The measurement of small amounts of liquids is very important in fields like, health, chemistry, microbiology and genetics. The most common used instruments for delivery of liquids, in the order of the microliter, are micropipettes or piston pipettes, of fixed or variable volume, with positive or air displacement operation. The method used in the calibration of micropipettes is the gravimetric method, which is the determination of the delivered mass of distilled water, at a reference

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... of 20 ºC. This method is based on ISO 8655 and ISO 4787. In order to verify the influence of specific experimental details of the normalized procedure described in ISO 8655-6, several experimental tests were performed by the Volume Laboratory of The Portuguese Institute of Quality, namely: Angle variation of aspiration and delivery of liquid; Immersion depth of the tip; Aspiration and delivery velocity; Type of tip and Altitude. This study will allow the improvement of the calibration procedure of micropipettes and the harmonization of the results between laboratories. (2013) 306010 th metrology International Congress of Metrology, This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2 0 , which . permits unrestricted use, distributi and reproduction in any medium, provided the original work is properly cited. on, Article available at