Handling liquids in the laboratory comes with its own set of challenges. Whether samples are viscous, light-sensitive, or require stringent aseptic conditions, special techniques are often necessary. This guide will discuss best practices for pipetting difficult liquids while maintaining accuracy and reproducibility.

Table of Contents

• Pipetting Low and High Density Liquids
• Tips for Precision and Care with Sensitive Samples
• Aseptic Techniques for Strict Sterility Requirements
• Handling Fluorescent and Light-Sensitive Substances
• Common Pipetting Mistakes to Avoid
• Improving Your Pipetting Form and Technique
• Considerations for 384-Well Pipetting
• When to Use Electronic Pipettes

Pipetting Low and High Density Liquids

For low density liquids like PCR reagents, extra-narrow pipette tips are preferred as they allow for more consistent aspiration of small volumes. Higher density liquids over 1 g/mL may pipette better with standard-width tips due to their slightly wider diameter opening. The correct tip choice ensures accuracy and reproducibility.

Tips for Precision and Care with Sensitive Samples

When top precision or expensive/sensitive samples require extra care, low-retention tips are recommended. Their ultra-smooth interiors minimize sample loss. Individually wrapped sterile tips maintain asepsis for each transfer. Black microtubes protect light-sensitive fluorescent and ethidium bromide samples better than amber tubes.

Aseptic Techniques for Strict Sterility Requirements

A reference article suggests individually wrapped tips for the strictest aseptic work, as each tip is sterile-packaged. Alternative methods like biosafety cabinets can also be considered.

Handling Fluorescent and Light-Sensitive Substances

In addition to black microtubes, samples may be wrapped in foil to block potentially damaging light. When working with photoactive compounds, only use containers and equipment rated for protection from the wavelengths of interest.

Common Pipetting Mistakes to Avoid

A common error is improper technique that compromises accuracy and precision. Following best practices meticulously is key to obtaining reliable data.

When to Use Electronic Pipettes

-For high-volume repetitive pipetting, electronic instruments can help increase throughput while maintaining quality. Their programming functions further minimize human error.

-For the section on pipetting low and high density liquids, more specifics could be provided on density thresholds and how liquid properties affect aspiration force and control. Examples of common low and high density reagents may help readers identify which tips to use.

-When discussing tips for precision and sensitive samples, expanding on low-retention coating technologies could convey their benefits. Individual wrapping maintains sterility but is more costly - when is this level of asepsis truly necessary?

-Strict sterility techniques are critical for cell culture and other sensitive work. The biosafety cabinet is ideal but not always available. Additional controls like sterile method training, change room procedures, and designated pipetting areas could ensure contamination risks are minimized.

-For light-sensitive substances, details on common fluorescent probes, phototoxic compounds, and appropriate lighting/enclosure conditions would equip readers to fully protect their samples. Action spectra and lighting specifications would add value.

-Explicit examples of frequent pipetting mistakes could feature, such as improper expulsion angles, inconsistent pressures, and contaminated equipment. Photos showing correct vs incorrect techniques may help drive the points home.

-When are electronic pipettes most worthwhile over standard models? Large sample volumes, complex multi-channel transfers, statistical analysis requiring high-precision, automated liquid handlers, and integrated weigh stations are realistic scenarios that benefit significantly from digital instrumentation. Overall reproducibility and data integrity are improved.

-Additional conclusion points may stress the value of optimized pipetting for obtaining high quality, reproducible results. Reviewing procedures regularly helps catch and remedy inefficiencies before they impact research outcomes. Proper training records also ensure all lab members maintain consistent, compliant techniques over time.

-Expanding on these ideas would produce a more comprehensive best practices guide suitable for both novice and experienced laboratory personnel handling difficult liquids. Let me know if any sections require more background or context.