bims-metlip Biomed News
on Methods and protocols in metabolomics and lipidomics
Issue of 2022‒01‒09
thirty-four papers selected by
Sofia Costa
Icahn School of Medicine at Mount Sinai

  1. Expert Rev Proteomics. 2022 Jan 06.
      INTRODUCTION: : Ion mobility-mass spectrometry is an emerging technology in the clinical setting for high throughput and high confidence molecular characterization from complex biological samples. Ion mobility spectrometry can provide isomer separations on the basis of molecular structure, the ability of which is increasing through technological developments that afford enhanced resolving power. Integrating multiple separation dimensions, such as liquid chromatography-ion mobility-mass spectrometry (LC-IM-MS) provide dramatic enhancements in the mitigation of molecular interferences for high accuracy clinical measurements.AREAS COVERED: : Multidimensional separations with LC-IM-MS provide better selectivity and sensitivity in molecular analysis. Mass spectrometry imaging of tissues to inform spatial molecular distribution is improved by complementary ion mobility analyses. Biomarker identification in surgical environments is enhanced by intraoperative biochemical analysis with mass spectrometry and holds promise for integration with ion mobility spectrometry. New prospects in high resolving power ion mobility are enhancing analysis capabilities, such as distinguishing isomeric compounds.
    EXPERT OPINION: : Ion mobility-mass spectrometry holds many prospects for the field of isomer identification, molecular imaging, and intraoperative tumor margin delineation in clinical settings. These advantages are afforded while maintaining fast analysis times and subsequently high throughput. High resolving power ion mobility will enhance these advantages further, in particular for analyses requiring high confidence isobaric selectivity and detection.
    Keywords:  high-resolution ion mobility; ion mobility-mass spectrometry; isobars and isomers; mass spectrometry imaging; metabolomics; multidimensional separations
  2. Turk J Pharm Sci. 2021 Dec 31. 18(6): 761-769
      Objectives: Dopamine (DA) is a prominent biochemically complex neurotransmitter and immunomodulator. The quantification of DA could contribute to a better understanding of how endocrine system, cardiovascular and renal functions are regulated. The study aims to develop a rapid, precise, and extremely sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for routine clinical quantification of DA in urine.Materials and Methods: Urine samples were extracted via one simple and rapid liquid-liquid extraction technique; then analyzed using a sensitive LC-MS/MS method developed by multiple reaction monitoring mode.
    Results: DA and internal standard (IS) retention durations were found to be 2.28 min and 2.24 min, respectively. The mean extraction recovery of DA and DA-IS in urine was above 95.62%. DA calibration curve in urine was linear (r2≥0.998) ranging from 20 ng/mL to 1000 ng/mL. The maximum intra-day and inter-day precisions were 5.87 and 2.81, respectively and coefficients of variation were 10.55% and 7.57%, respectively.
    Conclusion: A rapid, precise, sensitive and quantitative LC-MS/MS detection of DA without the use of derivatization, evaporation, reconstitution and ion-pairing reagents has been developed with a simple and non-invasive sample technique for clinical laboratory applications, basic neuroscience research and drug development studies.
    Keywords:  Dopamine; LC-MS/MS; method validation; urine
  3. J Mass Spectrom Adv Clin Lab. 2022 Jan;23 7-13
      Ion mobility spectrometry (IMS) is an analytical technique where ions are separated in the gas phase based on their mobility through a buffer gas in the presence of an electric field. An ion passing through an IMS device has a characteristic collisional cross section (CCS) value that depends on the buffer gas used. IMS can be coupled with mass spectrometry (MS), which characterizes an ion based on a mass-to-charge ratio (m/z), to increase analytical specificity and provide further physicochemical information. In particular, IMS-MS is of ever-increasing interest for the analysis of lipids, which can be problematic to accurately identify and quantify in bodily fluids by liquid chromatography (LC) with MS alone due to the presence of isomers, isobars, and structurally similar analogs. IMS provides an additional layer of separation when combined with front-end LC approaches, thereby, enhancing peak capacity and analytical specificity. CCS (and also ion mobility drift time) can be plotted against m/z ion intensity and/or LC retention time in order to generate in-depth molecular profiles of a sample. Utilization of IMS-MS for routine clinical laboratory testing remains relatively unexplored, but areas do exist for potential implementation. A brief update is provided here on lipid analysis using IMS-MS with a perspective on some applications in the clinical laboratory.
    Keywords:  CCS, collisional cross section; CV, compensation voltage; CVD, cardiovascular disease; Clinical analysis; DG, diacylglycerol; DMS, differential mobility spectrometry; DTIMS, drift tube ion mobility spectrometry; EV, elution voltage; FAIMS, field asymmetric waveform ion mobility spectrometry; FIA, flow injection analysis; FTICR, fourier-transform ion cyclotron resonance; HDL, high-density-lipoprotein; HRMS, high-resolution mass spectrometry; IMS, ion mobility spectrometry; IMS-MS, ion mobility spectrometry-mass spectrometry; Ion mobility spectrometry; LC, liquid chromatography; LDL, low-density-lipoprotein; LPC, lysophosphatidylcholine; Lipids; MALDI, matrix-assisted laser desorption/ionization; MS, mass spectrometry; Mass spectrometry; NBS, newborn screening; PC, glycerophosphocholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; RF, radio frequency; SLIM, structures for loss less ion manipulations; SM, sphingomyelin; SV, separation voltage; TG, triglyceride; TIMS, trapped ion mobility spectrometry; TOF, time-of-flight; TWIMS, traveling wave ion mobility spectrometry; VLDL, very-low-density lipoprotein; m/z, mass-to-charge ratio
  4. Anal Chem. 2022 Jan 05.
      Molecular networking (MN) has become a popular data analysis method for untargeted mass spectrometry (MS)/MS-based metabolomics. Recently, MN has been suggested as a powerful tool for drug metabolite identification, but its effectiveness for drug metabolism studies has not yet been benchmarked against existing strategies. In this study, we compared the performance of MN, mass defect filtering, Agilent MassHunter Metabolite ID, and Agilent Mass Profiler Professional workflows to annotate metabolites of sildenafil generated in an in vitro liver microsome-based metabolism study. Totally, 28 previously known metabolites with 15 additional unknown isomers and 25 unknown metabolites were found in this study. The comparison demonstrated that MN exhibited performances comparable or superior to those of the existing tools in terms of the number of detected metabolites (27 known metabolites and 22 unknown metabolites), ratio of false positives, and the amount of time and effort required for human labor-based postprocessing, which provided evidence of the efficiency of MN as a drug metabolite identification tool.
  5. Chem Pharm Bull (Tokyo). 2022 ;70(1): 12-18
      Due to the globalization of food production and distribution, the food chain has become increasingly complex, making it more difficult to evaluate unexpected food changes. Therefore, establishing sensitive, robust, and cost-effective analytical platforms to efficiently extract and analyze the food-chemicals in complex food matrices is essential, however, challenging. LC/MS-based metabolomics is the key to obtain a broad overview of human metabolism and understand novel food science. Various metabolomics approaches (e.g., targeted and/or untargeted) and sample preparation techniques in food analysis have their own advantages and limitations. Selecting an analytical platform that matches the characteristics of the analytes is important for food analysis. This review highlighted the recent trends and applications of metabolomics based on "foodomics" by LC-MS and provides the perspectives and insights into the methodology and various sample preparation techniques in food analysis.
    Keywords:  LC-MS; food analysis; foodomics; metabolomics; sample preparation
  6. Prog Lipid Res. 2022 Jan 04. pii: S0163-7827(21)00061-8. [Epub ahead of print] 101145
      Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is an indispensable tool in modern lipid research since it is fast, sensitive, tolerates sample impurities and provides spectra without major analyte fragmentation. We will discuss some methodological aspects, the related ion-forming processes and the MALDI MS characteristics of the different lipid classes (with the focus on glycerophospholipids) and the progress, which was achieved during the last ten years. Particular attention will be given to quantitative aspects of MALDI MS since this is widely considered as the most serious drawback of the method. Although the detailed role of the matrix is not yet completely understood, it will be explicitly shown that the careful choice of the matrix is crucial (besides the careful evaluation of the positive and negative ion mass spectra) in order to be able to detect all lipid classes of interest. Two developments will be highlighted: spatially resolved Imaging MS is nowadays well established and the distribution of lipids in tissues merits increasing interest because lipids are readily detectable and represent ubiquitous compounds. It will also be shown that a combination of MALDI MS with thin-layer chromatography (TLC) enables a fast spatially resolved screening of an entire TLC plate which makes the method competitive with LC/MS.
    Keywords:  Lipids; MALDI-TOF MS; Mass spectrometric imaging; Matrix; Phospholipids
  7. Forensic Sci Int. 2021 Dec 16. pii: S0379-0738(21)00471-0. [Epub ahead of print]331 111151
      Liquid chromatography tandem mass spectrometry (LC-MS/MS) is often regarded as a highly reliable methodology for confirmatory testing in analytical toxicology, especially for detection of new psychoactive substances (NPS) by clinical and forensic laboratories. However, false positives still do occur and erroneous reporting can have substantial legal implications. In this study, we investigated into the mechanism behind a clinically implausible, but apparently analytically sound, finding of a NPS (4-hydroxy-N-methyl-N-ethyltryptamine; 4-HO-MET) in a urine specimen for toxicology screening by LC-MS/MS. We discovered that a ropinirole metabolite (N-despropyl-ropinirole) was the culprit of interference as it shares high structural similarities with 4-HO-MET. The chemical similarities eluded various rigorous regulatory guidelines for compound identification utilizing computer-aided spectral library matching. After careful scrutiny of the mass spectra and comparison with a reference specimen, the compound was correctly identified. Our findings emphasize the important synergy between scientists and pathologists in considering the clinical context, especially drug history, in clinical and forensic toxicology analysis on biological specimens. Mass spectra should be reviewed for relative ion ratios in case of doubt. Understanding drug metabolism is essential for troubleshooting and result interpretation.
    Keywords:  4-HO-MET; Analytical interference; LC-MS/MS; New psychoactive substance; Ropinirole
  8. Front Chem. 2021 ;9 807868
      Mass spectrometry imaging (MSI) serves as an emerging tool for spatial profiling of metabolic dysfunction in ischemic tissue. Prior to MSI data analysis, commonly used staining methods, e.g., triphenyltetrazole chloride (TTC) staining, need to be implemented on the adjacent tissue for delineating lesion area and evaluating infarction, resulting in extra consumption of the tissue sample as well as morphological mismatch. Here, we propose an in situ ratiometric MSI method for simultaneous demarcation of lesion border and spatial annotation of metabolic and enzymatic signatures in ischemic tissue on identical tissue sections. In this method, the ion abundance ratio of a reactant pair in the TCA cycle, e.g., fumarate to malate, is extracted pixel-by-pixel from an ambient MSI dataset of ischemic tissue and used as a surrogate indicator for metabolic activity of mitochondria to delineate lesion area as if the tissue has been chemically stained. This method is shown to be precise and robust in identifying lesions in brain tissues and tissue samples from different ischemic models including heart, liver, and kidney. Furthermore, the proposed method allows screening and predicting metabolic and enzymatic alterations which are related to mitochondrial dysfunction. Being capable of concurrent lesion identification, in situ metabolomics analysis, and screening of enzymatic alterations, the ratiometric MSI method bears great potential to explore ischemic damages at both metabolic and enzymatic levels in biological research.
    Keywords:  TCA cycle; ischemia; mass spectrometry imaging; metabolic enzyme; ratiometric analysis
  9. Comput Struct Biotechnol J. 2022 ;20 65-78
      Lung cancer, one of the most common causes of cancer-related death worldwide, has been associated with high treatment cost and imposed great burdens. The 5-year postoperative survival rate of lung cancer (13%) is lower than many other leading cancers indicating the urgent needs to dissect its pathogenic mechanisms and discover specific biomarkers. Although several proteins have been proposed to be potential candidates for the diagnosis of lung cancer, they present low accuracy in clinical settings. Metabolomics has thus emerged as a very promising tool for biomarker discovery. To date, many lung cancer-related metabolites have been highlighted in the literature but no database is available for scientists to retrieve this information. Herein, we construct and introduce the first Lung Cancer Metabolome Database (LCMD), a freely available online database depositing 2013 lung cancer-related metabolites identified from 65 mass spectrometry-based lung cancer metabolomics studies. Researchers are able to explore LCMD via two ways. Firstly, by applying various filters in the "Browse Metabolites" mode, users can access a list of lung cancer-related metabolites that satisfy the filter specifications. For each metabolite, users can acquire the value of the fold change (cancer/normal), statistical significance (p-value) of the fold change, and the comparative research designs of all the mass spectrometry-based lung cancer metabolomics studies that identify this metabolite. Secondly, by applying various filters in the "Browse Studies" mode, users can obtain a list of mass spectrometry-based lung cancer metabolomics studies that satisfy the filter specifications. For each study, users can view the type of studied specimen, mass spectrometry (MS) method, MS data processing software, and differential analysis method, as well as all the identified lung cancer-related metabolites. Furthermore, the overview of each study is clearly illustrated by a graphical summary. The LCMD ( is the first database that brings together the meaningful information of lung cancer-related metabolites. The development of the LCMD is envisioned to promote the biomarker discovery of lung cancer.
    Keywords:  Biomarker; Database; HMDB, Human Metabolome Database; LCMD, Lung Cancer Metabolome Database; Lung cancer; Mass spectrometry; Metabolite; Metabolome; Metabolomics; NSCLC, Non-Small-Cell Lung Carcinoma; VIP, Variable Importance in Projection
  10. Biomed Chromatogr. 2022 Jan 02.
      Proximal tubular damage is an important prognostic determinant in various chronic kidney diseases (CKDs). Currently available diagnostic methods do not allow for early disease detection, and are neither efficient. Indoxyl sulfate (IS) is an endogenous metabolite and protein-bound uremic toxin that is eliminated via renal secretion, but accumulates in plasma during tubular dysfunction. Therefore, it may be suitable as a tubular function marker. To evaluate this, a fast bioanalytical method was developed and validated for IS in various species and a kidney cell line using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An isotope-labeled IS potassium salt as internal standard and acetonitrile (ACN) as protein precipitant were used for sample pre-treatment. The analyte was separated on a Polaris 3 C18-A column by gradient elution using 0.1% formic acid in water and ACN, and detected by negative electrospray ionization in selected reaction monitoring mode. The within-day (≤ 4.0%) and between-day (≤ 4.3%) precisions and accuracies (97.7 to 107.3%) were within the acceptable range. The analyte showed sufficient stability at all conditions investigated. Finally, applying this assay, significantly higher plasma and lower urine concentrations of IS were observed in mice with diabetic nephropathy with tubular damage, which encourages validation towards its use as biomarker.
    Keywords:  LC-MS/MS; chronic kidney diseases; indoxyl sulfate; renal tubular function; uremic toxins
  11. J Chromatogr B Analyt Technol Biomed Life Sci. 2021 Dec 16. pii: S1570-0232(21)00566-3. [Epub ahead of print]1189 123085
      The hallmarks of cancer include metabolism with deregulating cellular energetics. Dysfunctions in succinate dehydrogenase (SDH) metabolic enzyme activity, leading to an abnormal accumulation of succinic acid has been described in solid tumors but also in inflammation and ischemia reperfusion injury. Succinic acid is a potential biomarker of SDH related pathologies for diagnostic, evaluation of treatment response and follow-up of the disease. We developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method allowing a rapid, accurate and precise quantification of succinic acid levels in clinical (serum, urine) and preclinical (cellular pellets, supernatants) samples. 13C4 succinic acid disodium salt was used as internal standard and added to samples before a solid phase extraction (SPE) on Phenomenex STRATATM XL-A (200 mg - 3 mL) 33 µm cartridges. This method is automated by a Freedom EVO® platform from TECAN and succinic acid is separated on a C18 column combined to a Xevo® TQ-S micro Waters mass spectrometer with electrospray ionization (ESI) source. This biomedical analysis allows standard curves to be linear over the range 1.0-135.5 µM with r2 values > 0.999 and low matrix effects (<9.1 %). This method, which is validated according updated European Medicine Agency (EMA) guidelines, is accurate between-run (<11.0 %) and within-run (<7.8 %), precise between-run (<14.4 CV %) and within-run (<3.7 CV %), and is suitable for clinical and preclinical applications.
    Keywords:  Biomarker; Endogenous compounds; Liquid chromatography tandem mass spectrometry; Oncometabolite; Succinate dehydrogenase dysfunctions; Succinic acid
  12. Biomed Chromatogr. 2022 Jan 03. e5315
      A novel mass spectrometry based analytical method for simultaneous analysis of the antiviral drugs acyclovir, its metabolite 9-carboxymethoxymethylguanine, ganciclovir and penciclovir in serum is described. These antiviral drugs are active against herpes virus infections. Acyclovir and penciclovir are regarded as safe and effective medicines with mild side effects such as headache and gastrointestinal discomfort, ganciclovir is regarded as more toxic and is known to cause e.g., bone marrow suppression. Acyclovir main metabolite 9-carboxymethoxymethylguanine is a presumptive neurotoxin and should be monitored in patients with impaired renal function or in cases with neurotoxic symptoms. Sample prepared using protein precipitation with 1% formic acid in methanol containing isotopically labelled internal standard. Chromatographic separation on a biphenyl column and mass spectrometric detection performed in MRM mode on a Xevo TQ-S micro with ESI in positive ion mode, within 3 minutes. Inter-day assay accuracies for the quality controls varied between 95 to 104 % and intra-day assay between 93 to 105%. Inter-day and intra-day assay imprecision for the quality controls ranged between 1.4 to 4.2% and 1.7 to 6.5% respectively. The lower limit of quantification for all four substances was 0.156 μmol/L. An accurate and reproducible method for therapeutic drug monitoring.
    Keywords:  LC-MS/MS; antiviral agents; serum analysis; therapeutic drug monitoring; validation
  13. Rapid Commun Mass Spectrom. 2022 Jan 07. e9253
      Generating figures of mass spectra fit for publication is often very time consuming. Often, software for analysis of mass spectra has very limited options for customizing the figure for publication. We developed R scripts for the visualization and labelling of mass spectra, but we found that requiring researchers to use R created a significant barrier-of-entry. Hence, we developed a web-hosted version, hosted at make these scripts available to all users. This tool allows for broad customization of graphical parameters such as figure resolution and margins as well as axis customization and various colouring/sizing line width options. The peak labelling function allows selective display of information such as m/z, intensity and S/N ratio as well as custom text labels. Additionally, our tool allows extracting peak information for user defined m/z values from large numbers of mass lists. This makes it possible for researchers to quickly examine the peaks of interest in their data set without the need to manually browse the data. With this tool, we hope to save researcher's time in making figures for publication purposes. This website provides an easy tool for plotting and labelling mass spectra to generate publication quality figures.
  14. Anal Bioanal Chem. 2022 Jan 05.
      The aim of the present research was the application of the linear retention index (LRI) system for the identification of non-psychoactive cannabinoids using a portable LC instrument. The miniaturization, viz. the use of very low quantities of mobile phase, enabled the development of a compact mobile system to be used for in situ analysis, also according to a green and cost-saving approach. In particular, new capillary LC (cap-LC) methods coupled with UV detection were developed for the analysis of extracts of Cannabis sativa L. Two setups were explored to achieve the efficient separation of twenty-four cannabinoids: a single column setup which exploited a sub-2 µm packing to increase the chromatographic resolution, and a dual-column setup based on the serial connection of two different stationary phases, each coupled to an UV detector. The latter allowed the determination of two LRI values for each analyte, thus increasing the identification power. Moreover, since two different wavelengths were used on the LED-based UV detectors, the ratio of the absorbances measured on each chromatographic trace represented a third identification criterion, thus fulfilling the recommendations of the Scientific Working Group for The Analysis of Seized Drugs (SWDRUG) about the categories of analytical techniques to be used and the minimum number of parameters required for the unambiguous identification of drugs. The obtained results could be used for the development of a novel analytical method for fast and automatic in situ forensic investigations and hemp breeding programs, also minimizing the consumption of both sample and solvent.
    Keywords:  Breeding programs; Cannabis sativa; Capillary LC; Forensic analysis; Miniaturization; Portable instrumentation
  15. Se Pu. 2022 Jan;40(1): 41-47
      Chlorpropham is a plant growth regulator and a herbicide. It is commonly used in the post-harvest treatment of potato to inhibit germination. It can also be used for flower thinning and fruit thinning of fruit trees, and for controlling annual gramineous weeds and a few broad-leaved weeds. Improper or excessive use of chlorpropham in crop cultivation will affect the safety of animal-derived food and impair human health through the food chain and water cycle. Therefore, accurate quantification of chlorpropham is imperative for risk assessment and mitigating risks to food safety. A method based on solid phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) was established for the determination of chlorpropham in animal-derived food. First, the pretreatment conditions were optimized. To purify the samples and remove impurities, SPE column cartridges with different packing materials such as PXC, PXA, Florisil, and PLS were investigated. Based on the retention of chlorpropham, the ProElut PLS SPE column was selected as the pretreatment purification column. The washing solution and eluents were then optimized. When water was used as the washing solution, chlorpropham remained adsorbed on the SPE column and was not eluted along with other water-soluble substances. When the proportion of acetonitrile exceeded 40%, chlorpropham adsorbed on the filler of the SPE column could be gradually washed down. Acetonitrile-water solution(30∶70, v/v) was used for washing the SPE column. The elution ability of seven eluents for chlorpropham on the SPE column was then investigated. Among them, pure methanol, pure acetonitrile, and 1% (v/v) formic acid-methanol showed better elution effect. Considering that acetonitrile was used in the sample extraction, it was chosen as the mobile phase eluent. Subsequently, the chromatographic conditions and MS parameters were optimized. By examining the ionization cracking of chlorpropham, the quasimolecular ions and corresponding fragmentations in the chlorpropham primary MS were determined. The separation effect of three C18 columns was investigated. Based on the retention ability and peak effect of chlorpropham on the column, the Agilent ZORBAX SB-C18 (150 mm×2.1 mm, 5 μm) column was used for chlorpropham separation. The response of chlorpropham in the positive and negative ionization modes was investigated and optimized. The results showed that the response was better in the positive ion mode than that in the negative ion mode. After optimizing the chromatographic conditions and MS parameters, the sensitivity of the method was improved. Finally, the analytes were separated on the Agilent ZORBAX SB-C18 (150 mm×2.1 mm, 5 μm) under a gradient elution program using acetonitrile and 0.2% (v/v) formic acid aqueous solution as the mobile phases. The analytes were detected in the multiple reaction monitoring (MRM) mode under positive electrospray ionization (ESI+) conditions. The standard curve solutions were prepared using the matrix solution and quantified by the external standard method. The results showed a good linear relationship in the range of 0.5-100.0 μg/L, with correlation coefficients (r2) greater than 0.9929. The limit of quantification (LOQ) of this method was 3 μg/kg (S/N ≥ 10). At three spiked levels (0.003, 0.006, and 0.060 mg/kg) in 13 animal-derived foods (pork, milk, beef, chicken, duck, egg, chicken gizzard, duck egg, pork kidney, pork liver, beef liver, mutton, duck gizzard), the average recoveries were in the range of 74.9% to 97.6%, and the RSDs were in the range of 2.9% to 9.5% (n=6). Sixty batches of animal-derived food available on the market were analyzed by the developed method, and chlorpropham was not detected in any of these foods. The developed method is rapid, sensitive, and accurate, and it is suitable for the qualitative and quantitative detection of chlorpropham in a variety of animal-derived foods.
    Keywords:  animal derived foods; chlorpropham; residues; solid phase extraction (SPE); ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS)
  16. Brief Bioinform. 2022 Jan 03. pii: bbab535. [Epub ahead of print]
      Large metabolomics datasets inevitably contain unwanted technical variations which can obscure meaningful biological signals and affect how this information is applied to personalized healthcare. Many methods have been developed to handle unwanted variations. However, the underlying assumptions of many existing methods only hold for a few specific scenarios. Some tools remove technical variations with models trained on quality control (QC) samples which may not generalize well on subject samples. Additionally, almost none of the existing methods supports datasets with multiple types of QC samples, which greatly limits their performance and flexibility. To address these issues, a non-parametric method TIGER (Technical variation elImination with ensemble learninG architEctuRe) is developed in this study and released as an R package ( TIGER integrates the random forest algorithm into an adaptable ensemble learning architecture. Evaluation results show that TIGER outperforms four popular methods with respect to robustness and reliability on three human cohort datasets constructed with targeted or untargeted metabolomics data. Additionally, a case study aiming to identify age-associated metabolites is performed to illustrate how TIGER can be used for cross-kit adjustment in a longitudinal analysis with experimental data of three time-points generated by different analytical kits. A dynamic website is developed to help evaluate the performance of TIGER and examine the patterns revealed in our longitudinal analysis ( Overall, TIGER is expected to be a powerful tool for metabolomics data analysis.
    Keywords:  ensemble learning; longitudinal analysis; machine learning; metabolomics; predictive modelling
  17. Cell Metab. 2022 Jan 04. pii: S1550-4131(21)00533-7. [Epub ahead of print]34(1): 21-34
      Metabolite identification represents a major challenge, and opportunity, for biochemistry. The collective characterization and quantification of metabolites in living organisms, with its many successes, represents a major biochemical knowledgebase and the foundation of metabolism's rebirth in the 21st century; yet, characterizing newly observed metabolites has been an enduring obstacle. Crystallography and NMR spectroscopy have been of extraordinary importance, although their applicability in resolving metabolism's fine structure has been restricted by their intrinsic requirement of sufficient and sufficiently pure materials. Mass spectrometry has been a key technology, especially when coupled with high-performance separation technologies and emerging informatic and database solutions. Even more so, the collective of artificial intelligence technologies are rapidly evolving to help solve the metabolite characterization conundrum. This perspective describes this challenge, how it was historically addressed, and how metabolomics is evolving to address it today and in the future.
    Keywords:  artificial intelligence; biochemistry; mass spectrometry; metabolites; nuclear magnetic resonance; structure; unknowns
  18. J Chromatogr A. 2021 Dec 24. pii: S0021-9673(21)00865-7. [Epub ahead of print]1663 462743
      Synthetic cannabinoids (SCs) are new psychoactive substances that function as endocannabinoid CB1 and CB2 receptor agonists. Abuse of SCs can lead to symptoms such as confusion, dizziness, and even death. At present, Synthetic cannabinoids constitute one of the largest groups of new psychoactive substances and become popular recreational drugs of abuse for their psychoactive properties. The continuous transformation of SCs also leads to an endless emergence of new types. An efficient, high-throughput screening method is therefore very important for their identification. This paper describes a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method for simultaneously screening 179 SCs and 80 SC metabolites in blood and urine. Simple acetonitrile was used to precipitate the blood and urine proteins, and the supernatants obtained after centrifugation were analyzed. The LC-HRMS run time was 20 min. The mass spectrometer used an ESI source with a scanning range of m/z 100-1000. LC-HRMS provided accurate mass, retention time, and fragment ions for qualitative analysis. The method validation results showed that the limits of detection (LODs) for over 80% compounds were 5 ng/mL in blood and urine samples. At low concentrations (50 ng/mL), 229 compounds (95.8%) in the blood showed recoveries of more than 50%, and 232 compounds (97.1%) had matrix effects greater than 80%. In the urine, 219 compounds (91.6%) had recoveries above 50%, and the matrix effects of 234 compounds (97.9%) were greater than 80%. This method was successfully applied to actual forensic cases.
    Keywords:  Blood sample; Fragment; LC-HRMS; Synthetic cannabinoids and metabolites; Urine sample
  19. J Mass Spectrom Adv Clin Lab. 2022 Jan;23 1-6
      As the demand for laboratory testing by mass spectrometry increases, so does the need for automated methods for data analysis. Clinical mass spectrometry (MS) data is particularly well-suited for machine learning (ML) methods, which deal nicely with structured and discrete data elements. The alignment of these two fields offers a promising synergy that can be used to optimize workflows, improve result quality, and enhance our understanding of high-dimensional datasets and their inherent relationship with disease. In recent years, there has been an increasing number of publications that examine the capabilities of ML-based software in the context of chromatography and MS. However, given the historically distant nature between the fields of clinical chemistry and computer science, there is an opportunity to improve technological literacy of ML-based software within the clinical laboratory scientist community. To this end, we present a basic overview of ML and a tutorial of an ML-based experiment using a previously published MS dataset. The purpose of this paper is to describe the fundamental principles of supervised ML, outline the steps that are classically involved in an ML-based experiment, and discuss the purpose of good ML practice in the context of a binary MS classification problem.
    Keywords:  Amino acid; Artificial intelligence; CART, Classification and Regression Trees; ML, Machine Learning; MS, Mass Spectrometry; Mass spectrometry; NLL, Negative Log Loss; PAA, Plasma Amino Acid; PR, Precision-Recall; PRAUC, Area Under the Precision-Recall Curve; RL, Reinforcement Learning; ROC, Receiver Operator Curve; SCF, Supplemental Code File; Supervised machine learning; XGBT, Extreme Gradient Boosted Trees; Xgboost
  20. Nucleic Acids Res. 2022 Jan 07. 50(D1): D622-D631
      The Human Metabolome Database or HMDB ( has been providing comprehensive reference information about human metabolites and their associated biological, physiological and chemical properties since 2007. Over the past 15 years, the HMDB has grown and evolved significantly to meet the needs of the metabolomics community and respond to continuing changes in internet and computing technology. This year's update, HMDB 5.0, brings a number of important improvements and upgrades to the database. These should make the HMDB more useful and more appealing to a larger cross-section of users. In particular, these improvements include: (i) a significant increase in the number of metabolite entries (from 114 100 to 217 920 compounds); (ii) enhancements to the quality and depth of metabolite descriptions; (iii) the addition of new structure, spectral and pathway visualization tools; (iv) the inclusion of many new and much more accurately predicted spectral data sets, including predicted NMR spectra, more accurately predicted MS spectra, predicted retention indices and predicted collision cross section data and (v) enhancements to the HMDB's search functions to facilitate better compound identification. Many other minor improvements and updates to the content, the interface, and general performance of the HMDB website have also been made. Overall, we believe these upgrades and updates should greatly enhance the HMDB's ease of use and its potential applications not only in human metabolomics but also in exposomics, lipidomics, nutritional science, biochemistry and clinical chemistry.
  21. Biomed Chromatogr. 2022 Jan 06. e5326
      A bioanalytical method for the quantification of rosiglitazone on rat plasma and tissues (adipose tissue, heart, brain, bone, and kidney) using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed and validated. Chromatographic separation was achieved on Gemini C18 column (50mm x 4.6mm, 3μm) using mobile phase consists of 10mM ammonium formate (pH 4.0) and acetonitrile (10:90, v/v) at a flow rate of 0.8 mL/min and injection volume of 10μL (Internal standard - Pioglitazone). LC-MS detection was performed with multiple reaction monitoring mode (MRM) using target ions at m/z→358.0 and m/z → 357.67 for rosiglitazone and pioglitazone (IS) respectively. The calibration curve showed a good correlation coefficient (r2 ) over the concentration range of 1-10000 ng/mL. The mean percentage recoveries of rosiglitazone were found to be over the range of 92.54-96.64 % with detection and lower quantification limit of 0.6 ng/mL and 1.0 ng/mL, respectively. The developed method was validated as per USFDA guidelines and successfully utilized to measure rosiglitazone in plasma and tissue samples. Further, the developed method can be utilized for validating specific organ targeting delivery systems of rosiglitazone in addition to conventional dosage forms.
    Keywords:  Pharmacokinetic studies; Rosiglitazone; liquid chromatography-tandem mass spectrometry; tissue distribution studies
  22. J Pharm Biomed Anal. 2021 Dec 29. pii: S0731-7085(21)00668-3. [Epub ahead of print]210 114557
      Metabolomics, a technique that profiles global small molecules in biological samples, has been a pivotal tool for disease diagnosis and mechanism research. The sample type in metabolomics covers a wide range, including a variety of body fluids, tissues, and cells. However, little attention was paid to the smaller, relatively independent partition systems in cells, namely the organelles. The organelles are specific compartments/places where diverse metabolic activities are happening in an orderly manner. Metabolic disorders of organelles were found to occur in various pathological conditions such as inherited metabolic diseases, diabetes, cancer, and neurodegenerative diseases. However, at the cellular level, the metabolic outcomes of organelles and cytoplasm are superimposed interactively, making it difficult to describe the changes in subcellular compartments. Therefore, characterizing the metabolic pool in the compartmentalized system is of great significance for understanding the role of organelles in physiological functions and diseases. So far, there are very few research articles or reviews related to subcellular metabolomics. In this review, subcellular fractionation and metabolite analysis methods, as well as the application of subcellular metabolomics in the physiological and pathological studies are systematically reviewed, as a practical reference to promote the continued advancement in subcellular metabolomics.
    Keywords:  Chemical derivatization; Mass spectrometry; Metabolic profiling; Organelles; Subcellular isolation; Subcellular metabolomics
  23. Chem Pharm Bull (Tokyo). 2022 ;70(1): 37-42
      Eugenols (Eugs) such as eugenol (Eug), methyleugenol (MeEug), and linalool (Lin) in basil product are the main bioactive components of basil products and have a terminal double-bond. A sensitive HPLC-fluorescence method for Eugs derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) was developed. Good separation of DIB-Eugs was achieved within 20 min on an Atlantis T3 column (50 × 2.1 mm i.d., 3 µm) with a mobile phase of methanol-water. The calibration curves obtained with Eug standards showed good linearities in the range of 0.1-50 µM (r ≥ 0.999). The limits of detection at a signal-to-noise ratio (S/N) = 3 for Eug, MeEug, and Lin were 1.0, 6.0, and 4.8 nM, respectively. The limits of quantitation (S/N = 10) of the Eugs were lower than 19.9 nM. The accuracies for the Eugs were within 96.8-104.6%. The intra- and inter-day precisions as relative standard deviations for the Eugs were less than 1.2 and 9.6% (n = 3). The recoveries of Eug, MeEug, and Lin were 99.0 ± 0.1, 98.0 ± 0.2, and 96.0 ± 0.4% (n = 3), respectively. The DIB-Eugs were confirmed to be stable for 2 h (>90%) at room temperature and 24 h (>95%) at 4 °C. These parameters of the proposed method were useful for the simultaneous determination of Eugs in basil products. Therefore, the developed method may be a powerful tool for the quality evaluation of dried commercially available basil products.
    Keywords:  4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI); eugenol; fluorescence derivatization; linalool; methyleugenol; terminal double bond
  24. Zhongguo Zhong Yao Za Zhi. 2021 Dec;46(24): 6447-6453
      A reliable QuEChERS-ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) analysis method was developed for the simultaneous determination of 13 steroid hormones(nrolone, androstenedione, methyltestosterone, testosterone, norethindrone, medroxyprogesterone, progesterone, diethylstilbestrol, hexan-stilbestrol, estradiol, estrotriol, cortisone, hydrocortisone) in Testis et Penis Cervi. The samples were extracted with methanol and purified by QuEChERS. Subsequently, the samples were separated by ACQUITY BEH C_(18) column and detected in the multiple reaction monitoring(MRM) mode under electrospray ionization in the positive and negative ion modes, respectively. Significant differences in the content of thirteen steroid hormones in Testis et Penis Cervi between the sika deer at different periods and the red deer were observed. The content of testosterone(10.88 μg·kg~(-1)) and hydrocortisone(12.82 μg·kg~(-1)) in Testis et Penis Cervi derived from rutting sika deer was significantly higher than the content of testosterone(1.05 μg·kg~(-1)) and hydrocortisone(0.73 μg·kg~(-1)) from antler growth stage. The content of progesterone in Testis et Penis Cervi derived from red deer was 6.07 μg·kg~(-1), significantly higher than that from sika deer. The content of progesterone in the testicle of red deer reached 27.46 μg·kg~(-1), 4.5 times greater than that in the penis of red deer. The sensitivity, accuracy, and precision of the method can meet the detection requirements, and the developed method is suitable for the measurement of hormones in animal-derived food.
    Keywords:  QuEChERS; Testis et Penis Cervi; UPLC-MS/MS; detection; hormone
  25. Biomed Chromatogr. 2022 Jan 02. e5308
      sKynurenine (KYN) is synthesized from an essential amino acid, tryptophan by tryptophan 2,3-dioxygenase or indoleamine 2,3-dioxygenase via N-formyl- KYN in vivo. Subsequently, KYN acts as a precursor of some neuroactive metabolites such as kynurenic acid, quinolinic acid, and an important enzyme co-factor, nicotine adenine dinucleotide. These metabolites of tryptophan are a part of the "kynurenine pathway." In addition, KYN functions as an endogenous ligand for the aryl hydrocarbon receptor, which acts as a transcription factor. The levels of tryptophan metabolites are important for the assessment of the stage of neurological disorders, and hence, have garnered significant interest for clinical diagnosis. In this review, the detection of kynurenine, kynurenic acid, quinolinic acid, and other tryptophan metabolites performed via chromatographic methods such as HPLC using UV absorbance, fluorescence, and chromatographic-mass spectrometric detection is summarized.
    Keywords:  Kynurenic acid; Kynurenine; Kynurenine pathway; Quinolinic acid; Tryptophan
  26. IEEE Trans Biomed Eng. 2022 Jan 04. PP
      OBJECTIVE: A common phase of early-stage oncological treatment is the surgical resection of cancerous tissue. The presence of cancer cells on the resection margin, referred to as positive margin, is correlated with the recurrence of cancer and may require re-operation, negatively impacting many facets of patient outcomes. There exists a significant gap in the surgeons ability to intraoperatively delineate between tissues. Mass spectrometry methods have shown considerable promise as intraoperative tissue profiling tools that can assist with the complete resection of cancer. To do so, the vastness of the information collected through these modalities must be digested, relying on robust and efficient extraction of insights through data analysis pipelines.METHODS: We review clinical mass spectrometry literature and prioritize intraoperatively applied modalities. We also survey the data analysis methods employed in these studies.
    RESULTS: Our review outlines the advantages and shortcomings of mass spectrometry imaging and point-based tissue probing methods. For each modality, we identify statistical, linear transformation and machine learning techniques that demonstrate high performance in classifying cancerous tissues across several organ systems. A limited number of studies presented results captured intraoperatively.
    CONCLUSION: Through continued research of data centric techniques, like mass spectrometry, and the development of robust analysis approaches, intraoperative margin assessment is becoming feasible.
    SIGNIFICANCE: By establishing the relatively short history of mass spectrometry techniques applied to surgical studies, we hope to inform future applications and aid in the selection of suitable data analysis frameworks for the development of intraoperative margin detection technologies.
  27. J Pharm Biomed Anal. 2021 Dec 30. pii: S0731-7085(21)00663-4. [Epub ahead of print]210 114552
      A new sample preparation method named in-syringe gas-assisted density tunable dispersive liquid phase microextraction based on solidification of floating organic droplet has been introduced. This method was coupled with high-performance liquid chromatography-tandem mass spectrometry and used for the extraction and quantification of amikacin in plasma and exhaled breath condensate (EBC) samples of the patients receiving amikacin. In the proposed approach, an inert gas is bubbled into a syringe barrel containing aqueous solution of the analyte and a mixture of low density extraction solvent and volatile density modifier. Consequently, the density modifier is evaporated and the analyte is migrated into the released extractant droplets. Basic parameters affecting efficiency of the developed method were optimized. Under optimum conditions, the method limits of detection were 0.06 and 0.29 ng/mL in EBC and plasma, respectively. The extraction recoveries were 90% and 87% in EBC and plasma, respectively. Also, the obtained relative standard deviations were below 9.5% and 9.8% for EBC and plasma, respectively. Considering these results, the developed method provides a quick and efficient way to determine amikacin in patients' biological fluids and can be used widely in drug monitoring and clinical studies.
    Keywords:  Amikacin; Biological fluids; Dispersive liquid phase microextraction; High–performance liquid chromatography; Tandem mass spectrometry
  28. Zhongguo Zhong Yao Za Zhi. 2021 Dec;46(24): 6435-6446
      A sensitive and efficient method was established and validated for qualitative and quantitative analysis of total alkaloids from the extract of Eurycoma longifolia by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry(HPLC-Q-TOF-MS) combined with ultra-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry(UPLC-QQQ-MS/MS). The HPLC-Q-TOF-MS conditions are as follows: Welch Ultimate XB-C_(18) column(4.6 mm×250 mm, 5 μm) with acetonitrile(containing 0.1% formic acid)-0.1% formic acid in water as mobile phase for gradient elution. The UPLC-QQQ-MS/MS conditions are as below: Agilent Eclipse Plus C_(18) column(2.1 mm×50 mm, 1.8 μm) with acetonitrile(containing 0.1% formic acid) and 0.1% formic acid in water as mobile phase for gradient elution. MS data were collected by electrospray ionization in positive ion mode. According to the comparison with reference standards and the accurate masses of molecules, a total of 17 alkaloids in E. longifolia extract were identified by HPLC-Q-TOF-MS. The UPLC-QQQ-MS/MS quantitative analysis result of 3 alkaloids showed that the linear ranges of them were good(r≥0.999 7) and the overall recoveries ranged from 108.8%-110.2%, with RSDs of 2.9%-5.3%. The method is accurate, reliable, and efficient, which can comprehensively reflect the constituents and content of alkaloids in E. longifolia. The result can serve as a reference for further elucidating its therapeutic material basis and quality control.
    Keywords:  Eurycoma longifolia; HPLC-Q-TOF-MS; UPLC-QQQ-MS/MS; alkaloid; qualitative analysis; quantitative analysis
  29. Methods Mol Biol. 2022 ;2433 217-226
      Metabolomics is the systems-scale study of the biochemical intermediates of metabolism. This approach has great potential to uncover how metabolic intermediates are used and generated in cell-free expression systems, something that is to date not well understood. Here, we present a detailed metabolomics protocol for characterization of the small molecules in cell-free systems. We specifically focus on the analysis of Escherichia coli lysate-based cell-free systems using gas chromatography coupled to mass spectrometry. Measuring and monitoring the metabolic changes in cell-free systems can provide insight into the ways that metabolites affect the productivity of cell-free reactions, ultimately allowing for more informed engineering and optimization efforts for cell-free systems.
    Keywords:  Cell-free expression systems; Escherichia coli; Gas chromatography-mass spectrometry; Metabolites; Metabolomics
  30. Int J Cosmet Sci. 2022 Jan 05.
      OBJECTIVE: This study aimed to develop and validate a rapid, simple, accurate, and precise analytical method for the quantification of L-AA in vitamin C serums. Moreover, the developed method was further applied to determine L-AA in eight different brands of vitamin C serums. A complementary study was also carried out to evaluate the stability of L-AA in the vitamin C serum samples after 15, 30, 45, and 60 days of storage at ambient temperature (15 ºC to 35 ºC).METHODS: Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was applied.
    RESULTS: Quantitative analyses were performed with a total chromatographic run time of 1.5 min by matrix-matched calibration, and the analytical curve was linear over the range of 1-1700 μg L-1 with a correlation coefficient of 0.9998. The limits of detection (LOD) and quantification (LOQ) were 0.3 and 1.0 μg L-1 , respectively. Intra- and inter-assay precisions, expressed in terms of relative standard deviation (RSD), ranged from 0.3% and 2.2%, respectively, and recoveries in two concentration levels (1 and 5 µg L-1 ) were 103.9% and 101.2%, respectively. The proposed analytical method was successfully applied to determine de L-AA content of eight commercial vitamin C serum samples. The stability of the target analyte in samples stored at ambient temperature (15 ºC to 35 ºC) was evaluated throughout 60 days with a 15-day interval between analyses. At 0 days, L-AA content in samples ranged from 1.05 - 169.91 mg L-1 , decreasing over time.
    CONCLUSION: The proposed method could be powerful in routine analyses to ensure the quality of L-AA vitamin C serums since it proved a simple, reliable, fast, precise, accurate, and sensitive analytical method.
    Keywords:  analytical method; chemical analysis; cosmetic; natural antioxidant; penetration; quality control; stability
  31. Food Chem. 2021 Dec 29. pii: S0308-8146(21)02968-X. [Epub ahead of print]377 131962
      In this study, a highly sensitive method for analysis of 4 cyanogenic glycosides (CNGs) in cold-pressed flaxseed oil was developed by using cigarette filter fiber-based SPE and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The cold-pressed flaxseed oil was diluted with 5% (v/v) isopropanol/n-hexane solution and loaded to a cigarette filters fiber-based SPE column for CNG enrichment and purification. Under optimized conditions, four CNGs could be detected with limits of detection ranging from 1.3 to 4.4 pg/mL. The linear range was 0.05-50 ng/ml with a linear correlation coefficient (r) > 0.9935. CNG recovery ranged from 113% to 133%, and the relative standard deviation was between 0.8% and 20.5%. Finally, the proposed method was applied to the determination of CNGs in nine cold-pressed flaxseed oils.
    Keywords:  Cigarette filters; Cyanogenic glycosides; UPLC–MS/MS
  32. J Sep Sci. 2022 Jan 04.
      Regadenoson, the first selective adenosine A2A receptor agonist, is used to perform exercise stress test during radionuclide myocardial perfusion imaging. To detect the concentration of regadenoson in human plasma, a simple, fast, and sensitive tandem mass spectrometry method was established herein. Acetonitrile was used as a protein precipitation agent. Chromatographic separation was completed in 6.5 minutes using a BEH HILIC Column (50 × 2.1 mm, 1.7 μm, Waters, USA). The mobile phase consisted of 10 mmol/L ammonium acetate/acetonitrile (gradient elution). To quantify regadenoson and regadenoson-d3, an API 4000 mass spectrometry in multiple reaction monitoring mode with transitions of 391.3→259.2 and 394.3→262.2, respectively, was utilized. The calibration curve was linear in the range of 0.100-50.0 μg/L, and the intra-batch and inter-batch precisions were < 9.7% and < 13.0 %, respectively, and the accuracy was 2.0-6.9%. There was no apparent matrix effect for regadenoson or regadenoson-d3. The developed method was used to study the pharmacokinetic characteristics of regadenoson in healthy Chinese subjects. This article is protected by copyright. All rights reserved.
    Keywords:  Hydrophilic Interaction Liquid Chromatography-Tandem Mass Spectrometry; Pharmacokinetics; Regadenoson
  33. Se Pu. 2022 Jan;40(1): 100-106
      An online derivatization device for the analysis of polar organic compounds by gas chromatography-mass spectrometry (GC-MS) is designed. The derivatization reaction occurs in the hot GC injection port, and this is also known as injection port derivatization (IPD). IPD is usually performed in two ways: 1) direct IPD and 2) ion-pair extraction, followed by IPD. In both cases, the derivatization reagent reacts in liquid form. However, a method for online derivatization using gaseous derivatization reagents is provided. A special needle is designed and placed on the carrier gas transfer line to the injection port. The carrier gas is introduced into a glass bottle containing the derivative reagent (N-methyl-N-(trimethylsilyl)trifluoroacetamide, MSTFA), and then, the gaseous derivative reagent in the headspace is pressed out and introduced into the injection port of the GC instrument at a constant speed. The filter to be analyzed is placed directly in the liner, and the polar organic compounds on the filter react with gaseous MSTFA at 310 ℃ for 10 min in the injection port. During derivatization, the column oven is maintained at room temperature, and all the derivatives stay on the column head. When the reaction is complete, the MSTFA supply is ceased. The oven temperature is programmed, and the solvent delay is set until the excessive MSTFA is removed. The derivatives are allowed to pass through the column and analyzed by the MS detector. To prevent a large number of derivative reagents from entering the column, the injection port is set in split mode with a split ratio of 5∶1. Variables such as the injection-port temperature and derivatization time are investigated. The GC-MS responses of the ten silylated derivatives increase with increasing injection-port temperature (290-310 ℃), indicating that high temperatures can enhance the silylation efficiency. The derivatization times were also investigated. The GC-MS responses increased with an increase in the reaction time from 0 to 10 min, while higher temperatures or longer reaction times lead to the loss of some derivatives. The reproducibility of the derivatization reaction was 0.27% to 7.28%, and the linear correlation coefficient was 0.976-0.996. This device can be used for the online silylation of most polar organic compounds such as organic acids, alcohols, and phenols. The advantage of this device over offline derivatization is that the derivatization reagent and derivatives are protected by helium, which eliminates the risk of decomposition caused by moisture in the air, and the high temperature assists the reaction. The analytes were directly desorbed on the filter and derived online, and the sample quantity required was only 1/200 of that in the traditional solvent extraction method. Meanwhile, only the gaseous part of the headspace in the derivative reagent bottle was used, and the amount of derivative reagent was greatly reduced. Additionally, the operation is simple and solvent free, the entire analytical procedure was executed in a "green" manner. A PM2.5 filter was analyzed, and 26 different polar compounds were successfully derived, including monoacids, binary acids, aromatic acids, and alcohols, covering most of the common target polar compounds in atmospheric chemical analysis. Polyols such as glucose and sorbose that bear 5-6 hydroxyl groups and have large steric hindrance were also successfully derived. This device is expected to be an efficient and convenient analytical tool for tracing the sources of organic matter in atmospheric particles such as soil dust, biomass combustion, cooking oil smoke, and automobile exhaust, or for investigating atmospheric photochemical reactions. This gas-phase derivatization provides new insights for the development of chromatographic analysis methods for polar compounds. This device is simple and modular, and it has a wide range of applications; it is suitable for different brands of gas chromatographs and has great prospects for commercialization.
    Keywords:  atmospheric particulate matter; device; gas chromatography (GC); mass spectrometry (MS); online derivation; polar organic compounds; silylation reaction
  34. Biomed Chromatogr. 2022 Jan 03. e5317
      Low flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for mass spectrometry have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow liquid chromatography , the types of columns employed, and strategies for multi-dimensionality of separations, which is key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend towards biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy to use platform.
    Keywords:  Nano-LC; bioanalysis; targeted quantitation