Rapid Quantification of 4,4'-Methylenedianiline by Surface-Enhanced Raman Spectroscopy.

Methylenedianiline (MDA) is a common industrial chemical with health and product safety concerns. Common analysis methods require many steps including extraction and derivatization ending in GC/MS or HPLC analysis, which minimize its use as an on-line or at-line technique. The procedure can take hours, prohibiting its use as a real-time decision-making tool as well as using valuable resources and laboratory space. The new method presented here has been validated for MDA quantification in industrial grease samples over the concentration range of 1-40 ppm 4,4'-MDA. We present comparative results to the currently accepted method with excellent fidelity. This analytical method using surface-enhanced Raman spectroscopy reduces sample preparation and analysis time by more than an hour while preserving method accuracy, specificity, and dynamic range.

Low-cost bioanalysis on paper-based and its hybrid microfluidic platforms.

Low-cost assays have broad applications ranging from human health diagnostics and food safety inspection to environmental analysis. Hence, low-cost assays are especially attractive for rural areas and developing countries, where financial resources are limited. Recently, paper-based microfluidic devices have emerged as a low-cost platform which greatly accelerates the point of care (POC) analysis in low-resource settings. This paper reviews recent advances of low-cost bioanalysis on paper-based microfluidic platforms, including fully paper-based and paper hybrid microfluidic platforms. In this review paper, we first summarized the fabrication techniques of fully paper-based microfluidic platforms, followed with their applications in human health diagnostics and food safety analysis. Then we highlighted paper hybrid microfluidic platforms and their applications, because hybrid platforms could draw benefits from multiple device substrates. Finally, we discussed the current limitations and perspective trends of paper-based microfluidic platforms for low-cost assays.

Analysis of carbonaceous biomarkers with the Mars Organic Analyzer microchip capillary electrophoresis system: aldehydes and ketones.

A microchip CE method is developed for the analysis of two oxidized forms of carbon, aldehydes and ketones, with the Mars Organic Analyzer (MOA). Fluorescent derivitization is achieved in ∼ 15 min by hydrazone formation with Cascade Blue hydrazide in 30 mM borate pH 5-6. The microchip CE separation and analysis method is optimized via separation in 30 mM borate buffer, pH 9.5, at 20°C. A carbonyl standard consisting of ten aldehydes and ketones found in extraterrestrial matter is successfully separated; the resulting LOD depends on the reactivity of the compound and range from 70 pM for formaldehyde to 2 µM for benzophenone. To explore the utility of this method for analyzing complex samples, analyses of several fermented beverages are conducted, identifying ten aldehydes and ketones ranging from 30 nM to 5 mM. A Martian regolith simulant sample, consisting of a basalt matrix spiked with soluble ions and acetone, is designed and analyzed, but acetone is found to have a limited detectable lifetime under simulant Martian conditions. This work establishes the capability of the MOA for studying aldehydes and ketones, a critical class of oxidized organic molecules of interest in planetary and in terrestrial environmental and health studies.

Multichannel capillary electrophoresis microdevice and instrumentation for in situ planetary analysis of organic molecules and biomarkers.

The Multichannel Mars Organic Analyzer (McMOA), a portable instrument for the sensitive microchip capillary electrophoresis (CE) analysis of organic compounds such as amino acid biomarkers and polycyclic aromatic hydrocarbons (PAHs), is developed. The instrument uses a four-layer microchip, containing eight CE analysis systems integrated with a microfluidic network for autonomous fluidic processing. The McMOA has improved optical components that integrate 405 nm laser excitation with a linear-scanning optical system capable of multichannel real-time fluorescence spectroscopic analysis. The instrumental limit of detection is 6 pM (glycine). Microfluidic programs are executed to perform the automated sequential analysis of an amine-containing sample in each channel as well as eight consecutive analyses of alternating samples on the same channel, demonstrating less than 1% cross-contamination. The McMOA is used to identify the unique fluorescence spectra of nine components in a PAH standard and then applied to the analysis of a sediment sample from Lake Erie. The presence of benzo[a]pyrene and perylene in this sample is confirmed, and a peak coeluting with anthanthrene is disqualified based on spectral analysis. The McMOA exploits lab-on-a-chip technologies to fully integrate complex autonomous operations demonstrating the facile engineering of microchip-CE platforms for the analysis of a wide variety of organic compounds in planetary exploration.