title: Indirect identification of isoprenoid quinones in Escherichia coli by LC-MS with atmospheric pressure chemical ionization in negative mode.
abstract: A novel analytical method was applied for identification of isoprenoid quinones in Escherichia coli by liquid chromatography atmospheric press chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of sample were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Ubiquinone-7 (UQ-7), Ubiquinone-8 (UQ-8) and Mequinone-8 (MK-8) were determined directly using combined information on retention time, molecular ion mass, fragment ion masses and UV characteristic spectrometry without any standard reagent. It was found that UQ-8 was the major component of isoprenoid quinones in Escherichia coli under aerobic condition. Compared with UQ-8, the relative abundance of UQ-7 and MK-8 is only 15% and 14%, respectively. The average recoveries of UQ-6, UQ-10 and vitamin K(1) in Escherichia coli were investigated by standard spiking experiment. The recoveries were achieved in the range from 94 to 106%, and the relative standard deviations (RSD) of the triplicate analysis of the spiked samples (UQ-6, UQ-10 and vitamin K(1)) ranged from 3 to 8%. The detection limits of LC-NI-APCI-MS were estimated to be 5, 40 and 0.8 microg/g dry cell for UQ-6, UQ-10 and vitamin K(1), respectively.
authors.affiliation: College of Environmental Science and Engineering, Ocean University of China, No. 5 Yushan Road, Qingdao 266003, China. mengchungao@hotmail.com
authors.forename: Mengchun
authors.initials: M
authors.lastname: Gao
authors.forename: HongJun
authors.initials: H
authors.lastname: Liu
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: JianYing
authors.initials: J
authors.lastname: Hu
authors.forename: Bing
authors.initials: B
authors.lastname: Shao
mesh_terms: D002853:Chromatography, Liquid; D004926:Escherichia coli / Q000737:chemistry*; D013058:Mass Spectrometry; D011809:Quinones / Q000032:analysis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013729:Terpenes / Q000032:analysis / Q000302:isolation & purification*; D014451:Ubiquinone / Q000032:analysis / Q000302:isolation & purification; D010837:Vitamin K 1 / Q000032:analysis / Q000302:isolation & purification; D024482:Vitamin K 2 / Q000031:analogs & derivatives* / Q000032:analysis / Q000302:isolation & purification
chemical_list: D011809:Quinones; D013729:Terpenes; C032165:ubiquinone 6; D024482:Vitamin K 2; D014451:Ubiquinone; C024223:vitamin MK 8; D010837:Vitamin K 1; C030778:ubiquinone 8; C025204:Ubiquinone Q2; C030777:ubiquinone 7