Browsing by Author "Chang, Chia-Hsien"

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A compact 3D-printed interface for coupling open digital microchips with Venturi easy ambient sonic-spray ionization mass spectrometry
(2015-01-01)
Hu, Jie-Bi
;
Chen, Ting-Ru
;
Chang, Chia-Hsien
;
Cheng, Ji-Yen
;
Chen, Yu-Chie
Digital microfluidics (DMF) based on the electrowetting-on-dielectric phenomenon is a convenient way of handling microlitre-volume aliquots of solutions prior to analysis. Although it was shown to be compatible with on-line mass spectrometric detection, due to numerous technical obstacles, the implementation of DMF in conjunction with MS is still beyond the reach of many analytical laboratories. Here we present a facile method for coupling open DMF microchips to mass spectrometers using Venturi easy ambient sonic-spray ionization operated at atmospheric pressure. The proposed interface comprises a 3D-printed body that can easily be "clipped" at the inlet of a standard mass spectrometer. The accessory features all the necessary connections for an open-architecture DMF microchip with T-shaped electrode arrangement, thermostatting of the microchip, purification of air (to prevent accidental contamination of the microchip), a Venturi pump, and two microfluidic pumps to facilitate transfer of samples and reagents onto the microchip. The system also incorporates a touch-screen panel and remote control for user-friendly operation. It is based on the use of popular open-source electronic modules, and can readily be assembled at low expense.
Capillary Action-Supported Contact less Atmospheric Pressure Ionization for the Combined Sampling and Mass Spectrometric Analysis of Biomolecules
(2011-04-15)
Hsieh, Cheng-Huan
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Chang, Chia-Hsien
;
Urban, Pawel L.
;
Chen, Yu-Chie
;
應用化學系
It is proposed that a short tapered capillary can be utilized as a nanoliter-volume sampling tool and sample emitter for generation of gas-phase ions in front of the mass spectrometer, without the need for using an additional electric power supply, a gas supply, or a syringe pump. A wide range of molecules can be analyzed in pure solutions and complex matrixes (cell extract, urine, and plant tissue) with no or minimum sample preparation. Singly and multiply charged ions can be detected in either positive or negative-ion mode. Because of the nanoliter-volume sampling and low spectral background, the mass detection limit for bradykinin is in the low attomole range. Other advantages include simplicity, disposability, and low cost. The putative mechanism of the ion formation in this capillary-action supported contactless spray emitter is discussed.
Microscale MALDI Imaging of Outer-Layer Lipids in Intact Egg Chambers from Drosophila melanogaster
(2011-05-15)
Urban, Pawel L.
;
Chang, Chia-Hsien
;
Wu, June-Tai
;
Chen, Yu-Chie
;
應用化學系
Fruit fly (Drosophila melanogaster) is a standard model organism used in genetics and molecular biology. Phospholipids are building blocks of cellular membranes, and components of a complex signaling network Here, we present a facile method, based on matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS), for molecular imaging of phospholipid distributions in submillimeter-sized components of the fruit fly reproductive system. Individual egg chambers were deposited on a specially prepared MALDI target comprising an aluminum slide with a rough surface created by ablation with a microsecond-laser: this helped to immobilize biological specimens, remove excess of saline solution by adhesive forces, carry out microscopic observations, and facilitated distribution of the MALDI matrix. A continuous-flow ultrasound-assisted spray was used for the deposition of MALDI matrix (9-aminoacridine) onto the sample. The upper surface of the specimen was then scanned with a 355-nm solid-state laser with a preset beam focus of 10 mu m to obtain negative-ion mode MALDI-MS images. Overall, this provided sufficient spatial resolution to reveal micrometer-scale gradient-like patterns of phospholipids along the anterior/posterior axis of egg chambers. Several phosphatidylinositols are seen to be segregated according to the number of unsaturated bonds, with an elevated abundance of polyunsaturated phosphatidylinositols within the oocyte compartment.