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Panax ginseng C.A.Mey is a famous natural herbal medicine worldwide. Mountain-cultivated ginseng (MCG) and garden-cultivated ginseng (GCG) are two types of Panax ginseng. There is a significant difference in economic benefits between MCG and GCG, which can always lead to problems such as adulteration and substitution of MCG with lower-priced alternatives. We explored the quality marker of ginseng at the intact protein level and established a foundation for the quality control of ginseng. Cellulose nanocrystal assisted sample preparation combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) equipped with a high mass detector was performed to analyze intact proteins in ginseng. The results revealed that the ribonuclease-like storage protein is the most abundant protein in MCG and GCG. Meanwhile, the molecular weight of the ribonuclease-like storage protein showed great difference between different ginseng species, which is 26.2 kDa in MCG and 24.2 kDa in GCG. The ribonuclease-like storage protein glycosylation modification difference provides data support for the differentiation between MCG and GCG. This study showed that glycosylated modified ribonuclease-like storage protein can be a crucial quality marker of ginseng, facilitating the rapid distinction between MCG and GCG., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Tobacco smoke exposure significantly increases the level of global nucleoside damage. To evaluate all aspects of nucleic acid (NA) modifications, NA adductomics analyzes DNA, RNA and nucleobase adducts and provides comprehensive data. Liquid chromatography-tandem triple quadrupole mass spectrometry (LC-QQQ-MS/MS) and LC-Zeno-TOF-MS/MS were employed to screen for DNA, RNA and nucleobase adducts, as part of the analytical platform that was designed to combine high sensitivity and high resolution detection. We identified and distinguished urine nucleoside adducts via precursor ion and neutral loss scanning. A total of 245 potential adducts were detected, of which 28 were known adducts. The smoking group had significantly higher concentrations of nucleoside adducts in rat urine than the control group, based on MRM scanning, which was then used to perform relative quantitative analysis of these adducts. Urine nucleoside adducts were further confirmed using LC-Zeno-TOF-MS/MS. This highlights the potential of untargeted detection methods to provide comprehensive data on both known and unknown adducts. These approaches can be used to investigate the interactions among oxidative and alkylation stresses, and epigenetic modifications caused by exposure to tobacco smoke., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Currently, it is of great urgency to develop a rapid pre-classification and screening method for suspected drugs as the constantly springing up of new psychoactive substances. In most researches, psychoactive substances classification approaches depended on the similar chemical structures and pharmacological action with known drugs. Such approaches could not face the complicated circumstance of emerging new psychoactive substances. Herein, mass spectrometry imaging and convolutional neural networks (CNN) were used for preliminary screening and pre-classification of suspected psychoactive substances. Mass spectrometry imaging was performed simultaneously on two brain slices as one was from blank group and another one was from psychoactive substance-induced group. Then, fused neurotransmitter variation mass spectrometry images (Nv-MSIs) reflecting the difference of neurotransmitters between two slices were achieved through two homemade programs. A CNN model was developed to classify the Nv-MSIs. Compared with traditional classification methods, CNN achieved better estimation accuracy and required minimal data preprocessing. Also, the specific region on Nv-MSIs and weight of each neurotransmitter that affected the classification most could be unraveled by CNN. Finally, the method was successfully applied to assist the identification of a new psychoactive substance seized recently. This sample was identified as cannabinoids, which greatly promoted the screening process., Competing Interests: Declaration of competing interest We declare that none of the authors have competing financial or non-financial interests as defined by Nature research., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The combination of electrochemistry and mass spectrometry is a powerful analytical tool for studying redox reaction mechanisms and identifying products or intermediates. However, the previously reported devices all require bespoke fabrication and are too complicated to be assembled and used by others. Crucially, the long ion transport distance and small spray volumes make it difficult to capture the short-lived intermediates. We present a practical mass spectrometric method in which surface-modified carbon fiber paper is innovatively applied to detect electrogenerated intermediates. Treating carbon fiber paper with dilute nitric acid removes its surface impurities, enhancing the capability of electro-redox. Electrospray ionization and redox reaction occur simultaneously on the tip of the paper. Transient electro-redox species generate and transfer into gas phase as soon as the appearance of spray. Rapid transport of quantities of electrogenerated ions to the mass spectrometer inlet makes it possible for mass spectrometric identification on the millisecond scale. The short-lived radical cations and iminium ions were successfully captured, reflecting the starting step of the cross-dehydrogenation coupling reaction. The real-time oxidation and online functionalization reactions of tertiary amines were achieved using this device without additional oxidants and electrolytes. In this way we could achieve in-depth mechanistic understanding and rapid screening of serial reactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Carbon fiber paper (CFP) is commonly used as a proton exchange membrane in fuel cells due to its prominent areal electrosorption capacity, exceptional conductivity and excellent chemical stability. In this paper, we first explored the feasibility of carbon fiber paper as a specific paper substrate in paper spray ionization mass spectrometry (PSI-MS). The results demonstrated that CFPSI-MS combines the merits of PSI and carbon fiber ionization (CFI) and exhibits better performance of various compound analyses than either of these techniques alone. The application of CFP can highly enhance the signal stability and detection sensitivity of a diverse array of analytes, especially in negative ionization mode. The ion intensity of target analytes such as saccharides and flavonoids was improved 2-90-fold. Many nonpolar/low-polarity analytes, such as polycyclic aromatic hydrocarbons, which are difficult to ionize by traditional PSI-MS, were successfully detected by CFPSI-MS with a 2.5 kV high voltage. Moreover, CFPSI-MS presents high sensitivity in semiquantitative analysis, and the limits of detection (LODs) of cyclic adenosine monophosphate (CAMP), naringin and tivantinib in whole blood were improved 2-100-fold compared to those in traditional PSI-MS. In real sample analysis, CFPSI-MS also exhibits excellent capability in human breath analysis and blood metabolomic profiling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Although matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a simple, rapid, and high-throughput assay, its microchannel plate (MCP) detector is limited by the low sensitivity and ion saturation effect when analyzing macromolecules. Herein, we introduced a strategy that combined MALDI-TOF MS with electron multiplier (EM) for the direct analysis of exosomal proteins isolated from human plasma and serum. The results demonstrated that EM yielded a higher sensitivity than MCP detector in high-mass range (m/z 5000-100000). Through the analysis of MALDI-TOF MS coupled with EM, chemokine (C-X-C motif) ligand 12 (CXCL12) ion at m/z 7960 and its degradation products at m/z 7927, 7587, and 7553 were identified as characteristic exosomal proteins in plasma. CXCL4 ion at m/z 7765 was identified as a characteristic protein in serum exosomes. Additionally, the peak intensity of CXCL12 and CXCL4 standards exhibited great linear relationship (CXCL12, R 2  = 0.989; CXCL4, R 2  = 0.986) with the concentrations (ranging from 0.1 to 20 μg/mL) when using EM as detector. In conjunction with ultrasonic assisted matrix coating technology (UAMCT), this assay repeatability in our lab has been excellent with coefficient of variation (CV%) of 4.6% for CXCL12 and 9.3% for CXCL4. Finally, the spectra demonstrated that the intensity of exosome related peaks was significantly enhanced in plasma and serum of patients with Parkinson's disease (PD) (m/z 7553, P < 0.01; m/z 7587, P < 0.01; m/z 7927, P < 0.001; m/z 7980, P < 0.001; m/z 7765, P < 0.01), Alzheimer's disease (AD) (m/z 7553, P < 0.001; m/z 7587, P < 0.001; m/z 7927, P < 0.001; m/z 7980, P < 0.001), and ischemic cerebrovascular disease (ICD) (m/z 7553, P < 0.05; m/z 7587, P < 0.05; m/z 7927, P < 0.01; m/z 7980, P < 0.05; m/z 7765, P < 0.05) compared to that in healthy persons. The fingerprint information of CXCL12 in plasma exosomes has better clinical relevance than serum exosome CXCL4 in MALDI-TOF MS analysis., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Ultrasonic extraction and nebulization in real-time/carbon fiber ionization mass spectrometry (UEN/CFI-MS) was developed to screen the synthetic drugs adulterated into herbal products such as antidiabetic drug, antihypertensive drug, and hypolipidemic drug. Recently, ambient ionization MS techniques have achieved great advance for rapid analysis of sample surface. However, direct analysis of the analytes inside samples remains a challenge due to a lack of effective online sample extraction procedures. Owing to disappointing desorption efficiency, analytes inside the sample suffer from low detecting sensitivity when applying ambient ionization MS techniques. In this study, online ultrasonic extraction combined with carbon fiber ionization was used for real-time extraction, nebulization and detection of the analytes inside samples. The ultrasonic atomizer could produce a high-frequency vibration to realize online extraction and nebulization of sample. Then, the produced sample droplets could be immediately ionized by the carbon fiber ionization mass spectrometry. UEN/CFI-MS has shown great compatibility to solvents and compounds with a wide range of polarity and has few limitations for the shape of sample. UEN/CFI-MS was successfully applied for the rapid screening of synthetic drugs adulterated into herbal products. Among 37 batches of herbal products, 1 batch of Chinese patent medicine and 6 batches of dietary supplements were detected to be adulterated with the synthetic chemicals without labeling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Routine microbial identification by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has been achieved based on the spectra of ribosomal proteins with molecular masses between 2000 and 20000Da. It is a rapid, cost-effective, and simple method to characterize different species of microorganisms. But for some subspecies of molds, there are high similarities between their spectra in 2000-20000Da, it makes them indistinguishable in this mass range. Based on the specialized metabolite production, there are obvious differences between the high resolution spectra of the same samples in 600-2000Da. It allows the rapid discrimination of these microbial subspecies. The ability of the method to discriminate microbial subspecies was demonstrated by characterizing three different Aspergillus niger strains. Furthermore, this approach has been applied to discriminate two different Acremonium alternatum strains which were collected from mildew plants. It demonstrated the applicability of the method to the actual samples. The high resolution MS in the range of 600-2000Da was presented as a complementary approach for the routine method in 2000-20000Da. The molds could be identified into species-level group by the spectra between 2000 and 20000Da and the strains within each group could be further discriminated based on differences in metabolites. The spectra between 2000 and 20000Da and the spectra between 600 and 2000Da were obtained from the same samples, which extracted with the same method. There is no need of additional pre-processing to obtain the high resolution spectra. It potentially provides a powerful tool for the fast and accurate identification of microbial subspecies., (Copyright © 2019 Elsevier B.V. All rights reserved.)

It is difficult to conduct rapid quantitative studies by direct analysis of mass spectrometry because of the matrix effects. In order to overcome the matrix effects in rapid quantitative analysis of complex sample and to find a rapid mass spectrometry method for capsaicin quantitation, the thermal desorption carbon fiber ionization mass spectrometry (TD-CFI-MS) was developed and optimized. TD-CFI-MS allows timesaving, less cost, less solvent consumption and no auxiliary gas. In this method the metal ceramics heater (MCH) was used for analyte desorption. The protonated water clusters in carbon fiber ion source provided proton for analytes through ion-molecular interactions. Desorption and ionization processes were separated in time and space so the analyte was less affected by the matrix during ionization, and the signal intensity of the analyte was enhanced. The matrix effects were investigated by the quantitative analysis of capsaicin in various samples using TD-CFI-MS, and the results were within 93.3-97.6% which indicated that almost no significant effects on the quantitation of capsaicin by this method. Finally, TD-CFI-MS was successfully applied for the quantitation of capsaicin in various real samples including foods and medicines indicating that this technique was a valuable strategy., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ambient flame ionization (AFI) coupled with triple quadrupole tandem mass spectrometry was developed for quantitative analysis of sodium saccharin (SAC) in various food samples. Typically, the micro-flame by the combustion of n-butane provided a heating zone for fast desorption and ionization of analytes in milliseconds. Then high ion abundance of analyte could be produced in a short time, which made AFI-MS possess a very high sensitivity for SAC detection and was particularly appropriate for the quantification in multiple reaction monitor (MRM) mode. Liquid samples were introduced into outer flame using dip-it tips in order to facilitate a rapid and high-throughput analysis. Saccharin-d4 was used as the internal standard to compensate for the variations of the ion intensities. With a minimal sample preparation, a linear range of 4-100 μg/mL was developed with all linear relationships of different matrices (including coke, juice, liquors, sunflower seeds and sweetmeats) greater than 0.992. Recoveries for coke and apple matrices were ranged from 88.4% to 108.9% at the concentration of 5, 20, 80 μg/mL and the limits of detection (LODs) were in the range of 0.12-0.21 μg/mL. Furthermore, the feasibility of this method was exhibited by the quantification analysis of SAC in seventeen real samples. These results indicated that AFI-MS was a valuable strategy for rapid screening detection and precise quantification analysis of SAC in food., (Copyright © 2018 Elsevier B.V. All rights reserved.)

9-Xanthydrol was introduced as an assisted-extraction-reagent to quantify ethyl carbamate (EC) in wines by heart-cutting multidimensional gas chromatography coupled with mass spectrometry (MDGC-MS). 9-Xanthydrol could help to increase the extraction efficiency, because it could react with ethyl carbamate to form the low-polar product, which facilitated the transfer of ethyl carbamate into organic phase. Then the reaction product was decomposed in high temperature, so ethyl carbamate could be obtained again in injector port. Heart-cutting multidimensional gas chromatography coupled with mass spectrometry was used not only for avoiding 9-xanthydrol interference but also for getting a larger volume injector, higher sensitivity and lower limit of detection. The method was optimized and validated in terms of sample volume, sodium chloride, the acid concentration, the 9-xanthydrol concentration and the reaction time. Good linear relationship (R 2  = 0.9998) over the concentration range of 2.00 μg L -1 - 200.00 μg L -1 was obtained. The limit of detection (LOD, 0.02 μg L -1 ) and quantification (LOQ, 0.10 μg L -1 ) were lower than previously reported. The RSDs of precision (repeatability and reproducibility) were lower than 8.15%, and the recovery (96.17-99.25%) and accuracy (99.21-110.93%) were validated as well. This methodology was applied to the quantification of ethyl carbamate in several different fermented wines with values ranging from 13.05 to 155.20  μg L -1 ., (Copyright © 2017 Elsevier B.V. All rights reserved.)

N-(1-chloroalkyl)pyridinium quaternization was developed for the derivatization of fatty aldehydes. Differing from common pre-charged reagents, non-charged pyridine and thionyl chloride were designed to add permanently charged tag on aldehydes. Pyridine was far less competitive than charged derivatives in ionization. Thionyl chloride in excess was quenched by deionized water, converting into less residual sulfur dioxide bubbles. Thus solutions could be tested directly by mass spectrometry without further post-treatments. Pyridine-d5 labeled fatty aldehydes were prepared as internal standards. Mixed derivatives were then analyzed by high performance liquid chromatography coupled to positive electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Analytical parameters including reaction yield, stability, precision, linearity, and detection limits (LODs < 0.3 pg mL(-1)) were carefully validated. This method facilitated the analysis low content (ng mL(-1)) levels of free aliphatic aldehydes (C6C18) in human thyroid carcinoma and para-carcinoma tissue with a simple pretreatment procedure. Content of long chain nonvolatile aldehydes (C10C18) remarkably increased in thyroid carcinoma tissues (p < 0.05)., (Copyright © 2016. Published by Elsevier B.V.)

A rapid method for fatty acids (FAs) comparative profiling based on carboxyl-specific stable isotope labeling (SIL) and direct infusion electrospray ionization-ion mobility-mass spectrometry (ESI-IM-MS) is established. The design of the method takes advantage of the three-dimensional characteristics of IM-MS including drift time, m/z and ion intensity, for comparison of d0-/d6-2,4-dimethoxy-6-piperazin-1-yl pyrimidine (DMPP)-labeled FAs. In particular, without chromatographic separation, the method allowed direct FAs profiling in complex samples due to the advantageous priority of DMPP in signal enhancement as well as the extra resolution that IM-MS offered. Additionally, the d0-/d6-DMPP-labeled FAs showed expected features, including very similar drift times, 6 Da mass deviations, specific reporter ions, similar MS responses, and adherence to the drift time rule regarding the influence of carbon chain length and unsaturation on relative drift times. Therefore, the introduction of isotope analogs minimized the matrix effect and variations in quantification and ensured accurate identification of non-targeted FAs by those typical features. Peak intensity ratios between d0-/d6-DMPP-labeled ions were subsequently used in relative quantification for the detected FAs. The established strategy has been applied successfully in the rapid profiling of trace free FAs between normal and cancerous human thyroid tissues. Sixteen free FAs were found with the increased level with a statistically significant difference (p < 0.05) compared to the normal tissue samples. The integrated SIL technique and ESI-IM-MS are expected to serve as an alternative tool for high-throughput analysis of FAs in complex samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

In this work, 0.08 mmol L(-1) of phthalic acid was introduced as a mobile phase additive to quantify free amino acids (AAs) by hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization tandem mass spectrometry (ESI-MS/MS). The addition of phthalic acid significantly increased the signal intensity of protonated AA ions, resulting from the decrease of the relative abundance of AA sodium adducts. Meanwhile, the chromatographic peak shapes of AAs were optimized. As a consequence, there was a noticeable increase in the sensitivity of detection for AAs. The limits of detection (LOD) and quantification (LOQ) of the AAs ranged from 0.0500 to 20.0 ng mL(-1) and from 0.100 to 50.0 ng mL(-1), respectively, which were 4-50 times lower compared to the values measured without the addition of phthalic acid. The enhanced detection and separation of AAs were obtained by merely adding phthalic acid to the mobile phase without changing other conditions. Eventually, this simple method was validated and successfully applied to the analysis of twenty-four kinds of free AAs in human thyroid carcinoma and para-carcinoma tissues, demonstrating a significant increase of most AAs in thyroid carcinoma tissues (p<0.05)., (Copyright © 2015. Published by Elsevier B.V.)

A highly sensitive method was developed for the identification and quantification of fatty alcohols in biological tissues. In the presence of pyridine-d0 and triflic anhydride (Tf2O), fatty alcohols were converted into permanently charged N-alkylpyridinium ions. Stable isotope-labeled derivatives were generated by pyridine-d5 and added as internal standard (IS). The mixture was analyzed by liquid chromatography coupled to positive electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). This method was optimized and validated in terms of reaction time, derivatization efficiency, stability, desalting, and ion suppression effect. Besides, fatty alcohols exhibited good linear relationship (r(2)>0.993) over the concentration range of 10 ngmL(-1)-1 μgmL(-1). The limits of detection (LODs) were lowered from previously reported 0.1 ngmL(-1) to 0.25 pgmL(-1). Precision (RSD%<15.6%), accuracy (93.0-107.2%), matrix effect, and recovery (in thyroid tissues) were validated as well. Finally, this method was applied for the analysis of ten even carbon-numbered fatty alcohols (C8-C24) in human thyroid carcinoma and para-carcinoma tissues, revealing a significant decrease of fatty alcohols (free and esterified) in thyroid carcinoma tissues (p<0.05)., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A strategy for suspected-target screening of pesticide residues in complicated matrices was exploited using gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS). The screening workflow followed three key steps of, initial detection, preliminary identification, and final confirmation. The initial detection of components in a matrix was done by a high resolution mass spectrum deconvolution; the preliminary identification of suspected pesticides was based on a special retention index/mass spectrum (RI/MS) library that contained both the first-stage mass spectra (MS(1) spectra) and retention indices; and the final confirmation was accomplished by accurate mass measurements of representative ions with their response ratios from the MS(1) spectra or representative product ions from the second-stage mass spectra (MS(2) spectra). To evaluate the applicability of the workflow in real samples, three matrices of apple, spinach, and scallion, each spiked with 165 test pesticides in a set of concentrations, were selected as the models. The results showed that the use of high-resolution TOF enabled effective extractions of spectra from noisy chromatograms, which was based on a narrow mass window (5 mDa) and suspected-target compounds identified by the similarity match of deconvoluted full mass spectra and filtering of linear RIs. On average, over 74% of pesticides at 50 ng/mL could be identified using deconvolution and the RI/MS library. Over 80% of pesticides at 5 ng/mL or lower concentrations could be confirmed in each matrix using at least two representative ions with their response ratios from the MS(1) spectra. In addition, the application of product ion spectra was capable of confirming suspected pesticides with specificity for some pesticides in complicated matrices. In conclusion, GC-QTOF MS combined with the RI/MS library seems to be one of the most efficient tools for the analysis of suspected-target pesticide residues in complicated matrices., (Copyright © 2014 Elsevier B.V. All rights reserved.)

IMAC strategy is widely used in phosphopeptide enrichment, but most of the current eluents contain large amount of salt, which must be discarded before MS detection. Here, we present techniques to elute phosphopeptides with low ionization efficiency reagents, which could be left in the eluate for direct MS analysis, thus saving desalting and the following steps. Several reagents were studied, including 5-sulfosalicylic acid dihydrate, acetyl acetone and glyphosate. The results show that glyphosate has very outstanding advantages: only monophosphopeptides can be eluted with glyphosate solution, while all phosphopeptides can be eluted with negatively charged glyphosate ions with pH9. Moreover, the high ionic strength can minimize nonspecific electrostatic interactions in elution step and limit the generation of potential phosphopeptide-metal ion adducts such as sodium or Fe(3+) counterparts. S/N of phosphopeptides could be enhanced 3-5 folds in MALDI MS detection and phosphopeptide recovery is greatly improved while compared with its counterparts eluted by commonly used elution buffers. By applying this reagent into IMAC elution, the whole experimental process could be more convenient, time-saving and cost-saving, which is of great importance to the enrichment and detection of phosphopeptides in phosphoproteomics research., Biological Significance: This potent desalting-free and signal enhanced elution method can improve the sensitivity and detection of phosphopeptides in MALDI TOF MS analysis, both time saving and cost saving. With these advantages, it's highly appropriate for the high throughout analysis of phosphoproteomics., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A novel isotope labeling reagent d(0)-/d(6)-2, 4-dimethoxy-6-piperazin-1-yl pyrimidine (DMPP) has been developed for derivatization toward the carboxyl group based on carbodiimide chemistry for mass spectrometry (MS) analysis. The strengths of this derivatization strategy involve fast labeling (15s), low chemical background and general access to most carboxylic analytes. This has been demonstrated using a series of compounds containing carboxylic acids, including peptides and proteins. To enhance the MS response of the derivatized analytes, the design of DMPP has been based on integration of the theoretical consideration of high gas-phase hydrogenation capacity and hydrophobicity. In addition, the high abundance product ions at m/z 225 and m/z 231 from d(0)-/d(6)-DMPP labeled carboxylic acids indicate high efficiency of the gas-phase cleavage induced by the labeling reagent. Quantitative determination of these ions can also be used in single reaction monitoring to achieve extremely high sensitivity toward the target analytes. This has subsequently been used to determine trace free fatty acids in human urine. Furthermore, the DMPP labeled peptides also provide additional sequence information in MALDI-MS/MS because of the formation of sequence-related isotope fragment ions. This DMPP-oriented labeling technique is expected to be a promising tool for the MS detection of many varieties of compounds containing carboxyl groups., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A method for the rapid simultaneous screening and identification of multiple pesticide residues in vegetables was established using a novel database and gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS). A total of 187 pesticides with different chemical species were measured by GC-QTOF MS to create the database, which collected the retention time and exact masses of ions from the first-stage mass spectrum (MS(1) spectrum) and second-stage mass spectrum (MS(2) spectrum) for each pesticide. The workflow of the created database consisted of "MS(1) screening" for possible pesticides by chemical formula match and "MS(2) identification" for structural confirmation of product ion by accurate mass measurement. To evaluate the applicability of the database, a spinach matrix was prepared by solid phase extraction, spiked with a mixture of 50 pesticides at seven concentrations between 0.1 and 10ppb, and analyzed by GC-QTOF MS. It was found that all of the 50 pesticides with concentrations as low as 5ppb were detected in the "MS(1) screening" step and accurate masses were identified with errors less than 2.5mDa in the "MS(2) identification" step, indicating high sensitivity, accuracy, selectivity and specificity. Finally, to validate the applicability, the new method was applied to four fresh celery, rape, scallion and spinach vegetables from a local market. As a result, a total of 13 pesticides were found, with 11 in celery, 9 in rape, 3 in scallion and 2 in spinach. In conclusion, GC-QTOF MS combined with an exact mass database is one of the most efficient tools for the analysis of pesticide residues in vegetables., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Based on our previous report on N-alkylpyridinium isotope quaternization (NAPIQ) for the analysis of cholesterol and fatty alcohols, we have further developed the NAPIQ method for wider applications in screening various small compounds. The reaction scope and improvement were investigated via the screening of compounds with different reaction sites. The experimental results showed that the NAPIQ strategy was suitable not only for steroids with alcoholic or α,β-unsaturated ketone moieties, but could also be applied to label carbohydrates by changing the reaction solvent. The byproducts from target compounds with multiple groups could be reduced by improving the reaction conditions. The derivatization method significantly improved the detection sensitivity for these compounds in matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric (MALDI-FTMS) analysis. The detection sensitivity and selectivity of the NAPIQ method were higher than conventionally used Girard reagents. Finally, endogenous steroids in urine samples were screened using the NAPIQ method. NAPIQ was proven to be an efficient alternative method for analyzing steroids and carbohydrates, without the need for isotopically coded internal standards., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A simple and practical approach to improve the sensitivity of acetylcholinesterase (AChE)-inhibited method has been developed for monitoring organophosphorous (OP) pesticide residues. In this work, matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) was used to detect AChE activity. Due to its good salt-tolerance and low sample consumption, MALDI-FTMS facilitates rapid and high-throughput screening of OP pesticides. Here we describe a new method to obtain low detection limits via employing external reagents. Among candidate compounds, n-octylphosphonic acid (n-Octyl-PA) displays assistant effect to enhance AChE inhibition by OP pesticides. In presence of n-Octyl-PA, the percentages of AChE inhibition still kept correlation with OP pesticide concentrations. The detection limits were improved significantly even by 10(2)-10(3) folds in comparison with conventional enzyme-inhibited methods. Different detection limits of OP pesticides with different toxicities were as low as 0.005 μg L(-1) for high toxic pesticides and 0.05 μg L(-1) for low toxic pesticides. Besides, the reliability of results from this method to analyze cowpea samples had been demonstrated by liquid-chromatography tandem mass spectrometry (LC-MS/MS). The application of this commercial available assistant agent shows great promise to detect OP compounds in complicated biological matrix and broadens the mind for high sensitivity detection of OP pesticide residues in agricultural products., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Isotope-coded reagents have been developed for labeling of amino acids, phenols and fatty acids, but not for alcohols. In this work, a simple reaction based on direct N-alkylpyridinium isotope quaternization (NAPIQ) was developed for mild derivatization of cholesterol and fatty alcohols. Different from the conventional quaternary reagents with cations on themselves, two simple and charge-neutral reagents: pyridine and d(5)-pyridine directly attached N-cationic tag onto the target compounds in the presence of trifluoromethanesulfonic anhydride (Tf(2)O) without tedious sample preparation. The derivatization completed in 5 min and achieved charge labeling of the target compounds, which significantly improved the detection limits of analytes by 10(3)-folds in further analysis by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS). The use of commercially available d(0)/d(5)-pyridine pairs facilitated isotope-coded chemical derivatization and avoided the use of isotope-labeled internal standards; the excess pyridine did not affect the signals of analytes. Utility of the NAPIQ method was examined in the identification of cholesterol and fatty alcohols in small amount of human hair sample (<0.5mg). The fluctuation of total cholesterol in human body was profiled during time by quantitatively comparing the different segments of a single strand of hair. This study combines the direct pyridinium quaternization with MALDI-FTMS, which offers a perspective and an alternative tool for the identification and quantification of substances in biological matrix by comparing d(0)/d(5) pairs, especially when isotope-labeled internal standards are unavailable., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Extraction and derivatization in single drop (EDSD) coupled to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) was utilized to determine small molecular aldehydes (SMAs) in single puff smoke. A methanol solution of diphenylamine, 2,5-dihydroxybenzoic acid was used for extraction/derivatization of SMAs and a microdrop of the extraction solution containing the ionic derivatization products of SMAs could be directly deposited in the MALDI target to perform the measurement of SMAs in the cigarette smoke on puff level by MALDI-FTICR-MS. As a result, a consecutive operation of sample pre-treating and MALDI sample plate preparation was achieved. SMAs were derivatized by the reaction with diphenylamine and transformed a stable Schiff base bearing a quaternary ammonium group, and the sensitivity of analysis for SMAs was significantly improved. Good sample homogeneity in in-dot was achieved by adding diphenylamine into the solvent for EDSD and a satisfying repeatability (R.S.D.=7.3% for formaldehyde, n=5) of MALDI-FTICR-MS signals was obtained. This solvent- and reagent-minimized approach with an automatic potential provided a simple, rapid, and accurate procedure for the determination of SMAs in smoke.