Evaluación del error debido a la evaporación en el método gravimétrico de calibración de micro pipetas

Authors

  • Andrea Sica Departamento de Metrología, Laboratorio Tecnológico del Uruguay (LATU), Uruguay
  • Pablo Constantino Departamento de Metrología, Laboratorio Tecnológico del Uruguay (LATU), Uruguay
  • Gonzalo Heijo Aphos SRL. Uruguay
  • Juan Andrés Fabretti Aphos SRL. Uruguay
  • Claudia Santo Departamento de Metrología, Laboratorio Tecnológico del Uruguay (LATU), Uruguay

DOI:

https://doi.org/10.26461/04.03

Abstract

The calibration of piston pipettes by the gravimetric method consists on filling the instrument with distilled water and a subsequent deliver into an open vessel, located on the balance where the weighing is performed. One of the most frequent errors in calibrations by this method is caused by the phenomenon of evaporation. The purpose of this study is to quantify that error and to evaluate modifications to the conventional gravimetric method in order to decrease it.

To study the magnitude of this effect, we estimate the value of the volume delivered before the evaporation process, plotting the mass vs time and extrapolating the value of mass at zero time. This value is compared with the value obtained from direct reading after the stabilization of the balance, that is one minute after dispensing.
We study a way to reduce evaporation performing delivery in a vessel with vegetable oil, since by having a lower density than water the delivery is occluded in, minimizing evaporation. This quantitative variation of this method is compared with the conventional gravimetric method to evaluate the impact of this change in evaporation effect.
We conclude that the alternative procedure of delivering in a vessel with oil provides operational benefits, yielding comparable calibration results.
Keywords: gravimetry, evaporation, discharge, oil, advantages.

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How to Cite

Sica, A., Constantino, P., Heijo, G., Fabretti, J. A., & Santo, C. (2011). Evaluación del error debido a la evaporación en el método gravimétrico de calibración de micro pipetas. INNOTEC, (4 ene-dic), 15–18. https://doi.org/10.26461/04.03

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