After reading this chapter, prepare a streetwise protocol explaining how to use a pipettor to deliver a specific volume, say \(500 \mu \mathrm{L}\) (e.g. using a Gilson Pipetman \(^{\oplus}\) or an alternative if your department does not use this type). Ask another student to evaluate your protocol and provide you with feedback - either by reading through your protocol or by trying it out with a pipettor as part of a class exercise (check with a member of staff before you attempt this in a laboratory).

Excelling in laboratory techniques is vital for anyone working in scientific fields, especially when dealing with chemicals and biological samples. For students, mastering the proper use of a pipettor is foundational. A pipettor, also known as a micropipette, is a laboratory tool commonly used to transport a measured volume of liquid accurately. Familiarity with the different parts of a pipettor is critical before one starts using it. The plunger button, for example, is paramount for drawing up and dispensing the liquid. The volume adjustment knob is equally important as it allows the user to select the exact volume required for the experiment.

Before using a pipettor, one should always ensure the device is calibrated correctly for accurate volume measurement. After adjusting the volume, the next step is attaching a sterile pipette tip. It's crucial to avoid touching the tip with hands, as this can contaminate the sample. Instead, use the pipettor's tip ejector button to attach and detach tips without direct contact. Drawing up the liquid requires a steady hand — depress the plunger to the first stop before immersing the tip into the liquid, then gently release to fill the tip. When dispensing, touch the tip to the vessel wall and press the plunger smoothly to avoid splashing or forming bubbles, which can affect measurement accuracy. Lastly, remember to eject and dispose of the used tip properly.

In the realm of chemistry, precise volume measurement is non-negotiable. The success of experiments often hinges on the accuracy of liquid volumes dispensed. Using a micropipette to measure out a specific volume, such as the required \(500 \mu \mathrm{L}\), involves understanding the measurements marked on the device and its volume limitations. Each pipettor is designed for a certain range of volumes and typically has a digital or analog dial to set the desired amount.

Measuring volumes smaller than the minimum or exceeding the maximum can lead to significant errors and poor experiment outcomes. Proper technique is also critical when measuring out volumes. To ensure consistency, depress the pipettor's plunger with the same force each time, and make sure to draw up and dispense the liquid at the same speed. Viscosity and temperature of the liquid can affect the volume measurement, so it's important to calibrate the pipettor if the conditions deviate significantly from standard laboratory settings. By adhering to strict volume measurement practices, one ensures the reliability and repeatability of scientific experiments.

Calibration of pipettors is an essential procedure that ensures the accuracy and precision of liquid dispensing. Regular calibration checks are necessary because even the most durable pipettors can drift from their set volumes over time due to wear and use. Calibration involves verifying and adjusting the delivered volume against a known standard. This process can be performed by weighing the water dispensed by the pipette and comparing it with the theoretical weight at a specific temperature and pressure.

Users can perform a quick 'in-lab calibration' by dispensing water into a pre-weighed vessel and calculating the volume based on the weight gained. For more thorough and compliant calibrations, especially in regulated industries, one should employ professional calibration services equipped with high-precision balances and environmental controls to minimize error. Keeping a record of calibration checks and their outcomes is also part of good laboratory practice, which ensures data integrity and reliability of the experiment outcomes.

Maintaining sterility during pipetting procedures is crucial in many laboratory settings, especially those involving microbiology, cell culture, or any applications where contamination can lead to erroneous results. The sterile pipetting procedure begins with using sterile, disposable tips that are certified free from DNase, RNase, and pyrogens. When attaching the tip to the pipettor, it is important to avoid contact with non-sterile surfaces, including hands. Aseptic techniques, such as working near a flame or within a laminar flow hood, offer extra precaution.

Once the tip is secured, only the sterile portion should come into contact with the liquid and the target container. After liquid delivery, the tip should be ejected directly into an appropriate waste receptacle without contact with any other surfaces to avoid cross-contamination. Lastly, if the pipettor itself has come into contact with non-sterile liquids or surfaces, it needs to be decontaminated to prevent it from being a source of contamination in future procedures. Following these sterile pipetting practices protects the integrity of samples and prevents the compromise of experimental results.