Molecular Ions Research Articles

Extended magenta aurora as revealed by citizen science

During large geomagnetic storms, red auroras are typically observed from low-latitude countries such as Japan. The color arises from a specific emission line of oxygen atoms at high altitudes. However, during the May 10-11th 2024 superstorm, magenta auroras were observed above Japan instead of the typical red. In this study, we demonstrate that the magenta hue is created by a mixture of red (O) and a blue (N2+) aurora at extremely high altitudes. The blue color originates from the N2+ first negative emission band caused by both resonant scattering of the upwelling molecular ions and heavy particle precipitation during the storm. This study is primarily driven by observations from citizen scientists, and confirmed and quantified with observations from spacecraft and modeling techniques. Additionally, we show that high solar activity, terrestrial season, and the preheating of the atmosphere all contribute to the occurrence of magenta aurora. This study showcases the value and richness of citizen science, and we anticipate that such approaches will become increasingly important in the future.

Possibility of identifying 1H-indolylaminium trifluoroacetates with antimicrobial activity by mass spectrometry

The present study proposes a convenient approach to identify a series of novel substituted 1H-indol-5-,6-ylaminium trifluoroacetates with antimicrobial activity based on mass spectral data obtained using direct injection into an ion source at an elevated temperature when the salts decompose with the release of counterions: acids and organic bases – substituted 1H-indolylamines. By the presence of ions with m/z 69, 45, 28, 17 in the spectra, it is judged that the salts are formed by trifluoroacetic acid. Using the available literature data on the mass spectrometry of substituted indoles, aromatic amines, and carboxylic acids, substantiated schemes for the decomposition of molecular ions of organic bases, 1H-indolylamines, are compiled and discussed, in which the mechanism of formation and the structure of fragment ions arising under electron ionization conditions are given. The revealed general, as well as individual for individual representatives with a certain character and place of substitution in the indole bicycle, patterns of behavior of 1H-indolylamine radical ions under conditions of high-temperature mass spectral imaging make it possible to judge their structure and, in general, the structure of 1H-indolylamine trifluoroacetates. The approach used in this work can also be used to prove compounds of a similar group based on the analysis of their mass spectra.

Cold Molecular Ions via Autoionization below the Dissociation Limit

Several diatomic transition metal oxides, rare-earth metal oxides, and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6) eV above the ionization energy. Published by the American Physical Society 2024

Adsorption of Polycyclic Aromatics on Crystal Surface of Coordination Cages: Photophysical Properties and Förster Resonance Energy Transfer.

Self-assembly reactions of PdX2 (X- = NO3-, BF4-, ClO4-, ReO4-, PF6-, and CF3SO3-) with 9,10-bis((isoquinolin-5-yloxy)methyl)anthracene (L) in Me2SO give rise to single crystals of coordination cages, [X@Pd2L4]X3, irrespective of X- anions, in high yields. The intracage Pd···Pd distance is significantly sensitive to the nestled X- anion, which can serve as a gauge for recognition of ubiquitous polyatomic anions. One interesting feature is that, via π-π interactions, various polycyclic aromatics (PAs) are characteristically adsorbed on the crystal surface of designed coordination cages with a wall of anthranyl moiety. This unprecedented ensemble system shows an efficient Förster resonance energy transfer (FRET) process from the anthracene (ANT) to pyrene (PYR) via a large degree of spectral overlap between the ANT emission and PYR absorption bands, in contrast to a simple mixture of ANT and PYR.

Back-decay of the muonic molecular ion (αμt)_{01}^{2+} resonantly formed in (tμ)_{1s} + ^{4}HeH^{+} collision

Abstract Resonant formation of the muonic molecular ion (αμt)_{01}^{2+} in the collision of the muonic tritium atom with the helium hydride ion, (tμ)_{1s} + ^{4}HeH^{+} →[(αμt)_{01}^{2+},p,ee]^{+}, is proposed. The (αμt)_{01}^{2+} ion is formed in the rotational-vibrational state (0,1) as one of the two nuclei of the final complex. Back-decay process [(αμt)_{01}^{2+} ,p,ee]^{+}_{K,n}→(tμ)_{1s} + ^4HeH^{+}_{K'n'}, where K and n (K' and n') is the rotational and vibrational quantum number, respectively, is considered in detail and the corresponding decay widths for all possible rotational-vibrational (K,n)→(K',n') transitions are calculated. Numerous inelastic decay channels of (αμt)_{01}^{2+} are also presented and discussed. The possible fast resonant formation of the (αμt)_{01}^{2+} ion may provide an interesting tool for experimental studies of t(α,γ)^{7}Li nuclear fusion, which is one of the most important reactions in Big-Bang nucleosynthesis models. Studying this reaction may prove important for solving the lithium problem.

Structural Phase Transitions of Mg2NiH4 Induced by NiH4 Molecular Ion Distortion and Metal Lattice Deformation under High Pressures.

Experimental observations indicate that pressure treatments transform the monoclinic and orthorhombic low-temperature phases of Mg2NiH4 into an unresolved pseudocubic phase even at room temperatures, resembling the temperature-induced phase transformation of the material. This pressure-induced phase transformation is anticipated to involve deformations of the tetrahedrally bonded NiH4 molecular ion and the metal lattice. However, the precise mechanism underlying this transformation remains unclear. To elucidate this behavior, this study adopted first-principles density functional theory calculations to investigate the effect of applied pressure on the observed phase transition. The results revealed that the phase transition from the low-temperature phases to the pseudocubic phase occurs at approximately 8-9 GPa. Furthermore, at this pressure, the metal lattice deforms into an antifluorite-like structure, and the NiH4 molecular ion undergoes substantial distortion, resulting in the alignment of hydrogen atoms along the crystal axes of the metal lattice. Furthermore, through a comprehensive structural exploration, we successfully identified several tetragonal and orthorhombic models that are energetically more stable than the low-temperature phases at low pressures. These models are potential candidates for elucidating the pseudocubic phase observed in experiments. Overall, our findings are anticipated to enhance the current understanding of the structural changes occurring during pressure and temperature-induced phase transitions.

Collision cross sections of large positive fullerene molecular ions and their use as ion mobility calibrants in trapped ion mobility mass spectrometry.

Positive-ion laser desorption/ionization (LDI) of fullerenes contained in soot as produced by the Krätschmer-Huffman process delivers a wide range of fullerene molecular ions from C56+• to above C300+•. Here, the collision cross section (CCS) values of those fullerene molecular ions are determined using a trapped ion mobility-quadrupole-time-of-flight (TIMS-Q-TOF) instrument. While CCS values in the range from C60+• to C96+• are already known with high accuracy, those of ions from C98+• onward had yet to be determined. The fullerene molecular ions covered in this work have CCS values from about 200 to 440Å2. The fullerene molecular ion series is evenly spaced at C2 differences in composition, and thus, small CCS differences of just 2.2-3.5Å2 were determined across the entire range. Fullerene M+• ions may be employed as mobility calibrants, in particular, when very narrow 1/K0 ranges are being analyzed to achieve high TIMS resolving power. In addition, due to the simple elemental composition, M+• ions of fullerenes could also serve for mass calibration. This study describes the determination of CCS values of fullerene molecular ions from C56+• to C240+• and the application of ions from C56+• to C220+• to calibrate the ion mobility scale of a Bruker timsTOFflex instrument in any combination of LDI, matrix-assisted laser desorption/ionization (MALDI), and electrospray ionization (ESI) modes in the CCS range from about 200 to 420Å2. This use was exemplified along with ions from Agilent Tune Mix, leucine-enkephalin, angiotensin I, angiotensin II, and substance P.

Comprehensive Data Evaluation Methods Used in Developing the SWGDRUG Mass Spectral Reference Library for Seized Drug Identification.

The mass spectral library of the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) is the most comprehensive free reference database of its kind in the world. It provides reliable mass spectra for identification of seized drugs, their metabolites, and related forensic compounds when using gas chromatography/mass spectrometry (GC/MS). The SWGDRUG library (version 3.13) contains spectra for 3598 compounds. All spectra are evaluated by the Mass Spectrometry Data Center (MSDC) at the National Institute of Standards and Technology (NIST). Over the past few years, new evaluation methods aided by improved software have been developed. First, all chemical information, such as chemical structure and name, is confirmed. Second, the product ions in each spectrum are verified to match the compound structure using the NIST MS Interpreter software tool. Subsequently, the mass spectra are compared to the same or similar compounds across six different mass spectral reference libraries using three distinct library search methods. Additionally, the NIST Artificial Intelligence Retention Indices (AIRI) software is used to help confirm the corresponding compounds of spectra, especially for those without molecular ions. Low-quality and incorrect spectra are rejected for inclusion in the library.

Simultaneous Probing of Electron Density and Temperature Dynamics Inside Air Plasma with Intense Terahertz Pulses

AbstractAir plasma induced by ultrafast laser pulses is an extraordinary source of electromagnetic waves, emitting microwave, terahertz (THz) radiation, and cavityless lasing in the near‐infrared and visible ranges. The temporal dynamics of the electron density have been revealed by optical pump‐probe techniques, while the evolution of the electron temperature remains elusive due to a lack of suitable methods. Here, it is demonstrated that the intense THz‐field‐enhanced fluorescence emission from the excited molecules of nitrogen is a novel tool that allows to explore the complex dynamics of the plasma density and electron temperature simultaneously. Two relaxation times of electrons in air plasma are observed and interpreted as a competition between the excitation of a triplet state by laser or THz‐field‐heated electrons and the dissociative recombination of nitrogen molecular ions. Based on the theoretical simulations, the tens of picoseconds relaxation process is attributed to the ultrafast temperature decrease, while the longer relaxation in the range of hundreds of picoseconds is ascribed to the decay of electron density. The temporal relaxation of both the electron density and temperature revealed by applying an intense THz field provides further insights into the laser‐air plasma interaction and will benefit the engineering of this exceptional source.

Bacteria from the Amycolatopsis genus associated with a toxic bird secrete protective secondary metabolites

Uropygial gland secretions of birds consist of host and bacteria derived compounds and play a major sanitary and feather-protective role. Here we report on our microbiome studies of the New Guinean toxic bird Pachycephala schlegelii and the isolation of a member of the Amycolatopsis genus from the uropygial gland secretions. Bioactivity studies in combination with co-cultures, MALDI imaging and HR-MS/MS-based network analyses unveil the basis of its activity against keratinolytic bacteria and fungal skin pathogens. We trace the protective antimicrobial activity of Amycolatopsis sp. PS_44_ISF1 to the production of rifamycin congeners, ciromicin A and of two yet unreported compound families. We perform NMR and HR-MS/MS studies to determine the relative structures of six members belonging to a yet unreported lipopeptide family of pachycephalamides and of one representative of the demiguisins, a new hexapeptide family. We then use a combination of phylogenomic, transcriptomic and knock-out studies to identify the underlying biosynthetic gene clusters responsible for the production of pachycephalamides and demiguisins. Our metabolomics data allow us to map molecular ion features of the identified metabolites in extracts of P. schlegelii feathers, verifying their presence in the ecological setting where they exert their presumed active role for hosts. Our study shows that members of the Actinomycetota may play a role in avian feather protection.

Theoretical study on the spectrum properties of tellurium iodide cation

The molecular potential energy function plays an important role in many fields. In this paper, the icMRCI + Q method was utilized to compute the potential energy and dipole moments for 22 Λ-S states and 51 Ω states of the TeI+ system. Two basis sets (AVQZ-PP and AWCVQZ-PP) were employed to compute the TeI+ system, with the results indicating that the AVQZ-PP basis set yielded more accurate results. Therefore, all calculations in this paper are based on this basis set. Furthermore, to ensure the accuracy of the results, a comparison was conducted on the spectral parameters of the ground state and two excited states of the molecular ion within the same main group. Given the significant impact of spin–orbit coupling, as indicated by the calculated SO matrix elements, our discussion will predominantly center on the avoidance of crossovers in the Ω states. Finally, the Franck-Condon factors, Einstein coefficients and radiative lifetime between these two states were calculated from the data of the transition between the X3Σ0+-↔11Σ0++ of the TeI+ molecule.

Predicting Collision-Induced-Dissociation Tandem Mass Spectra (CID-MS/MS) Using Ab Initio Molecular Dynamics.

Compound identification is at the center of metabolomics, usually by comparing experimental mass spectra against library spectra. However, most compounds are not commercially available to generate library spectra. Hence, for such compounds, MS/MS spectra need to be predicted. Machine learning and heuristic models have largely failed except for lipids. Here, quantum chemistry software can be used to predict mass spectra. However, quantum chemistry predictions for collision induced dissociation (CID) mass spectra in LC-MS/MS are rare. We present the CIDMD (Collision-Induced Dissociation via Molecular Dynamics) framework to model CID-based MS/MS spectra. It uses first-principles molecular dynamics (MD) to simulate the physical process of molecular collisions in CID tandem mass spectrometry. First, molecular ions are constructed at specific protonation sites. Using density functional theory, these protonated ions are targeted by argon collider gas atoms at user-specified velocities. Subsequent bond breakages are simulated over time for at least 1,000 fs. Each simulation is repeated multiple times from various collisional directions. Fragmentations are accumulated over those repeated collisions to generate CIDMD in silico mass spectra. Twelve small metabolites (<205 Da) were selected to test the accuracy of this framework in comparison to experimental MS/MS spectra. When testing different protomers, collider velocities, number of simulations, simulation time and impact factor b cutoffs, we yielded 261 predicted mass spectra. These in silico spectra resulted in entropy similarity scores of an average 624 ± 189 for all 261 spectra compared to their corresponding experimental spectra, which improved to 828 ± 77 when using optimal parameters of the most probable protomers for 12 molecules. With increasing molecular mass, higher velocities achieved better results. Similarly, different protomers showed large differences in fragmentation; hence, with increasing numbers of protomers and tautomers, the average CIDMD prediction accuracy decreased. Mechanistic details showed that specific fragment ions can be produced from different protomers via multiple fragmentation pathways. We propose that CIDMD is a suitable tool to predict mass spectra of small metabolites like produced by the gut microbiome.

Beyond Artists' Colors: A Spectral Reference Database for the Identification of β-Naphthol and Triarylcarbonium Colorants by MeVSIMS.

β-Naphthol and triarylcarbonium colorants were often used by modern and contemporary artists in materials such as inks and paints. Their poor stability and ability to fade upon exposure to light make their identification in artworks crucial for planning exhibitions and preventive conservation. Secondary ion mass spectrometry with MeV primary ions (MeV SIMS) is necessary when analyzing synthetic organic colorants (SOCs) with similar molecular structures due to its advantages in high sensitivity and soft ionization, which causes a low fragmentation of organic molecules. In this work, we applied MeV SIMS with 5 MeV Si4+ to identify selected β-naphthol and triarylcarbonium colorants from the 19th/20th century Materials Collection kept at the Academy of Fine Arts Vienna. The collection contains SOCs from renowned companies, such as I.G. Farben and I.C.I., and serves as a unique source of reference materials in the analysis of artworks. Previous research on these colorants with X-ray fluorescence analysis (XRF), micro-Raman, and Fourier transform infrared (FTIR) spectroscopies failed in the case of colorant mixtures. Similar spectral features of the SOCs within one chemical class and their low concentrations in mixtures did not lead to their identification using these techniques. MeV SIMS detected molecular ions or protonated molecules in the positive-ion mode. In the negative-ion mode, the functional groups (NO2 - and SO3 -) of β-naphthol lakes/pigments and heteropolyacid species (WO3 - and MoO3 -) characteristic of triarylcarbonium toners were determined. The results demonstrate that MeV SIMS is highly effective for identifying β-naphthol and triarylcarbonium colorants in mixtures and distinguishing between pigments, toners, lakes, and dyes.

Computationally-Assisted Discovery and Assignment of a New Class of 6/6/5/5 Fused-Ring Diterpene Acting as Pregnane X Receptor Ligands from Isodon serra.

We report here the orchestration of molecular ion networking (MoIN) and a set of computationally assisted structural elucidation approaches in the discovery and assignment of a new class of rearranged 4,5-seco-abietane diterpenoids including serra A (1), which possesses an unusual 6/6/5/5 fused-ring skeleton system, together with two previously unreported diterpenoids serras B-C (2-3) and five known compounds were isolated from Isodon serra (I. serra). The structures were elucidated by spectroscopic analysis in conjunction with computationally assisted structure elucidation tools. In silico, serras A-C (1-3) bind well to PXR, suggesting their potential role in reducing inflammation. The results of serra A (1) with hPXR demonstrated agonist activity with an EC50 value of 15 μM. Serra A (1), graciliflorin F (4), gerardianin C (5), 11,12,15-trihydroxy-8,11,13-abietatrien-7-one (6), rabdosin D (7), and 15-hydroxysalprionin (8) exhibited promising anti-inflammatory activities in lipopolysaccharide (LPS)-induced RAW 267.4 cells, and their inhibition rates on NO production were more than 65% at 10 μM.

Electron-driven processes in enantiomeric forms of glutamic acid initiated by low-energy resonance electron attachment.

Low-energy (0-14eV) resonance electron interaction and fragment species produced by dissociative electron attachment (DEA) for enantiomeric forms of glutamic acid (Glu) are studied under gas-phase conditions by means of DEA spectroscopy and density functional theory calculations. Contrary to a series of amino acids studied earlier employing the DEA technique, the most abundant species are not associated with the elimination of a hydrogen atom from the parent molecular negative ion. Besides this less intense closed-shell [Glu - H]- fragment, only two mass-selected negative ions, [Glu - 19]- and [Glu - 76]-, are detected within the same electron energy region, with the yield maximum observed at around 0.9eV. This value matches well the energy of vertical electron attachment into the lowest normally empty π* COOH molecular orbital of Glu located at 0.88eV according to the present B3LYP/6-31G(d) calculations. Although the detection of asymmetric DEA properties a priori is not accessible under the present experimental conditions, "chirality non-conservation" can be associated with some decay channels. Evidently, the measured spectra for the L- and D-forms are found to be identical, the results, nevertheless, being of interest for the forthcoming experiments utilizing spin-polarized electron beam as a chiral factor in the framework of conventional DEA technique.

Structure, and the laser cooling scheme for the XF− (X=Li, Na, K, Rb) molecule

For laser-cooling considerations, we have theoretically investigated the electronic structures of the XF− (X=Li, Na, K, Rb) molecule. The potential existence of anions is initially examined through the analysis of their affinity energies and dipole moments of the corresponding neutral molecules. Subsequently, we excluded the effect of spin–orbit coupling on the molecular. Then the calculations reveal that XF− (X=Li, Na, K, Rb) exhibits a highly diagonalized Franck-Condon factor and a short spontaneous radiation lifetime, facilitating the design of laser cooling schemes for each molecular ion. The findings provide an important reference for laser cooling experiments involving alkali metal fluoride anions.

Magnitude of Obesity Alone does not Alter the Alveolar Lipidome.

Obesity may lead to pulmonary dysfunction through complex and incompletely understood cellular and biochemical effects. Altered lung lipid metabolism has been identified as a potential mechanism of lung dysfunction in obesity. While murine models of obesity demonstrate changes in pulmonary surfactant phospholipid composition and function, data in humans are lacking. We measured untargeted shotgun lipidomes in two bronchoalveolar lavages (BAL) from apical and anteromedial pulmonary subsegments of 14 adult subjects (7 males and 7 females) with body mass indexes ranging from 24.3 to 50.9 kg/m2. The lipidome composition was characterized at the class, species, and fatty acyl / alkyl level using total lipid molecular ion signal intensities normalized to BAL protein concentration and epithelial lining fluid volumes. Multivariate analyses were conducted to identify potential changes with increasing BMI. The alveolar lipidomes contained the expected composition of surfactant associated phospholipids, sphingolipids, and sterols in addition to cardiolipin and intracellular signaling lipid species. No significant differences in lipidomes were detected between the two BAL regions. Though a small number of lipid species were associated with BMI in multivariate analyses, no robust differences in lipidome composition or specific lipid species were identified over the range of body habitus. The magnitude of obesity alone does not substantially alter the alveolar lipidome in patients without lung disease. Differences in lung function in patients with obesity and no lung disease are unlikely related to changes in alveolar lipid composition.

Light-Powered Propeller-like Transporter for Boosted Transmembrane Ion Transport.

Membrane-active molecular machines represent a recently emerging, yet important line of expansion in the field of artificial transmembrane transporters. Their hitherto demonstrated limited types (molecular swing, ion fishers, shuttlers, rotors, etc.) certainly call for new inspiring developments. Here, we report a very first motorized ion-transporting carrier-type transporter, i.e., a modularly tunable, light-powered propeller-like transporter derived from Feringa's molecular motor for consistently boosting transmembrane ion transport under continuous UV light irradiation. Based on the EC50 values, the molecular propeller-mediated ion transport activities under UV light irradiation for 300 s are 2.31, 1.74, 2.29, 2.80, and 2.92 times those values obtained without irradiation for Li+, Na+, K+, Rb+, and Cs+ ions, respectively, with EC50 value as low as 0.71 mol % for K+ ion under light irradiation.

Gas-Phase Structures of Fucosylated Oligosaccharides: Alkali Metal and Halogen Influences.

Fucosylated carbohydrate antigens play critical roles in physiology and pathology with function linked to their structural details. However, the separation and structural characterization of isomeric fucosylated epitopes remain challenging analytically. Here, we report for the first time the influence of alkali metal cations (Li+, Na+, K+, Rb+, and Cs+) and halogen anions (Cl-, Br-, and I-) on the gas-phase conformational landscapes of common fucosylated trisaccharides (Lewis A, X, and H types 1 and 2) and tetrasaccharides (Lewis B and Y) using trapped ion mobility spectrometry coupled to mass spectrometry and theoretical calculations. Inspection of the mobility profiles of individual standards showed a dependence on the number of mobility bands with the oligosaccharide and the alkali metal and halogen; collision cross sections are reported for all of the observed species. Results showed that trisaccharides (Lewis A, X, and H types 1 and 2) can be best mobility resolved in the positive mode using the [M + Li]+ molecular ion form (baseline resolution r ≈ 2.88 between Lewis X and A); tetrasaccharides can be best mobility resolved in the negative mode using the [M + I]- molecular ion form (baseline separation r ≈ 1.35 between Lewis B and Y). The correlation between the number of oligosaccharide conformers as a function of the molecular ion adduct was studied using density functional theory. Theoretical calculations revealed that smaller cations can form more stable structures based on the number of coordinations, while larger cations induced greater oligosaccharide reorganizations; candidate structures are proposed to better understand the gas-phase oligosaccharide rearrangement trends. Inspection of the candidate structures suggests that the interplay between ion size/charge density and molecular structure dictated the conformational preferences and, consequently, the number of mobility bands and the mobility separation across isomers. This work provides a fundamental understanding of the gas-phase structural dynamics of fucosylated oligosaccharides and their interaction with alkali metals and halogens.

Sewage and Organic Pollution Compounds in Nairobi River Urban Sediments Characterized by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS).

Nairobi River sediments from locations adjacent to the Kawangware and Kiambio slums were analyzed via Fourier transform ion cyclotron resonance mass spectrometry with atmospheric pressure photoionization (APPI-FT-ICR-MS). The data from these ultrahigh resolution, untargeted measurements provided new insights into the impacts of local anthropogenic activity, which included likely benzo- and dibenzothiophene pollution with a suspected petrogenic origin, and prominent surfactant-like compositions. Other features in the data included highly abundant tetra-oxygenated compounds, and oxygenated nitrogen compounds with sphingolipid interpretations. Most notably, several hydrocarbon and oxygenated compound classes in the sediment data featured intensity patterns consistent with steroid molecular formulas, including those associated with sewage contamination investigatory work. In support of this interpretation, standards of cholesterol, β-sitosterol, stigmasterol, coprostanol, cholestanol, and 5α-sitostanol were analyzed via APPI, to explore steroid ionization behavior. Generally, these analytes produced radical molecular ions ([M]•+), and water-loss pseudo molecular ion species ([M-H2O]•+ and [M+H-H2O]+), among various other less intense contributions. The absence of pseudo molecular protonated species ([M+H]+) was notable for these compounds, because these are often assumed to form with APPI. The standard measurements demonstrated how steroids can create the observed intensity patterns in FT-ICR-MS data, and hence these patterns have the potential to indicate sewage contamination in the analysis of other complex environmental samples. The steroid interpretation for the Kawangware and Kiambio data was further verified by subjecting the steroid standard radical molecular ions to collision-induced dissociation and comparing the detected fragments to those for the corresponding isolated ions from a Kawangware sediment sample.