= Micropipette
A laboratory <micropipette> is a <pipette> for transferring small measured quantities of liquid, commonly expressed in <microlitres>. In piston-operated models, the displacement mechanism matters. An <air-displacement pipette> leaves an air cushion between piston and sample, whereas a <positive-displacement pipette> places the piston directly against the liquid.<Gilson Guide to Pipetting>[second edition, pp. 8–11, working principles]{ref}
Weighing a delivered sample provides a concrete check. In a simplified calculation that neglects air buoyancy and <evaporation>, liquid <volume (thermodynamics)> follows from <mass> $m$ and <density> $\rho$:
$$
V=\frac{m}{\rho}.
$$
For an assumed $\rho=1.000\,\mathrm{mg/\mu L}$, a delivered mass of $99.5\,\mathrm{mg}$ corresponds to $99.5\,\mathrm{\mu L}$. Relative to a nominal $100\,\mathrm{\mu L}$ setting, the deviation is $-0.5\%$. These are illustrative values, not calibration data.
A repeated series can distinguish a displaced mean from wide scatter: <measurement accuracy> and <standard deviation> describe different aspects of performance. Actual gravimetric checks account for temperature-dependent water <density>, air buoyancy and evaporation losses. The manufacturer's method uses a conversion factor and an evaporation correction, showing why a displayed volume alone does not establish the quantity delivered.<Gilson Guide to Pipetting>[pp. 46–49, systematic/random error, gravimetric conversion and repeated weighings]{ref}
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