A&S Graduate Studies
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A&S Graduate Studies
[PAST EVENT] Guangzhi Qu, Physics - Oral Exam for the Ph.D.
July 1, 2016
10am - 1pm
Abstract:
Matrix Assisted Laser Desorption/Ionization (MALDI) is a time-of-flight mass spectrometry commonly used to detect a wide mass range of biomarkers. However, MALDI requires a high laser pulse energy to create ions with a mass higher than 50,000 Daltons. That high laser energy increases the net ion production but it also degrades the instrument's mass resolution. This project uses a Room Temperature Ionization Liquid (RTIL) as a liquid matrix with a self healing surface instead of a standard crystal matrix to increase shot to shot reproducibility, enabling a systematic study of the origin of the resolution degradation. This study shows that the main source of the resolution degradation is the ionic space charge which delays the ejection of ions into the acceleration region, essentially increasing the ionization pulse time to be as long as hundreds of nanoseconds. This study includes simulation and experimental results to document this effect.
Bio:
Guangzhi Qu was born on October 23, 1984 and grew up in Dalian, Liaoning, China. After graduating from Dalian Yuming High School in 2003, he enrolled at University of Science and Technology of China in Hefei, Anhui, China. He graduated with a Bachelor of Science degree in Physics in 2007. In fall of 2007 he enrolled in the Ph.D. program at William & Mary in Williamsburg, Virginia.
Matrix Assisted Laser Desorption/Ionization (MALDI) is a time-of-flight mass spectrometry commonly used to detect a wide mass range of biomarkers. However, MALDI requires a high laser pulse energy to create ions with a mass higher than 50,000 Daltons. That high laser energy increases the net ion production but it also degrades the instrument's mass resolution. This project uses a Room Temperature Ionization Liquid (RTIL) as a liquid matrix with a self healing surface instead of a standard crystal matrix to increase shot to shot reproducibility, enabling a systematic study of the origin of the resolution degradation. This study shows that the main source of the resolution degradation is the ionic space charge which delays the ejection of ions into the acceleration region, essentially increasing the ionization pulse time to be as long as hundreds of nanoseconds. This study includes simulation and experimental results to document this effect.
Bio:
Guangzhi Qu was born on October 23, 1984 and grew up in Dalian, Liaoning, China. After graduating from Dalian Yuming High School in 2003, he enrolled at University of Science and Technology of China in Hefei, Anhui, China. He graduated with a Bachelor of Science degree in Physics in 2007. In fall of 2007 he enrolled in the Ph.D. program at William & Mary in Williamsburg, Virginia.