Functionalized Metal Oxides As A Stationary Phase And A Surface Template For Micro Gas Chromatography Separation Columns

Abstract

The present invention provides a detector and method for detecting substances in complex mixtures. The detector includes a microfabricated preconcentrator, a separation column with an on-chip thermal conductivity detector, a controller for controlling flow and thermal management and a user interface. The thermal conductivity detector includes a first resistor located at an inlet of the separation column and a second resistor located at an outlet of the separation column.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Nos. 62 / 011,612 filed Jun. 13, 2014, 62 / 069,344 filed Oct. 28, 2014, and 62 / 114,137 filed Feb. 10, 2015 herein incorporated by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT[0002]This invention was made with government support under 1) contract number ECCS1002279 awarded by the National Science Foundation of the United States 2) by the National Science Foundation (NSF) under CAREER Award no. ECCS-0747600 and NIOSH Grant 5R21OH010330 and 3) under contract number 1R210H010330 awarded by the National Institutes of Health of the United States. The government has certain rights in the invention.INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC[0003]Not applicable.BACKGROUND OF THE INVENTION[0004]Gas chromatography (GC) is a reliable chemical analysis technique that is used to separate and identify the constituents of complex gas mixtures. GC has applica...

AI Technical Summary

Benefits of technology

[0013]In other embodiments, the present invention uses ALD with self-limiting gas phase chemical reactions for deposition, making it suitable for micromachined columns having very high-aspect ratios. The use of ALD for stationary phase coating ensures good selectivity, separations and retention of different compounds. The inherent properties of atomic layer deposition provide an easy route to practically coat any microfabricated column architecture. The metal oxide thin film provides surface properties that can improve the binding of polymer-based stationary phases and thus can act as a template for deposition of these polymeric phases. Moreover, the techniques of the present invention also provide innovative wafer-level coating approaches that are compatible with standard CMOS and MEMS processes.

[0014]In other embodiments, ALD treated / silane functionalized columns are used to efficiently separate a multicomponent sample mixture and yielded 4200 plates per meter. The ALD based stationary phase is found to be stable after multiple injections and at high operating temperatures.

[0015]In another embodiment, the present invention provides a method that facilitates a simple and wafer level coating scheme that provides a highly controllable film thickness. The inherent properties of atomic layer deposition provide an easy route to coat very challenging microfabricated column designs.

Problems solved by technology

Traditional bench-top GC instruments, though widely used, are bulky and expensive as well as time and energy intensive.

Although these adsorbent / gas-solid stationary phases have shown attractive features for the separation of complex mixtures, the application of these coating schemes for very narrow-width (150 μm) rectangular microchannels has not been straightforward as summarized in Table 1:

The current adsorbent based coating schemes for these particular column designs suffer from factors such as low-yield, chip-level coating, high processing temperatures and require elaborate experimentation.

Moreover, these methods present a major hindrance towards the monolithic integration of different μGC components on a single chip.

Prolonged exposure to VOCs can cause serious health effects including liver, kidney, and nervous system diseases and can even cause cancer.

μGCs have not been used in the detection of VOCs in aqueous matrices due to incompatibility of the systems with aqueous matrices.

Water saturates the adsorbent in the micro-thermal preconcentrator (μTPC) by capturing available adsorption sites and also damages most common polymer based stationary phases resulting in changes in the retention time, selectivity and column bleeding.

They cannot be used for on-site monitoring of the aqueous sample and rely on transporting samples to laboratories.

Nevertheless, the systems are large, expensive, require a trained technician and rely on conventional purge and trap mechanisms.

This technique requires manual intervention and multiple steps including sampling, storage, and shipping before analysis, and therefore is susceptible to higher losses and has longer measurement cycles.

There have been attempts at miniaturizing GC-MS systems, but such systems are still bulky, expensive, and consume high amounts of power.

PD-based systems suffer from selectivity issues and require filtering at the source, which renders them ineffective and expensive for multi-compound analysis.

However, this technique requires human intervention, and its use is limited by slow response and large uncertainty.

Several commercial high performance portable gas chromatography systems have been reported, but they are still bulky, energy inefficient, and expensive for real-time environmental monitoring applications.

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