(1) According to the structure of the reaction device, automatic biochemical analyzers are mainly divided into two categories: flow systems and discrete systems.

1. Flow pattern means that the chemical reaction of the sample to be tested with the same test item mixed with reagents is completed in the same pipeline flow process. This is the first generation of automatic biochemical analyzer.

2. Discrete means that the chemical reaction of each sample to be tested after mixing with reagent is completed in its own reaction cup. There are several kinds of branches.

(1) Typical discrete automatic biochemical analyzer. This instrument is the most widely used.

(2) Centrifugal automatic biochemical analyzer, in which each sample to be tested is mixed with reagent in its own reaction tank under the action of centrifugal force to complete chemical reaction and determination. Because the mixing, reaction and detection are almost completed at the same time, the analysis efficiency is high.

3. The bag-type automatic biochemical analyzer replaces the reaction cup and colorimetric cup with reagent bag, and each sample to be tested reacts and determines in its own reagent bag.

4. The solid-phase reagent self-defined biochemical analyzer (also called automatic analyzer for dry chemical formula) is to fix the reagent on a carrier such as film or filter paper, and drop each sample to be tested on the corresponding test strip for reaction and determination. Its advantages are quick operation and easy carrying.

(2) Basic structure of typical discrete automatic biochemical analyzer

1. sample system

Samples include calibrators, quality controls and patient samples. The system usually consists of sample loading, conveying and distribution devices.

Common sample loading and conveying equipment are:

(1) Sample tray, that is, the turntable for placing samples has one or more circles inside and outside, which is placed alone or nested with reagent turntable or reaction turntable, and rotates with the sample distribution arm during operation. Some use replaceable sample trays, which are divided into working areas and standby areas, in which a plurality of arc-shaped sample sectors are placed as transfer tables, and instruments are automatically placed and replaced during determination, all of which have certain requirements on the height, diameter and depth of sample cups or test tubes placed on the sample trays, some need special sample cups, and some can directly use blood collection test tubes. The number of sample trays and the number of calibrators, quality controls, routine samples and emergency samples are usually fixed. These should be chosen according to the needs of the work.

(2) The racks for belt or track sampling are discontinuous, usually 65,438+00 racks. The conveyor belt is driven by a stepping motor, the racks move forward in turn, and then the racks move laterally to a fixed position one by one, and the samples are sampled by the sample distribution arm.

(3) The chain injection test tube is fixedly installed on the circulating transmission chain and horizontally moved to the sampling position, and then some instruments can clean the test tube.

Most dispensing and sampling devices consist of syringes, stepper motors or transfer pumps, sampling arms and sample probes. ① Violet sperm unit. According to the diameter of the syringe and the moving distance of the piston, the sample or reagent is inhaled quantitatively. Its accuracy determines the accuracy of sample addition, which can generally be as accurate as 1 microliter. When the syringe leaks, the first consideration is whether the probe is blocked, and the second is the wear of the syringe piston. Some liquid filling systems use volumetric injection pump and numerical control pulse stepping motor to improve accuracy. (2) The sample probe is connected with the sample adding arm to directly suck the sample. The probes are all equipped with liquid level sensors to prevent probe damage and reduce carrying pollution. Some are equipped with jam detection and alarm systems. When the blood clot 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 sample to the next sample. Some also have intelligent anti-collision devices. When encountering obstacles, the probe immediately stops moving and gives an alarm. Even so, it is still a weak link in irregular operation. In order to protect the probe, the specifications, placement, liquid level height and other setting conditions of the sample container shall not be changed at will, unless it needs to be set in advance according to the height and minimum liquid level height of the sample container. On some instruments, the sampler and the liquid feeder are combined to complete the addition of samples and reagents or diluents at one time. ③ Sampling arm. Connect the probe and move between the sample cup (reagent bottle) and the reaction cup to complete sampling and sample addition (reagent addition). Its movement mode has a certain relationship with the working efficiency and working life of the instrument. (4) The valve is used to determine the direction of liquid flow. ⑤ Dilution system. Pre-dilution, post-dilution or double dilution of samples, serial dilution of standard reserve solution, etc. Different instruments have different dilution methods, so we should pay attention to identification. The reagent system also has a dilution function:

2. The reagent system generally consists of reagent storage, distribution and liquid addition devices.

(1) The reagent bin is usually combined with the reagent turntable. Most instruments set the reagent bin as a cold room to improve the stability period of on-line reagents.

(2) Distribution unit. Similar to the example system. The reagent probe can often preheat the reagent, and the initial amount of reagent 2(R2) probe in the double reagent system should be low to match the reagents with different ratios of R 1/R2.

(3) reagent bottle. There are different shapes and sizes. For example, COBAS Milla PLUS instrument has specifications such as 4, 10, 15 and 35ML, and the bottom of the bottle is concave. Olympus AU600 instrument has specifications such as 30, 60ML and Hitachi 7060 instrument has specifications such as 20, 50 and 100ML. The remaining dead volume and replacement frequency of reagent bottle should be reasonably selected according to the workload and reagent specifications. The specially designed cassette is small in size, evaporation-proof and easy to store.

(4) Matching reagents often have bar codes, and the instrument is equipped with a bar code inspection system, which can check the type, batch number, inventory, expiration date, calibration curve, etc. of reagents, such as BECKMANCX7.

(5) The reagent bottle cap automatic opening and closing system is more conducive to reagent preservation. Some instruments can be added and replaced during operation, while others must be suspended.

3. Bar code reading system

Generally, it consists of scanning system, signal shaping and decoder. The scanning system uses a light source to scan bar code symbols with black bars and blanks. Because the light reflected by bars and spaces is different, the reflected light duration of bar symbols with different widths is different, resulting in reflected light with different intensities, which is received by photoelectric conversion elements and converted into electrical signals with corresponding intensities. Finally, it is processed by signal shaping and interpreted by the decoder. The system automatically identifies sample racks and sample numbers, reagents, calibrators and their batch numbers and expiration dates, and some can also identify calibration curves and other information.

The commonly used barcode types in the laboratory are CODE 39, CODE 128, 2 OF 5 STANDARD, INTERLEAVED2OF 5, etc. To edit the sample barcode, a barcode input device is needed, and the barcode reading system should match the barcode. There are automatic test tube distribution and barcode paste preparation systems.

4. Reaction system

(1) The reaction plate is equipped with a series of reaction cuvettes, mostly in the form of turntables. In the process of reaction determination, it rotates among the sample adding arm, the liquid adding arm, the stirring rod, the light path and the cleaning device according to a fixed procedure. Some instruments are sucked into the cuvette for color comparison after completing the reaction in the cuvette. Now it is more common to react and detect in a cuvette, which is more efficient and especially suitable for continuous monitoring. Colorimetric cups are mostly made of hard timely glass, hard glass and acrylic plastic that does not absorb ultraviolet rays. , different service life. DIMENSION series cuvettes are manufactured automatically in the machine, sealed automatically, free from cleaning and pollution. The flow cell type is mainly used for small analyzers. The volume is generally in the tens of microliters, but the pumping pipeline takes up more reaction liquid, and multiple samples are used continuously, which increases the chance of cross-contamination.

Peristaltic pump Semi-automatic biochemical analyzer needs peristaltic pump to pump the reaction solution into the flow colorimetric cell for determination. It is required to calibrate the peristaltic pump regularly, that is, to check whether the amount of liquid sucked by the pump is accurate by sucking a certain amount of water. Pump calibration function is usually provided.

(2) The mixing unit adopts multi-head rotary stirring rod (double-head and double-washing stirring system). Stirring rods are usually coated with Teflon non-stick coating to avoid liquid adhesion.

(3) Temperature Control Device The biochemical analyzer keeps the incubation temperature regulated and constant through a constant temperature control device, which is also controlled by a computer. The ideal incubation temperature fluctuation should be less than 0.65438 0℃. There are three ways to keep the temperature constant. ① Constant air bath temperature: that is, there is air between the cuvette and the heater. Air bath is characterized by convenience, rapidity and no need of special materials, but its stability and uniformity are slightly worse than that of water bath. Roche's COBAS and 0LYMPUS AU2700 systems adopt air bath constant temperature mode. ② Water bath circulation: that is, water is filled around the cuvette, and the heater controls the water temperature. The characteristic of constant temperature in water bath is constant temperature, but special preservatives are needed to ensure the cleanliness of water quality, and circulating water should be replaced regularly. Hitachi system biochemical analyzer adopts water bath circulating constant temperature device. ⑧ Constant temperature liquid circulation indirect heating type: The structural principle is that a special constant temperature liquid (tasteless, pollution-free, inert and non-evaporating) flows around the cuvette. There is a very small air slit between the cuvette and the thermostatic liquid, and the thermostatic liquid reaches a constant temperature by heating the air in the slit, so its temperature stability is better than that of dry type, and it does not need special maintenance compared with water bath circulation type.

Step 5 clean the system

The probe and the stirring rod are automatically cleaned by the rapids. The cleaning device usually consists of a liquid suction needle, a liquid discharge needle and a wiping brush. The cleaning workflow is to suck out the reaction, inhale the injected pure water, suck it dry and dry it. There are two kinds of cleaning solutions: alkaline and acidic. Generally speaking, after the reaction solution is sucked out, the instrument is cleaned with alkaline solution, then with acidic solution, and finally with deionized water for three times. The function of the wiping brush is to suck away the water hanging on the cup wall, and there is a negative pressure device inside the brush body. Pay attention to whether the wiping brush is worn during use.

It is worth noting that conventional washing can not remove the residue experiment, so special treatment should be carried out to reduce cross-contamination or residual pollution. For example, cholates in cholesterol determination reagents interfere with the determination of serum total bile acids. In the process of eliminating cross-contamination, a program can be input to instruct the total bile acid not to be determined in the colorimetric cup for testing cholesterol. If it is unavoidable, the instrument will specially clean the cuvette to prevent cross-contamination.

Automatically control the water temperature of washing water close to the temperature of the constant temperature reaction tank, ensure the constant temperature of the reaction system, and increase the decontamination power. It seems that it is more efficient and economical to adopt targeted cleaning after emergency measurement than to adopt a fixed comprehensive cleaning procedure. The water consumption of different instruments varies greatly.

Abbott AEROSET automatic biochemical analyzer and other systems have intelligent cleaning function and optimal sample sequence selection function (OSS). That is, the instrument automatically changes the detection order according to the combination of cross-contamination items between reagents or samples to avoid the analysis items that affect each other; When it is really unavoidable, choose a special cleaning agent for automatic cleaning.

6. Chromaticity system

(1) most light sources are halogen lamps, and the working wavelength is 325 ~ 800 nm. Halogen lamps have a short life, generally only 1 000 ~ L 500 hours. When the luminous intensity of the lamp is insufficient, the instrument will automatically give an alarm and should be replaced in time. Some biochemical analyzers use long-life xenon lamps, which can work for several years in 24-hour standby, and the working wavelength is 285-750NM.

(2) Colorimetric cup The colorimetric cup of the automatic biochemical analyzer is also a reaction cup. The optical diameter of the cuvette varies from 0.5 cm to 0.7 cm, and it is usually made of timely or high-quality plastic. For reagents with small optical diameter, when the optical diameter of the cuvette is less than 1 CM, some instruments can be automatically corrected to 1CM. The automatic flushing device of the colorimetric cup of biochemical analyzer automatically washes and sucks up repeatedly after the colorimetric analysis of the instrument is completed, and the colorimetric cup continues to be recycled after the automatic detection is qualified. Unqualified cuvettes should be replaced in time. If a seasonal cuvette is used, it should be inspected and cleaned regularly.

(3) All kinds of automatic biochemical analyzers of monochromator and detector adopt visible-ultraviolet absorption spectrometry, that is, in the light region of 200-700NM, the change of absorbance of chromophore at a specific wavelength is monitored, and the microcomputer software system is assisted to calculate and complete the determination. The quantitative basis of visible ultraviolet absorption spectrum is Lambert-Beer law.

The traditional photometric measurement generally adopts pre-splitting, that is, the light between the light source lamp and the sample cup is split by using a filter, prism or grating, and the monochromatic light complementary to the sample is obtained through an adjustable slit, and then it is irradiated on the sample cup, and then the photoelectric tube or photoelectric tube is used as a detector to measure the absorption (absorbance) of the monochromatic light by the sample.

However, most modern biochemical analyzers use post-spectral measurement technology. Post-spectral measurement: first, a beam of white light (mixed light) is irradiated on the sample cup, then it is split by grating, and a row of light-emitting diodes are placed behind the grating as detectors. The advantage of post-splitting is that it does not need to move any parts in the colorimetric system of the instrument, and it can be determined at the same time at two or more wavelengths, which can reduce the noise of colorimetric analysis, improve the accuracy of analysis and reduce the failure rate.

The monochromator of biochemical instruments, that is, beam splitter, has two kinds: interference filter and grating beam splitter. There are two kinds of interference filters: plug-in and turntable. Plug-in is to insert the required filter into the filter slot. Disc type is to install all the filters equipped with the instrument in the disc, and rotate them to the required filters when using. Interference filter is cheap, but it is easy to get damp and moldy, which affects the accuracy of test results. This kind of filter is often used in semi-automatic biochemical analyzer.

Grating splitting can be divided into holographic reflection grating and etched concave grating. The former is made by covering a layer of metal film on glass, which is easy to be corroded and has some differences; The latter is to carve the selected wavelength on concave glass, which is wear-resistant, corrosion-resistant and phase-free. Most automatic biochemical analyzers use grating light splitting.

7. Program control system

The computer is the brain of the automatic biochemical analyzer. The injection and identification of samples and reagents, bar code identification, constant temperature control, washing control, result printing, quality control monitoring and various fault alarms of instruments are all controlled by computers. The instrument is getting better from generation to generation, and the degree of automation is getting higher and higher. Some instruments can even complete some routine maintenance procedures. The data processing function of automatic biochemical analyzer is becoming more and more perfect, such as absorbance in the reaction process, indoor quality control results statistics of various determination methods and calibration methods, etc. , can be processed by biochemical analyzer. The computer can also adjust the patient's data, the performance index of the instrument and the running state of the instrument. Quality control and patient results in automatic biochemical analyzer can also be managed through the interface between instrument computer and laboratory information system (LIS).

The program controller is the hardware part of the system. Mainly includes:

(1) microprocessor and host. Used for all units and overall control of the instrument, it should have powerful functions such as program-controlled operation, fault diagnosis, various data processing and storage. Generally, it is configured according to the needs of instrument functions and the mainstream products in the computer hardware market.

(2) CRT monitor unit. Usually through the keyboard, mouse, touch screen and other operations.

(3) System and supporting software. Most of them use WINDOWS-NT or WINDOWS interface, full graphical design, multi-menu selection, information guidance, fault alarm, help prompt and man-machine "dialogue", which is convenient and intuitive, and many instruments have real-time response curve display.

(4) Data can be transmitted with other computers, printers and other devices through data interfaces such as RS 232 C, and the instrument can directly ask the host computer for the basic data and test items of patients/samples through the artificial intelligence bidirectional communication system (host query). Some of them have remote communication and monitoring functions, which can be used for remote testing, maintenance and inspection, and realize networked work.

Automatic biochemical analyzer adopts automatic analysis controlled by program. Once the analysis program is determined, the instrument can automatically complete the measurement, calculation and report according to the programmed program by simply inputting the measurement items or codes. The specific control programs vary from instrument to instrument, and are generally divided into fixed programs and self-compiled programs. The fixed procedure is preset by the instrument manufacturer and often matches the specified reagent; Some cannot be changed, and some can be modified by users. When used in combination with matching reagents, it is not only convenient to work, reliable in quality, but also expensive. The self-compiled program is flexible and practical, which is convenient for developing new projects and emphasizes the flexibility of the program. For example, in the process of batch determination, emergency specimen determination should be inserted at any time without interfering with the original procedure; The determination of a single emergency specimen is simple and convenient, consumes less, and can be pre-diluted or repeated flexibly.

Second, the instrument general workflow

The correct application of biochemical analyzer should not only master the principle of determination technology, but also have enough understanding of the working flow and determination calculation method of specific instruments.

(A) the general workflow

You can check the workflow through the measuring cycle of the instrument. Pay attention to the cuvette blank reading point (CB), sample addition point (S), reagent addition point (R 1, R2, ...), reagent blank reading point (RB), determination reading point (P), time interval of each point and total cycle time, etc. Generally, each instrument is equipped with a reaction turntable at a fixed position and a reaction determination cycle at a fixed time, with sample reagent and diluent levels and determination reading points. For examPLe, when Hitachi 7 170 is 10 minutes from P 1 to P34, the sample is added before PO, RL is before pl, R2 is between P5 and P6, R3 is between P 16 and P 17, and R4 is between P33 and P34.

(2) Data processing and calculation methods

The absorbance data read by the instrument at each absorbance reading point may not be included in the calculation of human body concentration. The instrument often calculates the original data of absorbance according to the definition of the instrument and the requirements set by the operator, converts it into so-called reaction data, and then calculates the concentration according to the coefficient or formula. Examples are as follows:

The absorbance at the measuring point (a) of 1.Hitach 7 170 is calculated as (ax+ax- 1)/2. Actual absorbance = absorbance data × 10 000.

2.0 LYHPUS AU600 reagent blank data: reagent blank at P0 point (Rb) = absorbance of blank at P0 point in colorimetric glass water (WB); Reagent blank (RB) at any determination point. The absorbance at this time is the blank (WB) of colorimetric glass water.

3.3' s response data. Monarch 1 000 two-point endpoint method. (end absorbance-end blank absorbance)-(starting absorbance-starting blank absorbance).

4. The reaction data of endpoint method (including reagent blank, endpoint method) of 4.AU600 = endpoint absorbance -P0 point absorbance (reagent blank, RB). Reaction data of endpoint method (no reagent blank, endpoint). Method) = endpoint absorbance-colorimetric glass blank (WB).

5. reaction data of 5.AU600 two-point method (blank in itself) = [measurement point reading after adding the second reagent -P0 point reading]-[measurement point reading before adding the second reagent -PO point reading].

Third, the main operating procedures

(1) Operating procedures before instrument operation

Mainly for the basic settings of the instrument:

When the length is necessary, the test item settings include test name, code, test configuration file, test round and test order.

2. The parameter setting of each test includes the setting of parameters such as the ratio between tests and the result check.

3. Reagent setting According to the relevant test parameters, set the reagent position and reagent bottle specification for each test, and set the reagent batch number and expiration date if necessary.

4. Calibrator Settings Set the position, concentration and quantity of calibrators.

5. Quality control settings are based on quality control requirements. Set the quantity of quality control materials, quality control rules, quality control items and corresponding quality control parameters.

6. Sample tube settings include sample tube type, residual liquid height (dead volume), identification method, etc.

7. Other settings include data transmission mode, result report format, audit mode and audit standard.

(II) Conventional operating procedures

Start-up (preheating and maintenance)-Set the start-up conditions (date and time index, rounds, starting number of samples, etc. )-Apply for calibration, quality control and patient measurement items (including rack number, cup number or serial number) as required. Can continue to be used in the determination process) _ Load calibrators, quality control materials and patient specimens-Load reagents-Check the initial state of the instrument (if the barcode system is not used, especially if the samples are identified in sequence, check whether the initial number of the determination is consistent with the sample rack number and application number)-Calibration and quality control determination-Check calibration and quality control results-Patient specimen determination-Monitor the determination process (reagent inspection, observation and analysis results, editing and correction)-Data. Maintenance after determination.

(3) inspection and analysis of the determination results

1. Understand and be familiar with the meanings and functions of various warning symbols of instruments. Using various warning symbols can improve the efficiency of finding and solving problems on the premise of setting parameters correctly.

2. Be familiar with and flexibly use the relevant operation screen (interface) of the instrument, such as observing the reaction time process curve with the reaction monitor; Review and analyze calibration curves with calibration traces; Understand the average value of patients' measured values in different periods by statistical method and analyze the data; Use data editing to check and correct measurement data.

3. The calibration check should make full use of the functions set by the instrument, monitor the fluctuation of the calibration curve, calculate the absorbance value of each calibration point (the blank value and blank rate value of the reagent cannot be ignored), and compare it with the past. If necessary, the reaction time course curve should be further checked. We must combine the quality control data to grasp the experimental conditions.

4. In the examination of patients' results, it is an important basic skill to learn to analyze the curves and data of reaction time process besides visual observation or understanding the characteristics of specimens with serum indicators, and paying attention to and understanding the clinical data and diagnosis.

Fourth, the basic determination method

(a) the END POINT method (end point method)

According to the absorption spectrum characteristics and absorbance of reaction products when the reaction reaches equilibrium, the method of quantitative analysis of substances. For general chemical reactions, the reaction end point is when the reaction is completed (or the positive and negative reactions are in dynamic equilibrium) and the reaction products are stable. For antigen-antibody reaction, the end point is that antigen and antibody react completely to form the largest and stable immune complex. On the reaction time history curve, it is a section parallel to the X axis. In the measurement and calculation methods, it is generally divided into one-point method and two-point method.

1. One-point method takes the absorbance value of air blank (GB), water blank (WB) or reagent blank (RB) before the reagent is mixed with the sample as the determination calculation base point, and subtracts the blank reading from the absorbance reading at the end of the reaction to obtain the reaction absorbance. Compared with the absorbance of the calibration solution under the same conditions, the determination result is obtained. It is often used in conjunction with one-point calibration method, that is, a calibration concentration is used, and the calibration curve crosses zero and is linear. Multi-point calibration is also applied.

2. Two-point endpoint method, namely endpoint-starting point method, takes a certain time point after the reagent and sample are mixed as the starting point, and subtracts the starting point reading from the absorbance reading at the end of the reaction. Under certain conditions, the specificity of the sample to the reaction or the reaction itself (mainly refers to chromaticity interference) can be reduced. Commonly used double reagents, a point before adding R2 is often used as the starting point of determination. In some cases, R2 can also be used as a starting point. If a single reagent is used, it is difficult to use when the main reaction starts too fast or the initial reading point of the instrument is limited.

The difference between the fixed method and the two-point endpoint method is that the endpoint of the measurement reading is not in the reaction equilibrium section, but is selected according to the methodology. Such as serum creatinine (picric acid method).

3. The three-point endpoint method, namely the double endpoint method, is used to measure two reactions in one channel at a time. Such as simultaneous determination of free fatty acids and triglycerides. Some instruments (such as Hitachi series) are equipped with this method.

(B) CONTINUOUS MONITORING METHOD (continuous monitoring method)

Also known as rate analysis. That is, the reaction process is continuously monitored, and quantitative analysis is carried out according to the measured product formation speed or substrate consumption. On the reaction time-history curve, the reaction is a constant-speed segment (the slope is constant), which is often used to determine the linear reaction period of enzyme activity.

1. The continuous monitoring method is a zero-order reaction rate method, also known as the slope method. In a long reaction period (at least 90- 120 seconds), the absorbance value is read at regular intervals (generally 2-30 seconds), and at least 4 points are read to obtain 3 △ a; Generally, continuous readings are processed by the least square method, and those with short reading intervals are processed by the rate time (TR) multipoint method. Take all readings of the linear reaction part and get the reaction rate △A/MIN in unit time. This method must be based on the zero-order reaction, because only under the zero-order reaction, the change of absorbance per unit time (reaction rate △A/MIN) is directly proportional to the enzyme activity. This method relatively reduces the analysis error and greatly improves the analysis speed and accuracy. The semi-automatic biochemical analyzer uses a single sample for continuous monitoring, which is quite time-consuming. To apply the continuous monitoring method, firstly, samples with high, medium and low concentrations in the linear range should be prepared, and the reaction time-history curves should be made respectively, so as to understand the whole reaction process at different concentrations and determine the delay time and linear monitoring period.

2. The two-point rate method is the so-called quasi-first-order rate method. In the reaction, two time points, T 1 and T 2, are selected, the absorbance A 1 and A2 are read, and (A2-A 1), (T2-T 1)=△A, △ T are calculated. There are two main differences between this method and the end-point two-point method: the last reading. Compared with the continuous monitoring method, its disadvantages are that T 1 and T 2 are artificially determined, and there are many uncertain factors, which can not guarantee the linearity of the reaction during T 1-T 2 and affect the accuracy of the results. Before routine determination, a pretest should be conducted to determine the linear time period. If the reaction is not linear within the selected time period (for example, the zero-order reaction period is short and the instrument cannot be set or determined), the end-point method can only be used. It has the advantage of simple method. When the enzyme activity is low and the absorbance value is small, it is not limited by the continuous monitoring time point of the instrument, which increases the determination time period and reduces the reading error.

3. Rate B method is used to determine the correlation between two reactions in one channel at a time. It can be used not only for two experimental measurements, but also for automatic compensation of interference and/or sample blank. The principle of the latter application is to deduct the continuous influence of the first reaction rate from the second reaction (main reaction) on the premise that the first reaction (interference reaction) is always linear by using the microcomputer automatic processing of the instrument. For example, it is used to eliminate the negative interference of absorbance decrease when bilirubin is converted into biliverdin and creatinine determination by picric acid method. Some instruments (such as Hitachi series) are equipped with this method.

(3) Blank correction

In spectrophotometry, blank solution is often used to adjust the absorbance zero of the instrument or to offset some interference factors in the determination. In the determination of biochemical analyzer, in addition to using double or multi-wavelength two-point method to eliminate background interference, special blank determination is often used to deduct its influence from the absorbance of the sample. Correct selection of blank correction plays an important role in improving accuracy.

1. reagent blank is generally divided into reagent blank and reagent blank under method type and calibration mode. The reagent blank should be determined separately or together with calibration, and sample cups or reagent blank racks filled with deionized water should be pre-selected. The absorbance of each measuring point of the calibrator or patient sample should be deducted from the reagent blank absorbance or blank rate value of the corresponding measuring point. In the method without reagent blank, the water blank in the reaction cup is directly used as the determination reference value.

In many instruments, reagent blank determination is similar to calibration determination, and it is not real-time determination when determining patient samples. Therefore, we should pay attention to the determination frequency to avoid the calculation error caused by the change of reagent blank caused by the change of reagent batch number or quality.

2. The blank of the sample is mainly to eliminate the interference of turbidity or chromaticity of the sample itself. The blank channel method is commonly used, and the calibration result is equal to the color reaction channel result-blank channel result. Most instruments need to occupy the measuring channel, which reduces the analysis speed by half, but the accuracy of eliminating interference is higher than that of two-point end point.

References:

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