Enjoy contamination-free pipetting with the BioMaster Positive Displacement Pipette, an adjustable pipette for the volume range from 1 µL to 20 µL. With the Positive Displacement Tip, the pipette functions according to the positive-displacement principle; thus, the formation of aerosols—a common cause of contamination—is eliminated.

I have noticed that more solution is used for "reverse pipetting" than for normal pipetting. What is the reason for this?That is correct, and is also intentional. Normal (forwards) pipetting with solutions with a high level of vapor pressure or highly viscous solutions cannot guarantee that the entire volume is correctly pipetted. Reverse pipetting is therefore recommended, resulting in more volume being aspirated than is necessary. When dispensing, the entire volume is then correctly dispensed. The excess aspirated solution remains in the tip and must be discarded.

Can you recommend me any literature on reverse pipetting?You will find information about this in our Application No. 10 - use of pipetting systems in the laboratory.

When pipetting volumes 10 µl, should the pipette tip be wetted with liquid before pipetting?Regardless of the volume, the tip should be wetted by multiple filling and emptying of the tip before dispensing. When calibrating for the 50µl volume, the evaporation errors of the test liquid should be taken into account when weighing. See EN ISO 8655.

What can you recommend with regards to the handling of viscous liquids?Our recommendation: 1. Biomaster pipette with Mastertips (positive-displacement principle) 2. Reverse pipetting (see page 214 of Main Catalogue 12002) 3. Multipette plus, Multipette stream or Multipette Xstream.

Is there an Eppendorf pipette which can be used to pipette 40 % polyethylene glycol 8000 (PEG)?Yes, direct-displacement pipettes like the Multipette stream or Xstream, for example, can be used.

What is the best way to pipette chloroform?A positive displacement pipette, e.g. the Biomaster (with Mastertips), the Multipette plus, the Multipette stream or Multipette Xstream (with Combitip plus) is suitable for this purpose. When using an air cushion pipette you should always pipette in reverse and pre-moisten the tip several times in order to saturate the air cushion. See also the info in the main catalog 2002, page 214.

What is the best way to pipette diethyl ether?Diethyl ether has such a high vapor pressure that it would leak out of the tip immediately when a normal pipette is used. For this reason, it can only be pipetted using a positive-displacement pipette, such as our Biomaster pipettes with Mastertips for 2 - 20 µl. The Varipette 4720 and Multipette/Multipette plus, Multipette stream or Multipette Xstream are available for larger volumes.

Are Eppendorf pipettes resistant to acetonitrile?Yes.

What should be considered when pipetting methanol with air-cushion pipettes?Due to the increased steam pressure we recommend pre-wetting the pipette tips 2-3 times and possibly pipetting in reverse (take-up with blowout, discharge without blowout).

What is the best pipette for pipetting a 99% solution of n-amyl alcohol?A 99 % solution of n-amyl alcohol is a highly viscous solution for which we recommend a pipette which works on the direct-displacement principle, e.g. the Multipette pro.

Are Eppendorf pipettes resistant to hexane?Yes, they are resistant.

What is the best way to dispense organic solvent?This is best done with a Multipette. The Multipette functions according to the direct displacement principle and is therefore suitable for dispensing solutions with high vapor pressures. The solvent vapors do not come into direct contact with the pipette. In addition, the Combitips have a high chemical resistance.

I would like to pipette dichloromethane and n-hexanol very precisely. Can I use air cushion pipettes for this application?No. Both dichloromethane and n-hexanol have a very high vapor pressure, so direct-displacement pipettes, e.g. the Eppendorf Biomaster, the Multipette plus, Multipette stream or Multipette Xstream, have to be used for accurate pipetting.

Are your pipettes free of nucleic acids?No, we cannot guarantee this. Of course we work carefully and cleanly in production, but no special measures are taken to prevent the infiltration of human nucleic acids. For sterile work, or to protect your pipette from contamination, we recommend using positive displacement pipettes, for example, our Biomaster or Filtertips. To decontaminate the pipette we recommend boiling in Glycin/HCl buffer (pH2). We would be happy to send the protocol for this; please contact our Application-Hotline (support@eppendorf.com).

How can I remove DNA contamination from my pipette?Please check, first of all, if the material of your pipette is suitable for the described procedures. To remove DNA contamination from your pipette, you can: - autoclave your pipette (see operating manual) - sterilize your pipette with UV light - treat the lower part of your pipette with a glycine-HCl buffer (pH 2.0)* - treat your pipette with a 5-10 % sodium hypochlorite solution. * We would be happy to send the protocol for this; please contact our Application-Hotline (support@eppendorf.com)

How can radioactive contamination be removed from Eppendorf pipettes?Following contamination of pipettes with radioactive liquids, we recommend putting the contaminated parts in a complex-forming liquid or special cleaning solution. After that, rinse very thoroughly with distilled water and dry. Grease piston lightly afterwards (see Application 10). This procedure is good for removing radioactive material.

Do Eppendorf pipettes always need to be greased?No, they do not need to be greased from the point of view of maintenance. The pistons only need greasing if the pipettes have got very dirty and have been cleaned with organic solvents.

Can the pipette withstand evacuation (applying a vacuum)?No, air cushion pipettes should not generally be used under vacuum, as the pressure ratios are not right.

How should warm or cold liquids be pipetted?Exactly in the same way as liquids at room temperature. But it should be noted that the solutions could behave quite differently. In addition, the quantities and thus the measurement results can vary. This is the reason that our pipettes are tested with the tips and with distilled water after acclimatization in a room at 20 °C, only.

Are the handles of Eppendorf pipettes made of a special material to minimize temperature effects during pipetting?Temperature effects are minimized in our pipettes by their design. We accordingly use a special polypropylene which satisfies the particular requirements on a pipette handle.

What does the conformity symbol "H" on the pipette pack stand for?The conformity symbol is subject to German calibration regulations responsible for volumetric measuring equipment. This is only required in Germany. In future, the CE symbol will be applied directly to the pipette to indicate conformity with European standards.

Do Eppendorf pipettes always have to be kept in a stand or can they also be put down on the laboratory bench?They can be put down on the laboratory bench - but never with a full tip.

I very frequently work with different chemicals. Can you tell me from which point I need to adjust my pipettes?Adjustment, in other words altering the stroke of the pipette, is required for air cushion pipettes with solutions of a density 1.2 mg/µl. In theory, therefore, the pipette should be adjusted for every liquid and every volume. Variable manual pipettes are automatically turned into "fixed-volume pipettes" by being adjusted, as they can only be adjusted to the specific liquid at one volume and not across the entire dispensing range. For the correct procedure, please see the operating instructions for your particular pipette!

How do I determine the volume values when weighing a pipette?The measuring values of the analysis scale are multiplied by the correction factor Z (see SOP pipettes). This takes into account the density of the water at the relevant temperature and the relevant air.

What does UKAS mean in the context of calibration and certification of pipettes?UKAS = United Kingdom Accreditation Service, responsible for accreditation and certification in the UK.

What does EN ISO 8655 cover?From December 2002, EN ISO 8655 replaced DIN 12650 and other national European standards. Like DIN 12650 etc., it is aimed at: - manufacturers, as a basis for their quality assurance program, - testing institutions, as a basis for independent certification, - users, as a basis for routine testing of accuracy.

What do the terms random error (imprecision) and systematic error (inaccuracy) mean in a pipette calibration?The random measurement deviation (imprecision) describes the mean variation of the dispensed volumes from the mean value of the dispensed volumes, and is determined by calculating the repeat standard deviation of (usually) 10 measurements. The systematic measurement deviation (inaccuracy) describes the deviation of the dispensed volume from the nominal volume or from the selected volume of the piston stroke device, and is determined by establishing the mean value of (usually) 10 measurements.

Why are the Z factors listed in our SOP different from factors which can be derived from density reference values (of water)?The Z factor is included in EN ISO 8655-6 and was incorporated into our SOP. As we understand it, it was incorporated in the standard by the Physikalisch Technische Bundesanstalt in Braunschweig. The Z factor describes the density of water at a particular temperature using a 5th degree polynomial. Furthermore, the density of water is corrected by the density of air (derived from air pressure) and a fixed correction value for balances. These corrections are the key reasons for the deviation from density values in various books of tables.

Which DIN 12650 standard applies to single-channel, piston-stroke pipettes?DIN 12650 was replaced by EN ISO 8655 in December 2002 and applies with immediate effect to piston-stroke pipettes and dispensers.

What conditions should be observed when calibrating pipettes?The temperature of pipettes, test liquid and room should be identical. In other words, at least 2 hours should be allowed for everything to come to temperature. If this is not the case, an error can occur in air cushion pipettes as a result of the effects of differences in temperature, leading to fluctuating measured values (see EN ISO 8655). We recommend our standard operating procedure (SOP) for pipettes as a source of basic information on pipette calibration. Furthermore, we would like to draw your attention to our Liquid Handling training program: dispensing systems in the laboratory - principles, maintenance, quality assurance. You can find out more about this training program on our Eppendorf.com home page under the heading "Training".

To what value should a variable pipette be calibrated?According to the EN ISO 8655 standard a variable pipette should be calibrated to 3 volumes: 1. Nominal volume, 2. 50 % of nominal volume, 3. Smallest value which can be set or 10 % of nominal volume.

What is the nominal volume of a variable pipette?The nominal volume of a variable pipette is always the maximum volume. With a 100 - 1,000 µl pipette it is therefore 1,000 µl.

I very frequently work with different chemicals. Can I still perform pipette calibration using water?Calibration, i.e. checking a pipette on a balance, is always performed using distilled or deionized water (see EN-ISO 8655).

We work every day a great deal with our pipettes. How often should we calibrate our pipettes?The user decides upon the frequency of calibration, the number of test volumes and the number of measurements for each test volume within the framework of monitoring his test materials. This can vary depending upon the frequency of use of the pipette, the number of users of the device, the aggressiveness of the liquids to be dispensed and the error limits deemed acceptable by the user. However, an inspection should be carried out at least once a year. See also EN ISO 8655, Part 6.

During weighing (pipette calibration) I obtained steadily decreasing measuring results. Why is this?The weight fluctuations you measured would appear to be a temperature problem. Please ensure that the pipette, the distilled water used for testing, the tips etc. are all at the same temperature. It is recommended that the pipettes be placed in the weighing room at least 2 hours before the test is performed. Whilst measuring, ensure that transfer of heat from your hands is kept to a minimum (otherwise weight fluctuations may occur!) Tip: do not constantly grasp the pipette in the palm of your hand! We recommend our standard operating procedure (SOP) for pipettes as a source of basic information on pipette calibration. Furthermore, we would like to draw your attention to our Liquid Handling book: "Liquid Handling - Laboratory Practice" Order no. ADOSI 39020

Are the values given for the systematic error (inaccuracy) and random error (imprecision) for air-cushion pipettes also applicable when reverse pipetting?Yes, these limits also apply to reverse pipetting.

Why does the measuring protocol for the Eppendorf pipettes affixed to the operating instructions contain only two volumes for inaccuracy and imprecision, whilst in the catalogue and the Technical Data of the operating instructions, you quote the values for three volumes in each case?For all our pipettes, we guarantee the values for accuracy and precision for the three volumes quoted in the Technical Data (catalogue, operating instructions). This is what the conformity symbol with which all our pipettes are marked stands for. For cost reasons, we list only two volume values on the measuring protocol for each pipette.

How are multi-channel pipettes tested?All channels of a multi-channel pipette have to be tested individually. For this one tip is attached only to the channel to be tested. Hence the number of pipetting steps is drastically increased.

Is the pipette grease free of resins?Yes, the pipette grease supplied by Eppendorf is pure silicone grease.

According to which criteria are pipettes tested for conformity?The contents of the EN/ISO 8655 apply for conformity testing