Precautions For Pipette Tips

　　The current pipette tips on the market are made of polypropylene plastic (a colorless and transparent plastic with high chemical inertness and a wide temperature range). However, the same polypropylene can also have a big quality difference: high-quality tips are generally made of natural polypropylene, while cheap tips are likely to be made of recycled polypropylene plastic (in this case, we can only say that its main component is polypropylene). In addition, most tips will add a small number of additives during the manufacturing process. The more common additives are:

　　1. Color rendering material. The commonly known blue tips (1000ul) and yellow tips (200ul) on the market are the addition of corresponding color-developing materials to polypropylene (as a user, you must hope for high-quality masterbatches, not cheap industrial pigments) );

　　2. Release agent. It is mainly used to help the tip to break away from the mold quickly after forming. In this case, the more additives there are, the higher the probability that undesired chemical reactions may occur during pipetting. So the safest thing is to not add additives. However, due to the relatively high requirements for the production process, pipette tips without additives are really rare in the market, so our users can only choose pipette tips with fewer additives when choosing.

　　Second is the packaging of the pipette tips

　　The packaging forms of pipette tips are mainly bagged and boxed. In a relatively mature market, box packaging accounts for the majority; while in our country's market, bag packaging is currently the absolute mainstream—the main reason is that bag packaging is cheap. The so-called bagging means that the tips are packed in plastic ziplock bags, 500 or 1000 per bag (the number of large-range tips per bag will be much less). Most users will manually put the tips into the tip box after buying the bagged tips, which increases the chance of contaminating the tips in the process! In addition, in recent years, there has also been a new form of tip packaging (refill packs (8 or 10 plates of tips stacked in a tower shape, which can quickly put tips into the tip box without touching the tips)). This type of tip requires less storage space, reduces the use of plastic, and thus achieves the purpose of environmental protection. At present, this form of tip packaging has a very small share in our country.

　　Finally, there is the price of pipette tips.

　　Let’s talk about bagged tips first (based on three specifications of 10ul, 200ul, and 1000ul, 1000 per bag). Bag tips are mainly divided into three grades:

　　One is an imported suction head. The most expensive one is Eppendorf, which costs 400-500 yuan per bag;

　　Second, imported brands, domestic production (that is, the so-called "fake foreign devils"). The representative brand of this grade is Axygen, its price is generally 60-80 yuan, and the market share of Axygen tips is quite high;

　　Third, domestic suction tips, but domestic suction tip manufacturers are generally small in scale, poor in a production environment, and not strict in product control or even none at all. The price range of domestic suction heads is generally 30-60 yuan. Generally, the price of boxed tips is 1.5-2.5 times that of bagged tips, and refill tips are 10-20% cheaper than boxed tips.

　　In the previous article, I discussed the material, packaging, and price of pipette tips with you. There are some things that our users don’t usually mention but are also very important: special tips, tip adaptability, tip biofouling, and filter tips.

　　First, the special suction head.

　　Special tips are specially designed tips for special samples or special applications. There are mainly the following categories: the first type is gel tips (also known as spotting tips): the tips of tips are flat or very thin, and are mainly used for electrophoresis experiments; the second type is wide-mouth tips: suction tips The caliber of the tip is larger than that of ordinary tips, and it is mainly used for pipetting macromolecular solutions such as proteins; the third type is low adsorption tips: the inner wall of these tips has been specially treated to reduce the surface adsorption force, and can be used for pipetting viscous Liquid; the fourth category is extended tips: mainly used for liquid extraction in containers such as volumetric bottles; the fifth category is external piston tips: mainly used for special applications such as external piston pipettes and continuous dispensers. on the pipette.

　　Second, the adaptability of the pipette tip.

　　The adaptability of pipette tips is a point that users are paying more and more attention to. Why? Because not all tips can be used on any brand of pipettes with the corresponding range, we remind us again that users must pay attention to the adaptability of tips when purchasing tips. Mainly we can understand the adaptability of the tip from the following aspects: first, the specificity of the tip. Certain series of pipettes of some brands can only use their standard tips, and other tips cannot be used. For example, Rainin's multi-channel pipette must use its own LTS tips; second, the degree of tip adaptation. The most common situation is that a pipette can use a variety of tips, but the effect of pipetting after loading different tips is different. In general, the standard tips are still the best, but some brands of tips are still good, such as Axygen tips. Third, the volume of the tip and the pipette should be adapted. In general, the volume of the tip should be greater than or equal to the maximum volume of the pipette. For example, a 200ul tip can be used for pipettes with a maximum volume of 20ul, 100ul, and 200ul; fourth, a large volume pipette (5ml, 10ml, and 20ml) tip specificity. Large-capacity pipettes of major pipette brands often need to use their standard tips, and it is difficult to find alternatives. Therefore, if we need to buy tips, it is recommended to tell the supplier the type of tip we are using or at least provide the brand and volume of the pipette we are using.

　　Third, biological pollution.

　　Now, more and more users will request tips free of RNase, DNase, DNA, pyrogen, and ATP contamination. This is a good phenomenon, but I have to remind two more points: First, high-temperature sterilized tips cannot completely guarantee the absence of biological contamination, and steps such as gamma-ray treatment are required to ensure that there is no biological contamination. Therefore, it is almost impossible for users to process ordinary tips into non-biologically contaminated tips by themselves, and the purchased non-biologically contaminated boxed tips must provide corresponding certificates, indicating the test data of the corresponding items. Tips without data on the certificate or even without a certificate cannot prove that they are completely pollution-free; second, bagged tips cannot guarantee any biological contamination. As long as the tip comes into contact with the air, there is a possibility of biological contamination, and the ordinary ziplock bag cannot guarantee that the tip will not come into contact with the air during storage and transportation; in addition, the zip lock bag is sometimes punctured by the tip occur. Therefore, if you have relatively high requirements for the suction head, you must ask the disposable medical consumables supplier to find out whether the suction head has a certificate indicating the test data of the corresponding item when purchasing.

　　Fourth, with a filter tip.

　　A filter tip has a filter element (usually white) on the upper end of the tip. This filter element is generally made of polypropylene, similar to the structure of a cigarette filter. Due to the existence of this filter element, the pipetted sample cannot enter the interior of the pipette, thereby protecting the parts of the pipette from contamination and corrosion, and more importantly, it can also ensure that there will be no cross-contamination between samples. Therefore, filter tips are also an important tool for pipetting volatile and corrosive samples. Of course, the price of filter tips is higher than that of ordinary tips, and their domestic market share is very low. Moreover, there are still very few domestic filter tips, and their filtering effect is not satisfactory.