Total Ion Current Chromatograms Research Articles

Methylation-GC-MS/FID-Based Glycosidic Linkage Analysis of Unfractionated Polysaccharides in Red Seaweeds.

Glycosidic linkage analysis was conducted on the unfractionated polysaccharides in alcohol-insoluble residues (AIRs) prepared from six red seaweeds (Gracilariopsis sp., Prionitis sp., Mastocarpus papillatus, Callophyllis sp., Mazzaella splendens, and Palmaria palmata) using GC-MS/FID analysis of partially methylated alditol acetates (PMAAs). The cell walls of P. palmata primarily contained mixed-linkage xylans and small amounts of sulfated galactans and cellulose. In contrast, the unfractionated polysaccharides of the other five species were rich in galactans displaying diverse 3,6-anhydro-galactose and galactose linkages with varied sulfation patterns. Different levels of cellulose were also observed. This glycosidic linkage method offers advantages for cellulose analysis over traditional monosaccharide analysis that is known for underrepresenting glucose in crystalline cellulose. Relative linkage compositions calculated from GC-MS and GC-FID measurements showed that anhydro sugar linkages generated more responses in the latter detection method. This improved linkage workflow presents a useful tool for studying polysaccharide structural variations across red seaweed species. Furthermore, for the first time, relative linkage compositions from GC-MS and GC-FID measurements, along with normalized FID and total ion current (TIC) chromatograms without peak assignments, were analyzed using principal component analysis (PCA) as a proof-of-concept demonstration of the technique's potential to differentiate various red seaweed species.

Characterization of the Volatile Constituents of Plai (Zingiber purpureum) by Gas Chromatography-Mass Spectrometry.

Zingiber purpureum Roscoe, known as plai in Thailand, is a perennial plant of the Zingiberaceae family and has traditionally been used in Southeast Asian countries to treat inflammation, pain, and asthma. In this study, we performed the characterization of the volatile constituents in ethyl acetate extracts of plai. Ethyl acetate extracts derived from the rhizomes of plai were subjected to gas chromatography-mass spectrometry, and the key peaks in the total ion current chromatograms were annotated or identified. In total, twenty-one compounds were identified using isolation procedures or standards, and nine compounds were annotated by comparing their Kovats retention index (RI) and electron ionization (EI) mass spectra with those in the literature. Most of the identifications were inconsistent with the tentative annotations found via library search and suggested that some peaks were incorrectly assigned in previous studies. Thus, to avoid further misannotations and contribute to the research on dereplication, the RI value, EI mass spectral data, and NMR spectroscopy data of the isolated compounds are reported.

Synthesis, spectral characterizations, vibrational spectroscopy, DFT-computations, antibacterial, antioxidant, and molecular docking studies of the novel (Z)-2-(5-((10-hexyl-10H-phenothiazin-3-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl) acetic acid

The Synthesized novel compound of (Z)-2-(5-((10-hexyl-10H-phenothiazin-3-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl) acetic acid (PTZTZ) was charecterized by nuclear magnetic resonance (1H, 13C), FTIR, UV–Visible, (Total Ion Current) Chromatogram, and ESI full mass spectrum analyses. The determination of DFT analyses of the PTZTZ optimized structure, geometric parameters, UV–Visible Spectroscopy, and FTIR, and their experimental measurement was compared with the resultant estimated results. The frontier molecular orbitals (FMOs), Mulliken's population analysis, and molecular electrostatic potential (MEP) of the title molecule were revealed by theoretical calculations using Gaussian 09 and the fundamental set B3LYP/6-311++G (d,p) level. According to Pharmacological Screening, the title compound showed strong bactericidal activity with a maximum zone of inhibition of (19.8 ± 0.5 mm) at 2.5 g/mL against Proteus mirabilis (MTCC 1771) and scavenging activity analysis of DPPH scavenging trait ranging from (38.8 ± 0.6% to 88.6 ± 4.0%), (H2O2) Hydrogen peroxide exhibited maximal scavenging property of 74.10.2% (p < 0.05), ABTS reducing potential exhibited maximum trait ranging from (39.1 ± 1.2% to 77.8 ± 6.4%), and Ferric reducing antioxidant power (FRAP) exhibited maximum Ferric reducing antioxidant power (FRAP) potential trait ranging from (16.0 ± 0.6% to 43.6 ± 0.5%). Using Discovery Studio 4.0 and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) profile analysis tools, in-silico molecular docking studies revealed the active pocket of the 1HD2 protein to evaluate the evaluation of genotoxicology. Using molecular docking, the compound PTZTZ displayed a greater binding interaction energy of -240.3 (Kcal/mol) against the target protein. The greatest results of this research show that phenothiazine derivatives have superior activity and extremely low binding energy toward the active pocket of protein. In DFT investigations, the title compound demonstrated a minimal energy band gap.

Simultaneous quantification of all B vitamins and selected biosynthetic precursors in seawater and bacteria by means of different mass spectrometric approaches

B vitamins have high microbiological relevance in the marine environment, but their very low concentrations and the chemical heterogeneity of the individual vitamins make their analysis challenging. Mass spectrometric analysis of B vitamins in environmental samples at trace levels has mainly been performed using triple quadrupole mass spectrometers operated in targeted analysis mode. The development of such a method can be laborious and error prone. Additionally, high-resolution mass spectrometers can be used to measure a sample in full scan mode and subsequently search the total ion current chromatogram for extracted ion chromatograms of targeted vitamins. Three different analytical approaches for trace analysis of all B vitamins and some of their biosynthetic precursors were optimized and compared on two different mass spectrometers. A triple quadrupole mass spectrometer in selected reaction monitoring mode, and a high-resolution orbitrap mass spectrometer in parallel reaction monitoring, as well as in full scan mode were employed. Detection limits down to 10 ng/L were achieved with all three techniques. The methods were applied to a marine water sample from the North Sea and to the cell extract of a bacterial culture of Phaeobacter inhibens. Most vitamins and precursors were found in the bacterial cell extract and the seawater sample with all three measuring methods. The results of this study emphasize that, in addition to tandem mass spectrometry, high-resolution full scan mass spectrometry is a promising technique for the simultaneous detection of structurally diverse B vitamins in complex natural samples. This enables highly sensitive measurements without loss of detailed mass spectrometric information, which is inevitable when using a triple quadrupole system in MS/MS mode.Graphical abstract

The effect of alternating fragmentor voltages of LC-MS in full scan mode on data quality: A comparative study

The use of chemometrics for liquid chromatography-full scan mass spectrometry data analysis has become popular in untargeted metabolomics and targeted quantitative analysis. However, MS parameters that affect data quality are often neglected by researchers. The present study aims to investigate the effect of in-source fragmentor voltage, a key parameter in full scan mode, on the quality of LC-MS data mainly from the perspective of quantitative analysis. Published full scan LC-MS data recorded at four alternating fragmentor voltages were analyzed by self-weighted alternating trilinear decomposition (SWATLD) algorithm. Predicted results and analytical figures of merit of analytes were selected as key indicators for evaluating data quality. Fragmentor voltage indirectly affects figures of merit of an analyte by changing its total ion current chromatogram (TIC) intensity and extent of in-source fragmentation (ISF). No significant correlation is observed between selectivity (SEL) and fragmentor voltage. Sensitivity (SEN) and limit of detection (LOD) are mainly influenced by the TIC intensity of the analyte. Hence, considering the uncertainty effect of fragmentor voltage on SEL, as a compromise, fragmentor voltage at which the analyte has the maximum TIC intensity will be selected as the optimum one, which can ensure better SEN and LOD results. This work may provide new insights into the quality evaluation of full scan LC-MS data recorded at different fragmentor voltages, and help researchers to achieve the best analytical performance when conducting targeted quantitative analysis.

Stability of Wheat Floret Metabolites during Untargeted Metabolomics Studies.

A typical metabolomic analysis consists of a multi-step procedure. Variation can be introduced in any analysis segment if proper care in quality assurance is not taken, thus compromising the final results. Sample stability is one of those factors. Although sophisticated studies addressing sample decay over time have been performed in the medical field, they are emerging in plant metabolomics. Here, we focus on the stability of wheat floret extracts on queue inside an auto-injector held at 25 °C. The objective was to locate an analytical time window from extraction to injection with no significant difference occurring in the sample. Total ion current chromatograms, principal component analysis, and volcano plots were used to measure changes in the samples. Results indicate a maximum work window time of 7:45 h for Steele-ND wheat methanolic extractions in an auto-sampler at 25 °C. Comparisons showed a significant gradual increase in the number and intensity of compounds observed that may be caused by the degradation of other molecules in the sample extract. The approach can be applied as preliminary work in a metabolite profiling study, helping to set the appropriate workload to produce confident results.

Non‐invasive and non‐destructive Raman spectroscopic characterization of some Brazilian ethnographic resins

AbstractThe chemical investigation of museum collection items can provide key information on the provenance and technical aspects involved in their production and, additionally, can help in the establishment of restoration and conservation strategies of rare or valuable assets. Natural organic materials are challenging because of their chemical complexity and expected degradation. In this work, eight ethnographic resins from different sites in the Amazon and central areas in Brazil were studied by FT‐Raman spectroscopy aiming at the non‐invasive and non‐destructive identification of their chemical composition; chromatographic methods (Thin Layer Chromatography and Gas Chromatography–Mass Spectrometry—TLC and GC‐MS, respectively) were used as destructive confirmatory techniques. The samples were classified into five groups, each one presenting a common set of spectroscopic features: diterpenoid resins with chemical composition similar to the Brazil copal in some cases with carotenoids in their composition as did the triterpenoid resins also identified. Additionally, two gums (polysaccharides) were detected, and two very dark samples only generated a thermal or a luminescent background (1064 and 632.8 nm excitation, respectively). Total ion current (TIC) chromatograms from these very dark samples only showed peaks assigned to fatty acids probably because the resinous compounds were not soluble in the solvent used in GC‐MS analysis. These results show that resin‐containing museum assets in the Brazilian ethnographic context can be studied directly by Raman spectroscopy, contributing to a better understand of the culture of indigenous peoples from resin provenance, uses and processing for example. The results will be used as a database to be compared with certified reference samples, when available.

Coelomic fluid of Echinometra mathaei: The new prospects for medicinal antioxidants

Echinoid pigments have various biological properties such as antioxidant, cytotoxic, and antibacterial activities. We aimed to evaluate the extraction of cell-free coelomic fluid (CFCF) and coelomocyte lysate (CL) as well as qualitatively and quantitatively identify the coelomic fluid of Echinometra mathaei as a new source of polyhydroxylatednaphthoquinone (PHNQ) antioxidant pigments. Based on the High Performance liquid chromatography–electrospray mass spectrometry (HPLC-MS) analysis in negative mode, the main quinonoid (PHNQ) pigments were identified and quantified. This study also illustrated the total ion current chromatograms and related mass spectra of Spinochrome A, Spinochrome B, Spinochrome C, and Echinochrome A in CL and SpinochromeC in CFCF samples. The ions at 221, 279, 265 and 263 m/z correspond to the pseudo-molecular [M − H] ions of Spinochrome B, Spinochrome C, Echinochrome A, and Spinochrome A, respectively. These components have previously been noted from the shells and spines of sea urchins but identification of PHNQs pigments in CL and CFCF of E. mathaei using LC-MS was introduced for the first time. The results also showed that, the highest DPPH radical scavenging activity of CFCF (88.12 DPPH% scavenging at 70 μg/mL, IC50 = <10 μg/mL). The findings clearly suggest that the coelomic fluid of E. mathaei could be served as the promising as well as potential natural antioxidants in the medical and pharmaceutical industries and could replace the increasing prices of the commercial antioxidants products.

Identification of Components in Citri Sarcodactylis Fructus from Different Origins via UPLC-Q-Exactive Orbitrap/MS.

To systematically analyze the chemical constituents of Citri Sarcodactylis Fructus (CSF) from different origins, an efficient approach based on ultraperformance liquid chromatography plus Q-Exactive Orbitrap tandem mass spectrometry (UPLC-Q-Exactive Orbitrap/MS) detection for the discrimination of chemical components from of 15 batches of CSF from four main origins was used in this research. Through parent peaks, fragment peaks, fragmentation characteristics, and comparative analysis with the literature and reference standards, a total of 77 components from the methanol extracts including 18 coumarins, 24 flavonoids, seven organic acids, three limonoids, and 25 other compounds were detected and identified. Among them, 15 components have not been reported previously in the CSF. Notably, the stachydrine peak initially showed a higher content in the total ion current chromatogram. Overall, CSF produced in the Zhejiang province contained a richer variety of chemical compositions. These observations provided a theoretical basis for the further quality assessment and application of CSF.

Detection-confirmation-standardization-quantification: a novel method for the quantitative analysis of active components in traditional Chinese medicines

Background Quantitative analysis of the active ingredients of Traditional Chinese Medicine is a research tendency. The objective of this study was to build a novel method, namely, Detection-confirmation-standardization-quantification (DCSQ), for the quantitative analysis of active components in traditional Chinese medicines, without individual reference standard. Methods Danshen (the dried root of Radix Salvia miltiorrhiza) was used as the matrix. The “extraction” function in high-performance liquid chromatography-mass (HPLC-MS) instrument was used to find the peaks corresponding to cryptotanshinone, tanshinone I, and tanshinone IIA in the total ion current (TIC) chromatogram of Danshen. The multicomponent reference standard (MCRS) containing the three tanshinones mainly was prepared by preparative HPLC. The contents of them in the resulting MCRS were determined by NMR; moreover, the constituents of the MCRS were confirmed. The MCRS containing known content of the three tanshinones was used as the reference standard for the quantitative analysis of cryptotanshinone, tanshinone I and tanshinone IIA in Danshen Samples by analytical HPLC. Results The optimized HPLC conditions for the quantitative analysis of the active components in Danshen were established, and the assignments of the extracted peaks were confirmed by analyzing the characteristic fragments in their MS/MS product ion spectra and UV spectra. Then, the MCRS containing the three tanshinones were successfully prepared. The results of determination about the contents by NMR showed linearity fitted with high likelihood and calibration curves possessed high linearity. The results of determination on Danshen Samples obtained through DCSQ exhibited minimal deviations, in contrast to those obtained through individual reference standards. Conclusion The establishing DCSQ is independent and convenient for the quantitative analysis of the active components in TCMs by MCRS, without individual reference standard. This method is a great advance in quantitative analysis for complex composition, especially TCMs.

GC × GC-TOFMS and chemometrics approach for comparative study of volatile compound release by tobacco heating system as a function of temperature

Tobacco heating products (THPs) are designed to heat tobacco to produce a nicotine-containing aerosol without combustion. Although THP aerosol is less complex mixture than cigarette smoking, there are a few reports related to the relationship between its chemical composition and its taste and aroma profiles. This study, therefore, aims to characterise the chemical composition of particulate phase aerosol (PPA) in a model THP system heated at different temperatures (100 °C; 150 °C; 200 °C; 240 °C; and 290 °C). The particulate phase of collected THP aerosol was extracted and analysed by GC × GC-TOFMS. The bidimensional total ion current (TIC) chromatograms were analysed using the SIMPLISMA algorithm, together with Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA) to extract key compounds. The semi-quantification was carried out based on similarity (Match), reverse match factor (R. Match) and linear retentions index (LRI). A total of 123 compounds responsible for important taste and aroma characteristics were identified and quantified in the model THP PPA. Although the concentration of compounds increased with the heating temperature, their release rate could be clustered into six groups based on HCA. Four of them, representing 92% of evaluated compounds showed a maximum release ratio at 290 °C, with distinct release behaviours that could fit into either linear, second order polynomial and exponential models. The purposed approach is useful for characterizing volatile compounds related to the taste and aroma profile in the THP system. In addition, these findings suggested that selecting a suitable heating temperature is a critical factor in THP system design in order to optimise tobacco taste and aroma.

Integrated qualitative analysis of polymer sample by pyrolysis-gas chromatography combined with high-resolution mass spectrometry: Using accurate mass measurement results from both electron ionization and soft ionization.

Gas chromatography/mass spectrometry (GC/MS) is a powerful analytical tool used to separate and then identify volatile compounds through library database searches. However, as not all compounds are registered in these databases, it is not uncommon to detect unregistered components. Therefore, new analytical techniques were developed that utilize methods of identification beyond database searches alone. Acquire data by using electron ionization (EI) and soft ionization (SI) with high-resolution mass spectrometry (HRMS). Use the EI mass spectra to library search for matches. Use the SI mass spectra for accurate mass analysis of the EI molecular ions. Conduct an isotope pattern analysis of the molecular ion to refine the possible candidate compositions. Use these compositions as a constraint for the accurate mass analysis of the EI fragment ions. If a given molecular ion formula is not correct, the EI fragment ions will not show good matches. Finally, all analytical results are integrated into a color-coded qualitative analysis report. The capabilities of this new integrated analytical method were assessed for a polymer resin sample that was measured by using pyrolysis-gas chromatography/high resolution time-of-flight mass spectrometry. A total of 161 compounds were detected in the total ion current chromatogram, and 154 of these compounds were identified as having only one chemical formula candidate with this new integrated qualitative analysis method. This new integrated qualitative analysis method gives analytical results independent of library search results. It can be applied to a variety of SI methods including chemical ionization, photoionization, field ionization, and low-energy EI.

Development of an Enhanced Total Ion Current Chromatogram Algorithm to Improve Untargeted Peak Detection.

Accurate analyte peak detection from the background noise is a fundamental step in data analysis. Often, this is initially performed on the total ion current chromatogram (TIC), which is the summed signal from all mass spectral channels. Despite the detection of many of the most abundant peaks within a chromatogram, a large fraction of peaks remains undetected in the standard TIC due to their signal being below the limit of detection. To find peaks obscured by background noise, an untargeted peak detection method termed the "enhanced TIC algorithm" was developed for comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS). The reported algorithm utilizes the entire mass spectral dimension to find regions of analytical signal above a threshold while zeroing the background noise. The resulting chromatographic data is summed together to create the enhanced TIC. The utility of the enhanced TIC algorithm is demonstrated using serial dilutions from a 10 parts-per-thousand (ppth) test mixture. For the chromatograms collected at 1 and 10 parts-per-million (ppm), the enhanced TIC algorithm recovered 62% and 93%, respectively, of the original peaks observed in the 10 ppth mixture, while the standard TIC recovered only 0% and 45%, respectively. The improvement in signal enhancement was also shown on a separation of a yeast cell metabolite extract, where the enhanced TIC found 33-64% more peaks than the standard TIC. Chromatographic simulations with increasing levels of background noise were also conducted to compare the enhanced and standard TICs in the context of statistical overlap theory (SOT). Simulated chromatograms with lower signal-to-noise were more accurately modeled by the SOT after enhanced TIC processing compared to those processed by the standard TIC. The enhanced TIC method demonstrates an immense benefit in peak discovery to improve data analysis efforts.

GC/MS analysis on anorectics adulterated in traditional chinese medicines

A gas chromatography/mass spectrometry analytic method was developed for simultaneously identifying and quantitating anorectics synthetic drugs illegally adulterated in traditional Chinese medicines (TCM). A model sample of TCM (Farng-Feng-Tong-Shewg-Saan) was spiked with 11 kinds of synthetic drugs: amphetamine, methamphetamine, methylphenidate, clobenzorex, phentermine, fenfluramine, phenylpropanolamine, caffeine, mazindol, diazepam, diethylpropion. The sample was extracted with methanol. The GC/MS conditions were as follows: initial temperature 70°C, holding 2 mins., ramping rate was 10°C/min by linear, final temperature 280°C, holding 5 mins. The samples were scanned by HP5973 GC/MSD with a quadrupole mass filter in an electron impact mode (70eV), and a total ion current (TIC) chromatogram was obtained with multiple peaks. Comparison was made of the mass chromatograms and retention time of each peak with a created library. The matching quality of each synthetic drug spiked in TCM was not less than 85%. The retention time of each ingredient was consisted with the data created in the library. In quantitative analysis, this method with selected ion monitoring (SIM) analysis was performed. Dextromethophan HBr (50 μg/) was used as internal standard. Excellent calibration curves of each analytic compounds had ploted, and correlation coefficients were between 0.9967 and 0.9999, The RSD of interday and intraday studies was between 3.48∼5.52% and 3.07∼6.66%. The results showed that the established method is quite suitable for determination of anorectics adulterated in TCM samples. By this method, the following was found: 0.44 mg/tab of mazindol in high-fibrous food tablets; 24.35 mg/cap of clobenzorex, 1.06 mg/cap of caffeine, and 0.54 mg/cap of diazepam in herbal capsules; 28.42 mg/cap of phentermine in slimming capsules; 27.33 mg/pack of phentermine and 11,75 mg/sachet of caffeine in TCM dispensing packs.

Untargeted/Targeted 2D Gas Chromatography/Mass Spectrometry Detection of the Total Volatile Tea Metabolome.

Identifying all analytes in a natural product is a daunting challenge, even if fractionated by volatility. In this study, comprehensive two-dimensional gas chromatography/mass spectrometry (GC×GC-MS) was used to investigate relative distribution of volatiles in green, pu-erh tea from leaves collected at two different elevations (1162 m and 1651 m). A total of 317 high and 280 low elevation compounds were detected, many of them known to have sensory and health beneficial properties. The samples were evaluated by two different software. The first, GC Image, used feature-based detection algorithms to identify spectral patterns and peak-regions, leading to tentative identification of 107 compounds. The software produced a composite map illustrating differences in the samples. The second, Ion Analytics, employed spectral deconvolution algorithms to detect target compounds, then subtracted their spectra from the total ion current chromatogram to reveal untargeted compounds. Compound identities were more easily assigned, since chromatogram complexities were reduced. Of the 317 compounds, for example, 34% were positively identified and 42% were tentatively identified, leaving 24% as unknowns. This study demonstrated the targeted/untargeted approach taken simplifies the analysis time for large data sets, leading to a better understanding of the chemistry behind biological phenomena.

A new potential anti‐cancer beta‐carboline derivative decreases the expression levels of key proteins involved in glioma aggressiveness: A proteomic investigation

Gliomas remain highly fatal due to their high resistance to current therapies. Deregulation of protein synthesis contributes to cancer onset and progression and is a source of rising interest for new drugs. CM16, a harmine derivative with predicted high blood-brain barrier penetration, exerts antiproliferative effects partly through translation inhibition. We evaluated herein how CM16 alters the proteome of glioma cells. The analysis of the gel-free LC/MS and auto-MS/MS data showed that CM16 induces time- and concentration-dependent significant changes in the total ion current chromatograms. In addition, we observed spontaneous clustering of the samples according to their treatment condition and their proper classification by unsupervised and supervised analyses, respectively. A two-dimensional gel-based approach analysis allowed us to identify that treatment with CM16 may downregulate four key proteins involved in glioma aggressiveness and associated with poor patient survival (HspB1, BTF3, PGAM1, and cofilin), while it may upregulate galectin-1 and Ebp1. Consistently with the protein synthesis inhibition properties of CM16, HspB1, Ebp1, and BTF3 exert known roles in protein synthesis. In conclusion, the downregulation of HspB1, BTF3, PGAM1 and cofilin bring new insights in CM16 antiproliferative effects, further supporting CM16 as an interesting protein synthesis inhibitor to combat glioma.

A rapid dicrimination of wheat, walnut and hazelnut flour samples using chemometric algorithms on GC/MS data

There is a worldwide growing trend in developing methods for determining authenticity and detecting adulteration in food products. In this study an approach utilizing gas chromatography—mass spectrometry (GS/MS) combined with chemometric multivariate data analysis was proposed in order to determine discrimination and classification possibilities of flour samples produced from 16 genotypes of wheat, 9 genotypes of hazelnut, and 8 genotypes of walnut, grown in the Vojvodina region, Republic of Serbia. Plant samples were milled into flour, lipid fraction was extracted with n-hexane and derivatized using a 0.2 M TMSH solution and analyzed on a GC/MS device. Molecular ions of eluting lipid components were selected, isolated from total ion current chromatograms and their peaks employed in further data processing. Unsupervised exploratory data analysis techniques: principal component analysis (PCA), expression heat mapping, hierarchical cluster analysis (HCA) and principal coordinate analysis (PCoA) were used to select the most important variables, and to explore their potential in discrimination of investigated flour samples according to belonging botanical origin. PCA and heat maps demonstrated that molecular ions of methyl esters of four fatty acids: 270 (palmitic), 294 (linoleic), 296 (oleic), and 298 (stearic), were most discriminative variables, HCA and PCoA showed a clear and strong separations between groups of analyzed samples. A support vector machine (SVM) algorithm was employed in order to classify samples in three groups. The performance of the classification SVM model was excellent, achieving high coefficient of determination of 98.6, with only 1 value being misclassified.

Polyethyleneimine as weak anionic exchanger adsorbent for clean-up in pesticide residue analysis of fruits and vegetables

Pesticide residue analysis in fruits and vegetables is generally performed with the QuEChERS method, when clean-up is mainly achieved with primary secondary amine (PSA) by dispersive solid phase extraction (dSPE). In this work, we present a rapid and efficient method for the clean-up of fruit and vegetable extracts with polyethyleneimine (PEI) as alternative to PSA. Clean-up of QuEChERS extracts with a mixture of branched PEI adsorbed on magnesium sulfate and silica gel was realized in 10 min, when several polar matrix components were clearly reduced. The success of the clean-up for representative matrices was visualized by both high-performance thin-layer chromatography with different detection options and total ion current chromatograms of liquid chromatography–mass spectrometry analyses. Generally, dSPE clean-up with PEI was at least equally effective as dSPE with PSA, but PEI clearly superimposed PSA in terms of adsorption capabilities towards fatty acids. After clean-up of fatty acid mixtures with 150 and 300 mg/L, total fatty acids were reduced by 98% and 99%, respectively, while PSA left two- and three-fold quantities. Additionally, the susceptibility of base-labile pesticides towards PEI as compared to PSA generally was negligible, further supporting the high suitability of PEI for clean-up in pesticide residue analysis. Thus, clean-up with PEI enables a clear reduction of various matrix compounds in fruit and vegetable extracts and provides a rapid, convenient and low-cost alternative to the existing dSPE methods with PSA.

Analysis of Active Metabolites of Sophora flavescens for Indoleamine 2,3-dioxygenase and Monoamine Oxidases using Ultra-Performance Liquid Chromatography-Quadrupole time-of-Flight Mass Spectrometry

As part of ongoing research on natural products derived from medicinal plants for enzyme inhibition, known dibenzoyl derivatives (1–3, 11 and 20), pterocarpans (4, 15 and 19), flavanones (5, 7, 10, 12–14, 18, 21–24, 26, 27, 29, 31–33, 35, 36, and 38–46), flavones (6, 16, 28, 30 and 37), isoflavones (8 and 17), furocoumarins (9), and chalcones (25 and 34) have been tentatively identified within fractions of Sophora flavescens roots (SFR) using the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTof-MS) technique. The extract and column fractions inhibited indoleamine 2,3-dioxygenase (IDO) and monoamine oxidases (MAOs) differently depending on the metabolite groups. The majority of rich fractions were shown to have residual activities of 49–59% at 10 μg/mL (IDO) and 11.7–34.9% at 50 μg/mL (MAOs) or below. In the total ion current (TIC) chromatogram, significant markers for the metabolites of the bioactive-guided fractions were identified; pterocarpans (4, 15 and 19), flavanones (5, 10, 12–14, 18, 21–23, 26, 29 31–33, 35, 36, and 38–46), isoflavones (8 and 17), furocoumarins (9), dibenzoyl derivatives (11 and 20), flavones (16, 28, 30 and 37), and chalcones (25 and 34) were evaluated among forty-six analyzed metabolites. Possible bioactive markers could be deduced using a data library and previous references, and information regarding spectroscopic characterization and optimal target metabolites was obtained.

Using Cross-Correlation with Pattern Recognition Entropy to Obtain Reduced Total Ion Current Chromatograms from Raw Liquid Chromatography-Mass Spectrometry Data

Abstract Total ion current chromatograms (TICCs) generated by liquid chromatography-mass spectrometry (LC-MS) are prone to noise from chemical and electronic sources. This noise can severely impact the detection of analytes in a mixture. Recently, we introduced a new variable selection tool based on Pattern Recognition Entropy (PRE) that selects good quality (high signal-to-noise ratio) mass chromatograms from an LC-MS dataset and thereby creates a reduced TICC with low noise and a flat background (J. Chrom. A.2018, 1558, 21–28). PRE, which is based on Shannon’s entropy, was shown to be a straightforward and powerful shape recognition tool for this problem. However, while the chromatographic signals in the reduced TICC from PRE were well resolved, some noise remained in the TICC, which suggested that the algorithm had selected some false positives, i.e., poor quality mass chromatograms. In this paper, we report an improved version of the PRE algorithm that utilizes a second variable selection filter based on cross-correlation (CC). As a check on the ability of PRE and CC to select high quality mass chromatograms, every mass chromatogram in our data set (1451 in total) was individually inspected and rated as either high quality (green), intermediate quality (yellow), or poor quality (red). A color-coded plot of the CC value vs. the PRE value for the mass chromatograms was created, which shows that, as expected, the higher quality mass chromatograms are localized in its upper left quadrant, which corresponds to lower PRE values and higher CC values. In our original paper on this topic, we recommended a threshold of 0.5 σ for PRE, which caused the algorithm to select 151 mass chromatograms out of 1451. Of these, 98 were of high quality, 6 were of intermediate quality, and 47 were of poor quality. Using a second threshold for CC, the algorithm retains all the high and intermediate quality mass chromatograms, while removing all 47 of the poor quality ones. The resulting TICC from the PRE-CC algorithm shows less noise compared to the TICC generated from the PRE approach alone. The PRE-CC algorithm is arguably a faster, simpler and more intuitive approach as compared to the widely used CODA_DW algorithm.