Analytical Sciences, Talk
A Droplet Microfluidic ICP-MS Sample Introduction System
Pascal Emilio Verboket1, Olga Borovinskaya1, Nicole Meyer1, Detlef Günther1, Petra Dittrich1
1ETH Zurich
Inductively coupled plasma mass spectrometry (ICP-MS) is an important tool for highly sensitive elemental analysis of single nanoparticles [1] or rare-earth isotope labeled cells [2]. These measurements require a discrete sample introduction system with a high transport efficiency. However, commercially available droplet injection modules are expensive, suffer from a narrow droplet size range, are prone to clogging and are difficult to clean. To overcome these drawbacks a robust, flexible, low cost and low-maintenance sample introduction system for measurements of nanoparticles and single cells by ICP-MS is of interest.

We present a novel method to interface a continuous-flow droplet microfluidic based system with ICP-MS, which enables sensitive elemental analysis of the content of picoliter size droplets containing solutions, cells or nanoparticles. Our system is build around a disposable Polydimethylsiloxane liquid-assisted droplet ejection (LADE) chip (see Figure 1.), which generates aqueous droplets and ejects them in to the ICP-MS. It can measure samples as small as 1 µl and opens the possibility to easily integrate further sample pretreatment steps into the microfluidic device.

In this study, the interface was used for the quantification of the iron content of red blood cells. Additionally, the optimization of the system and its potential for the integration of microfluidic sample pretreatment will be discussed.

In summary, we have demonstrated a droplet-based microfluidic chip as sample introduction system for ICP-MS. Our system is disposable, easy to use and robust. We have shown its use for single cell analysis.
Figure 1. LADE-chip made entirely of Polydimethylsiloxane. The fluid channels are filled with a blue dye for visualization.
[1] Francisco Laborda, Javier Jiménez-Lamana, Eduardo Bolea, Juan R. Castillo, J. Anal. At. Spectrom. 2011, 26, 1362-1371.
[2] Sean C. Bendall, Erin F. Simonds, Peng Qiu, El-ad D. Amir, Peter O. Krutzik, Rachel Finck, Robert V. Bruggner, Rachel Melamed, Angelica Trejo, Olga I. Ornatsky, Robert S. Balderas, Sylvia K. Plevritis, Karen Sachs, Dana Pe’er, Scott D. Tanner, Garry P. Nolan, Science 2011, 332, 687-696.