Congrats to Emily on the New Publication in Analyst!

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A linear mass concentration detector for solvent gradient polymer separations

Abstract

Characterization of copolymers requires the measurement of two distributions—molecular weight (MW) and chemical composition (CC). Molecular weight distributions (MWD) are traditionally determined using size exclusion chromatography (SEC) run under isocratic solvent conditions. Chemical composition distributions (CCD) are often determined using liquid adsorption chromatography (LC) with solvent gradients. The use of solvent gradients, however, often limits options of compatible detectors. A gradient compatible, universal linear mass concentration detector is a longstanding unmet need. Many industrially-relevant polymers lack chromophores or other discriminating moieties requiring detectors with a universal response. Differential refractive index (dRI) is incompatible with gradient elution due to its small dynamic range. Charged aerosol detectors (CAD) and evaporative light scattering detectors (ELSD) are probably the most promising options for gradient elution detection, but both suffer from a nonlinear mass concentration response. Silicon photonic microring resonators are optical sensors that are responsive to changes in the local refractive index (RI). The substantial dynamic range of this technology makes it attractive for refractive index-based detection during solvent gradient elution. Previously, the microring resonator platform was used as a SEC detector to characterize the MWD of broadly dispersed polystyrene (PS) standards. In this study, we demonstrate the gradient compatibility of the microring resonator platform for polymer detection by quantifying the CCD of polymer blend components. Control experiments were run with UV and ELSD detection, highlighting the uniqueness of the platform as a linear mass concentration detector with a universal detector response.

You can read the full publication here!

separationsNOW Highlights Lab's Work with Capillary Electrophoresis

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Here’s a snippet from the article:

All the main detection techniques commonly used with capillary electrophoresis (CE) can only detect analytes with specific properties. Fluorescence detectors can only detect analytes that fluoresce, UV detectors can only detect analytes that absorb UV light and amperometric detectors can only detect analytes that can be oxidized or reduced at an electrode. Even mass spectrometry, which is generally considered a universal detection technique, can only detect analytes separated by CE that can be efficiently converted into ions by electrospray ionization.

The one detection technique that can work with CE and is truly universal is refractive index (RI) detection, in which analytes are detected by changes they cause in the extent to which light is bent, or refracted, as it passes through the CE buffer. The problem is that RI detection isn’t particularly sensitive, especially at the small scales of CE.

You can read the full article here!

New Publication from John in Analytical Chemistry

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Silicon Photonic Microring Resonator Arrays as a Universal Detector for Capillary Electrophoresis

Abstract

Electrophoretic separations conventionally rely on chromogenic, fluorogenic, or redox properties for analyte detection that, in many instances, involve chemical modification of samples prior to analysis. For analytes natively lacking chemical signatures, refractive index-based measurements are appealing as a method to detect these molecules without pre-treatment. Microring resonators are a type of whispering gallery mode sensor capable of detecting bulk changes in refractive index. Here, we demonstrate the use of silicon photonic microring resonator arrays as a post-column detector for capillary electrophoresis. In this approach, we establish the universal detection capabilities of microrings through calibration with analytes lacking unique spectral signatures. Separations of small molecule mixtures are demonstrated using capillary zone electrophoresis. For these separations, the microring resonators maintain a linear response over several orders of magnitude in concentration for three candidate small molecules. Successful separation of three sugars with direct detection is also demonstrated. We further present the successful separation and detection of three model proteins, exemplifying the promise of microring resonators arrays as a biocompatible detector for capillary electrophoresis. Additionally, the spatially offset, array-based nature of the sensing platform enables real-time analysis of analyte mobility and performance characterization—a combination that is not typically provided using single-point detectors.

You can find the full publication here!

New Review from Mari and Heather in Current Opinion in Environmental Science & Health

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Recent advances in environmental and clinical analysis using microring resonator–based sensors

ABSTRACT

Progress in the development of biosensors has dramatically improved analytical techniques. Biosensors have advantages over more conventional analytical techniques arising from attributes such as straightforward analyses, higher throughput, miniaturization, smaller sample input, and lower cost. Microring optical resonators have emerged in the area of optical sensors as an exceptional choice because of their sensitivity, ease of fabrication, multiplexity capability, and label-free detection. In this article, the sensing principle of these sensors is described. In addition, we summarize and highlight their most recent and relevant applications in environmental and clinical detection analysis.


Click here to read the manuscript!

The Bailey Lab Wins Awards at Karle Symposium

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This year, members of the Bailey Lab presented their work at the Karle Symposium and won awards for their hard work. Emily Mordan received second place among graduate student presenters for her talk, “Linear Gradient Compatible Refractive Index Based Detector for Polymer Composition Characterization.” Colleen, Cole, and Shannon all earned awards for their poster presentations, too!

Way to go, everyone! You can stay posted on future publications by following us here!

Colleen and Steve Earn Awards at MBSTP Symposium!

Members of the Bailey group just wrapped up presenting at UM’s Microfluidics in Biomedical Sciences Training Program Symposium. Among all of the thought-provoking presentations, Colleen Riordan was able to take home a best poster award for her presentation on a "Microfluidic Platform for Optimizing the Formation of Nanodisc Libraries from Whole Cell Lysate“. Steve Doonan walked away with an award for his talk titled “Development of the Droplet CAR-Wash Platform for Picoliter-Scale Epigenetic Analysis“.

The Bailey lab greatly appreciates the opportunity to share their work and learn from campus colleagues. For those interested in learning about microfluidics and seeing what MBSTP has to offer, you can follow this link http://umich.edu/~ufluids/ to find out more. See you next year!

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