Precision and accuracy of pipetting are influenced by a number of factors

Precision and accuracy of pipetting are influenced by a number of factors

Overview

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  • Date: 04 Jan,2023

In chemistry, biology, and medicine, a pipette is a typical laboratory instrument used to convey a predetermined volume of liquid, frequently as a media dispenser. The success of your pipetting results will depend on how accurately you read the pipette volume when doing delicate research. Using precise, high-quality instruments is the greatest method to be sure you are reading your pipette volume correctly. Understanding and perfecting an ideal pipetting technique is crucial as the demands for accuracy and precision in your laboratory increase.

A pipette is used in scientific studies that call for great accuracy to properly measure and transfer small volumes of liquid.

However, failure of the equipment or operator error could be the causes of error in pipette measurements. Any variation in the amounts distributed could have an impact on the results and repeatability of an experiment, such as the results of qPCR.

Factors Affecting the Accuracy of Pipettes:

Temperature

Accurate pipetting is significantly impacted by temperature. The temperature difference between the delivery device and the liquid is the element that has the biggest impact. Thermal expansion effects specific to the situation occur in the air gap (dead air volume) between the liquid surface and the piston. Along with other consequences, this either decreases or raises the volume of liquid inhaled into the tip.

Density

The amount of liquid that is sucked into the tip is influenced by density (mass/volume ratio). Compared to a comparable procedure using water, less of a liquid with a higher density is sucked. The result is the opposite for liquids with lower densities. This results from the flexible dead air volume and the gravitational pull of the earth. Liquid density varies with temperature as well. Usually, the density of liquids varies with temperature as well. When the temperature is 20 °C/68 °F, the density of water is typically 0.998 kg/dm3, that of ethanol is 0.79 kg/dm3, and that of sulfuric acid (95-98% h2SO4) is 1.84 kg/dm3.

Altitude

Through air pressure, geographic altitude influences accuracy. Higher altitudes result in lower air pressure and a lower Z conversion factor.

Additionally, the boiling point of some liquids drops significantly relatively close to room temperature, drastically increasing the evaporation loss.

Reagent volatilization:

High volatility reagents absorb steam, which enters the gun head and raises internal pressure. As a result, an error happens when the liquid is forced out because the pressure increases.

Selecting the Incorrect Pipetting Mode

During pipetting, the operator frequently makes random or subjective decisions on whether to use the backward or forward mode. However, viscous samples should be the only ones that use reverse mode. The plunger is fully depressed (beyond the first stop) to aspirate the sample while in reverse mode, and then only partially depressed (to the first stop) to deliver it. For this reason, utilising forward mode with viscous fluids causes under-delivery whereas using reverse mode with watery solutions causes over-delivery.

Pipetting in a Slant

Sample loss occurs when the pipette tip touches the walls of the container during aspiration. Additionally, when pipetting small volumes, withdrawing the pipette at an angle can result in volume variance due to surface tension effects. Error can be reduced by pulling the pipette straight out of the container.

References:

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2.Klingenberg, M (2005). “When a common problem meets an ingenious mind”. EMBO Rep. 6 (9): 797–800. doi: 10.1038/sj.embor.7400520. PMC 1369176. PMID 16138087.

3.Zinnen, Tom (June 2004), The Micropipette Story, retrieved November 12, 2011

4.Shohl, Alfred T. (February 1928). “A Pipet for Micro-Analyses”. Journal of the American Chemical Society. 50 (2): 417. doi:10.1021/ja01389a502.

5.”FrameA”. Retrieved 3 March 2016.

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