Since the 1950s, when Skeggs first introduced the principles of a clinical biochemistry analyzer, various fully automated biochemistry analyzers and diagnostic reagents have made great strides with the development of scientific technology, especially in medicine. According to the structure and principles of the instruments, they can be divided into four categories: continuous flow (pipeline), discrete, centrifugal, and dry plate type.
The characteristic of the pipeline analyzer is that the chemical reaction between the same determined test samples and reagents is completed in the same pipeline through the flow process.
This type of instrument is generally divided into an air segmentation system and a non-segmentation system. The so-called air segmentation system means that a small segment of air separates each sample, reagent, and mixed reaction liquid in the inhalation pipeline; while the non-segmentation system relies on reagent blanks or buffer solutions to separate the reaction liquid of each sample.
In the pipeline fully automated biochemistry analyzer, the air segmentation system is the most common and most typical. The complete set of instruments is composed of several components, such as a sample tray, a proportioning pump, a mixing tube, a dialyzer, a thermostat, a colorimeter, and a recorder. The circles inside the pipeline indicate bubbles, which can separate the sample and reagent into many liquid columns and have a certain stirring effect. However, bubbles affect the colorimetry and must be removed before colorimetry.
The single-channel pipeline analyzer has only one pipeline system, so it can only analyze a single project of analysis at the same time, which limits its clinical application. Combining several single-channel pipeline analyzers to simultaneously test several items for one sample is called a multi-channel pipeline analyzer. The channel refers to the number of items that can be analyzed simultaneously. This concept has been used until now, but most of the analyzers on the market now are discrete automatic biochemistry analyzers, and the number of channels is determined by the number of reagent positions provided by the reagent compartment.
The centrifugal analyzer is a kind of analyzer that developed after 1969. Its distinctive feature is that the chemical reactor is installed in the rotor position of the centrifuge, and the circular reactant is called a rotor. The sample and reagent are first placed in the rotor. When the centrifuge is started, the sample and reagent in the circular disc are mixed by the action of centrifugal force, and finally flow into the colorimetric slot outside the circular disc and are detected by the colorimeter.
The characteristics of this type of analyzer are:
1. In the entire analysis process, each step of mixing, reacting, and detecting each sample and reagent is almost completed simultaneously, which is different from the “sequential analysis” of pipeline and discrete analyzers, and is designed based on the principle of “synchronous analysis”.
2. The sample and reagent volume are both at the micro level (the sample is 1-50μl, and the reagent is 120-300μl), and the analysis is fast (over 600 samples per hour can be analyzed).
3. The rotor is the special structure of this type of fully automated biochemistry analyzer. The early rotor consisted of six components: a transfer disc, a colorimetric slot, upper and lower glass rollers, and upper and lower covers. It has been replaced by a molded plastic product.
The so-called discrete means that the program is arranged by manual operation and replaced by rhythmic mechanical operation. All links are connected by a conveyor belt, and operations are performed in order.
The main difference between the discrete fully automated biochemistry analyzer and the pipeline analyzer in structure is that the former has each sample and reagent react in their respective test tubes, while the latter reacts in the same pipeline. The former uses a diluter composed of a sampler and a liquid feeder to sample and add reagents, instead of a proportioning pump. The former generally does not have a dialyzer, and if protein interference needs to be excluded, it needs to be processed separately.
In summary, the discrete analyzer has overcome most of the fatal deficiencies of the centrifugal analyzer. In the early stages, since the centrifugal analyzer simultaneously reacted on multiple samples, it saved time and was faster than the discrete analyzer. But now, due to technological advancement, the speed of the discrete analyzer has increased, and in high-speed analysis, the separation of adding and detecting in the centrifugal analyzer has become a bottleneck for speed, so the discrete analyzer has completely replaced the centrifugal analyzer.
Dry plate analyzer was introduced in the 1980s. After adding a quantitative serum, a color reaction occurs in front of the dry plate, and quantitative analysis can be performed by detecting the reflected light using a photometer. This method completely eliminates liquid reagents, so it is called dry chemistry.
The dry plate not only includes reagents, but can also be composed of electrodes, so this type of analyzer can also measure electrolytes. These dry plates are disposable, so they are relatively expensive.
