Carbonate 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 (C) 2003 John Wiley Sons, Ltd.

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 ReO4− primary ion gun; an ion trap SIMS instrument equipped with ReO4−; 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 (σ130) for intact TEN+ (mz 130), induced by ReO4−, was measured at 670 Å2 using the quadrupole, and 560 Å2 using the ion trap. The σ130 induced by Ga+ was measured at 450Å2 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 Å2), for similar compounds in a more fluid matrix (gelatin). The comparison was extended by measuring the cross-section using ReO4− projectiles and a gelatin matrix: σ130 in this case was 480 Å2, which is of the order of 150% greater than the same experiment using Ga+. It is concluded that ReO4− 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 ReO4− 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.

The surfaces of copper chloride salts were investigated using three different secondary ion mass spectrometry (SIMS) instruments: a quadrupole instrument equipped with an ReO4− primary ion, a time-of-flight (ToF) instrument equipped with a Ga+ primary ion, and an ion trap instrument equipped with ReO4−. The research was conducted to identify copper chloride species sputtered from the surface of the copper chloride salts and to attempt to relate these species to the composition of the salt. Rich anion spectra were recorded using all three instruments for CuCl2 and CuCl, which were dominated by CuCl3− and CuCl2−. Other copper chloride adduct ions were also observed at higher masses. An examination of these ions revealed Cu primarily in the +1 and +2 oxidation state, irrespective of the oxidation state of the original salt. The presence of the Cu(+1)-bearing ions originating from the Cu(+2) salt has been attributed to reduction processes occurring during the bombardment event. However, oxidation processes must also be occurring, because Cu(+2)-bearing ions are observed in the spectra of the Cu(+1) salt. In contrast to the anion spectra, the only Cu-bearing cations contained in the CuCl(1,2) spectrum were acquired using the quadrupole- and ToF-SIMS corresponded to Cu+ and low abundance Cu2Cl+ and Cu3Cl2+ [(all Cu(+1)]. CuCl(1,2) were further investigated using the ion trap SIMS instrument: in these analyses, abundant cation clusters could be observed in addition to Cu+. The ions have been grouped into one of four categories: highly oxidized, one e− oxidized, redox neutral, and reduced. The most abundant species were redox neutral [e.g. (CuCl2)2CuCl+)] and one e− oxidized (e.g. (CuCl2)3+). Keywords: SIMS; Cluster ions; MS/MS; Ion trap; Copper chloride