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In the field of point-of-care testing (POCT), dry chemistry is a core technology that cannot be overlooked. It represents not only convenience and rapid response, but also serves as a critical enabler of accurate diagnostics in homes, community clinics, and emergency settings.
I. Principles of Dry Chemistry
Dry chemistry, often referred to as dry reagent chemistry in professional contexts, is an analytical technique developed in contrast to traditional “wet chemistry.”
Its core concept is the immobilization of all or part of the required reagents in solid form onto a specific carrier matrix. The liquid component of the sample serves as the reaction medium. Through permeation, chromatography, or diffusion, the sample interacts with the immobilized reagents, triggering a specific chemical reaction that produces a color change. This signal enables qualitative or quantitative analysis of the target analyte.
Dry chemistry is widely applied in the measurement of liver function, renal function, myocardial enzyme panels, blood glucose, blood lipids, uric acid, and other key clinical indicators.
II. Differences Between Dry Chemistry and Wet Chemistry
| Features | Dry Chemistry | Wet Chemistry |
| Reagent Form | Solid phase | Liquid phase |
| Reaction Carrier | Microporous membrane | Cuvette / Reaction chamber |
| Workflow | Simple, completed in one or a few steps | Complex, requires multiple dilution and mixing steps |
| Analysis Speed | Very fast (tens of seconds to 1 minute) | Relatively slow (tens of minutes) |
| Sample Volume | Very small (5–20 μL) | Larger (>100 μL) |
| Main Applications | Bedside testing, home self-testing, primary care settings | Central laboratories, hospital clinical labs |
Overall, the key characteristics of dry biochemistry include:
- Rapid turnaround: Results available within tens of seconds to one minute.
- Ease of operation: No complex instrumentation required; suitable for on-site and home use.
- Low sample requirement: Only a small volume of whole blood, plasma, or urine is needed.
- Convenient storage and transport: Stable under ambient, dry conditions.
III. Application of Cobetter Filter in Dry Chemistry
1. Single-Layer Dry Chemistry
In the “single-layer” design, all chemical reagents, catalysts, and color developers are integrated into one physical layer—for example, in urine testing. Cotton fiber filter paper is a key component, and selecting a material with high water absorption, high absorption rate, and strong wet strength is critical for producing effective products.
Cobetter offers a range of high-quality cotton fiber products suitable for dry chemistry test strips: CF-03, CF-04, CF-31. These products meet the uniformity requirements of impregnation-based assays and do not react with adsorbed active chemical substances. The following shows SEM analysis images.
2. Multi-layer Dry Chemistry
Multi-layer dry chemistry test strips typically consist of 2 to 4 functional layers. From top to bottom, these are: diffusion layer, blood separation layer, precipitation layer, and reaction layer. Each layer serves a specific purpose, working together to handle the sample and generate a detectable signal. Cobetter offers specialized membranes tailored to the performance requirements of each functional layer, fully supporting accurate and stable dry chemistry testing.
2.1 Diffusion Layer
Key Function: Ensures uniform sample distribution and rapid spreading
Membrane Options: Cobetter nylon mesh / polyester mesh
2.2 Blood Separation Layer
Key Function: Filters red blood cells, removes interfering substances, and isolates plasma
Membrane Options: Cobetter RB series glass fiber blood separation membrane / Cobetter PSM plasma separation membrane
Cobetter RB Series Glass Fiber Blood Separation Membranes
The RB series blood separation membranes are made of glass fiber and offer high flow rate, high retention, and high loading capacity. They efficiently capture red blood cells from whole blood and separate plasma for subsequent testing. Key advantages include strong retention capability, high red blood cell removal rate, high plasma recovery, and low protein binding.
Cobetter PSM plasma separation membrane
The PSM series plasma separation membranes, developed by Cobetter for POCT diagnostics, are a novel type of filtration membrane designed for “three-in-one” functionality. Each layer performs a precise role: the top layer filters blood, the middle layer precipitates impurities, and the bottom layer carries out the reaction. This one-step design ensures both accuracy and efficiency in test results.
2.3 Precipitation Layer
Key Function: Assists in precipitating and removing impurities, enhancing test specificity.
Membrane Choice: Cobetter Polyethersulfone EA Series
2.4 Reaction Layer
Key Function: Serves as the carrier for colorimetric reaction reagents, immobilizing reagents such as enzymes, substrates, buffers, and stabilizers.
Membrane Choice: Cobetter Polyethersulfone EAX Series / Nylon Membrane FD Series
Cobetter Polyethersulfone (PES) Membranes
Cobetter PES membranes feature a highly asymmetric structure with uniform pores and a high porosity (>75%), offering excellent permeability and rapid wetting characteristics. This ensures high flow rates with minimal background interference. The product line provides a wide range of pore sizes from 0.1 μm to 10 μm (0.1, 0.2, 0.45, 0.65, 0.8, 1, 3, 5, 8, 10 μm), enabling stepwise filtration. Thanks to outstanding batch-to-batch consistency and stability, these membranes are particularly suited for the precipitation and reaction layers in multilayer dry chemistry tests, providing reliable support for precise diagnostics.
In the fast-paced world of point-of-care testing, every reliable diagnosis depends on the solid support of the materials behind the scenes. Cobetter may not appear on the final test report, but as an “invisible guardian,” we are embedded at the heart of every test strip. We firmly believe that excellence in technology stems from meticulous attention to every detail. In empowering dry chemistry, our pursuit never stops.
