Magnetic Extraction, Detection, and Isotope Analysis of Metal Ions Using Surface Modified Microspheres for Lab-on-a-Chip Applications

Abstract

Liquid–liquid extraction and ion-exchange chromatography are efficient methods for sequestration of metal ions, but these methods are poorly suitable for microfluidic miniaturization. Here we examine several methods for rapid extraction, fluorometric detection, and the subsequent isotope analysis of lanthanide ions sequestered on surface modified magnetic microspheres as a versatile platform for chemical manipulation. The assays involve immobilization of a mixed-ligand complex of luminescent lanthanide ions at the surface of polystyrene microspheres. Using the ion-exchange properties of these microspheres, this scheme can be extended to the detection of nonluminescent ions.

Keywords:

• magnetic separations
• ion-exchange chromatography
• microfluidics
• fluorometry
• isotope analysis
• antenna effect

ACKNOWLEDGMENTS

IAS and MDK thank P. Rickert and C. J. Mertz for their assistance and M. Jensen, R. Chiarizia, M. L. Dietz, L. Soderholm, and F. Stevens for many useful discussions. KR thanks S. P. Meserole, J. E. Reich, and A. Allen for their assistance. Work at Argonne was performed under the auspices of the Office of Science, Division of Chemical Science, US-DOE under contract No. DE-AC-02-06CH11357 and DTRA DOD contract 08-43151.

Notes

^a For a 2.5 wt% stock aqueous solution.

^b Median diameter.

^c Surface area per MM.

^d Surface density of groups.

^e Total number of groups per MM.

^a The standard assay for 1.5 × 10⁻⁸ M (23 ppb) Eu³⁺ and 1.5 mM TTA in 600 µL of 5 × 10⁻⁵ HNO₃ with 0.12 wt% of the modified MMs.

^b n = 6.