Static Static Secondary Ion Mass Spectrometry Research Articles

Organic Secondary Ion Mass Spectrometry: Signal Enhancement by Water Vapor Injection

The enhancement of the static secondary ion mass spectrometry (SIMS) signals resulting from the injection, closely to the sample surface, of H(2)O vapor at relatively high-pressure, was investigated for a set of organic materials. While the ion signals are generally improved with increasing H(2)O pressure upon 12 keV Ga(+) bombardment, a specific enhancement of the protonated ion intensity is clearly demonstrated in each case. For instance, the presence of H(2)O vapor induces an enhancement by one order of magnitude of the [M + H](+) static SIMS intensity for the antioxidant Irgafos 168 and a ∼1.5-fold increase for polymers such as poly(vinyl pyrrolidone).

Imaging secondary ion mass spectrometry of a paint cross section taken from an early Netherlandish painting by Rogier van der Weyden.

Static secondary ion mass spectrometry (SIMS) is introduced as an analytical technique for the examination of paint cross sections to obtain simultaneous information about the nature and distribution of pigments and the binding medium from a single sample. A sample taken from the virgin's blue robe in the panel painting The Descent from the Cross (Museo del Prado, Madrid) of the Early Netherlandish painter Rogier van der Weyden (1399/1400-1464) was selected for investigation. Data were compared with reference compounds and reference lead white linseed oil paint and egg tempera paint. The static SIMS technique gave position-sensitive mass spectra that were used to image the elemental distribution of pigments and the molecular signature of components of the oleaginous binding medium. SIMS ion images of sodium and aluminum superimposed with the blue pigment ultramarine and those of copper, lead, and calcium with the position of the mineral pigments of azurite, lead white, and chalk, respectively. Preserved monocarboxylic acids of palmitic and stearic acids present as fatty acids and fatty acid lead soaps pointed to the use of linseed oil as a binding medium. Images from the oleaginous binding medium fatty acids show a correlation with the three main paint layers. The observed palmitic/stearic acid ratios for the two ultramarine layers and azurite layers are 1.3, 1.4, and 1.8, respectively. Fatty acids and fatty acid soaps show highest ion yields near lead white, a mineral pigment that serves as a natural chemical drier and is proposed to act as a template for the initial grafting of the polyunsaturated triglycerides of the linseed oil. Almost no fatty acids were detected in other layers visible by light microscopy. The fatty acid lead soaps point toward a mature ionomeric oil paint system that developed over centuries. SIMS evidence for egg tempera, still used in the 15th century, is not detected in the paint cross section. SIMS images correlate well with SEM/EDX, FT-IR and light microscopic images and the SIMS spectral data additionally support the identification of pigment particles, lead soaps, and other binding medium components.

Enhancement of the static SIMS secondary ion yields of lipid moieties by ultrathin gold coating of aged oil paint surfaces

AbstractStatic secondary ion mass spectrometry (SIMS) is a powerful technique for identification and localization of pigments and binding media present in traditional paintings. Coating the surface of a cross‐section with a 20 Å thick gold layer improves the yields of secondary ions from the fatty acids and diacids. A chalk tablet containing 1% stearic acid, which was partially covered during gold deposition, is used as a test system to investigate the increase of the organic secondary ion yields upon gold deposition in SIMS imaging. A comparative study of a native and gold‐coated aged surface of a lead white‐containing linseed oil paint demonstrates the enhancement of the organic ion yields on a sample relevant for painting studies. The yields of oil paint‐derived negative ions increase by a factor of 3 whereas the yields of positive ions increase by a factor of 2–4. The different types of charged functional groups determine the degree of improvement in yield. Gold coating improves the ionization process of the fatty acids and does not influence their fragmentation. The dissociation of the lead white by the primary ion beam is reduced due to the gold coating. Copyright © 2004 John Wiley & Sons, Ltd.

Static SIMS analysis of carbonate on basic alkali‐bearing surfaces

AbstractCarbonate is a somewhat enigmatic anion in static secondary ion mass spectrometry (SIMS) because abundant ions containing intact CO32− are not detected when analyzing alkaline‐earth carbonate minerals common to the geochemical environment. In contrast, carbonate can be observed as an adduct ion when it is bound with alkali cations. In this study, carbonate was detected as the adduct Na2CO3·Na+ in the spectra of sodium carbonate, bicarbonate, hydroxide, oxalate, formate and nitrite and to a lesser extent nitrate. The appearance of the adduct Na2CO3·Na+ on hydroxide, oxalate, formate and nitrite surfaces was interpreted in terms of these basic surfaces fixing CO2 from the ambient atmosphere. The low abundance of Na2CO3·Na+ in the static SIMS spectrum of sodium nitrate, compared with a significantly higher abundance in salts having stronger conjugate bases, suggested that the basicity of the conjugate anions correlated with aggressive CO2 fixation; however, the appearance of Na2CO3·Na+ could not be explained simply in terms of solution basicity constants. The oxide molecular ion Na2O+ and adducts NaOH·Na+ and Na2O·Na+ also constituted part of the carbonate spectral signature, and were observed in spectra from all the salts studied. In addition to the carbonate and oxide ions, a low‐abundance oxalate ion series was observed that had the general formula Na2−xHxC2O4·Na+, where 0 < x < 2. Oxalate adsorption from the laboratory atmosphere was demonstrated but the oxalate ion series also was likely to be formed from reductive coupling occurring during the static SIMS bombardment event. The remarkable spectral similarity observed when comparing the sodium salts indicated that their surfaces shared common chemical speciation and that the chemistry of the surfaces was very different from the bulk of the particle. Copyright © 2003 John Wiley & Sons, Ltd.

Detection of fatty acids from intact microorganisms by molecular beam static secondary ion mass spectrometry

We report the use of a surface analysis approach, static secondary ion mass spectrometry (SIMS) equipped with a molecular (ReO 4 −) ion primary beam, to analyze the surface of intact microbial cells. SIMS spectra of 28 microorganisms were compared to fatty acid profiles determined by gas chromatographic analysis of transesterfied fatty acids extracted from the same organisms. The results indicate that surface bombardment using the molecular primary beam cleaved the ester linkage characteristic of bacteria at the glycerophosphate backbone of the phospholipid components of the cell membrane. This cleavage enables direct detection of the fatty acid conjugate base of intact microorganisms by static SIMS. The limit of detection for this approach is approximately 10 7 bacterial cells/cm 2. Multivariate statistical methods were applied in a graded approach to the SIMS microbial data. The results showed that the full data set could initially be statistically grouped based upon major differences in biochemical composition of the cell wall. The gram-positive bacteria were further statistically analyzed, followed by final analysis of a specific bacterial genus that was successfully grouped by species. Additionally, the use of SIMS to detect microbes on mineral surfaces is demonstrated by an analysis of Shewanella oneidensis on crushed hematite. The results of this study provide evidence for the potential of static SIMS to rapidly detect bacterial species based on ion fragments originating from cell membrane lipids directly from sample surfaces.

Application of atomic and molecular primary ions for TOF–SIMS analysis of additive containing polymer surfaces

The influence of primary ion mass and composition on secondary ion emission of the additive Irganox 1010 ( m=1176 u) in polyethylene was investigated. O +, Ar +, Xe +, O 2 +, CO 2 +, SF 5 +, C 7H 7 +, C 10H 8 +, C 6F 6 +, and C 10F 8 + with a total energy of 11 keV were used as primary ions under static secondary ion mass spectrometry (SIMS) conditions. Positive and negative molecular secondary ions characterizing the additive were determined and their yields were evaluated. For all characteristic secondary ions we found a strong yield enhancement with increasing mass for atomic primary ions and increasing number of constituents for molecular primary ions. This yield enhancement is saturated once the molecular primary ion is made of more than six heavy atoms. In addition this yield increase depends on the mass and structure of the considered secondary ion. We did not find any evidence for an influence of the chemical composition of the applied molecular primary ions on the secondary ion emission when static SIMS conditions were met. The improved imaging capabilities of molecular primary ions was demonstrated by comparing focused Ar + and SF 5 + primary ion beams when mapping characteristic secondary ion emission from a structured additive containing polypropylene surface.

Static SIMS: towards unfragmented mass spectra — the G-SIMS procedure

A study is presented of the effects of the different positive ion beam species: Ar +, Ga +, Xe +, Cs + and SF 5 + and of their energies from 4 to 25 keV, on the fragmentation behaviour in static Secondary Ion Mass Spectrometry (SIMS) spectra for samples of the polymers: polytetrafluoroethylene (PTFE), polystyrene (PS) and polycarbonate (PC). The overall effect of energy is found to be weak over the entire mass spectrum. However, large differences are observed in restricted mass ranges amongst fragmentation groups. The fragmentation is quantified in terms of the partition functions of the fragments from a plasma with effective temperature, T p. It is found that fragmentation is least for high mass projectiles at low energies, but that the trend is different for polyatomic ions. A methodology is developed, which unifies all of the fragmentation behaviour to a single plot — the Unified Cascade Gradient plot. An equivalence of mass and energy is shown and that the chemistry of the bombarding ion is unimportant. By extrapolation of the data to low T p, a new spectroscopy, known as gentle-SIMS or G-SIMS is formed. The G-SIMS spectrum is in the static regime. Significant peaks in the G-SIMS spectra are those peaks, which would be emitted from a surface plasma of very low temperature and thus have little post-emission rearrangement or fragmentation. Those peaks are, thus, directly characteristic of the material without rearrangement and provide a direct interpretation and identification. In the tests of the method described, this is supported and indicates that the G-SIMS analysis will be significantly less ambiguous than static SIMS so that interpretation will be possible in the absence of a relevant reference spectrum.

Secondary Ion Mass Spectrometric Characterization of Nail Polishes and Paint Surfaces

A variety of paint and fingernail polish samples, which were visually similar, but had different chemical compositions and formulations, was analyzed using quadrupole static secondary ion mass spectrometry (SIMS). Coating distinction was easily achieved in many cases because of the presence of dominant ions derived from the components of the coating, which could be observed in the SIMS spectra. In other instances, coating distinction was difficult within a product line because of spectral complexity; for this reason and because of the large numbers of spectra generated in this study, multivariate statistical techniques were employed, which allowed the meaningful classification and comparison of spectra. Partial Least Squares (PLS) and Principal Component Analysis (PCA) were applied to quadrupole SIMS data. PCA showed distinct spectral differences between most spectral groups, and also emphasized the reproducibility of the SIMS spectra. When using PLS analysis, reasonably accurate coating identification was achieved with the data. Overall, the PLS model is more than 90% effective in identifying the spectrum of a particular coating, and nearly 100% effective at telling which coating components represented in the PLS models are not present in a spectrum. The level of spectral variation caused by sample bombardment in the SIMS analysis was investigated using Fourier transform infrared spectroscopy (FT-IR) and quadrupole static SIMS. Changes in the FT-IR spectra were observed and were most likely a result of a number of factors involving the static SIMS analysis. However, the bulk of the sample is unaltered and may be used for further testing.

Structural Characterization, Electrochemical Reactivity, and Response Stability of Hydrogenated Glassy Carbon Electrodes

The physical structure, electrochemical reactivity, and response stability of hydrogenated glassy carbon (HGC) electrodes were investigated using atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SIMS), cyclic voltammetry, and chronocoulometry. The electrochemical results indicate that glassy carbon surfaces, modified in a hydrogen microwave plasma, exhibit lower background voltammetric currents, comparable electrochemical activity, enhanced S/B ratios, and improved response stability for several aqueous-based redox analytes, compared with polished (i.e., oxygenated) glassy carbon (GC). Also, negligible adsorption of anthraquinone-2,6-disulfonate (2,6-AQDS) occurs on HGC, unlike polished GC, a surface on which AQDS strongly physisorbs at high coverages. The hydrogenated surface contains very little surface oxygen (O/C ≤ 0.03) and is hydrophobic with a contact angle of >65°. Static SIMS measurements reveal a significant fracti...

Static SIMS investigation of tetraethylammonium bromide on soil particles using ReO 4− and Ga + projectiles

Tetraethylammonium (TEN +) adsorbed to soil particles (primarily silicate) was investigated using static secondary ion mass spectrometry (SIMS) in order to assess the behavior of the adsorbate under atomic and polyatomic projectile bombardment. Three different instruments were used for the investigation; a quadrupole-SIMS instrument equipped with a ReO 4 − primary ion gun; an ion trap SIMS instrument equipped with ReO 4 −; and an imaging time-of-flight (ToF) SIMS equipped with Ga +. In all experiments, TEN + was observed to decrease in abundance with increasing primary ion dose. The disappearance cross-section ( σ 130) for intact TEN + ( m z 130), induced by ReO 4 −, was measured at 670 Å 2 using the quadrupole, and 560 Å 2 using the ion trap. The σ 130 induced by Ga + was measured at 450Å 2 using the ToF-SIMS, indicating that the polyatomic projectile was perturbing an area 20–50% larger than the monoatomic. These values are significantly larger than Ga +-induced cross-sections in the literature (100–200 Å 2), for similar compounds in a more fluid matrix (gelatin). The comparison was extended by measuring the cross-section using ReO 4 − projectiles and a gelatin matrix: σ 130 in this case was 480 Å 2, which is of the order of 150% greater than the same experiment using Ga +. It is concluded that ReO 4 − produces a larger σ than does Ga +. In addition, the results suggest that disappearance cross-sections are larger on a refractory solid surface (silicate), than they are on a fluid surface (gelatin). The minimum detection limit was estimated for TEN + on soil using ReO 4 − with the quadrupole SIMS instrument, at approximately 5 × 10 −4 monolayers (ML), which corresponds to about 500 ppb. Consideration of this result suggests that a lower detection limit may be achievable using a brighter primary ion beam together with a trapped ion mass spectrometer.

Interaction of a model epoxy resin compound, diethanolamine, with aluminium surfaces studied by static SIMS and XPS

The interaction of diethanolamine, a model epoxy resin compound, with aluminium surfaces is characterised using static secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). Diethanolamine does not adsorb on γ-alumina but does adsorb on phosphoric acid anodised aluminium, suggesting that the adsorption site is a Bronsted acid. A static SIMS spectrum is obtained consistent with a protonated species and the XPS N 1s signal shows two states for the adsorbate. Diethanolamine on an ion-bombarded aluminium surface does not show the characteristic SIMS spectrum observed with the anodised substrate. It is postulated that the hydroxy groups of the diethanolamine form a dialkoxide covalently bound to the ion-bombarded aluminium. The corresponding XPS N 1s signal showed a single binding energy in the range of Lewis site interactions on alumina.The interaction of all three functionalities of the diethanolamine with the anodised aluminium surface results in stronger adsorption than for a similar difunctional compound, (methylamino)ethanol, indicating that both hydroxy groups are involved in hydrogen bonding to surface acid sites

AN FTIR AND STATIC SIMS STUDY OF THE ADSORPTION OF PROPYLENE ON Cu-ZSM-5 CATALYSTS

Diffuse reflectance infrared spectroscopy and static secondary ion mass spectrometry (SIMS) were employed to study the surface species formed during the adsorption and reaction of propylene on a copper-exchanged ZSM-5 catalyst. Propylene showed characteristics of chemisorption on Cu-ZSM-5 at room temperature and total decomposition to CO, CO2 and CH 4 at 350°C. The ir bands of =C–H stretching at 3101 cm -1, =C–C stretching at 916 cm -1 and C=CH 2 twisting at 575 cm -1 for propylene disappeared upon adsorption, indicating the breaking of the C=C double bond, while the decrease in the signal intensity of zeolite isolated and vicinal SiOH groups at 3700 and 3592 cm -1 implied that the adsorbed di-σ species was bound to zeolite SiO–. Static SIMS showed two distinguished peaks at 73 and 147 amu, which were assigned to the adsorbed species H2OSi2(C3H5O2) due to the interaction of propylene with ZSM-5 and Cu-ZSM-5. The adsorption and reaction of propylene were enhanced by the presence of Cu+ in ZSM-5. The mechanism for these processes was discussed.

Direct Surface Analysis of Pesticides on Soil, Leaves, Grass, and Stainless Steel by Static Secondary Ion Mass Spectrometry

Direct surface analyses by static secondary ion mass spectrometry (SIMS) were performed for the following pesticides adsorbed on dandelion leaves, grass, soil, and stainless steel samples: alachlor, atrazine, captan, carbofuran, chlorpyrifos, chlorsulfuron, chlorthal-dimethyl, cypermethrin, 2,4-D, diuron, glyphosate, malathion, methomyl, methyl arsonic acid, mocap, norflurazon, oxyfluorfen, paraquat, temik, and trifluralin. The purpose of this study was to evaluate static SIMS as a tool for pesticide analysis, principally for use in screening samples for pesticides. The advantage of direct surface analysis compared with conventional pesticide analysis methods is the elimination of sample pretreatment including extraction, which streamlines the analysis substantially; total analysis time for SIMS analysis was ca. 10 min/sample. Detection of 16 of the 20 pesticides on all four substrates was achieved. Of the remaining four pesticides, only one (trifluralin) was not detected on any of the samples. The minimum detectable quantity was determined for paraquat on soil in order to evaluate the efficacy of using SIMS as a screening tool. Paraquat was detected at 3 pg/mm2 (ca. 0.005 monolayers). The results of these studies suggest that SIMS is capable of direct surface detection of a range of pesticides, with low volatility, polar pesticides being the most easily detected.

Dynamic and static secondary ion mass spectrometry studies of the solvation of HCl by ice

H. A. Donsig and J. C. Vickerman, J. Chem. Soc., Faraday Trans., 1997, 93, 2755 DOI: 10.1039/A701724C

Study of the interaction of carbon fibre surfaces with a monofunctional epoxy resin

X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS) have been used to determine the chemical changes observed as a result of interactions between carbon fibre surfaces and epoxy resins. A comparison has been made between untreated, commercially treated and air plasma treated carbon fibres. Both positive and negative static SIMS results indicated the presence of nitrogen and oxygen containing fragments as a result of air plasma treatment, the spectra from commercially treated fibres were dominated by contaminants. Fibres were then sized in the monofunctional epoxy resin, 1,2-epoxy-3-phenoxypropane, and further analysis carried out to determine the chemical nature of the fibre-resin interface. Angle resolved XPS was used to confirm the presence of a layer of resin. Positive ion fragments from static SIMS data have been identified as species which have been formed as a result of the epoxy molecule chemically reacting with species on the fibre surface. Surface energy measurements have also been recorded and it is shown that the polar component of surface energy is greatly increased as a result of surface treatment. This increase is much greater for air plasma treated fibres than for commercially treated fibres. It is proposed that air plasma treatment of carbon fibres increases the interfacial adhesion in carbon fibre/epoxy composites, by the introduction of functional groups which form chemical bonds with the epoxy resin.

Rapid detection of tri- n-butyl phosphate on environmental surfaces using static SIMS

Static secondary ion mass spectrometry (SIMS) is an analytical method that can be used to detect the presence of tri- n-butyl phosphate (TBP) on environmental surfaces including minerals (e.g., basalts, quartz) and vegetation. Static SIMS instrumentation equipped with pulsed secondary ion extraction and a ReO 4 − primary ion gun permits the rapid acquisition of cation and anion mass spectra of samples surfaces with virtually no sample preparation: samples are merely attached to a sample holder using double-stick tape. SIM spectra were demonstrated to be sensitive to the mode of TBP adsorption to mineral surfaces: TBP adsorbed to Fe(II)-bearing phases, Fe(III)-bearing phases, silicate, and vegetation surfaces could be distinguished from one another. These results indicate that SIMS has broad applicability for the rapid characterization of environmental surfaces, and in some cases, is capable of identifying the mode of contaminant-surface interactions. The technique is also attractive because it can analyze milligram-size samples, and no waste is generated during analysis.

Sample charging during static SIMS studies of polymers

The effects of charging during the bombardment of poly(ethylene terephthalate) (PET) and poly(tetrafluoroethylene) (PTFE) with primary ion and atom beams are explored, with a view to developing our understanding of charge-compensation mechanisms in static secondary ion mass spectrometry (SIMS). A simple model based on a resistor and capacitor in parallel may be used to predict the behaviour of PET during atom bombardment, but PTFE exhibits anomalous behaviour, and the behaviour of both polymers during ion bombardment is complex. Simple models are inadequate to predict and explain charging phenomena in SIMS when common charge-compensation procedures are employed. An outline is sketched for a more complex model, but a full understanding will only be possible when we are able to develop an accurate description of the surface electrostatic phenomena which occur during ion and atom bombardment of polymers.

Characterization of plasma‐deposited styrene films by XPS and static SIMS

AbstractPlasma‐polymerized styrene films were studied by static secondary ion mass spectrometry (SIMS) and x‐ray photoelectron spectroscopy (XPS). The two techniques were found to yield complementary data regarding film chemical structure. Static SIMS proved to be highly sensitive to subtle changes in surface chemistry. For example, the static SIMS spectra exhibited features due to polymer cross‐linking and unsaturation. X‐ray photoelectron spectroscopy provided a good indication of the extent of oxygen incorporation into the plasma‐deposited films and characterization of time‐dependent changes in film composition.

Detection of Alkylmethylphosphonic Acids on Leaf Surfaces by Static Secondary Ion Mass Spectrometry

Detection of environmental degradation products of nerve agents directly from the surface of plant leaves using static secondary ion mass spectrometry (SIMS) is demonstrated. Pinacolylmethylphosphonic acid (PMPA), isopropylmethylphosphonic acid (IMPA), and ethylmethylphosphonic acid (EMPA) were spiked from aqueous solutions onto philodendron leaves prior to analysis by static SIMS. Fragment ions were observed in the anion SIMS spectra from all three compounds at m/z 63, 77, 79, and 95, which are attributed to PO[sub 2][sup [minus]], CH[sub 2]PO[sub 2][sup [minus]], PO[sub 3][sup [minus]], and CH[sub 3]PO[sub 2]OH[sup [minus]], respectively. Additionally, peaks due to [M - H][sup [minus]] were observed at m/z 179 for PMPA, m/z 137 for IMPA, and m/z 123 for EMPA. The minimum detection limits for PMPA and IMPA on philodendron leaves were estimated to be between 4 and 0.4 ng/mm[sup 2]. The minimum detection limit for EMPA on philodendron leaves was estimated to be between 40 and 4 ng/mm[sup 2]. SIMS analyses of IMPA adsorbed on 10 different crop leaves were also performed in order to investigate the general applicability of static SIMS for detection of alkylmethylphosphonic acids (AMPAs) on a wide variety of leaves. 30 refs., 11 figs., 4 tabs.

Static secondary ion mass spectrometry of adsorbed proteins

Static secondary ion mass spectrometry (SIMS) was used to analyze proteins adsorbed to biomaterial surfaces. A spectral interpretation protocol was established by examining homopolymers of 16 amino acids. This protocol allows for the assignment of peaks unique to the various amino acids. Static SIMS was used to analyze plasma proteins adsorbed to titanium. The various factors that contributed to the relative intensities observed in the spectra were explored. The potential application of the technique for studying protein-fouled materials was investigated by analyzing a fouled sensor membrane.