How is your pipette performing?

Chipo Samvura explains how lab technicians can get the best out of their pipettes

Many laboratory applications require the routine use of manual pipettes for the set-up of reagents and samples. Since this is often the first step in the process, subsequent success is dependent on accuracy and precision at this stage.

Application use may vary, but the necessity to produce accurate and reproducible data is universal. For example, when establishing a standard curve or amplified serial dilution, this inaccuracy could make a fundamental difference to your data or go unnoticed and lead to incorrect results. Inaccurate results can lead to published data being challenged or, at the very least, require that the experiment be repeated multiple times.

Whilst your pipette may appear to be functioning correctly there may be some inapparent issues that are affecting performance. These failures are most commonly caused by tiny cracks in the seal or a build-up of contamination inside the pipette, which can best be detected by a trained technician.

Most laboratory quality systems require a regular calibration and maintenance programme for pipettes. The pipettes should be regularly maintained according to the manufacturer’s instructions, which includes cleaning and greasing of pipettes, as well as replacement of wearable parts. Alongside maintenance, the pipettes should have their performance verified by calibration. This is the measurement of systematic and random error along with any necessary adjustments.

The maintenance interval is determined by factors such as pipetting frequency, liquids used, and the age and model of pipette. A minimum maintenance interval of one year is suggested, with calibration done annually or more often, such as every 3-6 months. If, for example, volatile liquids or solvents are used, maintenance should be done more regularly.

The calibration standard used by the service provider will likely be the single most important factor affecting the accuracy of your pipettes. Because calibration standards often vary from one service provider to another, it is wise to know the differences before selecting a service partner.

Calibration considerations

Pipettes that are calibrated to manufacturer specifications perform within optimal range as defined by the manufacturer. ISO 8655 is an international standard that governs pipette calibration and regardless of brand, calibration to this level may be to a higher level than the manufacturer specified performance. When calibrating a pipette to the manufacturer specifications or ISO 8655 standards, environmental conditions must be taken into account. Your service provider can have a big impact on the success of your experiments, so knowing what to look for, and what questions to ask, will save time, money and minimise your liability.

Standards compliance

For a full maintenance and calibration of pipettes, the calibration laboratory used should have at minimum full ISO 8655 compliance, including controlled environment in terms of temperature, vibration, and humidity; and accreditation according to ISO 17025 standard with traceability of measurements to international standards. Balances with a minimum of 5- and 6-decimals along with evaporation traps or draft shields are other requirements, as is appropriate software for recording results. The final must-have is professionally trained technicians who understand pipette technology and good pipetting practices, as well as requirements set by regulatory and quality systems.

Chipo Samvura is with Alpha Laboratories

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