1. Core Function: Physical barrier, completely avoiding cross-contamination of nucleic acids 

The core of molecular testing is to amplify and detect trace amounts of nucleic acids (at the pg/ng level). Even the slightest contamination of exogenous nucleic acids (such as positive samples, amplification products, and environmental nucleic acids) can lead to false positives. The filter membrane of the filter cartridge pipette can achieve bidirectional blocking, which is the most crucial value of this device: 

Prevent cross-contamination of samples → gun body → subsequent samples 

During the liquid transfer process, when the sample liquid (containing nucleic acids) is sucked into the pipette tip, the hydrophobic filter membrane will prevent the liquid from entering the interior of the pipette gun barrel. Even if there is excessive liquid absorption or the pipette tip is filled with liquid, the filter membrane will retain the nucleic acids and prevent them from adhering to the inner wall of the gun barrel. When transferring new samples in the future, there will be no residual nucleic acids inside the gun barrel, thus fundamentally eliminating the situation of "the previous positive sample contaminating the subsequent negative sample". 

Prevent contamination of the gun body → sample 

The interior of the pipette gun barrel may be contaminated with nucleases, aerosols, dust and other impurities due to operation or environmental factors. The filter membrane will prevent these impurities from falling into the sample inside the pipette tip, thus avoiding degradation of the sample (by nucleases) or the introduction of exogenous nucleic acids (through aerosols). 

Block atmospheric aerosols and prevent air-borne pollution from spreading 

In molecular testing, after PCR amplification, a large amount of nucleic acid aerosols (which escape when the cover is opened or during pipetting) are produced. These aerosols are highly likely to enter the pipette tip through the air and adhere to it. The filter membrane can trap the aerosols within the pipette tip, preventing them from being sucked into the gun body and spreading into the experimental environment, thus avoiding aerosol circulation pollution (one of the main causes of long-term pollution in the laboratory). 

II. Auxiliary Function: Optimizes pipetting performance and enhances experimental accuracy 

In molecular detection, it is often necessary to transfer very small volumes of liquid (such as 2 μL, 5 μL of primers/probes, and 10 μL of template). Errors in liquid transfer can directly lead to abnormal amplification efficiency and large deviations in Ct values. Filter cartridge pipettes can optimize the liquid flow through the filter membrane, thereby reducing common errors in micro-volume liquid transfer: 

Stabilize the liquid flow to avoid "backflow" and "stickiness" during liquid intake / discharge. 

The hydrophobic filter membrane can buffer the pressure changes during pipetting, allowing the liquid to be smoothly drawn in / expelled, avoiding liquid backflow (into the pipette barrel) or incomplete liquid discharge (liquid remaining at the tip of the pipette tip) due to sudden pressure changes; when performing micro-volume pipetting, the thoroughness of liquid discharge directly determines the accuracy of the actual volume of the liquid transferred, and reduces the dispersion of Ct values. 

Prevent backflow and protect precious samples 

When handling viscous liquids (such as enzyme solutions containing glycerol, or elution solutions after nucleic acid extraction) or when quickly aspirating liquids, backflow is prone to occur. The filter membrane can promptly block the liquid, preventing precious micro samples from being sucked into the gun body and causing loss, and also avoiding sample contamination. 

III. Adapt to specific scenarios of molecular testing and expand practical value 

Suitable for high-temperature / organic solvent environments, maintaining stability 

In molecular testing, one often comes into contact with absolute ethanol, isopropanol (for nucleic acid precipitation), TE buffer solution, and liquids after being heated in a water bath. The filter membranes of the filter tips are mostly made of polytetrafluoroethylene (PTFE), which is resistant to acids and alkalis, organic solvents, and high temperatures (≤121℃). After being sterilized by high-pressure steam, the hydrophobic properties and barrier performance of the filter membranes remain unchanged, meeting the aseptic and enzyme-free requirements for molecular experiments. 

Suitable for vacuum suction / negative pressure dispensing scenarios 

In the magnetic bead method and column method for nucleic acid extraction, negative pressure suction is often required to remove the waste liquid. The filter cartridge pipette can maintain the sealing of the filter membrane under negative pressure, preventing the waste liquid from being sucked into the negative pressure pump, and also preventing the impurities in the pump from being blown back and contaminating the samples. 

Enzyme-free and without endotoxin, suitable for nucleic acid/protein detection 

The filter tips specifically used for molecular detection are all produced through processes free of RNase, DNase, endotoxins and pyrogens, and are packaged independently. Once opened, they can be used directly without any additional processing. This avoids the degradation of nucleic acids by impurities in ordinary tips, ensuring that experiments requiring high nucleic acid integrity, such as RNA reverse transcription and fluorescence quantitative PCR, can be carried out without issues.