a-microfluidic-chip-for-icpms-sample-introduction

A Microfluidic Chip for ICPMS Sample Introduction

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma ...

ETH Zurich

Inductively coupled plasma mass spectrometry is increasingly used for non-traditional applications such as the analysis of solids at high spatial resolution when combined with laser ablation or the analysis of engineered nanoparticles. This report highlights recent projects and discusses the potentials and limitations these techniques offer. High-resolution laser ablation instrumentation allows element imaging at the μm-scale and can, therefore, be applied to, e.g., the mapping of metal isotope-labeled antibodies in biological tissues. Despite these advancements, the quantitative analysis of laser-produced aerosols is still a major concern. Here, the accuracy of analysis was found to strongly depend on particle size distribution but also on the morphology and composition of particles. In order to achieve a controlled supply of nanoparticles for analysis by inductively coupled plasma mass spectrometry, a dedicated microdroplet injection system was developed and characterized. This system allows a reproducible injection of single nanoparticles together with internal standards to determine their mass and composition.

Element analysis of small and even smaller objects by ICPMS and LA-ICPMS.

In this work, a novel droplet microfluidic sample introduction system for inductively coupled plasma mass spectrometry (ICPMS) is proposed and characterized. The cheap and disposable microfluidic chip generates droplets of an aqueous sample in a stream of perfluorohexane (PFH), which is also used to eject them as a liquid jet. The aqueous droplets remain intact during the ejection and can be transported into the ICP with >50% efficiency. The transport is realized via a custom-built system, which includes a membrane desolvator necessary for the PFH vapor removal. The introduction system presented here can generate highly monodisperse droplets in the size range of 40-60 μm at frequencies from 90 to 300 Hz. These droplets produced very stable signals with a relative standard deviation (RSD) comparable to the one achieved with a commercial droplet dispenser. Using the current system, samples with a total volume of <1 μL can be analyzed. Moreover, the capabilities of the setup for introduction and quantitative elemental analysis of single cells were described using a test system of bovine red blood cells. In the future, other modules of the modern microfludics can be integrated in the chip, such as on-chip sample pretreatment or parallel introduction of different samples.

A new microfluidics-based droplet dispenser for ICPMS.

This work investigated the potential of a high temporal resolution inductively coupled plasma time-of-flight mass spectrometer (ICPTOFMS) in combination with a microdroplet generator (MDG) for simultaneous mass quantification of different nanoparticles (NPs) in a mixture. For this purpose, a test system containing certified Au NPs, well characterized Ag NPs, and core-shell NPs composed of an Au core and an Ag shell was employed. Thanks to the full spectra coverage and rapid simultaneous detection of the TOFMS, the element composition of individual particles can be determined. The pure Ag NPs and the core-shell NPs could be differentiated despite the same mass of Ag they contain. Calibration with monodisperse droplets consisting of standard solutions allowed for the mass quantification of NPs without the use of NP certified materials. On the basis of this mass quantification, the sizes of NPs originating from the same aqueous suspension were simultaneously determined with an accuracy of 7-12%. The size-equivalent limits of detection estimated with the 3*σ criterion were 13 nm for Au and 16 nm for Ag. Estimation of the LODs using Poisson statistics resulted in 19 and 27 nm, respectively. In addition, the 30 μs temporal resolution of the ICPTOFMS allowed studying interactions of NPs with the ICP based on their transient MS signals. The results demonstrated a difference in vaporization behavior of the core-shell NPs and solutions and indicated that vaporization of the Ag shell takes place prior to the Au core.

Simultaneous mass quantification of nanoparticles of different composition in a mixture by microdroplet generator-ICPTOFMS.

Colloidal semiconductor nanocrystals (NCs) are widely studied as building blocks for novel solid-state materials. Inorganic surface functionalization, used to displace native organic capping ligands from NC surfaces, has been a major enabler of electronic solid-state devices based on colloidal NCs. At the same time, very little is known about the atomistic details of the organic-to-inorganic ligand exchange and binding motifs at the NC surface, severely limiting further progress in designing all-inorganic NCs and NC solids. Taking thiostannates (K4SnS4, K4Sn2S6, K6Sn2S7) as typical examples of chalcogenidometallate ligands and oleate-capped CdSe NCs as a model NC system, in this study we address these questions through the combined application of solution (1)H NMR spectroscopy, solution and solid-state (119)Sn NMR spectroscopy, far-infrared and X-ray absorption spectroscopies, elemental analysis, and by DFT modeling. We show that through the X-type oleate-to-thiostannate ligand exchange, CdSe NCs retain their Cd-rich stoichiometry, with a stoichiometric CdSe core and surface Cd adatoms serving as binding sites for terminal S atoms of the thiostannates ligands, leading to all-inorganic (CdSe)core[Cdm(Sn2S7)yK(6y-2m)]shell (taking Sn2S7(6-) ligand as an example). Thiostannates SnS4(4-) and Sn2S7(6-) retain (distorted) tetrahedral SnS4 geometry upon binding to NC surface. At the same time, experiments and simulations point to lower stability of Sn2S6(4-) (and SnS3(2-)) in most solvents and its lower adaptability to the NC surface caused by rigid Sn2S2 rings.

Article	Year
Element analysis of small and even smaller objects by ICPMS and LA-ICPMS. Chimia\| PubMed ID: 24801839	2014
A new microfluidics-based droplet dispenser for ICPMS. Analytical chemistry\| PubMed ID: 24805360	2014
Simultaneous mass quantification of nanoparticles of different composition in a mixture by microdroplet generator-ICPTOFMS. Analytical chemistry\| PubMed ID: 25014784	2014
Atomistic Description of Thiostannate-Capped CdSe Nanocrystals: Retention of Four-Coordinate SnS4 Motif and Preservation of Cd-Rich Stoichiometry. Journal of the American Chemical Society\| PubMed ID: 25597625	2015

Olga Borovinskaya

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