How to Pipette Volatile or Highly Contaminated Liquids

The world depends on scientists to follow accurate and safe research or analytical methods that often require the use of volatile or contaminated liquids. With the pandemic putting global communities at risk, lab managers need to adapt their operating procedures and protocols to be more performant and safe. Finding optimized pipetting solutions and products adapted to the different fluids handled in a workflow is challenging when dealing with highly contaminated or volatile liquids. Precision and accuracy require enhanced processes and the right instruments to ensure reliable, verifiable, and repeatable results.

Whether dealing with a volatile, viscous, or contaminated liquid, pipetting processes will depend on established controls that prevent cross-contamination, exposure and reduce systematic or measurement errors during every analytical workflow.

Key Considerations for Pipetting Contaminant, Volatile, or Viscous Fluids

Viscous, volatile, or contaminated liquid handling in a laboratory environment presents many challenges for technicians. Firstly, depending on the compound of interest, lab managers need to ensure staff safety during every step of the sampling process, and equipment must be used carefully to avoid any risk of contamination. Additionally, vapors inside the pipette may damage the mechanics inside the instrument in air displacement models. When used with a capillary piston (CP) tip, a positive displacement pipette eliminates the possibility of any vapors ending up in the internal parts and guarantees correct and accurate volumes when aspirating or dispensing fluids.

Additionally, the accuracy of the results will likely depend on the methodology employed during your workflows. While air displacement pipettes work for most general applications, they aren't suitable when carrying out an analytical study that requires volatile or viscous liquid handling.

Finding optimized pipetting solutions and products adapted to the different fluids handled in a workflow is challenging when dealing with highly contaminated or volatile liquids. Precision and accuracy require enhanced processes and the right instruments to ensure reliable, verifiable, and repeatable results.

The challenges present when using air displacement pipettes for viscous or volatile liquid handling include:

  • Pipette tip dripping – Volatile compounds react to atmospheric conditions, creating pressure inside the air displacement pipette that leads to dripping or leakage
  • Random errors - As density and viscosity of a sample increases, the random error rate in air displacement pipettes could increase to above 3% in samples like glycerol
  • Systematic errors – Similarly, systematic errors increase to above 4.5% in glycerol samples if using a regular air displacement pipette (whereas a positive-displacement pipette eliminates inaccurate results from bubbles in the sample or viscous liquid flowing slowly with film adhering to tip walls and decreasing the dispensed volume)
  • Contamination – Working with contaminated samples can cause sample carryover and generates a risk of contamination of the pipette or the user
  • Pipette damage – Working with volatile liquids may damage or corrode the inside of the pipettes when the vapor reaches the mechanical parts

Overcoming the Challenging Liquids with Positive-Displacement Pipettes

Unlike air displacement pipettes, in positive-displacement pipettes, the fluids are not in contact with an air cushion. Positive-displacement pipettes use an integrated piston inside the capillary, forming part of the disposable pipette tip. The properties of the fluids do not have any impact on the performance of the pipette. This characteristic makes a positive-displacement pipette the ideal solution for volatile, viscous, or contaminated liquid handling during any laboratory workflow.

Standard Operating Procedures (SOPs) are often implemented in laboratories to ensure workflows reduce the potential for systematic or random errors whenever sampling challenging liquids. Positive displacement pipettes like MICROMAN® E pipette are adapted to follow the SOPs and will reduce the risk of contamination, ensure sample integrity, and keep you protected while using the instrument.

Positive-Displacement Pipetting Workflow for Non-Aqueous Liquid Handling

The working mechanisms involved between air displacement and positive-displacement pipettes make them suitable for different steps within a specific workflow. If you are working with aqueous liquids, the tried and trusted air displacement pipettes will suffice. Whenever a volatile, contaminated, or viscous fluid is involved in the sampling workflow, you'll need to consider using a positive-displacement pipetting solution instead. This is due to the fluid's density and how it will react with air inside the pipette during the process.

While the workflows will be similar, there are slight differences required during the process. A standard pipetting workflow for contaminated or challenging liquid handling using a positive-displacement pipette will follow the four steps below.

  • Preparing the Positive-Displacement Pipette
  • Before fitting the pipette CP tip, you'll need to maintain the pipette in a vertical position at all times (similar to a standard air displacement pipette). Once you've fitted the CP tip, you can set the plunger to the first position by depressing and moving the piston to the appropriate position.

  • Aspirating the Volatile, Viscous, or Contaminated Liquid
  • You can now immerse the capillary (with its integrated piston) into the sample and release the plunger, allowing it to return to the rest position. According to the instrument's set volume, your sample will enter the tip through the orifice using the ambient force.

  • Dispensing the Volatile, Viscous, or Contaminated Liquid from the Pipette
  • You can dispense the liquid into the receiving vessel by depressing the plunger back to the first stop position. Once again, maintaining a vertical position is essential at all times during the aspiration, transfer, and dispensing steps of the workflow.

  • Ejecting the Spent Tip from the Positive-Displacement Pipette
  • After completing the preparation, aspiration, and dispensing steps of the workflow, eject the disposable tip to waste by depressing the plunger to the final (or second stop) position. This allows lab technicians to avoid touching the capillary and reduces the risk of contamination or transferring trace compounds from viscous, contaminated, or volatile fluids.

Gilson Liquid Handling Solutions for Pipetting Contaminant, Volatile or Viscous Samples

MICROMAN® E pipettes come with ease-of-use, ergonomic support, and convenient no-touch tip ejection for handling viscous, volatiles, or contaminated liquids. With Gilson's patented QuickSnap system, laboratory staff can reduce the number of steps required to fit a CP on the instrument.

Whether you're optimizing a workflow that includes volatile liquid handling or need to improve your process against errors during a contaminated liquid handling process, Gilson can assist with convenient, efficient, and accurate pipetting solutions. For all kinds of laboratory workflows, Gilson remains the preferred partner when opting for positive-displacement pipetting of volatile, viscous, or contaminated samples.

For more information about how we can help you manage problematic liquids (volatile and contaminated samples), get in touch today.

MICROMAN E Positive-Displacement Pipettes

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