Neutral Mass Spectrometry Research Articles

In silico structures, mass spectra and retention indices database development for purposes of chemical weapons convention

The Chemical Weapons Convention (CWC) is a science-based international treaty for the disarmament and non-proliferation of chemical weapons. However, reference Orgaization for prohibition of chemical weapons (OPCW) central analytical database (OCAD) of structures with mass spectra (MS) and retention indices (RI) includes only minor part of all possible chemical species defined in the Schedules of CWC. In this work we employed OCAD in silico augmentation based on chemoinformatics approach for chemical structures enumeration, MS data generation based on message passing neural network and based on P-alkyl molecular pairs RI prediction to support the verification activities as provided for in the CWC. Enumerated 879 noncyclic and 5270 monocyclic alcohols became the basis for generating hundreds of thousands molecules of Schedule 1 toxic chemicals like Sarin, Tabun, VX and Novichok. Trained on ordinary and neutral loss electron ionization mass spectrometry (EI-MS) a message-passing neural network (MPNN) outperformed other quantum chemistry and machine learning methods. Generated by this MPNN in silico EI-MS are very similar to the library's spectra and allowed to reach desired match factor above 800 within a scale of 0–1000. Statistical data for molecular pairs based on P-alkyl fragments was collected and used to predict RIs within desired 20 RI window for some toxic chemicals of Schedule 1.A.01, for which in the current OCAD version RIs are absent.

In Situ Helium Isotope Microimaging of Meteorites.

Isotope imaging is commonly used to investigate the localization of trace elements and their isotopes. In situ noble gas analysis of meteorites revealed the distribution of primordial noble gases that were trapped in the building blocks of asteroids and planets during the early stage of the solar system evolution. Solar wind noble gases are among the primordial gases present in meteorites and were trapped through exposure to solar wind. Micrometer-resolution in situ noble gas analysis has not been achieved due to the lack of sensitivity and spatial resolution. The microscale imaging technique is crucial for identifying the carrier phase of the solar wind noble gases. We have developed 4He isotope imaging utilizing secondary neutral mass spectrometry with strong field postionization. This technique achieved a lateral resolution of 2 μm and a 4He detection limit of 2 × 1017 cm-3. This development allows for the study of a solar wind gas-rich meteorite, Northwest Africa 801 carbonaceous chondrite, with micrometer resolution. The solar wind 4He carriers are fine-grained particles and are sparsely scattered in the matrix region.

Alkali-metal-based molecular-ion secondary ion mass spectrometry for precise quantitative analysis of low-dimensional materials without standards

Advancement in the understanding of fundamental aspects of Secondary Ion Mass Spectrometry (SIMS) has made this technique to be extremely powerful for quantitative materials analysis. The secondary ion emission process is a complex phenomenon involving various mechanisms to understand the mechanism. Among the existing mechanisms, the “electron-tunneling model” is the most accepted concept in the understanding of ionization probability for positive and negative ions. This model essentially concerns the survival probability of an ion emitted from the surface. As the intensity of secondary ions of a certain element depends strongly on the efficiency of ionization of a sputtered atom or molecule, the “local surface chemistry” plays a significant role in the secondary ion emission. This is purported as the “Matrix Effect” in SIMS, making the technique extremely challenging for quantification of materials in spite of the fact that it has the highest detection sensitivity (<ppb) and exceptional depth-resolution (<1[Formula: see text]nm). Therefore, it is required to correct the “matrix effect” for quantitative analysis. If the probing element (M) in its close proximity sees an alkali element (such as Li, Rb, K, Na and Cs, referred to as “A”) on the sample surface, the sputtered neutral atom (M0) of the probing element can attach an alkali-ion forming a quasi-molecular (MA)[Formula: see text] ion. Such a phenomenon can also occur if an alkali ion beam is chosen as the primary beam for sputtering. The MA[Formula: see text] molecular ion formation is directly related to the atomic polarizability of the element M. Since the sputtering of neutral atom (M0) is unconnected with the formation of MA[Formula: see text] ion, the “matrix effect” decreases dramatically in the analysis using MA[Formula: see text] ions. The phenomenon is very similar to the mechanism of “secondary neutral mass spectrometry” (SNMS). Although these (MA)[Formula: see text] molecular ions are potentially applicable in the direct quantification of materials without the need for “calibration standards”, it generally has a weak intensity. In such a case, the (MA)[Formula: see text] molecular ions are preferred in the analysis because of their higher detection sensitivity (by a few orders of magnitude in some cases), compared to that of (MA)[Formula: see text] molecular ions. Monitoring of the molecular ions is routinely preferred in conventional SIMS experiments to discriminate the sputtered ion species which are affected by mass interference or have poor dynamic ranges. For example, while making the SIMS analysis of GaAs, carbon as an impurity element is detected by monitoring (AsC)[Formula: see text] molecular ions instead of C− ions, because the C− ions have high background arising from the carbon-containing residual-gas species in the analysis chamber. Caesium is decidedly chosen for MCs[Formula: see text] or MCs[Formula: see text] molecular ions in SIMS because of the strongest reactivity and electropositive nature of caesium. This paper deals with a comprehensive discussion on the ion-emission phenomena in sputtering, the “matrix effect” and its compensation, and the potential application of the “MCs[Formula: see text]-SIMS” ([Formula: see text]) in the effective quantitative chemical analysis of materials. A special prominence has been given to the quantification of low-dimensional materials, superlattices and quantum-confined structures using this state-of-the-art “MCs[Formula: see text]-SIMS” approach in all complexities.

Ar cluster bombardment of phenylalanine deposited on graphene-Effect of kinetic energy and projectile size.

This study investigates the effects of kinetic energy and projectile size on particle emission from a phenylalanine overlayer adsorbed on a graphene bilayer during argon projectile bombardment. Projectiles of various sizes (1-1000 atoms) and kinetic energies (0.5-40keV) are used to study their impact on the ejection efficiency, mass distribution, and kinetic and angular spectra of the emitted substances. Particle ejection mechanisms are discussed in scenarios with and without sample perforation. Additionally, this study investigated the potential use of graphene in secondary ion mass spectrometry or neutral secondary mass spectrometry analyses.

In situ neutral desorption-extractive electrospray ionization mass spectrometry reveals red-blue light promoted the accumulation of amino acids and polyphenols in Anoectochilus roxburghii

Light quality affects plant leaf growth and its metabolism of amino acids and polyphenols. Anoectochilus roxburghii has been used for food, medicine, and ornamental purposes. To obtain the optimal light quality for improved accumulation of metabolites in A. roxburghii in vitro. The seedings were cultured under the white light (W), blue light (B), red light (R), red: blue light = 1:2 (R1B2), red: blue light = 1:1 (R1B1), red: blue light = 2:1 (R2B1). Twenty compounds in raw leaves were in situ rapidly identified within 20 s by neutral desorption-extractive electrospray ionization mass spectrometry (ND-EESI-MS) without any sample pretreatment, including eight amino acids, eleven polyphenols, and kinsenoside. Meanwhile, leaf area and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were evaluated. Our results showed that leaf area and antioxidant enzyme activities of the R2B1 were significantly higher than B or R group. The red-blue light increased the content of isoleucine, histidine, serine, arginine, and promoted the accumulation of caffeic acid, ferulic acid, quercetin, myricetin, kaempferol, and rutin in phenylpropane metabolism, especially in the R2B1, which could be used as the optimal light quality. ND-EESI-MS could enhance our understanding of the effect of light quality on the accumulation of amino acids and polyphenols in A. roxburghii.

Effect of the kinetic energy on particle ejection process from carbon nanotubes bombarded by kilo-electron-volt C60

Molecular dynamics computer simulations are employed to investigate processes leading to particle ejection from single-wall carbon nanotubes bombarded by keV C60 projectiles. The effect of the primary kinetic energy, the incidence angle, and the nanotube diameter on the ejection process is studied. Armchair nanotubes with diameters of 3.26, 5.4, and 8.2 nm are tested. C60 projectiles bombard these targets with kinetic energy between 3 and 50 keV and the angle of incidence ranging between 0° and 75°. The particle ejection yield is a result of the interplay between the amount of kinetic energy available for breaking interatomic bonds, the size of the bombarded area, and the size and form of projectiles hitting this area. Much of the initial kinetic energy is dissipated in the nanotubes as waves, especially for low-energy impacts. Computer simulations are used to find the optimal conditions leading to the gentle ejection of unfragmented organic molecules adsorbed on nanotube substrates. This knowledge may be helpful in the potential application of nanotube substrates in secondary ion mass spectrometry or secondary neutral mass spectrometry.

Atomic transport in amorphous Mo-Cu and Ta-Cu immiscible systems

Metastable binary systems with positive enthalpy of mixing have practically no diffusional data in literature. Experimental data on Cu diffusion in amorphous immiscible systems such as Mo-Cu and Ta-Cu are presented in this study. These studies were conducted in sputtered Ni/Mo1−xCux/Ni and Ni/Ta1−xCux/Ni tri-layers, where the nanocrystalline Ni layers acted as effective sinks for Cu atoms located in the amorphous layers. The secondary neutral mass spectrometry (SNMS) technique allowed us to observe the out-diffusion of Cu into the Ni sink layer at temperatures between 100 °C and 250 °C. Additionally, high-resolution transmission electron microscopy (HR-TEM) and energy dispersive spectroscopy (EDX) was used to characterize Mo-Cu and Ta-Cu layers. As a result of a coupled diffusion equation being solved for both amorphous (source) and polycrystalline (sink) layers, we were able to construct best-fit concentration profiles and calculate Cu diffusion parameters for both layers. We assumed bulk diffusion in amorphous films, while transport along moving grain boundaries was assumed in polycrystalline Ni layers. With this model, we were able to replicate the observed profile features at the amorphous/polycrystalline interface. Based on these evaluations, the pre-exponential factors and activation energies are 5 × 10−14 m2/s, 55.3 ± 12 kJ/mol in Mo-Cu and 1.2 × 10−12 m2/s, 76 ± 19 kJ/mol in Ta-Cu systems.

Multi-element isotopic analysis of hot particles from Chornobyl

Microscopic fuel fragments, so-called “hot particles”, were released during the 1986 accident at the Chornobyl nuclear powerplant and continue to contaminate the exclusion zone in northern Ukraine. Isotopic analysis can provide vital information about sample origin, history and contamination of the environment, though it has been underutilized due to the destructive nature of most mass spectrometric techniques, and inability to remove isobaric interference. Recent developments have diversified the range of elements that can be investigated through resonance ionization mass spectrometry (RIMS), notably in the fission products. The purpose of this study is to demonstrate the application of multi-element analysis on hot particles as relates to their burnup, particle formation in the accident, and weathering. The particles were analysed with two RIMS instruments: resonant-laser secondary neutral mass spectrometry (rL-SNMS) at the Institute for Radiation Protection and Radioecology (IRS) in Hannover, Germany, and laser ionization of neutrals (LION) at Lawrence Livermore National Laboratory (LLNL) in Livermore, USA. Comparable results across instruments show a range of burnup dependent isotope ratios for U and Pu and Cs, characteristic of RBMK-type reactors. Results for Rb, Ba and Sr show the influence of the environment, retention of Cs in the particles and time passed since fuel discharge.

Corrosion of Passive Aluminum Anodes in a Chloroaluminate Deep Eutectic Solvent for Secondary Batteries: The Bad, the Good, and the Ugly.

The passivity of aluminum is detrimental to its performance as an anode in batteries. Soaking of native oxide-covered aluminum in a chloroaluminate deep eutectic solvent gradually activates the electrode surface, which is reflected in a continuously decreasing open circuit potential. The underlying processes were studied by analyzing the 3 to 7 nm thick layer of native oxide after increasing periods of soaking with secondary neutral mass spectrometry, X-ray photoelectron spectroscopy, and energy-dispersive spectroscopy in a transmission electron microscope. They consistently show permeation of electrolyte species into the layer associated with gradual swelling. After extended periods of soaking at open circuit potentials, local deposits of a range of foreign metals have been found in scanning electron microscopy images of the electrode surface. The pitting corrosion is caused by trace metal ion impurities present in the electrolyte and results in highly nonuniform current density distribution during discharge/charge cycling of battery cells as shown by local deposits of aluminum. The processes during soaking at open circuit potentials have been monitored by electrochemical impedance spectroscopy and could be analyzed by fitting an equivalent circuit model for pitting corrosion.

Production and characterization of standard particles for rL-SNMS

In this work, uranium-and plutonium-baring particles were produced by fast iron co-precipitation for the purpose of creating homogeneous multi-element standards. A set of single isolated particles showing no inhomogeneities in the element distribution were selected. These particles were used to determine the maximal achievable suppression ratios for uranium in Resonant Laser Secondary Neutral Mass Spectrometry (rL-SNMS) measurements of plutonium. It was shown for the first time directly that suppression-ratios in the order of three magnitudes are achievable with a resonant two-step excitation scheme for non-destructive measurements.

Grain boundary diffusion of Si in polycrystalline copper film

Grain boundary (GB) diffusion of Si in polycrystalline Cu film was studied in the temperature range of 403–453 K, in the C-type kinetic regime. The amorphous Si layer (80 nm) and polycrystalline Cu layer (40 nm) were successively deposited by magnetron sputtering at room temperature onto a Si (111) wafer. Appearance of Si atoms on the copper surface due to GB diffusion through the copper layer was detected by low energy ion scattering spectroscopy with high sensitivity. The depth distribution of Si in Cu grain boundaries was revealed by secondary neutral mass spectrometry. Surface morphology of Cu films was investigated by scanning tunneling microscopy. Identification of Si chemical bonds on the surface layer was made by X-ray photoelectron spectroscopy. GB diffusion coefficients were estimated by the relation used for calculation of diffusant distribution from a constant source in assumption that the diffusion path equals to the film thickness at the moment of appearing Si atoms on the Cu surface. At 453 K we estimated the surface segregation factor and detected formation of Cu–O–Si atomic bonds on the Cu film surface.

A Study on Decisive Early Stages in White Etching Crack Formation Induced by Lubrication

The reliability of rolling bearings is affected by white etching crack (WEC) or white structure flaking (WSF) failures, causing tremendous commercial burdens for bearing manufacturers and operators. The research for the underlying failure mechanism has attracted interest from a large scientific community over decades. Despite the significant amount of efforts, a root cause of white etching cracking is still missing. Amongst other factors, lubricant chemistry is considered to be essential in WEC formation. The authors aim to elucidate this key parameter by provoking white etching crack formation on a FE8 bearing test rig using a well-described set of chemicals in high- and low-reference lubricants. Scanning electron microscopy and energy dispersive X-ray analysis prove the presence of a patchy tribofilm on the surface of bearing washers, leading most likely to a higher frictional torque at the early stages of operation when the low reference oil is used. Secondary neutral mass spectrometry (SNMS) shows a hydrogen containing tribofilm in the shallow subsurface of about 30 nm depth, suggesting that hydrogen proliferating into bearing material may subsequently facilitate crack propagation via dislocation pileups, leading to premature bearing failure.

Excited-State N Atoms Transform Aromatic Hydrocarbons into N-Heterocycles in Low-Temperature Plasmas.

The direct formation of N-heterocycles from aromatic hydrocarbons has been observed in nitrogen-based low-temperature plasmas; the mechanism of this unusual nitrogen-fixation reaction is the topic of this paper. We used homologous aromatic compounds to study their reaction with reactive nitrogen species (RNS) in a dielectric barrier discharge ionization (DBDI) source. Toluene (C7H8) served as a model compound to study the reaction in detail, which leads to the formation of two major products at "high" plasma voltage: a nitrogen-replacement product yielding protonated methylpyridine (C6H8N+) and a protonated nitrogen-addition (C7H8N+) product. We complemented those studies by a series of experiments probing the potential mechanism. Using a series of selected-ion flow tube experiments, we found that N+, N2+, and N4+ react with toluene to form a small abundance of the N-addition product, while N(4S) reacted with toluene cations to form a fragment ion. We created a model for the RNS in the plasma using variable electron and neutral density attachment mass spectrometry in a flowing afterglow Langmuir probe apparatus. These experiments suggested that excited-state nitrogen atoms could be responsible for the N-replacement product. Density functional theory calculations confirmed that the reaction of excited-state nitrogen N(2P) and N(2D) with toluene ions can directly form protonated methylpyridine, ejecting a carbon atom from the aromatic ring. N(2P) is responsible for this reaction in our DBDI source as it has a sufficient lifetime in the plasma and was detected by optical emission spectroscopy measurements, showing an increasing intensity of N(2P) with increasing voltage.

Actinide imaging in environmental hot particles from Chernobyl by rapid spatially resolved resonant laser secondary neutral mass spectrometry

Radioactive particles, so-called hot particles, are of great importance in the risk assessment of environmental pollution and human health hazards. Since most of these particles are only a couple of micrometers in size and thus have correspondingly small atomic inventory, information on origin and composition is difficult to obtain. Many analytical methods do not give insight into isotopic details or require the complete use up of the particle. Resonant laser secondary neutral mass spectrometry (rl-SNMS) has been proven to be a well-suited method for quasi-non-destructive analysis of trace elements. The technique provides high suppression of isobaric interferences and high spatial resolution without necessitating extensive chemical preparation. To measure multiple elements, it is often necessary to switch between laser excitation schemes, requiring elaborate adaptation of the laser setup. Here we present a novel rL-SNMS system capable of multi-element measurements in short succession without any manual adjustment to the laser system. For demonstration, ten micrometer sized hot particles from the Chernobyl Exclusion Zone are analyzed and the obtained isotopic ratios of uranium, plutonium and americium are discussed.

Distribution of trace impurities in microvolumes and analysis of concentration using laser sputtered neutral mass spectrometry

The performance of semiconductor devices has been improved by the miniaturization and the adoption of various materials. Together with this improvement, it has become difficult to measure the amount of injected impurities to control the electrical conductivity under the three-dimensional microstructure. As the volume decreases, the lower limit of the concentration that can be defined increases. In a 10-nm cubic region of silicon, there are approximately 64 000 atoms. One atom is approximately 16 ppm, and concentrations below that level cannot be defined. The limitation on the measurement accuracy of the PN junction position becomes unclear. Generally, the electrical characteristics of a semiconductor device are determined by the position of the PN junction and the concentrations in the P and N regions. In this paper, we elucidate the interface state of a minute PN junction. Based on the above, we will examine the lowest extent to which the concentration of impurities can be measured in a microvolume, with the current physical analysis technology, assuming ideal measurement conditions without any disturbance. Finally, we measure the sensitivity improvement of mass spectrometry using postionization technology with a femtosecond pulse infrared laser and demonstrate that it is possible to improve the performance of the impurity measurement.

Imaging of I, Re and Tc plant uptake on the single-cell scale using SIMS and rL-SNMS

In radioecological studies, there is a significant need for understanding the plant uptake of radionuclides on a cellular level. The present work applies mass spectrometry to image the radionuclide distribution within the cellular structures of plants at varying concentrations. In a first step, plants of Daucus carota and Pisum sativum labelled with iodine and rhenium were examined, at concentrations in the range of 10 mM. Cross sections of several plant parts were imaged by secondary ion mass spectrometry (SIMS) after cryogenation in order to preserve cell structure. In a second step, the distribution of 99Tc in the two plant species was determined. For radiological reasons, a concentration three orders of magnitude lower was used, rendering measurements with SIMS impossible. Therefore, resonant laser secondary neutral mass spectrometry (rL-SNMS) was used for the first time to image 99Tc with suppression of molecular isobaric interferences. The measurement of only about 1010 atoms of 99Tc atoms is demonstrated and the distribution of 99Tc within a single epidermal cell is imaged.

Development, characterization, and first application of a resonant laser secondary neutral mass spectrometry setup for the research of plutonium in the context of long-term nuclear waste storage

Plutonium is a major contributor to the radiotoxicity in a long-term nuclear waste repository; therefore, many studies have focused on interactions of plutonium with the technical, geotechnical, and geological barriers of a possible nuclear waste storage site. In order to gain new insights into the sorption on surfaces and diffusion of actinides through these complex heterogeneous materials, a highly sensitive method with spatial resolution is required. Resonant laser secondary neutral mass spectrometry (Laser-SNMS) uses the spatial resolution available in time-of-flight secondary ion mass spectrometry (TOF-SIMS) in combination with the high selectivity, sensitivity, and low background noise of resonance ionization mass spectrometry (RIMS) and is, therefore, a promising method for the study and analysis of the geochemical behavior of plutonium in long-term nuclear waste storage. The authors present an approach with a combined setup consisting of a commercial TOF-SIMS instrument and a Ti:sapphire (Ti:Sa) laser system, as well as its optimization, characterization, and improvements compared to the original proof of concept by Erdmann et al. (2009). As a first application, the spatial distributions of plutonium and other elements on the surface of a pyrite particle and a cement thin section were measured by Laser-SNMS and TOF-SIMS, respectively. These results exemplify the potential of these techniques for the surface analysis of heterogeneous materials in the context of nuclear safety research.

Electrodeposition of ternary compounds for novel PV application and optimisation of electrodeposited CdMnTe thin-films

Growth of polycrystalline CdMnTe ternary compound thin films has been carried out using cathodic electrodeposition technique at different cathodic potentials. The range of the cathodic potentials used in this work has been chosen according to the cyclic voltammogram results. The CdMnTe thin films were electroplated from electrolyte containing CdSO4, TeO2 and MnSO4 in an acidic aqueous medium. Glass/fluorine-doped tin oxide (FTO) substrates have been used to electrodeposit the semiconductor layers. The structural, compositional, morphological, optical and electrical properties of the CdMnTe thin films were studied using X-ray diffraction (XRD), Sputtered neutral-mass spectroscopy (SNMS), Scanning electron microscopy (SEM), UV–Vis spectroscopy and Photo-electro-chemical (PEC) cell measurements respectively. The primarily grown as-deposited (AD) layers went through two different post-growth surface treatment conditions- heat-treated in air in the presence of CdCl2 (CCT) and heat-treated in air in the presence of GaCl3 (GCT). Results from the XRD indicated the polycrystalline nature of the electrodeposited films. The electroplated films have cubic crystal structures and the preferred orientation was found to be along the (111) plane of CdMnTe. Inclusion of Mn has been qualitatively observed using SNMS measurement. The optical energy bandgaps of the thin films were found to be varying between ~ 1.90 and ~ 2.20 eV. Though all the layers after post-treatment showed p-type electrical conduction, both p and n-type conductivity were obtained at different cathodic potentials for as-deposited materials. Comparison of the deposited layers to other electrodeposited ternary compounds has also been discussed.

Mass spectral database for TOF-SIMS of stable isotopes of Sr and Zr

Nuclear accidents (e.g., at the Chernobyl and Fukushima Daiichi nuclear power plants) release considerable amounts of radioactive pollutants into the environment. Radioactive particles in dust and soil can range from a few micrometers to several micrometers in size. Detection of these micrometer-sized particles requires a fast and effective analytical method. Because time-of-flight secondary ion mass spectrometry (TOF-SIMS) exhibits high spatial resolution and parallel detection capability, it is suitable for analyzing micrometer-sized radioactive particles. However, due to isobaric interferences, TOF-SIMS cannot effectively distinguish between isobaric elements such as 90Sr and 90Zr. Resonant ionization sputtered neutral mass spectrometry (R-SNMS) eliminates isobaric interferences and enables the measurement of isotope ratios of isotopes approaching the detection limit. However, R-SNMS cannot be performed independently because its results are based on the TOF-SIMS spectra. This study provides a database of reference spectra for Sr and Zr stable isotopes, which can act as important reference for further analysis of radioactive particles in environmental samples.

A UPLC-MRM-MS method for comprehensive profiling of Amadori compound-modified phosphatidylethanolamines in human plasma.

Phosphatidylethanolamines (PEs) are targets of non-enzymatic glycation, a chemical process that occurs between glucose and primary amine-containing biomolecules. As the early-stage non-enzymatic glycation products of PE, Amadori-PEs are implicated in the pathogenesis of various diseases. However, only a few Amadori-PE molecular species have been identified so far; a comprehensive profiling of these glycated PE species is needed to establish their roles in disease pathology. Herein, based on our previous work using liquid chromatography-coupled neutral loss scanning and product ion scanning tandem mass spectrometry (LC-NLS-MS and LC-PIS-MS) in tandem, we extend identification of Amadori-PE to the low-abundance species, which is facilitated by using plasma lipids glycated in vitro. The confidence of identification is improved by high-resolution tandem mass spectrometry and chromatographic retention time regression. A LC-coupled multiple reaction monitoring mass spectrometry (LC-MRM-MS) assay is further developed for more sensitive quantitation of the Amadori compound-modified lipids. Using synthesized stable isotope-labeled Amadori lipids as internal standards, levels of 142 Amadori-PEs and 33 Amadori-LysoPEs are determined in the NIST human plasma standard reference material. These values may serve as an important reference for future investigations of Amadori-modified lipids in human diseases.