reagent probe can often preheat the reagent.


(3) Reagent bottle. There are different shapes and sizes. It should be selected according to the workload and reagent specifications, the residual dead volume of the reagent bottle and the replacement frequency. The uniquely designed card-type reagent kit is small in size, evaporation-proof and easy to store.


(4) The matching reagents often have barcodes. The instrument is equipped with a barcode inspection system to check and verify the type, batch number, inventory, expiration date and calibration curve of the reagents.


(5) The automatic opening and closing system of the reagent bottle cap is more conducive to the preservation of reagents. Some instruments can add and replace reagents during operation, while others must be done in a paused state.


3. Wash system


The probe and stirring rod are automatically rinsed by torrent and other methods. The cleaning device is generally composed of a liquid suction needle, a liquid discharge needle and a wiping brush. The cleaning process is to suck out the reaction liquid, suck it, inject pure water, suck it dry and wipe it dry. There are two types of cleaning liquids: alkaline and acidic. Generally speaking, after sucking out the reaction liquid, the instrument is first rinsed with alkaline liquid, then rinsed with acidic liquid, and finally rinsed three times with deionized water. The function of the wiping brush is to absorb the water dripping on the cup wall. There is a negative suction device inside the brush body. During use, pay attention to whether the wiping brush is worn.


The water temperature of the rinsing 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 cleaning power. Targeted cleaning after emergency measurement seems to be more efficient and economical than using a fixed comprehensive cleaning procedure. The water consumption varies greatly between instruments.


Automatic biochemical analyzer fault quick check method


1. Divide the biochemical analyzer into blocks


The first is the optical system; the second is the liquid distribution and transmission system; the third is the temperature control system. These three systems are connected to the computer through related circuits, and parameter selection operations are performed through software editing. Therefore, when the user encounters a problem, first determine which system the problem may occur in. Achieve rapid positioning. Under normal circumstances, there are few problems with the circuit, and most of them are problems with the optical system and distribution system, followed by the DC power supply system. The light energy detector in the optical system is generally closed, almost impossible to disassemble, and has a long life. The part that is most prone to problems is the light path from the bulb through the condenser through the reactant in the cuvette to the adapter mirror. Among them, the most common problem is the aging of the bulb. In some equipment, there will be an alarm prompt for insufficient light, which is conducive to rapid positioning according to the prompt content.


2. Fault location


There are actually levels to eliminate any kind of fault. One is from high to low, that is, starting from the big principle as mentioned above, and first functional block. The other is from low to high, that is, starting from the most direct fault manifestation. Some problems are relatively simple, and many machines have error reporting functions. According to the prompts, the fault point can be found directly.


In the positioning process, make full use of the self-alarm information of the machine. However, sometimes the error message is not the direct cause of the fault, and it is also necessary to analyze it according to the specific principle. Another method to quickly determine the soft and hard faults of the equipment is to determine whether the equipment has a software problem or a hardware problem based on the repeatability of the instrument inspection results. If the repeatability is poor, it may indicate that there may be a problem with the machine hardware; otherwise, it indicates that there is no problem with the machine itself and the technical documents may need to be re-edited.


3. DC power supply system


Most of the current medical equipment power supply systems use switching power supplies, which mainly consist of full-bridge rectifier circuits, start-up circuits, switch excitation circuits, voltage stabilization control circuits, output rectifier filter circuits, and various protection circuits and special circuits. As long as you are familiar with the working principle of the power supply, you can easily eliminate power supply failures, especially pay attention to the purity of the output voltage and voltage value and other parameters. When the machine fails, the power supply voltage should be detected first according to the fault point, and sometimes a large degree of maintenance effect can be obtained.


4. Maintenance summary


When repairing various medical equipment, especially large equipment, you must understand the principle before repairing it. Because it involves a lot of knowledge, functional block and positioning processing are the key to rapid maintenance.

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