Is there an Eppendorf pipette which can be used to pipette 40 % polyethylene glycol 8000 (PEG)?

Yes, for pipetting PEG instruments operating according to the positive displacement principle like the Biomaster or a Multipette/Repeater can be used.

What is the best way to pipette chloroform?

When pipetting chloroform, we recommend positive displacement instruments like Biomaster, Multipette/Repeater, and Varipette or an air cushion pipette (Research plus, Reference 2) in combination with the reverse pipetting technique (see Userguide 20 and 21 for details).

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 an air cushion pipette is used. For this reason, it can only be pipetted using a positive displacement pipette, such as Biomaster, Multipette/Repeater, and Varipette.

What should be considered when pipetting methanol with air cushion pipettes?

Due to the increased vapor pressure, we recommend that the tip is prewetted at least 3 times and that the reverse pipetting technique is used.

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. We recommend working with an instrument that operates according to the positive displacement principle like Multipette/Repeater, Varipette, or Biomaster.

What is the best way to dispense organic solvent?

It is best to use a positive displacement device like the Multipette/Repeater. Positive displacement devices are most suitable for precise and drip-free dispensing of liquids with high vapor pressure. As the liquid is enclosed in a tip with integrated piston, the solvent vapor does not come into direct contact with the instrument.

I would like to pipette dichloromethane and n-hexanol very precisely. Can I use air cushion pipettes for this application?

Both dichloromethane and n-hexanol have a very high vapor pressure. For that reason, positive displacement instruments like the Biomaster and the Multipette/Repeater should be used.

How can radioactive contamination be removed from Eppendorf pipettes?

Following contamination of pipettes with radioactive liquids, we recommend placing the contaminated parts in a complex-forming liquid or special cleaning solution. Then rinse very thoroughly with distilled water and dry. Grease piston lightly afterwards.

I often work with different chemicals. Can you tell me when I need to adjust my pipettes?

This belongs to the permissible errors of your specific application. In general an adjustment of air cushion pipettes, in other words altering the stroke of the pipette, is required for solutions of a density higher 1.2 mg/µL. Please be aware that variable manual pipettes turn into "fixed-volume pipettes" when being adjusted: They can only be adjusted to a specific liquid to one volume and not across the entire dispensing range. Eppendorf manual pipettes have a user adjustment for temporary adjustment purposes. This user adjustment can easily be set back to manufacturer settings without the need for recalibration. For the correct procedure and examples for settings of user adjustments for different liquids please see the operating instructions and CD enclosed to your pipette.

How do I determine the volume values when calibrating gravimetrically?

The measuring values of the analysis scales 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 EN ISO 8655 cover?

ISO 8655 addresses the needs of suppliers, test houses, and users and specifies the general requirements for piston-operated liquid handling devices. It is structured in seven chapters: ISO 8655-1: Terminology, general requirements, and user recommendations ISO 8655-2: Piston pipettes ISO 8655-3: Piston burettes ISO 8655-4: Dilutors ISO 8655-5: Dispensers ISO 8655-6: Gravimetric method for the determination of measurement error ISO 8655-7: Non-gravimetric methods for assessment of equipment performance (titration, photometry)

What do the terms random error and systematic error mean in a pipette calibration?

The systematic error 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. The random error 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.

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.

At which volumes should a variable pipette be calibrated?

According to the EN ISO 8655 standard, a variable pipette should be calibrated to 3 volumes during conformity testing: 1. Nominal volume, 2. 50 % of nominal volume, 3. Smallest value that 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. For 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).

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. While 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 while waiting for each measurement result! We recommend our standard operating procedure (SOP) for pipettes as a source of basic information on pipette calibration.

How are multi-channel pipettes tested?

According to ISO 8655, all channels of multi-channel pipettes are to be tested. All channels have to be filled but only the channel to be tested is measured. Because of the high number of measurements (8-channel pipette: 240 measurements, 12-channel pipette: 360 measurements), it makes sense to send the multi-channel pipette to a professional calibration lab. These labs have special constructions for balances to ensure that all channels are filled but only one channel is measured.

Is the pipette grease free of resins?

Yes, the pipette grease supplied by Eppendorf is free of resins.

How is the wall mount for pipettes attached to the wall?

The pipette holder is affixed to the wall with adhesive.

Is the Research plus resistant to concentrated acids?

In most cases, concentrated acids are not a problem. Please check the chemical resistance information on our homepage before use. Please note that aggressive chemicals used over a longer period of time may shorten the lifetime of the pipette.

In the adjustment manual of the Research plus, only two examples of liquids are given (50 % glycerol and 45 % cesium chloride). Are there more examples of liquids and their recommended setting on the adjustment display that have been tested?

Yes. Please find further information within Application Note 198.

Is a gravimetric test necessary after resetting the adjustment display to "0"?

From a technical point of view, a gravimetric test is not required. However, for certified laboratories a gravimetric test might be required for documentation purposes.

Is the Research plus compatible with hydrofluoric acid?

Yes. Please note that the use of aggressive chemicals like hydrofluoric acid over a longer period of time will reduce the lifetime of the pipette.

How many overnight cycles or total hours of UV irradiation can the Research plus withstand before any discoloration or change of the material will be visible?

We tested UV radiation under very intense conditions for 165 hours. There was no visible discoloration or change to the material.

Can the Research plus be autoclaved if the locking ring is installed to deactivate the spring loading?

Yes. The locking ring is made of PPS (polyphenylene sulfide) and therefore autoclavable (121 °C, 1 bar, 20 min).

Is the Research plus compatible with sodium hydroxide (größer10 %)?

Yes, the Research plus is compatible with sodium hydroxide größer 10 %.

Is the Research plus compatible with 65 % nitric acid?

Yes, in general, however, discoloration may take place and the piston seal may corrode. Please note that the use of aggressive chemicals like nitric acid over a longer period of time will reduce the lifetime of the pipette.

Do I need to disassemble the Research plus before autoclaving?

No. It can be autoclaved in one piece (121 °C, 1 bar, 20 min).

What are the settings of the Research plus pipette for liquids of different viscosities or specific densities?

The user manual of the Research plus mentions specific settings for some volumes of the most common liquid classes. These values are for orientation only as the systematic and random error are affected by many factors like, e.g., the mode of operation, the tip used, temperature. It is essential to check this data according to your own method.

Will water vapor enter the pipette while it is being autoclaved, causing water vapor to bead up on the inside of the numerical volume setting display?

Vapor will penetrate the inside of the pipette during autoclaving but this will not cause damage. We tested our pipettes with 175 autoclaving cycles (121 °C, 1 bar, 20 min). The number of tests chosen corresponds to an average of 5 years of use.

In part 3 of the operating manual of the Research plus, you recommend adjusting the volume setting from a higher value to a lower value. If required, the user should turn the value beyond the required value and then back again. What is the reason for such a recommendation?

For technical reasons, the results are generally more precise when a volume setting is carried out from a higher down to a lower value. This is valid for all manual pipettes.

How should contamination on the outside of the Research plus be removed?

Wet a cloth with water or 70% isopropanol and wipe off.

How should the Research plus be disinfected?

Wipe the outer surface with disinfectant, DNA/RNA decontamination agent, or 70 % isopropanol or a commercially available disinfectant. Check the chemical resistance of the pipettes using the chemical resistance table (website). After the exposure time of the disinfectant, rinse thoroughly with demineralized water. This step is especially important if subsequent decontamination, e.g., with UV-light or autoclaving, should be performed. The Research plus may be temporarily subjected to UV light under a sterile bench. We recommend the use of a Hg-lamp, 254 nm, 30 W. The distance between lamp and pipette should be approx. 60 cm. The Research plus is fully autoclavable.

How can I clean and maintain the Research plus?

The Research plus pipettes are easy to clean. Only the lower part should be cleaned on a regular basis in accordance with the frequency of use. The lower part of the single-channel and multi-channel Research plus pipettes can be removed easily as described in the operating manual of the Research plus or in our Application Note 198.

Which material is the Research plus made of?

Pipette parts which might come in contact with liquids are made of the following materials: PP (polypropylene), PEI (polyetherimide), PVDF (polyvinyliden fluoride), PC (polycarbonate), PPS (polyphenylene sulfide), and stainless steel.

When should the spring loading of the single-channel Research plus pipettes be deactivated?

For dispensing tasks in which a pipette tip is used over a long time or is slightly bent, it can be helpful to deactivate the spring loading of the tip cone by installing the locking ring. This can also be helpful for pipette tips which are not designed for Eppendorf pipette cones.

When pipetting foaming liquids (e.g. cell culture media) I‘m transferring foam which got trapped between the epT.I.PS. 384. How can I improve?

When pipetting foaming liquids it may happen that foam adhere between the tips. Make sure to pipette slowly avoiding foam formation. Importantly, do not immerse the tip too deeply into the liquid preventing foam getting caught between the tips.

What is the difference between factory setting and user adjustment?

The user adjustment for temporarily applications such as pipetting a liquid with a higher density than water. The little window shows the change. It can be set back to factory settings ""0"". A subsequent calibration is not necessary. The factory setting is a basic adjustment of the pipette. It should only be changed if the pipette exceeds the maximum permissible errors after calibration and all other factors which could have an influence have been excluded.

How often should pipettes be calibrated?

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 on 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 8655-6.

I have noticed that more solution is used for reverse pipetting than for normal pipetting. What is the reason for this?

Reverse pipetting means uptake of liquid including the blow-out volume and dispensing of liquid without the blow-out volume. Reverse pipetting is recommended to reduce the error with viscous or foaming liquids or when dispensing very small sample volumes. The excess solution aspirated remains in the tip and is discarded.

Can you recommend any literature on reverse pipetting?

Userguides 20 and 21 describe the technique and give application examples. They can be downloaded from the Knowledge Base on our website.

Should the pipette tip be wetted with liquid before pipetting volumes smaller than 10 µL?

Regardless of the volume, the air cushion should be wetted by multiple filling and emptying of the tip before dispensing.

What is the best way to pipette viscous liquids?

When pipetting viscous liquids, we recommend positive displacement instruments like Biomaster, Multipette/Repeater, and Varipette or an air cushion pipette (Research plus, Reference 2) in combination with the reverse pipetting technique (see Userguide 20 and 21 for details).

Are Eppendorf pipettes resistant to acetonitrile?

Yes, Eppendorf pipettes are resistant to acetonitrile but care must be taken to avoid damage to printing and display window.

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 nucleic acids. To protect your pipette from contamination, we recommend using positive displacement pipettes, for example, our Biomaster or filtertips (ep Dualfilter T.I.P.S. or ep Dualfilter T.I.P.S. SealMax).

Do Eppendorf pipettes always need to be greased?

No, the piston only has to be greased if grease-dissolving solutions like organic solvents have been used.

Can the pipette withstand evacuation (applying a vacuum)?

No, air cushion pipettes should not 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, however, please note that solutions may behave differently. In addition, the pipetting accuracy / precision may be outside the permissible error limits. In order to achieve maximum accuracy / precision, all components should have the same temperature: pipette, tips, liquid, and the surrounding air.

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 use a special polypropylene which satisfies the special requirements on a pipette handle.