Optical monitoring of single drop microextraction

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Single drop microextraction (SDME), the first liquid phase microextraction technique proposed, is a simple approach consisting of the extraction of the target analytes from the sample into a small drop of extractant. The characteristics of the drop, specially its chemical nature and mechanical stability, are key factors to guarantee the success of the extraction. Its chemical composition defines the affinity towards the target analytes which are, in fact, extracted depending on their solubility. The mechanical stability of the drop during the extraction is critical since the drop detachment would ruin the extraction.

The drop volume and handling increase the probability of that detachment. Researchers from Ukraine and Slovak Republic have already published in Analytical Chemistry journal a nice contribution to SDME that overcomes this shortcoming(1). In this case, an optical probe is used as the drop holder in such a way that the continuous UV-Vis monitoring of the drop is achieved. This workflow reduces the drop handling while allows the real time tracking of the process. This approach has been practically evaluated using the determination of sulfite in food samples as model analytical problem.

The extraction is quite simple. First of all, sulfite is in-matrix transformed into sulfur dioxide by the simple addition of hydrochloric acid. Sulfur dioxide is transferred to the headspace of the sample thanks to its inherent volatility and then to the aqueous single drop. The ability of sulfur dioxide to reduce Fe (III) to Fe (II) which finally reacts with 1,10 phenanthroline to form a red complex is used to monitor the process.

We strongly recommend the reading of this article. You will find a detailed explanation of the device, a deep optimization of the variables involved in the extraction and the practical application of the proposal. Do not forget the movie where the extraction is shown.

Reference

(1) Using an Optical Probe as the Microdrop Holder in Headspace Single Drop Microextraction: Determination of Sulfite in Food Samples. Link to the article

Comments

  1. sergyKOctober 14, 2016 at 10:09 AM

    video with a good quality

    https://www.youtube.com/watch?v=-iLGgghl7J4

    ReplyDelete

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