Q&A

This chapter contains the replies to the most frequently asked questions on HTL pipettes and SWIFTPET^® pipetting controller. Should below answers did not address your enquiry please feel free to contact your local HTL distributor or write a question directly to us (info@htl.com.pl).

Pipettes:

• How should I set the volume?
• How should I work with my HTL pipette? 
• How should I aspirate viscous liquids? 
• What is reverse pipetting technique?
• What is pre-rinsing pipetting technique?
• Which tips can I use with my HTL pipette? 
• How can I sterilize my pipette? 
• Is my pipette UV resistant?
• How should I work to keep my pipette in good shape for years?
• How do I check accuracy and precision of my pipette? 
• What do I do if my pipette works improperly?

SWIFTPET^®:

• How can I sterilize my SWIFTPET^®?
• Can I change the battery of SWIFTPET^®?

Pipettes

How should I set the volume?

The volume display shown by the counter has three digits, which should be read from top to bottom. In addition the lowest counter drum is printed in a scale which enables the setting of the volume in the minimum graduation range.
To set the required volume, use:

1. the lower section of the pipetting pushbutton (only single- and multichannel DISCOVERY⁺ pipettes)
   
   Pushbutton volume setting
2. black adjustment knob (V, VE, LABMATE⁺, MULTIMATE⁺, DISCOVERY⁺ pipettes)
   
   knob volume setting

All volume setting procedures should end in the reduction of volume setting from a position just above the desired level to that level. As further examples:

• When moving from a high volume setting to a lower value, the pushbutton or adjustment knob should be rotated at normal speed, clockwise, to take the setting just above the desired level. It should then be further rotated very slowly till the desired volume is shown on the digital volume display. In the event that you overshoot the desired setting, repeat the procedure by increasing the volume to a position just above the desired volume and then once again, reduce slowly to the desired level.


• When moving from a low volume setting to a higher value, the pushbutton or adjustment knob should be rotated at normal speed, anticlockwise, to take the setting to a position just above the desired level. Then reduce the reverse the rotation and slowly adjust back until the desired volume is shown on the digital display. Once again, in the event that you overshoot the desired setting, repeat the procedure by increasing the volume to a position just above the desired volume and then reduce slowly to the desired level.

More details are given in respective pipette manuals
See the film:
Volume setting

How should I work with my HTL pipette?

Proper technique of pipetting plays a tremendous role in reproducibility of measurement results. The most accurate pipette in inexperienced hands can give inaccurate results. Therefore in order to ensure highest repeatability of your precise tool it is essential to follow below guidelines:

1. Always use your pipette with a proper tip on. The charts of tip volumes appropriate for certain pipette models are posted on this website in chapters describing individual pipettes. Respective information is printed in pipettes' Instruction Manual 
2. Keep consistent pickup / dispense rhythm during the whole pipetting cycle
3. Keep consistent speed and smoothness of the pushbutton move
4. Keep consistent tip immersion depth
5. Maintain consistent angle of pipette while aspirating (min 30°)
6. Avoid air bubbles in the tip during aspiration.
   

Detailed instructions on how to operate the pipette step by step are given in respective pipette manuals
See the film:
Forward pipetting technique

How should I aspirate viscous and/or dense liquids?

For pipetting viscous and/or dense liquids other than forward pipetting techniques are recommended.
These are:

Besides, compensation for solutions of density much different from water is possible with HTL adjustable pipettes by setting the digital micrometer slightly higher or lower than the required volume. The amount of compensation must be determined empirically.

What is reverse pipetting technique?

The reverse pipetting is a technique especially recommended for pipetting solutions with a high viscosity or those that tend to foam. This method is also recommended for dispensing very small volumes. The advantage of this mode is reducing error due to film retention. The sequence of operations in the pipetting process is reversed, as follows:

1. Press the operating button to the second stop
2. Dip the tip into the liquid, then slowly release the operating button. This will fill the tip with a volume that is larger than the set volume. Wait 1-2 seconds to reach equilibrium in the tip and withdraw the tip from the solution, touching it against the edge of the reservoir to remove excess liquid.
3. Dispense the liquid into the receiving vessel by pressing the operating button gently and steadily to the first stop. This volume is equal to the set volume. Hold the button in this position. Some liquid will remain in the tip, and this should not be dispensed.
4. Remove the tip from the receiving vessel without blowing it out. The liquid remaining in the tip can be delivered into the original vessel or discarded together with the tip.
5. Release the operating button to the ready position.

Reverse pipetting is only possible with air displacement pipettes
See the film:
Reverse pipetting technique

What is pre-rinsing pipetting technique?

Pre-rinsing is another technique recommended when working with viscous and/or dense liquids. Some liquids show a tendency to cling to the inside and outside surfaces of the disposable tips (especially serum, protein-containing solutions, and organic solvents), resulting in an error that may be larger than the tolerance specified. To insure that this surface tension does not cause variations in the volumes you aspirate, always pre-wet the disposable tip with the sample before use. Aspirate some liquid and then dispense it back into the original container. Successive samples from this same tip will exhibit good reproducibility (low variance). Pre-wetting is recommended in most operations for improved accuracy
See the film:
Pipetting viscous and dense liquids

Which tips can I use with my HTL pipette?

HTL pipettes are designed to accommodate all universal tips available on the market. All popular tips shall seal on and eject from HTL shafts properly. In some rare cases when the geometry of the tip of other manufacturers differs from standard the pipette re-calibration might be necessary. While working with universal, tips make sure that they meet the following requirements:

• Disposable tips must seal properly on the shaft to assure an air-tight seal and avoid leaks.
• Tips must be soft and flexible so that the shaft is not scratched or worn prematurely.
• Tips must be free from flash and particulates. Microscopic flash at the orifice can result in poor precision and accuracy.
• The tip orifice should be round, smooth and of correct (small) diameter.
  

See the film:
The tip ejector adjusting

How can I sterilize my pipette?

Sterilization of LABMATE⁺, V3 Series and EPA PLUS^® pipettes

Shaft assay & tip ejector - all components of above pipettes which could get in contact with contaminating liquids or their vapors can be sterilized with isopropyl alcohol, popular sterilizing solutions or autoclaved in 121°C for 20 min. In order to autoclave these parts follow below steps:

1. unscrew the piston assay from the pipette handle and/or detach the tip ejector from the pipette
2. place them as a whole into the autoclave
3. cool and dry the parts before re-assembling
4. attach the shaft assay and the tip ejector back on their place.

Detachment of the shaft assembly and autoclaving does not affect the reproducibility as long as the piston is not taken out from the shaft. It is recommended that the accuracy and precision of the pipette is checked after 10 autoclaving cycles.

See the film:
LABMATE autoclaving procedure

Sterilization of MULTIMATE⁺

Handle,  pushbuttons and shaft - wipe with isopropyl alcohol or a popular sterilizing solution.

Sterilization of DISCOVERY⁺ Series and CLINIPET⁺ pipettes

DISCOVERY⁺ Series pipettes and CLINIPET⁺ pipettes can be whipped with alcohol, popular sterilizing solutions or autoclaved as a whole. In order to autoclave these pipette follow below steps:

1. Take the tip ejector off and loosen the cone nut (unscrew the shaft slightly)
2. Place the tip ejector and the pipette into autoclave
3. Cool and dry the pipette before tightening the nut and putting the ejector back on.

Autoclaving does not affect the reproducibility as long as the piston is not taken out from the shaft. It is recommended that the accuracy and precision of the pipette is checked after 10 autoclaving cycles.

See the film:
DISCOVERY⁺ autoclaving procedure
DISCOVERY⁺ multi autoclaving procedure

Is my pipette UV resistant?

All HTL pipettes undergo rigid UV resistance tests. The tests prove that even after intense and lengthy exposure to UV beams pipettes maintain their reproducibility and mechanical resistance. In some cases slight de-coloration of the outer parts may occur but its extent is smaller than in most of popular pipettes available on the market.

How should I work to keep my pipette in good shape for years?

HTL pipettes are known for their mechanical and chemical resistance as well as long lasting reproducibility. If the pipette is used in accordance with general guidelines listed in the Instruction Manual it is guaranteed to work without failure for at least 3 years. In order to keep the pipette in ideal shape however it is recommended that the following maintenance and operation rules are followed at all times:

1. Avoid flooding of your pipette (do not aspirate more liquid than the tip volume, keep your pipette in vertical position +/- 30° when liquid remains in the tip).
2. Should flooding occur, disassemble the pipette and clean with distilled water all the parts which came in contact with the liquid.
3. After every cleaning with distilled water lubricate the o-ring and the Teflon seal with the grease enclosed in the pipette box.
4. Check calibration of your pipette at least once a year.
5. Exchange the o-ring and the Teflon seal of the plunger every 60 000 pipetting cycles (2 years of very extensive usage).
6. Should you notice inconsistency of pushbutton move smoothness or scratches on the shaft contact your distributor for advise.

See the film:
Seals replacement
Cleaning and lubricating of the piston

How do I check accuracy and precision of my pipette?

Proper verification of the accuracy and precision of your pipette requires maintaining strict testing regime. The measurement results of your pipette may vary depending on:

1. The skill of pipette operator.
2. The conditions in the testing room.
3. The kind and temperature of measured liquid.
4. The sensitivity of the volumetric equipment.

Therefore in order to accurately determine the reproducibility of your pipette make sure to follow below rules:

1. Ensure that the test is performed by the skilled person maintaining steady rhythm and the speed of pipetting.
2. Perform the test under steady temperature
   b.2. Perform the test under steady humidity conditions (50% - 75%)
3. Perform the test with distilled or deionized water grade 3, conforming to ISO3696 of the same temperature than the testing room
   c.2 Use containers covered with lids for weighing volumes lower than 50µl
4. Perform the gravimetric test on calibrated, regularly serviced balance. The sensitivity of the balance should be appropriate for the volume of measured liquid as shown in below chart

   Volume tested (µl)	Measurement Accuracy (mg)	Standard Deviation (mg)
   ≥ 0,2-10	≤ 0,001	≤ 0,002
   ≥ 10-100	≤ 0,01	≤ 0,02
   ≥ 100-1000	≤ 0,1	≤ 0,2
   ≥ 1000	≤ 0,1	≤ 0,2

   d.2. Measure the temperature with calibrated termometer (maximum uncertainty 0,2°C)
   d.3. Measure the humidity with calibrated hygrometer (maximum uncertainty 10%)
   d.4. Measure the air pressure with calibrated barometer (maximum uncertainty 0,5kPa)

To find out about accuracy and precision measurement procedure click here: Accuracy>>

What do I do if my pipette works improperly?

1. Procedure of placing the quality claim
   Whenever you notice improper functioning of HTL equipment feel free contact your HTL distributor for advice. We also recommend that you take a look at the information on troubleshooting available at this website and in Instruction Manual of your product. It might occur that the reason of the malfunctioning is prosaic and that simple action can fix your tool. Should the problem noticed occurred to be more severe and your distributor asked you to return the product, please send it back to him together with filled Claim Form.

SWIFTPET^®

How can I sterilize my SWIFTPET^®?

The outer body of the SWIFTPET^® can be cleaning with isopropyl alcohol or any other popular sterilizing solution. Pipette holder the nosepiece and filter are fully autoclavable at 120°C, 20 min, 1 bar.

Can I change the battery of SWIFTPET^®?

Unlike most of the pipetting controllers available on the market the SWIFTPET^® does not require the exchange of battery. Placing the exchangeable battery in the electrically powered, electronic tool, working in potentially highly humid environment creates a great hazard for its durability. The door of the battery compartment is never 100% leak and vapor proof, regardless of its design. While working with the tool equipped with an exchangeable battery you risk that should liquid or its vapors enter the battery compartment your sensitive contacts shall rust and stop working.

On the other hand highly efficient, environmentally friendly battery of SWIFTPET^® is guaranteed to withstand at least 1000 charging cycles. Should you decided to charge your pipetting controller every day it would withstand at least 2,5 years of such treatment. In fact the capacity of your battery allows you to work extensively for at least 3 days without recharging when the battery is fully charged.