Optimizing Spray, Capillary Tube Voltage, Temperature and Gas Parameters for Electrospray Protein Ionization in Mass Spectrometry
Disciplines
Analytical Chemistry
Abstract (300 words maximum)
Electrospray ionization (ESI) is a soft technique incorporated in diverse types of mass spectrometers to produce gaseous analyte ions. This technique uses high voltage in the spray to generate ions and utilizes low voltage in the capillary tube to transmit the gaseous ions to the mass analyzer and detector. Besides employing high and low voltage, efficient formation of large gas-phased charged ions required high heat and gas flow to promote the evaporation of these ions. Optimizing these complex parameters is crucial in generating an increased number of gas analytes and transmitting them toward the mass analyzer and detector system. In this study, the voltages of the spray and capillary tube, temperature in the heater and capillary, and gas flow of the source were optimized for a model protein, Lysozyme. Protein sample was prepared with LC-MS water at a concentration of 20 micromolar and mass spectra were acquired from 200 to 4000 m/z with a flow rate of 10 µL/min. The spray voltage applied between 2-6 KV, in which both low and high voltage resulted instable ion current of Lysozyme. At 4 kV, the highest ion current is detected where 7+ charge state being the most intense. Various capillary tube lens voltages were applied from 0 to 250 V, the most stable and high ion current of Lysozyme sample was noticed when capillary tube voltage was set to 250V. The heater temperatures tested between 50-300°C displayed lots of variability with its charge state distribution ranging from 7+ to 11+. Ion current of the charge state distributions significantly reduced at high heater temperature (300°C). With the tested capillary temperatures from 200 to 450°C, the base peak fluctuated between 8+ and 9+ charge states. The sheath gas flow was tested in a range of 0 to 20 (arb) and the highest ion current was observed at 15. Our results showed that optimized parameters for Lysozyme prepared in water include heater temperature at 50° C, capillary temperature at 350 °C, spray voltage of 4 kV, sheath gas flow of 15 arb, tube lens at 250 V, and capillary voltage of 50 V.
Academic department under which the project should be listed
Chemistry and Biochemistry
Primary Investigator (PI) Name
Mohammad A. Halim
Optimizing Spray, Capillary Tube Voltage, Temperature and Gas Parameters for Electrospray Protein Ionization in Mass Spectrometry
Electrospray ionization (ESI) is a soft technique incorporated in diverse types of mass spectrometers to produce gaseous analyte ions. This technique uses high voltage in the spray to generate ions and utilizes low voltage in the capillary tube to transmit the gaseous ions to the mass analyzer and detector. Besides employing high and low voltage, efficient formation of large gas-phased charged ions required high heat and gas flow to promote the evaporation of these ions. Optimizing these complex parameters is crucial in generating an increased number of gas analytes and transmitting them toward the mass analyzer and detector system. In this study, the voltages of the spray and capillary tube, temperature in the heater and capillary, and gas flow of the source were optimized for a model protein, Lysozyme. Protein sample was prepared with LC-MS water at a concentration of 20 micromolar and mass spectra were acquired from 200 to 4000 m/z with a flow rate of 10 µL/min. The spray voltage applied between 2-6 KV, in which both low and high voltage resulted instable ion current of Lysozyme. At 4 kV, the highest ion current is detected where 7+ charge state being the most intense. Various capillary tube lens voltages were applied from 0 to 250 V, the most stable and high ion current of Lysozyme sample was noticed when capillary tube voltage was set to 250V. The heater temperatures tested between 50-300°C displayed lots of variability with its charge state distribution ranging from 7+ to 11+. Ion current of the charge state distributions significantly reduced at high heater temperature (300°C). With the tested capillary temperatures from 200 to 450°C, the base peak fluctuated between 8+ and 9+ charge states. The sheath gas flow was tested in a range of 0 to 20 (arb) and the highest ion current was observed at 15. Our results showed that optimized parameters for Lysozyme prepared in water include heater temperature at 50° C, capillary temperature at 350 °C, spray voltage of 4 kV, sheath gas flow of 15 arb, tube lens at 250 V, and capillary voltage of 50 V.