In the present work we have investigated the chemical sensitivity of a mass spectrometry imaging method MeV – SIMS. Primary ion beam within the MeV energy range domain was employed to bombard samples ...of two organic compounds; amino acid arginine, and peptide hormone angiotensin II (human), with average molecular weights of 174.2 u and 1046.2 u respectively. Secondary ion yield was measured as a function of number of molecules per area unit, and the detection limit was determined. For both molecular compounds and two different energies of primary 35Cl ion beam, the secondary ion yield exhibited a significant decrease below the area density of 1015 molecules/cm2, while the density of 1013 molecules/cm2 resulted in molecular peak / background ratio being lesser than 3, which is below the commonly used sensitivity threshold in other techniques. Other experiment related drawbacks to sensitivity were also discussed.
We report on the analysis of the onset and the intensity of metastable secondary ions, which are desorbed from the target material as a result of bombarding organic samples with MeV primary ions. The ...bimodal time-of-flight mass spectrometer, which can analyze secondary ion in linear and reflectron modes, was used for detection and characterization of such ions. The use of the bimodal mass spectrometer for this specific purpose is demonstrated on amino acid arginine, where three main fragments were detected. We have also analyzed the influence of the primary ion beam on the intensity of metastable ion signal. Results from chlorine ion beams with energies between 3 and 10 MeV have exhibited the importance of electronic sputtering on the product/precursor ion peak intensity ratio, which is significantly decreased when using primary ions with higher energy.
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•Fragmented metastable ions from MeV-SIMS can be observed as long tails of molecular peaks in mass spectra.•Quick characterization of fragments is obtained through linear mode, and more precise identification by reflectron mode.•Fragments with intensities fragment/parent >0.01 can be detected.•Higher energy primary ion beams induce less metastable secondary ions.•Fragmentation pathways are not affected by the primary ion beam energy.
Human hair absorbs numerous biomolecules from the body during its growth. This can act as a fingerprint to determine substance intake of an individual, which can be useful in forensic studies. The ...cocaine concentration profile along the growth axis of hair indicates the time evolution of the metabolic incorporation of cocaine usage. It could be either assessed by chemical extraction and further analysis of hair bundels, or by direct single hair fibre analysis with mass spectroscopy imaging (MSI). Within this work, we analyzed the cocaine distribution in individual hair samples using MeV-SIMS. Unlike conventional surface analysis methods, we demonstrate high yields of nonfragmented molecular ions from the surface of biological materials, resulting in high chemical sensitivity and non-destructive characterisation. Hair samples were prepared by longitudinally cutting along the axis of growth, leaving half-cylindrical shape to access the interior structure of the hair by the probing ion beam, and attached to the silicon wafer. A focused 5.8 MeV 35Cl6+ beam was scanned across the intact, chemically pristine hair structure. A non-fragmented protonated M+ H+ cocaine molecular peak at m/z = 304 was detected and localized along the cross-section of the hair. Its intensity exhibits strong fluctuations along the direction of the hair's growth, with pronounced peaks as narrow as 50 micrometres, corresponding to a metabolic incorporation time of approx. three hours.
The present work reports on cationization characteristics of organic molecules in alkali metal environment. Samples of arginine and polyethylene glycol polymers with average masses of 600, 1000 and ...1500 were mixed with sodium- and potassium trifluoroacetate of various concentrations, and analyzed through secondary ion mass spectrometry. Bombardment proceeded with ions within both keV and MeV energy domains. Added salts positively affected the secondary ion yield through attachment of Na or K to organic molecule. Ionization differences between swift (MeV) ions and cluster ions, commonly used for secondary ion mass spectrometry analysis, were studied for arginine and PEG 600. While for arginine, secondary ion yield enhancement was only by a factor of 2, when analysing with MeV ions, and no enhancement was observed with keV Bi3 clusters, all polyethylene glycol samples showed increase of the secondary ion yield by factors between 3 and 40, depending on the amount of potassium or sodium that was mixed into the matrix. Additionally, higher amounts of salts also resulted in decreased fragmentation probability for organic molecules, reducing the intensities of specific fragments by more than two orders of magnitude.
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•Added salts significantly increase secondary ion yield for both keV and MeV primary ions.•Ionization increase due to salt addition is greater with keV SIMS.•Added matrix reduces fragmentation – more with MeV-SIMS.•With secondary ion yields of approx. 10−2, submicron molecular imaging is feasible.
Purification and biochemical characterization of 11S globulin from chan (Hyptis suaveolens L. Poit) seeds Bojrquez-Velzquez, Esa; Gisela J. Lino-LpezauthorInstituto de Investigacin Lightbourn, Carretera las Pampas km 2.5, Cd., Jimnez, Chihuahua CP 33980, Mexico; Jos A. Huerta-OcampoauthorIPICyT, Instituto Potosino de Investigacin Cientfica y Tecnolgica A.C., Camino a la Presa San Jos No. 2055, Lomas 4a Seccin, San Luis Potos, SLP CP 78216, Mexico ...
2015
Journal Article
