What is the purpose of a filter tip?
Filter tips are used to prevent cross contamination or "carry over" from one sample to another. When samples are aspirated into a pipette tip, a fine mist or "aerosol" is created, which can get into the pipette. Even after changing the tip, the aerosol can contaminate the next sample. For most applications the carryover is minuscule. However, for sensitive applications such as PCR, even the smallest fragment carried over from the previously pipetted sample can cause problems. It would be quite awkward to disassemble and clean a pipette after every sample. Filter tips were invented to capture the aerosols. They protect both the pipette from contamination from samples and protect the samples from contamination from the pipette.
What is the difference between sealing filter tips and non-sealing filter tips?
Sealing filter tips have additives in the filter that are designed to prevent liquid from passing through the filter, much like the hydrophobic filter in an accu-jet® pro or macro™. They prevent a pipette from being contaminated by the sample. However, when the tip is sealed it is very hard to recover the sample from the tip. Often DNA samples are very small, and the loss of the sample may not be acceptable. Sealing filter tips can also be degraded by autoclaving - the steam seals up the tip. Also the additives can contaminate the sample. Non-sealing filter tips impair the flow of liquid through the filter, but do not stop it completely. This allows the liquid to be recovered easier. BRAND filter tips only contain polypropylene (the tip) and polyethylene (the filter). There are no additives to contaminate the sample. In addition, the tips are fully autoclavable.
How can I tell which filter tips fit which pipette? The nominal volumes are all different from the standard tips.
BRAND filter tips have three different collar sizes, designed to fit pipettes using 20µL/ultramicro/crystal, 200-300µL/"yellow" and 1,000µL/"blue" tips. Tips with ultra-micro collars have gray carrier plates and are 0.1-1µL, 0.5-10µL and 1-20µL. Tips with 200-300µL collars have yellow carrier plates, and are 2-20µL, 5-100µL and 5-200µL. 50-1,000µL filter tips fit 1,000µL collars and have blue carrier plates. BRAND sub-micro (0.1-1µL) pipettes using nano-cap tips can only use the 0.1-1µL filter tip.
Why might I choose a filtered pipette tip with a maximum volume smaller than the maximum capacity of my pipette?
A filter takes up physical space inside the pipette tip. Some pipettes have extended length tip cones to reduce the amount of dead air space within the tip to maximize accuracy. With these pipettes, it may be necessary to use a smaller volume filter tip to keep the tip cone from contacting the filter
Sometimes you will refer to "yellow" tips and "blue" tips in quotes. Why is that?
Originally, all 200µL pipette tips were colored yellow, and all 1,000µL tips were colored blue. People would refer to them by their colors, as it was easier than specifying the size. Later it was determined that some of the dyes used to color the tips could interfere with their work. So colorless versions were developed of the tips, but often they were still called "yellow" or "blue" even though the tips were no longer colored. BRAND tips, when purchased bulk are colored for easier identification, but are free of cadmium dyes, which was the most problematic. BRAND tips, when purchased in racks are colorless to ensure no problems. The plates on which the tips are inserted are colored yellow, blue, dark gray or green for easy identification. The dark gray carrier plates indicate our special nano-cap™ ultramicro tips, and green indicates our 300µL tips. Boxes of ultramicro tips have colorless carrier plates.
Are your tips "universal" tips?
There really isn't such a thing as a "universal" tip. All pipette manufacturers have slightly different dimensions on their tip cones - different diameters, different tapers, etc. However, BRAND tips fit most major brands of pipettes, and are specifically designed to work well with BRAND, most Eppendorf,Gilson, Rainin (excluding LTS), Sartorius/Biohit and Thermo/Finnpipette (excluding Clip-Tip) pipettes. They may fit well with other pipettes with similar designs. Ask for a sample.
Are your tips silicone- and latex-free?
Yes. All BRAND tips are free of silicone and latex.
Are BRAND tips free of oleamide and DiHEMDA?
Yes. BRAND exclusively uses raw materials that are free from di(2-hydroxyethyl) methyldodecylammonium (DIHEMDA) and 9-octadecenamide (oleamide) - additives that are often found in raw polypropylene. These additives can interfere with biological tests, leading to inaccurate results. Also, only highly polished molds are used, so no parting agents or demolding aids are needed.
RNAse-free, DNA-free, ATP-free, Endotoxin-free ... what do all those specifications on tips mean?
RNAse is an enzyme found in bacteria. It is used by the bacteria to break down foreign nucleic acids that might enter the bacteria, analogous to the way our immune system gets rid of bacteria. Likewise, presence of Adenosine Triphosphate (ATP), the energy currency of cells, and Deoxyribonucleic acid (DNA), indicate the presence of bacteria or other living things during the tip manufacturing process. Killing these bacteria by autoclaving will not remove or inactivate these biological products. If they are present, they can interfere with molecular work, such as PCR. Assays to directly determine the presence of DNA, RNAse or ATP are very difficult and expensive to do. Our BIO-CERT® tips are assayed for these molecules, and are certified free of these substances within tight limits. Many more routine sterile applications, such as cell culture, do not require the absence of DNA, RNase or ATP, however they can require the tips to be endotoxin-free.
Endotoxin is also a substance found on the surface of bacteria. It is very easy to detect via a extremely sensitive process called the Limulus Amebocyte Lysate Assay BRAND's sterile tips are tested this way regularly, and are found to be under 0.06 I.E./mL, which is the limit of detection. This indicates that the tips are free of bacteria, which infers that they are free of RNAse and DNAse. Because our PD-Tip™ syringe tips have a large amount of plastic in each tip, it is very difficult to be able to certify each lot of tips to be free of all of these chemicals. BIO-CERT® PD-Tip™ syringe tips are available for an additional fee.
What is a "lambda" as a unit of volume measurement?
A "lambda" (λ) is sometimes used as a shorthand for a microliter (µL). They are the same thing: 1,000µL = 1,000 λ = 1mL.