ple, when pipetting to microplates (Figure 1). However, many pipettors allow rotation only in one direction, since rotation in the other direction will disassemble the liquid end from the handle. In some models, the connecting nut has to be tightened after adjusting. To avoid accidental disassembling, which leads to a loss of accuracy or even leakage during pipetting, one should ensure that the pipettor chosen allows 360 free rotation without a need for tightening. The mLINE instrument features this ability. Pipettors that are color-coded and have large, clear numbers are easier to read and use. This is also the case with the mLINE unit; in addition, the volume adjustment is stepless, extremely light, and fast to adjust. Most importantly, the volume is locked after adjustment to avoid accidental alteration of the volume during pipetting.2
To avoid this, many pipettors on the market have adjustment systems that are extremely heavy to turn, particularly while wearing gloves.
Pipetting force, accuracy, and precision
There exists much
variation among different manufacturers in the specifications for
instrument accuracy and precision (Table 1). This regards not only the
guaranteed specifications but also the pipetting force, which has an
influence on accuracy. The force needed to depress the plunger to the
first position varies from 8.7 to 20 N, depending on the manufacturer
and the pipettor in use; for the blowout, that number goes up to 45 N
(4.5 kg).3 In conventional pipettors, the smaller the
volume, the more thumb force that is demanded to operate the plunger.
High force, together with small movements, cannot be repeated with the
same accuracy after hundreds of pipettings. If one is pipetting more
than 1000 samples a day with a conventional mechanical pipettor, it is
no surprise that serious fatigue in the muscles of the hand occurs,
which can ultimately lead to repetitive strain injuries (RSI).
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