Category Archives: analytical chemistry

Carolyn Oh–Optimizing and increasing throughput of capillary electrophoresis-electrospray ionization-mass spectrometry for single cell analysis of rat neurons

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Abstract: “Single cell analysis is fundamental in understanding the behavior and physiology of organisms. Aplysia californica (A. californica) is a well-studied organism in learning and memory due to its simple nervous system and large neuron sizes. Previous analyses have successfully detected and quantified 20 proteogenic amino acids and several neurotransmitters in sensory neurons from the pleural ganglia of A. californica. However, applying this to mammalian single cells has proven to be difficult since they have 10 to a thousand times smaller cell volumes compared to A. californica cells. Here, capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) was used due to its ability to analyze small sample volumes and identify metabolites in single rat cerebellar neurons. To apply this technique to mammalian neurons, a sample preparation protocol was optimized with a desalting step to increase analyte signal intensities by using microfluidic separations coupled to ESI-MS. This new approach enables a tenfold increase in sample analysis rate to 2 minutes per analysis, allowing for high-throughput CE-ESI-MS experiments compared to a laboratory operated system. Using the microfluidic system, we successfully detected lysine, histidine, arginine, tyramine, and dopamine, thus expanding upon previous work by developing a protocol for rat neuron analysis. Future plans include applying the developed procedure to single neurons in different regions of the rat brain.”

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Paul Grocki–Chemometric Analysis of Urinary Volatile Organic Compounds Discriminates Murine Breast Cancer Presence and Progression Over Time

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Abstract: “Previous studies demonstrated that volatile organic compounds (VOCs) in urine are potential biomarkers of breast cancer. An unanswered question is how urinary VOCs change over the course of tumor progression. To explore this, urine samples were collected from female Balb/c mice injected with 4T1.2 murine tumor cells in the tibia prior to tumor injection (20 samples) and over the next three weeks (12, 15, and 18 samples collected during weeks 1, 2, and 3 respectively). Samples were analyzed by headspace solid phase microextraction coupled to GC-MS QTOF. Univariate analysis showed many VOCs dysregulated by cancer, with some varying significantly during cancer progression and others not. PCA using panels of VOCs could distinguish both Cancer Weeks 1-3 from Control and Cancer Week 1 from Cancer Week 3 with > 90% sensitivity and specificity. Forward feature selection and linear discriminant analysis identified a unique panel of five VOCs that could distinguish Cancer Weeks 1 and 3 from Control with a fivefold cross validated (CV) area under the receiver operator characteristic (AUROC) equal to 0.95. The same model could also distinguish Cancer Week 1 from Cancer Week 3 with a fivefold CV AUROC equal to 0.97. The results of this study show that VOCs can be used to monitor breast cancer progression in mice models.

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Kerui Xu–Avocado oil, coconut oil, walnut oil as true oil phase for ion transfer at nanoscale liquid/liquid interfaces

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Abstract: “The interface between two immiscible electrolyte solutions (ITIES), formed between an organic (oil) phase and an aqueous phase, is crucial for chemical sensing and for studying all kinds of electron transfer and ion transfer reactions. Thus, solvents are critical in electrochemical reactions at ITIES. Though numerous organic phases, including viscous ionic liquid, have been reported in the literature, the use of true oils as an organic phase has scarcely been explored. In our study, we present true oils, including avocado oil, coconut oil, and walnut oil as novel organic solvents for ITIES. We observed well-defined potential windows and sigmoidal cyclic voltammograms for ion transfer. The ion transfer rate constants were also measured at true oil-water interfaces supported at nanopipette of ∼20–60 nm in radius. Furthermore, we proposed additional insights on the effect of solvent viscosity on the ion transfer rate at the liquid/liquid interface, with the viscosity of these true oils being ∼50–70 times that of 1, 2-dichloroethane. The standard ion transfer rate constants of tetrabutylammonium that we calculated are 0.21–0.32 cm / s at these true oil-water interface. This study opens up the possibility to expand ITIES platform to explore new reactions, playing significant roles in separation science, chemical sensing, chemical synthesis, catalysis, etc.”
Acknowledgment: NSF CAREER

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