Search

Lithium ion attachment mass spectrometry provides a non-specific, non-fragmenting, sensitive and robust method for the detection of volatile species in the gas phase. The design, manufacture and results of lithium based ion attachment ionisation sources for two different mass spectrometry systems are presented. In this study trace gas analysis is investigated using a modified Chemical Ionization Mass Spectrometer (CIMS) and vapour pressure measurements are made using a modified Knudsen Effusion Mass Spectrometer (KEMS). In the Li+ CIMS, where the Li+ ionization acts a soft and unselective ionization source, limits of detection of 0.2 ppt for formic acid, 15 ppt for nitric acid and 120 ppt for ammonia were achieved, allowing for ambient measurements of such species at atmospherically relevant concentrations. In the first application of Lithium ion attachment in ultra-high vacuum (UHV), vapor pressures of various atmospherically relevant species were measured with the adapted KEMS, giving measured values equivalent to previous results from electron impact KEMS. In the Li+ KEMS vapour pressures ＜10−3 mbar can be measured without any fragmentation, as is seen with the initial electron impact (EI) set up, allowing the vapor pressure of individual components within mixtures to be determined. [ABSTRACT FROM AUTHOR]

This paper presents the preparation and characterization of a single-excitation, dual-emission ratiometric optical Li+-sensing device using a newly designed and synthesized highly Li+-selective fluoroionophore (KBL-01) carrying 14-crown-4 ether with tetramethyl and benzene blocking subunits as Li+-binding site and boron-dipyrromethene as fluorophore. The indicator dye was covalently immobilized on the surface of a porous glass support having a large internal surface area using a silane-coupling agent. The resulting Li+-selective glass optode shows dual fluorescence emission response in pseudo-serum at varying Li+concentrations, allowing ratiometric signal processing. The obtained signal is independent of the presence of possibly interfering cations (Na+, K+, Mg2+and Ca2+) and pH. The sensor response was found to be reversible within the Li+concentration range from 10−4to 10−1M, and showed good repeatability and light stability. The plots of the ratiometric signal versusthe Li+concentrations in spiked real human serum go along with the response curve in pseudo-serum. These results indicate that the novel Li+-selective glass optode can be employed as a Li+-sensing device with high durability, sensitivity and accuracy for medical analyses. [ABSTRACT FROM AUTHOR]