Accurate mass determination,quantification and determination of detection limits in liquid chromatography–high-resolution time-of-flight mass spectrometry: Challenges and practical solutions

Uniform guidelines for the data processing and validation of qualitative and quantitative multi-residue analysis using full-spectrum high-resolution mass spectrometry are scarce.     

High-resolution laser ablation-inductively coupled plasma-mass spectrometry imaging of cisplatin-induced nephrotoxic side effects

Two-dimensional elemental mapping (bioimaging) via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was performed on 5 μm thick formalin-fixed, paraffin-embedded kidney tissue sections from Cynomolgus monkeys administered with increasing pharmacological doses of cisplatin. Laterally resolved pixels of 1 μm were achieved, enabling elemental analysis on a (sub-)cellular level. Zones of high Pt response were observed in the renal cortex, where proximal tubules are present, the epithelium of which is responsible for partial reabsorption of cisplatin. Histopathological evaluation, of hematoxylin and eosin-stained serial sections, adjacent to the sections probed via LA-ICP-MS, revealed minimal to mild cisplatin-related lesions (<100 μm) in the renal cortex. Necrotic proximal tubules with sloughed epithelial cells in their lumen could be linked directly to the areas with the highest accumulation of cisplatin, indicating a direct link between cellular concentration and toxicity, thereby providing more insight into the mechanisms through which renal damage occurs.     

Averaging scheme for atomic resolution off-axis electron holograms

All micrographs are limited by shot-noise, which is intrinsic to the detection process of electrons. For beam insensitive specimen this limitation can in principle easily be circumvented by prolonged exposure times. However, in the high-resolution regime several instrumental instabilities limit the applicable exposure time. Particularly in the case of off-axis holography the holograms are highly sensitive to the position and voltage of the electron-optical biprism. We present a novel reconstruction algorithm to average series of off-axis holograms while compensating for specimen drift, biprism drift, drift of biprism voltage, and drift of defocus, which all might cause problematic changes from exposure to exposure. We show an application of the algorithm utilizing also the possibilities of double biprism holography, which results in a high quality exit-wave reconstruction with 75 pm resolution at a very high signal-to-noise ratio.     

The ν12 band of C2D4

The Fourier transform infrared (FTIR) absorption spectrum of the ν₁₂ fundamental band of ethylene-d₄ (C₂D₄) was recorded in the 1017-1137 cm⁻¹ region with an unapodized resolution of 0.0063 cm⁻¹. Upper state (v₁₂ = 1) rovibrational constants consisting of three rotational and five quartic constants were improved by assigning and fitting 2103 infrared transitions using Watson’s A-reduced Hamiltonian in the I^r representation. The band centre of the A-type ν₁₂ band is found to be 1076.98480 ± 0.00002 cm⁻¹. The present analysis covering a wider wavenumber range and higher J and K_c values yielded upper state constants including the band centre which are more accurate than previously reported. The rms deviation of the upper state fit is 0.00045 cm⁻¹. Improved ground state rovibrational constants were also determined from the fit of 1247 ground state combination differences (GSCD) from the presently-assigned infrared transitions of the ν₁₂ band of C₂D₄. The rms deviation of the GSCD fit is 0.00049 cm⁻¹. In the rovibrational analysis, local frequency perturbations were not detected even at high J and K_a values. The calculated inertial defect Δ₁₂ is 0.32551 ± 0.00001 μŲ. The line intensities of the individual transitions in the ν₁₂ band were measured and the band strength of 39.8 ± 2.0 cm⁻² atm⁻¹ was derived for the ν₁₂ band of C₂D₄.     

High-resolution infrared spectrum of cyanogen

The high-resolution spectrum of cyanogen (¹⁴N¹²C¹²C¹⁴N) has been measured from 500 to 4900 cm⁻¹. For this isotopomer many combination levels with both degenerate fundamentals, ν₄ and ν₅, have been measured for the first time and the effects of vibrational l-type resonance are observed as well as rotational l-type resonance. The effects of the vibrational resonance coupling ν₂ and 2ν₄ have also been studied. The data have been combined with earlier measurements below 500 cm⁻¹ to give a comprehensive catalog of the vibrational energy levels and the rovibrational constants for the normal isotopomer of cyanogen. A comparison of the term value constants for the three major symmetric isotopomers is given and they are compared with a recent ab initio calculation. The present data were combined with earlier work on the two symmetric isotopomers, ¹³C₂¹⁴N₂ and ¹²C₂¹⁵N₂, to obtain the equilibrium bond lengths, r_CC = 138.109(60) pm and r_CN = 115.976(40) pm.     

15N216O在1650-3450 cm-1的高分辨红外光谱

采用傅里叶变换红外光谱仪记录了富含¹⁵N₂¹⁶O同位素的一氧化二氮样品在1650-3450 cm^-1波段的高分辨振转光谱,得到了该同位素分子超过7300吸收谱线位置的实验值,经分析实验精确度好于5.0×10^-4 cm^-1. 基于有效哈密顿量模型预测和带带转动分析,确定了所有吸收线的归属;获得了29个新吸收带的振转光谱参数,并优化了其他44个吸收带的光谱参数值. 并且发现有效哈     

Studies on the growth and characterization of tris (glycine) calcium(ΙΙ) dichloride—a nonlinear optical crystal

A systematic characterization of a novel nonlinear optical material tris (glycine) calcium(ΙΙ) dichloride (TGCC) is performed. The solubility and metastable zone width of TGCC were studied. TGCC single crystal of dimensions 34×23×5 mm³ was grown by the slow evaporation technique. Single crystal X-ray diffraction studies reveal that the crystal belongs to orthorhombic system. Energy dispersive X-ray analysis confirms the presence of elements in the crystal. Structural perfection of the as-grown single crystal was studied through multicrystal X-ray diffraction analysis. The thermal characteristics of TGCC were analyzed by thermogravimetric and differential thermal analysis and differential scanning calorimetry. The transmittance of TGCC crystal has been used to calculate the optical band gap of the crystal. Chemical etching studies of TGCC crystal was carried out. The dielectric and mechanical behavior of the crystals were analyzed. The second harmonic conversion property of TGCC was identified by the Kurtz and Perry powder technique and was observed to be higher than that of KDP.     

A new approach to untargeted integration of high resolution liquid chromatography–mass spectrometry data

Because of its high sensitivity and specificity, hyphenated mass spectrometry has become the predominant method to detect and quantify metabolites present in bio-samples relevant for all sorts of life science studies being executed. In contrast to targeted methods that are dedicated to specific features, global profiling acquisition methods allow new unspecific metabolites to be analyzed. The challenge with these so-called untargeted methods is the proper and automated extraction and integration of features that could be of relevance. We propose a new algorithm that enables untargeted integration of samples that are measured with high resolution liquid chromatography–mass spectrometry (LC–MS). In contrast to other approaches limited user interaction is needed allowing also less experienced users to integrate their data. The large amount of single features that are found within a sample is combined to a smaller list of, compound-related, grouped feature-sets representative for that sample. These feature-sets allow for easier interpretation and identification and as important, easier matching over samples. We show that the automatic obtained integration results for a set of known target metabolites match those generated with vendor software but that at least 10 times more feature-sets are extracted as well. We demonstrate our approach using high resolution LC–MS data acquired for 128 samples on a lipidomics platform. The data was also processed in a targeted manner (with a combination of automatic and manual integration) using vendor software for a set of 174 targets. As our untargeted extraction procedure is run per sample and per mass trace the implementation of it is scalable. Because of the generic approach, we envision that this data extraction lipids method will be used in a targeted as well as untargeted analysis of many different kinds of TOF-MS data, even CE- and GC–MS data or MRM. The Matlab package is available for download on request and efforts are directed toward a user-friendly Windows executable.     

Coherent Vibrational Dynamics and High-resolution Nonlinear Spectroscopy： A Comparison with the Air/DMSO Liquid Interface

We present a comparative study on the C-H stretching vibrations at air/DMSO （dimethyl sulfoxide） interface with both the free-induction decay （FID） coherent vibrational dynamics and the sub-wavenumber high resolution sum-frequency generation vibrational spectroscopy measurements. In principle the frequency-domain and time-domain spectroscopic measurements should generate identical information for a given molecular system. However, when the molecular systems are with several coupled or overlapping vibrational modes, obtain- ing detailed spectroscopic and coherent dynamics information is not as straightforward and rather difficult from either the time-domain or the frequency domain measurements. For the case of air/DMSO interface that is with moderately complex vibrational spectra, we show that the frequency-domain measurement with sub-wavenumber high-resolution sum-frequency generation vibrational spectroscopy is probably more advantageous than the time- domain measurement in obtaining quantitative understanding of the structure and coherent dynamics of the molecular interface.     

Rovibrational laser jet-cooled spectroscopy of the NH3–Ar complex in the ν2 umbrella region of NH3: comparison between new infrared data and an ab initio calculated spectrum*

ABSTRACT

Five ortho and para bands of the ν₂ umbrella mode of the NH₃–Ar van der Waals complex have been recorded at high resolution using jet-cooled infrared laser spectroscopy. A rovibrational analysis provides accurate band centres and upper state rotational constants for the Π_s(j?=?1,k?=?0)?←?Σ_a(j,k?=?0) and Σ_s(j?=?1,k?=?0)?←?Σ_a(j,k?=?0) ortho bands. The puzzling para bands observed in the region of the lower and upper components of the inversion splitting doublet have been assigned by comparison with rovibrational and tunnelling levels and transitions calculated ab initio. The latter calculations are based on the four-dimensional potential energy surface reported by Loreau et al. [J. Chem. Phys. 141, 224303 (2014)], which takes explicitly into account the umbrella motion of the ammonia molecule. The very good agreement found between Π_s/a,lower(j?=?1,k?=?1)?←?Σ_a(j?=?1,k?=?1) and Π_s/a,upper(j?=?1,k?=?1)?←?Σ_s(j?=?1,k?=?1) experimental and calculated transitions has been exploited to determine precisely two different inversion splittings in the ν₂ state (32.003(1) and 36.008(1)?cm^?1) from extrapolated Q(0) line frequencies and to obtain a qualitative picture of Coriolis couplings present in both the ν₂?=?0 and ν₂?=?1 states.