Pipette or Syringe: that is the question
Single-channel pipettes and syringes are common laboratory tools widely used for liquid handling purposes. They both have pros and cons and the choice of which tool to use strictly depends on the analytical task and the related issues.
Liquid-Liquid extraction is certainly one of the trickiest process in terms of liquid handling. The most common approach, especially for GC-MS applications, requires the sampling of the organic phase on the top. Sometimes though the organic phase might be chlorinated hence on the bottom or it might be the aqueous layer we are interested in. In that case, which tool would you use? Pipette or syringe?
Recently I had to ask myself the same question.
In our lab all our methods are automated so the syringe is always the tool of choice. Nevertheless, we do have pipettes and we use them regularly for testing manual steps. Comparison of manual versus automated method is quite common practice because it helps gathering a better understanding of their differences and similarities allowing a better translation from one to the other.
I had been working on the automation of a customer’s method where the final sample would have a top layer of residual oil from the sample matrix while the target analyte would be solubilised in the bottom aqueous layer. Hence, an aliquot from the bottom layer was needed to be transferred to an autosampler vial for injection.
And as they say: ‘The proof of the pudding is in the eating’.
As shown in the picture, the pipette tip wouldn’t be able to break the surface tension of the oil and would drag the organic layer down to the bottom without accessing the aqueous layer. The syringe needle on the other hand would just cut through the organic layer reaching the bottom without interference.
So in my case the answer was syringe (thankfully!). Which is the answer to your application?
If you would like to discuss this further, please do not hesitate to contact us now.