Development of a fully integrated analysis system for ions based on ion-selective optodes and centrifugal microfluidics

R. D. Johnson, I. H A Badr, G. Barrett, S. Lai, Y. Lu, M. J. Madou, Leonidas G Bachas

Research output: Contribution to journalArticle

105 Citations (Scopus)

Abstract

A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics platform and ion-selective optode membranes is described. The microfluidic architecture is composed of channels, five solution reservoirs, a measuring chamber, and a waste reservoir manufactured onto a disk-shaped substrate of poly(methyl methacrylate). Ion-selective optode membranes, composed of plasticized poly(vinyl chloride) impregnated with an ionophore, a proton chromoionophore, and a lipophilic anionic additive, were cast, with a spin-on device, onto a support layer and then immobilized on the disk. Fluid propulsion is achieved by the centrifugal force that results from spinning the disk, while a system of valves is built onto the disk to control flow. These valves operate based on fluid properties and fluid/substrate interactions and are controlled by the angular frequency of rotation. With this system, we have been able to deliver calibrant solutions, washing buffers, or "test" solutions to the measuring chamber where the optode membrane is located. An analysis system based on a potassium-selective optode has been characterized. Results indicate that optodes immobilized on the platform demonstrate theoretical responses in an absorbance mode of measurement. Samples of unknown concentration can be quantified to within 3% error by fitting the response function for a given optode membrane using an acid (for measuring the signal for a fully protonated chromoionophore), a base (for fully deprotonated chromoionophore), and two standard solutions. Further, the ability to measure ion concentrations by employing one standard solution in conjunction with acid and base and with two standards alone were studied to delineate whether the current architecture could be simplified. Finally, the efficacy of incorporating washing steps into the calibration protocol was investigated.

Original languageEnglish (US)
Pages (from-to)3940-3946
Number of pages7
JournalAnalytical Chemistry
Volume73
Issue number16
DOIs
StatePublished - Aug 15 2001
Externally publishedYes

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Microfluidics
Ions
Ion selective membranes
Washing
Fluids
Membranes
Vinyl Chloride
Acids
Ionophores
Polymethyl Methacrylate
Substrates
Flow control
Propulsion
Protons
Potassium
Buffers
Calibration

ASJC Scopus subject areas

  • Analytical Chemistry

Cite this

Development of a fully integrated analysis system for ions based on ion-selective optodes and centrifugal microfluidics. / Johnson, R. D.; Badr, I. H A; Barrett, G.; Lai, S.; Lu, Y.; Madou, M. J.; Bachas, Leonidas G.

In: Analytical Chemistry, Vol. 73, No. 16, 15.08.2001, p. 3940-3946.

Research output: Contribution to journalArticle

Johnson, R. D. ; Badr, I. H A ; Barrett, G. ; Lai, S. ; Lu, Y. ; Madou, M. J. ; Bachas, Leonidas G. / Development of a fully integrated analysis system for ions based on ion-selective optodes and centrifugal microfluidics. In: Analytical Chemistry. 2001 ; Vol. 73, No. 16. pp. 3940-3946.
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