Integration of serpentine channels for microchip electrophoresis with a palladium decoupler and electrochemical detection

Our plain-English summary of Integration of serpentine channels for microchip electrophoresis with a palladium decoupler and electrochemical detection, by A.L. Bowen, R.S. Martin (Electrophoresis, 2009).

The study

• Authors: A.L. Bowen, R.S. Martin
• Journal: Electrophoresis
• Published: 2009;30(19):3347-54
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Although it has been shown that microchip electrophoresis (MCE) with electrochemical detection can be used to separate and detect electroactive species, there is a need to increase the separation performance of these devices so that complex mixtures can be routinely analyzed. Previous work in the MCE has demonstrated that increasing the separation channel length leads to an increase in resolution between closely eluting analytes. This paper details the use of lengthened serpentine microchannels for MCE and electrochemical detection where a palladium decoupler is used to ground the separation voltage so that the working electrodes remain in the fluidic network. In this work, palladium electrodepositions were used to increase the decoupler surface area and more efficiently dissipate hydrogen produced at the decoupler. Dopamine and norepinephrine, which only differ in structure by a hydroxyl group, were used as model analytes. It was found that increasing the separation channel length led to improvements in both the resolution and the number of theoretical plates for these analytes. The use of a bilayer valving device, where PDMS-based valves are utilized for the injection process, along with serpentine microchannels and amperometric detection resulted in a multianalyte separation and an average of 28 700 theoretical plates. It was also shown that the increased channel length is beneficial when separating and detecting analytes from a high ionic strength matrix. This was demonstrated by monitoring the stimulated release of neurotransmitters from a confluent layer of PC 12 cells.

In plain English

This article does not concern asbestos. It was a laboratory chemistry study that tested ways to make small "lab-on-a-chip" devices separate and measure brain chemicals (neurotransmitters) better. The authors used longer, winding (serpentine) channels with a palladium part, called a decoupler, that grounds the separating voltage. They added extra palladium to the decoupler by electroplating. Without the added palladium, an 8-cm serpentine channel produced hydrogen bubbles at the decoupler immediately. With samples dissolved in a salty, cell-compatible solution, separation between norepinephrine and dopamine (resolution) was 1.9 on a 3-cm straight channel and 4.9 on an 8-cm serpentine channel. The number of theoretical plates, a measure of how sharp the separation is, was 960 versus 7,270 for norepinephrine and 800 versus 3,080 for dopamine. A valve-based serpentine chip separated five compounds with an average of 28,700 theoretical plates. It also separated norepinephrine and dopamine released from PC 12 cells that were preloaded with both chemicals, then stimulated off-chip. The authors concluded that longer channels improved separation. They reported a higher dopamine detection limit on the longer chip.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory analytical-chemistry methods study (microchip device development and testing); no human or animal subjects
• Who was studied: No people were studied. The authors used test solutions of neurotransmitters. They also used a laboratory cell line (PC 12 cells), which they first loaded with dopamine and norepinephrine and then stimulated off-chip to release them.
• Main results:
  • With an unmodified sputtered palladium decoupler, the 8-cm serpentine channel produced hydrogen bubbles at the decoupler straight away.
  • A platinum decoupler with no added palladium formed bubbles after 1 min at 150 V/cm. After palladium was deposited at 100 mV, the chip ran at 450 V/cm for 15 min.
  • 3-cm straight valving chip, samples in cell-compatible buffer, 250 V/cm: the resolution between norepinephrine and dopamine was 1.9, with 960 theoretical plates for norepinephrine and 800 for dopamine.
  • 8-cm, 2-turn serpentine valving chip, same conditions: the resolution between norepinephrine and dopamine was 4.9, with 7,270 theoretical plates for norepinephrine and 3,080 for dopamine.
  • The serpentine valving chip separated five compounds (norepinephrine, epinephrine, dopamine, catechol, hydroquinone) with an average of 28,700 theoretical plates. Hydroquinone generated 36,280 plates.
  • The smallest resolution in the five-compound separation was 1.6, between catechol and hydroquinone.
  • The PC 12 cells were stimulated off-chip, after being preloaded with norepinephrine and dopamine before analysis.
  • The stimulation of the PC 12 cells was carried out off-chip.
  • In the samples released by the stimulated PC 12 cells, the resolution between norepinephrine and dopamine was 3.9.
• The authors' conclusion: The authors concluded that increasing the channel length led to a baseline separation of dopamine and norepinephrine and to more theoretical plates.
• Limitations the authors state:
  • Using boric acid buffer, the detection limit for dopamine was higher on the 8-cm serpentine device than on the 3-cm straight device (printed as 6.7 and 1.1 "mM"). The authors attributed this probably to band broadening in the longer channels.
  • With wider, tapered turns, hydrogen bubbles that stop the separation formed consistently, even with added palladium on the decoupler.
  • Palladium deposited at 300 mV made a rough surface that periodically prevented the channel from sealing over the decoupler.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group, Hydroxyl Group.

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