查看更多>>摘要：Planar chiral halogenated ferrocenes have come in useful as synthetic intermediates over the years, allowing for the preparation of functionalized derivatives for catalysis, material science, optoelectronics, and medicinal chemistry. Despite their chemical interest, few halogenated planar chiral ferrocenes have been prepared in enantiopure form by asymmetric synthesis so far. Enantioselective HPLC on polysaccharide-based chiral stationary phases (CSPs) has been used for resolving planar chiral ferrocenes making both enantiomers available. However, the enantioseparation of derivatives containing halogens or alkyl groups exclusively remains rather challenging. Given this context, in this study the enantioseparation of eleven dihalogenated planar chiral ferrocenes was systematically explored by using five polysaccharide-based CSPs under multimodal elution conditions. Baseline enantioseparations were achieved for nine analytes with separation factors (α) ranging from 1.15 to 1.66. Thermodynamic quantities associated with the enantioseparations were derived from van't Hoff plots, and for 1-halo-2-(iodoethynyl)ferrocenes (1-halogen = F, Cl, Br) halogen-dependent thermodynamic profiles were identified on a cellulose tris(3,5-dimethylphenylcarbamate)-based column. The impact of CSP structure and mobile phase (MP) polarity on the enantioseparation was evaluated. In addition, with the aim to unravel the functions of halogen substituents in mechanisms and noncovalent interactions underlying selector-selectand complex formation at molecular level, local electron charge density of specific molecular regions of the interacting partners were evaluated in terms of calculated electrostatic potential (V) and related source function (SF) contributions. On this basis, the impact of halogen type and position on the enantioseparation was investigated by correlating theoretical and experimental data.
查看更多>>摘要：The influence of amino acid residue on μ-opioid receptor agonist tetrapeptide Tyr-Arg-Phe-Lys-NH2 analogue chromatographic behaviour on crown ether based chiral stationary phases has been investigated. S- and R-(3,3′-diphenyl-1,1′-binaphthyl)-20-crown-6 chiral selectors in commercially available CROWNPAK CR-I (+) and (-) columns are both each other enantiomers, thus, under the same LC conditions, retention of Tyr-Arg-Phe-Lys-NH2 DXXX enantiomers (fixed in D-tyrosine position) on S-chiral selector do not significantly differ from the retention times of their LXXX antipodes, obtained on R-chiral selector (and vice versa), allowing us to study the apparent separation of a specific tetrapeptide enantiomeric pair, without obtaining the actual racemate. Ten tetrapeptides (LLLL-isomers) have been synthesized with the aim to cover a wider range of different amino acid classes. Histidine, glutamic acid, cysteine, leucine and tryptophan were introduced at the N-terminus or Phe position of Tyr-Arg-Phe-Lys-NH2 tetrapeptide structure. The effects of the amino acid residue with emphasis on retention, enantioseparation, as well as the influence of position of the amino acid residue in tetrapeptide sequence, are discussed.
查看更多>>摘要：? 2022Online liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) has attracted much attention in the molecular characterization of crude oil. Neither open access nor commercially available petroleomics tools were developed specifically to process LC-HRMS data. Here, a novel data processing pipeline was specifically designed for LC-HRMS-based petroleomics data. A customizable formula database was established deriving from the detected sample, which could avoid the interference caused by a large number of redundant molecules in a conventionally theoretical molecular database. Molecular formula candidates were assigned by the formula database using a low noise threshold, and false-positive assignments were eliminated by the chromatographic retention behaviors. Multi-dimensional information was obtained, including heteroatom class, double bond equivalent (DBE), carbon number, retention time, and MS/MS spectra. The developed method was compared with a popular petroleomics software, similar relative abundance class distribution was obtained, and much more formulas of low abundant components were uniquely extracted by the developed method. Finally, it was applied to reveal variation between feed and product oils in hydrodenitrogenation. Significantly compositional and structural differences were revealed. The developed method provides a useful pipeline for molecular data mining of petroleum samples.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, porous aromatic frameworks (PAFs) with different pore size were evaluated for simultaneous adsorption of 16 polycyclic aromatic hydrocarbons (PAHs) with large difference in polarity and molecular size. Two other porous organic polymers containing electron pushing/withdrawing group were investigated along for a comparison, and PAF-120 with the pore size of appr. 2.1 nm exhibited the highest extraction efficiency. Based on water contact angle and molecular dynamics simulation, the adsorption of 16 PAHs on PAF-120 was attributed to hydrophobic interaction, π-π interaction and molecular sieving effect. PAF-120/PDMS coated stir bar was then prepared by physical adhesion, and a method of stir bar sorptive extraction-gas chromatography-flame ionization detector was established for trace PAHs analysis in environmental samples. Under the optimal experimental conditions, the limits of detection (S/N = 3) for 16 PAHs were found to be in the range of 42-375 ng/L, with the relative standard deviations of 4.1-14.6% (n = 7). The enrichment factors varied from 31 (Indeno[1,2,3-cd]pyrene) to 80-fold (anthracene), with the maximal enrichment factor of 100-fold. The proposed method was applied to the analysis of PAHs in local environmental water and atmospheric particle samples. None of the 16 PAHs were detected in the collected water samples. While for the collected atmospheric particles, 12 PAHs were detected in fine particulate matter (PM2.5) within the range of 0.6-2.8 ng/m3. For inhalable particulate matter (PM10) and total suspended particulate matter (TSP), 16 PAHs were all detected in the range of 0.6-3.8 ng/m3 and 0.6-5.9 ng/m3, respectively. Quantitative recoveries were obtained in recovery test, demonstrating the accuracy and application potential of the proposed method.
查看更多>>摘要：? 2022Alteration of the enantiorecognition ability of polysaccharide-based chiral columns in the shipping normal phase (NP) eluent after exposition to polar organic (PO) mode eluents can be conceived as an incomplete hysteresis cycle. Non-standard solvents provide a solution to overcome this issue with immobilized stationary phases, but a procedure was missing so far to regenerate coated stationary phases from the altered state. Recent results with alcohol mixtures within the PO mode showed that an appropriate order of standard solvents may also be suitable to complete hysteresis. Using an analogous approach, a simple protocol was established to regenerate the original NP retentions on various stationary phases containing amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) chiral selector after the change induced by flushing with 2-propanol or ethanol. The members of a chemically diverse compound set indicated that alterations in retentions and selectivities using different brands and types of ADMPC-based stationary phases can be quite different, but the recovery of the original state was very good for all of them. The proposed protocol eliminates the need of the costly dedication of a chiral column with ADMPC selector to either NP or PO mode. Furthermore, the limits of the alcohol content in the mobile phase compositions where the system is free of hysteresis were determined.
查看更多>>摘要：? 2022A newly designed magnetic layered double hydroxide composite modified with a natural deep eutectic solvent derived from choline chloride and sucrose was synthesized and applied as a sorbent for the enrichment of organochlorine pesticides. The magnetic solid phase extraction (MSPE) procedure was optimized via a small central composite design and response surface methodology. The MSPE method was able to preconcentrate the organochlorine residues in environmental samples prior to GC–MS analysis. Good analytical performance of the proposed method was observed with an enrichment factor of up to 158 and low limits of detection in the ranges of 0.002–0.015 μg·L?1 and 0.03–0.10 ng·g?1 for water and soil, respectively. Satisfactory recoveries for spiked water and soil samples were obtained in the ranges of 80.9–104.7% (RSDs<7.9) and 88.8–104.1% (RSDs<7.3), respectively. This finding highlights the role of natural deep eutectic solvents as modifying agents for magnetic layered double hydroxides, which enhance the efficiency of extraction of the target analytes. The developed MSPE/GC–MS procedure was sensitive and reliable for the determination of trace organochlorine residues in environmental samples.
查看更多>>摘要：? 2022Liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) has become the default platform for proteomics due to its specificity, sensitivity and sample compatibility. However, interactions between transition metals in LC systems and analytes containing phosphate groups result in poor chromatographic performance or even analyte loss. The use of systems where the metal surfaces had been treated with a hybrid inorganic/organic surface material to form an effective surface barrier mitigated these undesired interactions. When employed for the analysis of tryptic digests of Alpha and Beta Casein, along with synthetic “PhosphoMix” standards, the use of such a system showed significant improvements in chromatographic peak shape and analyte response together with superior spectral quality and sequence coverage. These improvements resulted in the detection of phosphorylated peptides ADEP[Formula presented]SESDLEIDK and ELSN[Formula presented]PLRENSFG[Formula presented]PLEFR from the PhosphoMix which went undetected with a standard, untreated LC system. The hybrid surface system thus offered significant advantages for the analysis of phosphopeptides compared to conventional LC/MS.
查看更多>>摘要：? 2022Hair is becoming a main matrix for forensic drug analyses due to its large detection window compared to traditional matrices (i.e. urine & blood) and the possibility of establishing the temporal pattern of drug consumption. However, the extremely time- and solvent-consuming nature of conventional sample treatments render it difficult for routine use of hair analysis in forensics. In this paper, this drawback was intended to be addressed by the use of hexanol-based supramolecular solvents (SUPRAS) with restricted-access properties. The aim was to develop a fast and interference-free sample treatment workflow for the determination of opioids, cocaine, amphetamines and their metabolites in human hair. The main variables affecting the extraction were optimized and the method was validated following the European Medical Agency guideline. Major advantages of the proposed method were the straightforward sample preparation, which combines a high extraction yield (93–107%) and matrix effect removal (93–102%SSE) in a single step, the high sample throughput, and the reduced volume of organic solvent required (100 μL of SUPRAS per sample), which makes sample treatment cost-effective and eco-friendly. Method quantification limits were lower enough for all the target drugs (0.5–1.1 pg mg?1) to allow their quantitation in human hair routine analyses. The method was successfully applied to the determination of drugs of abuse in a human hair control sample.
查看更多>>摘要：? 2022In the current study, natural cotton fiber was served as the supporter of water, and the water acted as an extractant for liquid-phase microextraction of polar components in low-polar edible oils. An in-syringe extraction device was constructed to facilitate the extraction process by simply loading a certain amount of cotton fibers between the syringe needle and the plastic syringe tube. Then, the extraction process can be conveniently conducted by pull-push the syringe plunger. It can be regarded as a new type of dynamic liquid-phase microextraction method while operated more convent. For the feasibility study, the novel in-syringe cotton fiber-supported liquid extraction (CF-SLECF-SLE) pretreatment method was applied to extract free 3-mono-chloropropane-1,2-diol (3-MCPD) in edible oils. Specifically, the cotton fibers supported a certain amount of water by successfully pulling-pushing 1 mL of water and 1 mL of HEX in/out twice, respectively. Then, 2.0 mL of diluted oil sample (containing 0.4 g oil) was loaded in and out four times for extraction, during which process 3-MCPD was extracted into the supported water. The extracted 3-MCPD was desorbed with 1 mL of ethyl acetate (EA), derivatized with trimethyl silane imidazole (TMSI), and analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). For three different spiked edible oils, the internal standard normalized matrix effect (IS-normalized ME) values were in ranges of 96.3–104.8% with RSD being 4.3%, benefiting the accurate quantitative analysis. The limit of quantification (LOQ) was calculated to be 2 ng/g, which met the regular determination requirement of 3-MCPD in edible oils. Satisfied linearity was obtained in 2–500 ng/g, with correlation coefficients (R2) being 0.998. The relative recoveries were in the ranges of 96.9–110.5%. The intra-/inter-day RSDs were less than 8.2% and 10.2%, respectively. The proposed method provides an efficient, simple, low-cost, and easy to automate strategy for determining free 3-MCPD in edible oils.
查看更多>>摘要：? 2022A new ‘shape-orientated’ continuous wavelet transform (CWT)-based algorithm employing an adapted Marr wavelet (AMW) with a shape matching index (SMI), defined as peak height normalized wavelet coefficient (C′max/H) for feature filtering, was developed for chromatographic peak detection and quantification. Exploiting the chromatographic profile of a candidate peak, AMW-SMI algorithm emphasizes more on the matching of the overall chromatographic profile to a reference Gaussian shape, while partly alleviates the requirement on the signal intensity derived from single or several data points, thus it allows the detection of low-intensity features from metabolites at low abundance. AMW-SMI imposes maximum and minimum thresholds on the ridgeline width and length to define a valid ridgeline, which corresponds to a more stably shaped chromatographic profile. The maximum wavelet coefficient Cmax′(a0,b0) on the valid ridgeline determines the translation b0 as the peak center. AMW-SMI detects the valley lines to define the peak boundaries, which is important to obtain accurate peak quantification. As a more ‘shape-orientated’ peak detection algorithm, various methods related to the ‘shape’ are introduced for feature filtering, out of which, the effective SNR (eSNR) is defined to evaluate if the shape is strong or good enough relative to the ‘shape noise’, and the SMI, which can quantitatively evaluate the shape quality regardless of the data intensities and peak width, is applied to filter out the poorly shaped false positives. AMW-SMI performs Gaussian fitting of all data points between the defined peak boundaries to refine the peak parameters, and the refined SMI, SNR and peak width can be applied for further feature filtering and reinforce the ‘shape-quality’ of final selected peaks. The performance of AMW-SMI is evaluated qualitatively (by recall, precision and F-score) and quantitatively (by ratio of isotopic features and triplicate RSD) on the LC-MS data of model mixtures of 21 human metabolite standards and 8 plant metabolite standards, and of serum sample spiked with the 21 human metabolite standards, and on the triplicate LC-MS data of the same sample of cell metabolomic extracts. Compared with XCMS (centWave) and MZmine 2 (ADAP), the proposed AMW-SMI algorithm can faithfully identify chromatographic peaks with significantly fewer false positives and demonstrated general superiority in terms of qualitative precision (robustness) and quantitative accuracy (by ratio of isotopic features), and comparable recall (sensitivity) and quantitative stability (by RSD of triplicate measurements).
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