A miniaturized, low-cost lens tube based laser-induced fluorescence detection system for automated microfluidic analysis of primary amines.

In situ analyses are essential to ascertain potential past or present habitability in celestial bodies. One technique that provides the sensitivity and miniaturization needed to successfully detect trace organics in the outer Solar System is laser-induced fluorescence (LIF) detection, which, when coupled with microfluidic systems, provides a powerful wet chemistry platform that can meet the size and resource consumption constraints of a remote analysis mission. Herein, a portable LIF detection module (44-mm long, 18-mm wide) was prototyped and utilized to quantify bulk organics in a liquid sample via manual and automated analysis utilizing a programmable microfluidic architecture. The experimental limit of detection (LOD) for primary amines was 11.8 µM. A sample (Y31B) collected from the Atacama Desert in Yungay, Chile, was analyzed manually and found to contain 300 ± 50 µM of bulk primary amine organics, while the automated microfluidic protocol found the sample to contain 289 ± 4 µM of primary amines. Automated analyses showed no statistically significant differences when compared to the manual analyses (t-test, C.I. 95%). Our results demonstrate that the coupling of programmable microfluidic devices with a custom lens tube-based LIF detector enables automated analysis of primary amines using a protocol appropriate for remote analyses. This technique is an invaluable tool for in situ analysis applications in distant, resource-restricted environments.

A modular, easy-to-use microcapillary electrophoresis system with laser-induced fluorescence for quantitative compositional analysis of trace organic molecules.

Microcapillary electrophoresis (µCE) enables high-resolution separations in miniaturized, automated microfluidic devices. Pairing this powerful separation technique with laser-induced fluorescence (LIF) enables a highly sensitive, quantitative, and compositional analysis of organic molecule monomers and short polymers, which are essential, ubiquitous components of life on Earth. Improving methods for their detection has applications to multiple scientific fields, particularly those related to medicine, industry, and space science. Here, a modular benchtop system using µCE with LIF detection was constructed and tested by analyzing standard amino acid samples of valine, serine, alanine, glycine, glutamic acid, and aspartic acid in multiple borate buffered solutions of increasing concentrations from 10 mM to 50 mM, all pH 9.5. The 35 mM borate buffer solution generated the highest resolution before Joule heating dominated. The limits of detection of alanine and glycine using 35 mM borate buffer were found to be 2.12 nM and 2.91 nM, respectively, comparable to other state-of-the-art µCE-LIF instruments. This benchtop system is amenable to a variety of detectors, including a photomultiplier tube, a silicon photomultiplier, or a spectrometer, and currently employs a spectrometer for facile multi-wavelength detection. Furthermore, the microdevice is easily exchanged to fit the desired application of the system, and optical components within the central filter cube can be easily replaced to target alternative fluorescent dyes. This work represents a significant step forward for the analysis of small organic molecules and biopolymers using µCE-LIF systems.