Liquid Chromatography Quadrupole Time-of-flight Mass Spectrometry Research Articles

A non-targeted approach to identify potential breast carcinogens in women firefighters after a fire event

BACKGROUND AND AIM: Female firefighters remain understudied in both exposure and epidemiology studies. Furthermore, occupational studies generally focus on toxic chemicals that are well characterized. The objective of this study was to identify potentially novel chemical exposures associated with a fire event among female firefighters. METHODS: We applied non-targeted analysis methods to three longitudinal serum samples collected in the days and weeks after a fire. To assess exposure to potential breast carcinogens among women workers after an urban structural fire event the Women Workers Biomonitoring Collaborative (WWBC), we recruited female firefighters in San Francisco and developed a biospecimen archive. Female firefighters (n=18) were recruited and provided 3 serum samples—within 48 hours, 1 week, and 1 month after fighting a fire. We applied a non-targeted analytical approach with liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF/MS) in both the positive and negative ionization modes. RESULTS:We detected over 20,000 features, representing potential chemical exposures in study participants. Exact masses of features were matched to a curated in-house library of 7,935 environmental chemicals and potential breast carcinogens, tentatively identifying 1,667 chemicals. MS/MS fragmentation analysis allowed us to further confirm 181 candidate chemicals based on the predicted fragmentation pattern of each chemical. These chemicals included per-/poly-fluoroalkyl substances, endocrine disrupting chemicals and chemicals associated with mammary tumor development. We will confirm the identity of at least 5 of these novel chemicals by re-running the samples with known standards. CONCLUSIONS:Non-targeted analytical approaches in carefully designed exposure studies can help “look beyond the lamp post” to identify novel exposures with health concerns. KEYWORDS: non-targeted analysis, generalized suspect screen, occupational exposures, internal exposome

Using non-targeted screening and silicone wristbands to investigate geographic differences in pollution exposures among maternal and cord sera

BACKGROUND AND AIM: Differential risk for adverse pregnancy outcomes in the Fresno and San Francisco regions of California may be influenced by chemical exposures in pregnant women that are not fully captured by traditional biomonitoring approaches. We compared multiple exposure assessment approaches and evaluated differences in chemical exposures among a cohort of pregnant women between the two locations. METHODS: We recruited 300 San Francisco and 75 Fresno mothers and collected maternal and cord sera which we screened for over 2,420 chemicals using high-resolution mass spectrometry using liquid chromatography – quadrupole time-of-flight mass spectrometry (LC-QTOF/MS). 26 of the Fresno participants wore silicone wristbands, which were screened for over 1,500 chemicals using targeted chemical analysis. We matched 75 San Francisco participants to the Fresno participants and used Fisher’s exact test to compare detection frequencies of chemicals in maternal and cord sera between the two locations. We also evaluated whether mothers living in Census tracts with high levels of pollution or pesticides according to CalEnviroScreen had significantly higher numbers of chemicals detected in their sera using Spearman’s rank correlation. RESULTS:We detected 2,167 features across the maternal and cord sera samples by the non-targeted approach. The numbers of suspect chemical features detected were not significantly different between San Francisco and Fresno. A higher number of chemicals tentatively identified as cosmetics or fragrances were significantly differentially detected among the Fresno participants (p0.05). The silicone wristbands also showed high levels of several chemicals used in fragrances, including ethylene brassylate, benzyl salicylate, tonalide, beta-ionone, and lilial. Fresno participants living in tracts with higher pesticide scores had significantly higher numbers of suspect pesticides in their sera (p0.05). CONCLUSIONS:Multiple exposure assessment approaches demonstrate the broad array of chemicals women are exposed to during pregnancy. Many of these chemicals have not been well-studied in terms of their effects on human health. KEYWORDS: exposome, reproductive outcomes, environmental disparities

Multivariate optimization of a two-way technique for extraction of pharmaceuticals in surface water using a combination of membrane assisted solvent extraction and a molecularly imprinted polymer

This work demonstrates development and evaluation of a two-way technique based on the combination of membrane assisted solvent extraction and a molecularly imprinted polymer (MASE-MIP) for selective and efficient extraction of five selected pharmaceuticals belonging to five different therapeutic classes. The pharmaceuticals were extracted from surface water samples followed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qTOF/MS) determination. A central composite design was applied to optimize the influence of the sample salt content, the stirring rate, the stirring time and the amount of MIP on the extraction of an anticonvulsant (carbamazepine), a cardiac stimulant (etilefrine), a muscle relaxant (methocarbamol), an antiretroviral (nevirapine) and an antidepressant (venlafaxine) from surface water. Optimization of the analytical method was performed by spiking water with a mixture of all five pharmaceuticals at 500 ng mL−1. Optimum extraction conditions for a sample volume of 18 mL were found to be 5 g of salt content, a stirring rate of 400 rpm, an extraction time of 60 min and 50 mg of MIP. The MASE-MIP-LC-qTOF/MS method gave detection and quantification limits ranging from 0.09 to 0.20 ng mL−1 and 0.31–0.69 ng mL−1, respectively. The spiked river water samples yielded recoveries ranging from 38 to 91% for the selected model compounds belonging to the five classes of pharmaceuticals. Upon the application of the developed analytical method in water analysis, all selected pharmaceuticals were detected in South African river water with nevirapine and venlafaxine being more prominent attaining the maximum concentrations of 1.64 and 2.48 ng mL−1, respectively.

Quantification of anti-SARS-CoV-2 antibodies in human serum with LC-QTOF-MS

The aim of this study was to develop the first quantitative serological test for anti-SARS-CoV-2 antibodies in human serum with liquid chromatography - quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Other assays, mostly immunoassays, are only qualitative or semi-quantitative, and hence, actual antibody concentrations after SARS-CoV-2 infection are unknown. In our assay, anti-SARS-CoV-2 antibodies were isolated with spike protein subunit 1 (S1) coupled to magnetic beads. IgG1 signature peptide GPSVFPLAPSSK was selected for quantification using ipilimumab calibration standards and SILuMAb K1 as the stable-isotope labeled internal standard. The anti-SARS-CoV-2 IgG1 calibration range was from 1.35 to 135 nM. Inter-assay accuracies were between 98.8%− 107% with inter-assay precisions between 8.37%− 13.5% measured at 3 concentration levels on three separate occasions. Anti-SARS-CoV-2 IgG1 antibodies were quantified in PCR-positive patients with mild to severe symptoms. IgM signature peptide DGFFGVPR was detected in patients that recently recovered from COVID-19. A unique and quantitative LC-QTOF-MS method to quantify anti-SARS-CoV-2 IgG1 in serum was successfully developed and its clinical applicability has been demonstrated.

Tetracycline Antibiotics: Elucidating the Electrochemical Fingerprint and Oxidation Pathway

Herein, a complete study of the electrochemical behavior of the most commonly used tetracycline antibiotics (TCs) on unmodified carbon screen-printed electrodes (SPEs) is presented. In addition, the oxidation pathway of TCs on SPE is elucidated, for the first time, with liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Square wave voltammetry (SWV) was used to study the electrochemical fingerprint (EF) of the antibiotics shaping the different oxidation processes of the TCs in a pH range from 2 to 12. Their characteristic structure and subsequent EF offer the possibility of distinguishing this class of antibiotics from other types. Under the optimized parameters, calibration curves of tetracycline (TET), doxycycline (DOXY), oxytetracycline (OXY), and chlortetracycline (CHL) in a Britton Robinson buffer solution (pH 9) exhibited a linear range between 5 and 100 µM with excellent reproducibilities (RSDTET = 3.01%, RSDDOXY = 3.29%, RSDOXY = 9.78% and RSDCHL = 6.88% at 10 µM, N = 3) and limits of detection (LOD) of LODTET = 4.15 µM, LODDOXY = 2.14 µM, LODOXY = 3.07 µM and LODCHL = 4.15 µM. Furthermore, binary, tertiary, and complex mixtures of all TCs were analyzed with SWV to investigate the corresponding EF. A dual pH screening (pH 4 and pH 9), together with the use of a custom-made Matlab script for data treatment, allowed for the successful confirmation of a single presence of TCs in the unknown samples. Overall, this work presents a straightforward study of the electrochemical behavior of TCs in SPE, allowing for the future on-site identification of residues of tetracycline antibiotics in real samples.

Quantification of fentanyl analogs in oral fluid using LC-QTOF-MS.

Oral fluid is a valuable alternative matrix for forensic toxicologists due to ease of observed collection, limited biohazardous exposure, and indications of recent drug use. Limited information is available for fentanyl analog prevalence, interpretation, or analysis in oral fluid. With increasing numbers of fentanyl-related driving under the influence of drug (DUID) cases appearing in the United States, the development of detection methods is critical. The purpose of the present study was to develop and validate a quantitative method for fentanyl analogs in oral fluid (collected via Quantisal™) using liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-QTOF-MS). Validation resulted in limits of detection and quantification ranging from 0.5 to 1ng/mL. Established linear range was 1-100ng/mL for all analytes, except acetyl fentanyl at 0.5-100ng/mL (R2 >0.994). Within- and between-run precision and bias were considered acceptable with maximum values of ±15.2%CV and ±14.1%, respectively. Matrix effects exhibited ionization enhancement for all analytes with intensified enhancement at a low concentration (9.3-47.4%). No interferences or carryover was observed. Fentanyl analogs were stable in processed extracts stored in the autosampler (4⁰ C) for 48h. The validated method was used to quantify fentanyl analogs in authentic oral fluid samples (n=17) from probationers/parolees. Fentanyl and 4-ANPP concentrations were 1.0-104.5ng/mL and 1.2-5.7ng/mL, respectively.

A Comprehensive Non-targeted Analysis Study of the Prenatal Exposome.

Recent technological advances in mass spectrometry have enabled us to screen biological samples for a very broad spectrum of chemical compounds allowing us to more comprehensively characterize the human exposome in critical periods of development. The goal of this study was three-fold: (1) to analyze 590 matched maternal and cord blood samples (total 295 pairs) using non-targeted analysis (NTA); (2) to examine the differences in chemical abundance between maternal and cord blood samples; and (3) to examine the associations between exogenous chemicals and endogenous metabolites. We analyzed all samples with high-resolution mass spectrometry using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) in both positive and negative electrospray ionization modes (ESI+ and ESI-) and in soft ionization (MS) and fragmentation (MS/MS) modes for prioritized features. We confirmed 19 unique compounds with analytical standards, we tentatively identified 73 compounds with MS/MS spectra matching, and we annotated 98 compounds using an annotation algorithm. We observed 103 significant associations in maternal and 128 in cord samples between compounds annotated as endogenous and compounds annotated as exogenous. An example of these relationships was an association between three poly and perfluoroalkyl substances (PFASs) and endogenous fatty acids in both the maternal and cord samples indicating potential interactions between PFASs and fatty acid regulating proteins.

Complex profiles of azaspiracid analogues in two culture strains of Azadinium poporum (Amphidomataceae, Dinophyceae) isolated from Japanese coastal waters determined by LC-MS/MS

Lipophilic marine biotoxins azaspiracids (AZAs) are produced by dinoflagellates Azadinium and Amphidoma. Recently, several strains of Azadinium poporum were isolated from Japanese coastal waters. In our present study, AZA analogues in two strains (mdd421 and HM536) of A. poporum were analyzed by several detection techniques on the liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-quadrupole time of flight mass spectrometry (LC-QTOFMS). The dominant AZA analogue in the Japanese A. poporum strains was AZA2. Other known AZA analogues were AZA11, AZA35, AZA2 methyl ester and AZA2 phosphate ester. Besides these AZAs, thirteen new AZA analogues were discovered in the two strains. A putative AZA analogue (Compound 1) with the smallest molecular weight ever found in nature was also discovered in the two strains. This is the first report describing detailed AZA profiles in Japanese isolates of A. poporum.

Exploration of antibacterial and antioxidative activity of seed/peel extracts of Southeast Asian fruit Durian ( Durio zibethinus ) for effective shelf‐life enhancement of preserved meat

This investigation was aimed to explore antibacterial and antioxidant compounds in Durio zibethinus (Durian) peel/seed extracts and their effectiveness in preventing meat decay. The antioxidant compound from D. zibethinus peel/seed extracts is determined using total phenolic content (TPC) and total flavonoid content (TFC). The antibacterial ability of sample extract was proven by the inhibition zone observed in the agar plate containing four foodborne pathogens. The results obtained proved that the antioxidant activity of a 9% concentration of both peels/seeds demonstrated more significant p value for all the measurements (p < .05). However, based on TFC and TPC, peels exhibited higher content compared to seeds. The visual observation meat treated with peel/seed extracts seemed to have low metMb accumulation as the brown discoloration slowly compared to control. The qualitative tandem liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF-MS) analysis led to the identification of 159 compounds and 79 compounds. All samples were moderately active towards the bacteria tested by representing halozones formation in size range from 12.0 to 21.0 mm. The pH of marinated meat with sample extract indicated that the meat is safe and not required immediate consumption after nine days. The results revealed the potential of utilizing D. zibethinus peels and seeds in prolonging the shelf life of meat. Practical applications Durian is a well-known fruit obtainable in southeast countries like Malaysia. Durian seed extract is an efficient food preservative that helps in preventing meat decay. Natural preservatives obtained from plant source are efficient compared to the chemical. Durian seed extract can be the best food preservative to prevent meat decay without causing any effects on its natural quality and shelf life.

Early Breast Cancer Detection Using Untargeted and Targeted Metabolomics.

Breast cancer (BC) is a common cause of morbidity and mortality, particularly in women. Moreover, the discovery of diagnostic biomarkers for early BC remains a challenging task. Previously, we [Jasbi et al. J. Chromatogr. B. 2019, 1105, 26-37] demonstrated a targeted metabolic profiling approach capable of identifying metabolite marker candidates that could enable highly sensitive and specific detection of BC. However, the coverage of this targeted method was limited and exhibited suboptimal classification of early BC (EBC). To expand the metabolome coverage and articulate a better panel of metabolites or mass spectral features for classification of EBC, we evaluated untargeted liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) data, both individually as well as in conjunction with previously published targeted LC-triple quadruple (QQQ)-MS data. Variable importance in projection scores were used to refine the biomarker panel, whereas orthogonal partial least squares-discriminant analysis was used to operationalize the enhanced biomarker panel for early diagnosis. In this approach, 33 altered metabolites/features were detected by LC-QTOF-MS from 124 BC patients and 86 healthy controls. For EBC diagnosis, significance testing and analysis of the area under receiver operating characteristic (AUROC) curve identified six metabolites/features [ethyl (R)-3-hydroxyhexanoate; caprylic acid; hypoxanthine; and m/z 358.0018, 354.0053, and 356.0037] with p < 0.05 and AUROC > 0.7. These metabolites informed the construction of EBC diagnostic models; evaluation of model performance for the prediction of EBC showed an AUROC = 0.938 (95% CI: 0.895-0.975), with sensitivity = 0.90 when specificity = 0.90. Using the combined untargeted and targeted data set, eight metabolic pathways of potential biological relevance were indicated to be significantly altered as a result of EBC. Metabolic pathway analysis showed fatty acid and aminoacyl-tRNA biosynthesis as well as inositol phosphate metabolism to be most impacted in response to the disease. The combination of untargeted and targeted metabolomics platforms has provided a highly predictive and accurate method for BC and EBC diagnosis from plasma samples. Furthermore, such a complementary approach yielded critical information regarding potential pathogenic mechanisms underlying EBC that, although critical to improved prognosis and enhanced survival, are understudied in the current literature. All mass spectrometry data and deidentified subject metadata analyzed in this study have been deposited to Mendeley Data and are publicly available (DOI: 10.17632/kcjg8ybk45.1).

Profiling of contemporary beer styles using liquid chromatography quadrupole time-of-flight mass spectrometry, multivariate analysis, and machine learning techniques

Although all beer is brewed using the same four classes of ingredients, contemporary beer styles show wide variation in flavor and color, suggesting differences in their chemical profiles. A selection of 32 beers covering five styles (India pale ale, blonde, stout, wheat, and sour) were investigated to determine chemical features, which discriminate between popular beer styles. The beers were analyzed in an untargeted fashion using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). The separation and detection method were tuned to include compounds from important beer components, namely iso-α-acids and phenolic compounds. Due to the sheer number of unknown compounds in beer, multivariate analysis and machine learning techniques were used to pinpoint some of the compounds most influential in distinguishing beer styles. It was determined that while many phenols and iso-α-acids were present in the beers, they were not the compounds most responsible for the variations between styles. However, it was possible to discriminate each beer style using multivariate analysis. Principal component analysis (PCA) was able to separate and cluster the individual beer samples by style. A combination of statistical tools were used to predict formulas for some of the most influential metabolites from each style. Machine learning models accurately classified patterns in the five beer styles, indicating that they can be precisely distinguished by their nonvolatile chemical profile.

Metabolic Profiling from an Asymptomatic Ferret Model of SARS-CoV-2 Infection.

Coronavirus disease (COVID-19) is a contagious respiratory disease that is causing significant global morbidity and mortality. Understanding the impact of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection on the host metabolism is still in its infancy but of great importance. Herein, we investigated the metabolic response during viral shedding and post-shedding in an asymptomatic SARS-CoV-2 ferret model (n = 6) challenged with two SARS-CoV-2 isolates. Virological and metabolic analyses were performed on (minimally invasive) collected oral swabs, rectal swabs, and nasal washes. Fragments of SARS-CoV-2 RNA were only found in the nasal wash samples in four of the six ferrets, and in the samples collected 3 to 9 days post-infection (referred to as viral shedding). Central carbon metabolism metabolites were analyzed during viral shedding and post-shedding periods using a dynamic Multiple Reaction Monitoring (dMRM) database and method. Subsequent untargeted metabolomics and lipidomics of the same samples were performed using a Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry (LC-QToF-MS) methodology, building upon the identified differentiated central carbon metabolism metabolites. Multivariate analysis of the acquired data identified 29 significant metabolites and three lipids that were subjected to pathway enrichment and impact analysis. The presence of viral shedding coincided with the challenge dose administered and significant changes in the citric acid cycle, purine metabolism, and pentose phosphate pathways, amongst others, in the host nasal wash samples. An elevated immune response in the host was also observed between the two isolates studied. These results support other metabolomic-based findings in clinical observational studies and indicate the utility of metabolomics applied to ferrets for further COVID-19 research that advances early diagnosis of asymptomatic and mild clinical COVID-19 infections, in addition to assessing the effectiveness of new or repurposed drug therapies.

Serum-Urine Matched Metabolomics for Predicting Progression of Henoch-Schonlein Purpura Nephritis.

Henoch-Schonlein purpura nephritis (HSPN) is a common glomerulonephritis secondary to Henoch-Schonlein purpura (HSP) that affects systemic metabolism. Currently, there is a rarity of biomarkers to predict the progression of HSPN. This work sought to screen metabolic markers to predict the progression of HSPN via serum-urine matched metabolomics. A total of 90 HSPN patients were enrolled, including 46 HSPN (+) patients with severe kidney damage (persistent proteinuria >0.3 g/day) and 44 HSPN (–) patients without obvious symptoms (proteinuria < 0.3 g/day). Untargeted metabolomics was determined by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q/TOF-MS). A total of 38 and 50 differential metabolites were, respectively, identified in serum and urine from the comparison between HSPN (+) and HSPN (–) patients. Altered metabolic pathways in HSPN (+) mainly included glycerophospholipid metabolism, pyruvate metabolism, and citrate cycle. A panel of choline and cis-vaccenic acid gave areas under the curve of 92.69% in serum and 72.43% in urine for differential diagnosis between HSPN (+) and HSPN (–). In addition, the two metabolites showed a significant association with clinical indices of HSPN. These results suggest that serum-urine matched metabolomics comprehensively characterized the metabolic differences between HSPN (+) and HSPN (–), and choline and cis-vaccenic acid could serve as biomarkers to predict HSPN progression.

Sensitive screening of synthetic cannabinoids using liquid chromatography quadrupole time-of-flight mass spectrometry after solid phase extraction.

Analysis of synthetic cannabinoids still poses a challenge for many institutions due to the number of available substances and the constantly changing drug market. Both new and well-known substances keep appearing and disappearing on the market, making it hard to adapt analytical methods in a timely manner. In this study, we developed a qualitative screening approach for synthetic cannabinoids and their metabolites by means of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Samples were measured in data-dependent auto-MS/MS mode and identified by fragment spectra, retention time and accurate mass. Two established solid phase extractions were compared using fortified serum and urine samples. Mixes of 199 synthetic cannabinoids and 110 metabolites were used in 1- and 10-ng/ml concentrations. Up to 93% of synthetic cannabinoids and 74% of metabolites were detected in fortified 1-ng/ml samples. From February 2018 to October 2020, we analyzed 1492 cases, of which 73 cases were positive for synthetic cannabinoids or metabolites. 5F-MDMB-PICA, 4F-MDMB-BINACA, MDMB-4en-PINACA, and 4F-MDMB-BICA were most frequently detected. Hydrolysis metabolites were detected in many blood samples, providing a longer detection window. Quantification was conducted via liquid chromatography triple quadrupole mass spectrometry after liquid-liquid extraction. Concentrations were mostly close to 1 ng/ml in blood samples. LC-QTOF-MS was able to detect substances above trace quantities (< 0.1 ng/ml) in most cases, therefore fulfilling its purpose as a sensitive general screening approach. Expansion of the screening library was uncomplicated and enables future additions for up to thousands of targets.

New synthetic cannabinoids carrying a cyclobutyl methyl side chain: Human Phase I metabolism and data on human cannabinoid receptor 1 binding and activation of Cumyl-CBMICA and Cumyl-CBMINACA.

Synthetic cannabinoids (SCs) represent a large group of new psychoactive substances (NPS), sustaining a high prevalence on the drug market since their first detection in 2008. Cumyl-CBMICA and Cumyl-CBMINACA, the first representatives of a new subclass of SCs characterized by a cyclobutyl methyl (CBM) moiety, were identified in July 2019 and February 2020. This work aimed at evaluating basic pharmacological characteristics and human Phase I metabolism of these compounds. Human Phase I metabolites were tentatively identified by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QToF-MS) of urine samples and confirmed by a pooled human liver microsome (pHLM) assay. The basic pharmacological evaluation was performed by applying a competitive ligand binding assay and a functional activation assay (GTPγS) using cell membranes carrying the human cannabinoid receptor 1 (hCB1 ). Investigation of the human Phase I metabolism resulted in the identification of specific urinary markers built by monohydroxylation or dihydroxylation. Although Cumyl-CBMICA was primarily hydroxylated at the indole ring, hydroxylation of Cumyl-CBMINACA mainly occurred at the CBM moiety. Both substances acted as agonists at the hCB1 receptor, although substantial differences could be observed. Cumyl-CBMINACA showed higher binding affinity (Ki = 1.32 vs. 29.3 nM), potency (EC50 = 55.4 vs. 497 nM), and efficacy (Emax = 207% vs. 168%) than its indole counterpart Cumyl-CBMICA. This study confirms that substitution of an indole by an indazole core tends to increase in vitro potency, which is potentially reflected by higher in vivo potency. The emergence and disappearance of SCs distributed via online shops carrying a CBM moiety once more demonstrate the "cat-and-mouse" game between manufacturers and legislation.

Photocatalytic degradation of imidacloprid in the flat-plate photoreactor under UVA and simulated solar irradiance conditions—The influence of operating conditions, kinetics and degradation pathway

This work reports the effectiveness of TiO2 photocatalysts modified by defect engineering methods. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) measurements and electron spin resonance (ESR) technique. The immobilized photocatalyst layer was prepared using an abrasive material as a support and a mineral binder. To the best of our knowledge, this is the first time that such type of the immobilized photocatalytic layer has been prepared and tested. A home-made flat-plate photoreactor (FPP) with artificial light sources was used for the degradation of an aqueous solution of imidacloprid using an immobilized TiO2. The effects of different operating variables such as irradiation source, recirculation flow rate, irradiated surface area and photoreactor volume on the photocatalytic performances were investigated. The hydrodynamic behavior of the flat-plate photoreactor (FPP) was studied utilizing a residence time distribution (RTD) technique using the axial dispersion model. Based on kinetic measurements it was found that the photocatalytic degradation of imidacloprid under the conditions used in this study can be described by a complex kinetic model that follows pseudo-zero order kinetics at the beginning of the degradation, and with the progress of the reaction at higher irradiation times changes to the pseudo-first order. Liquid chromatography - quadrupole time‐of‐flight mass spectrometry (LC‐QTOF‐MS) was used to identify imidacloprid degradation by-products as a function of irradiation time. Theoretical modeling of the geometry and electronic structure of imidacloprid in aqueous solution was performed using density functional theory (DFT) calculation. Based on the results of theoretical simulations and experimental measurements, the possible pathway for photodegradation of imidacloprid in aqueous phase after irradiation with UVA was proposed and discussed.

Characterization of in vitro phase I metabolites of methamnetamine in human liver microsomes by liquid chromatography-quadrupole time-of-flight mass spectrometry.

N-Methyl-1-(naphthalen-2-yl)propan-2-amine (methamnetamine, PAL-1046) is an amphetamine-based new psychoactive substance (NPS). Methamnetamine has been reported to cause excessive release of serotonin, and it is classified as an empathogen or entactogen. It is not regulated as a controlled substance in most countries, and there are no studies on its metabolism. In this study, in vitro phase I metabolism of methamnetamine in human liver microsomes (HLM) and flavin-containing monooxygenase (FMO) was investigated by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS). Eight metabolites of methamnetamine were identified and were structurally characterized achieved by a combination of accurate mass analysis and tandem mass spectrometry. The identified metabolic processes include N-demethylation, N-hydroxylation, aromatic hydroxylation, and a combination of these processes. N-Hydroxylated metabolites were confirmed based on expressed FMOs. The major metabolite was formed from methamnetamine via hydroxylation of the naphthalene ring after the in vitro phase I process. These results could help detect methamnetamine ingestion by NPS abusers.

Metabolite fingerprinting of oil palm (Elaeis guineensis Jacq.) root for the identification of altered metabolic pathways associated with basal stem rot (BSR) disease

Basal stem rot (BSR) disease caused by Ganoderma boninense has remained as one of the major obstacles in oil palm (Elaeis guineensis Jacq.) plantation. BSR is a destructive disease, which contributes to significant yield losses and impacts to the oil palm industry. However, to date, there is still no effective control of the disease. Metabolite fingerprinting is an established non-targeted screening approach to classify samples based on metabolite patterns that change in response to G. boninense infection in oil palm. This study aimed to compare the metabolic profiles of natural Ganoderma-infected and healthy control oil palm root samples using liquid chromatography-quadrupole/time-of-flight-mass spectrometry (LC-Q/TOF-MS) combined with multivariate data analysis (MVDA) and to identify potential metabolic pathway(s) involved in response to BSR. MVDA revealed differential metabolites from oil palm root associated with natural Ganoderma-infected vs. healthy oil palms. A systematic metabolic pathway analysis of differential metabolites discovered the significant involvement of amino acid metabolism, carbohydrate metabolism and biosynthesis of other secondary metabolites in response to BSR disease. Unravelling the metabolic mechanisms involved during pathogen attack provides new knowledge and fill gaps in the information related to the oil palm-Ganoderma pathosystem.

Development and validation of liquid chromatography-tandem mass spectrometry method for screening six selective androgen receptor modulators in dietary supplements

ABSTRACT Selective androgen receptor modulators (SARMs) are compounds with specific androgenic properties that have been investigated for the treatment of conditions such as muscle wasting disease. The reported androgenic properties have resulted in their use by athletes, and consequently they have been on the World Anti–Doping Agency prohibited list for more than a decade. To minimise the chance of an unattended positive doping test and to avoid potential serious health problems, adequate screening methods for the detection of a wide range of SARMs in these supplements is necessary. In this study, a rapid and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated simultaneously to screen and quantify six SARMs in dietary supplements, with confirmation by liquid chromatography-quadrupole-time of flight mass spectrometry (LC-Q-TOF/MS). The validated method was applied to 60 dietary supplements obtained by on-line and direct purchase from international vendors in 2020. Various SARMs were detected at high concentrations in 20 products which were advertised as having androgenic properties. For example, andarine was present at 7.2% in one product, and GW501516 was found at 3.49% in the another product. Furthermore, MK-677 and YK-11, not disclosed on the label, were detected in some products. YK-11 is easily hydrolysed in just a few hours. Although YK-11 is particularly unstable, such that the protonated ion [M + H]+ at m/z 431 for YK-11 was not detected, mass fragmentation, and a [M+ Na]+ ion at m/z 453.3 confirmed the presence of YK-11. Additionally, hydrolysed YK-11 under acidic conditions was confirmed by NMR spectral data, and 1H NMR and 13C NMR spectral data for YK-11 were in good agreement with literature data. This rapid and accurate LC-MS/MS method can therefore be successfully applied to screen and identify SARMs for the continuous control and supervision of dietary supplements.

Application of a simultaneous screening method for the detection of new psychoactive substances in various matrix samples using liquid chromatography/electrospray ionization tandem mass spectrometry and liquid chromatography/quadrupole time‐of‐flight mass spectrometry

Recently, new psychoactive substances (NPS) emerged as a public health risk. Particularly, their chemical structures are modified to avoid detection. Synthetic NPS with effects similar to those of illegal drugs have been recently detected and synthesised worldwide, including MDMB-FUBINACA and APINAC, making it essential to rapidly and accurately detect NPS. Fourteen NPS with similar structures were selected and their structures identified using 1 H and 13 C NMR spectroscopy. Additionally, we proposed the fragmentation pattern of each compound using LC-QTOF-MS. A simultaneous analytical method using ESI-LC-MS/MS was also developed and applied to real samples to detect 14 NPS. The method was validated based on the specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, matrix effect, and stability according to international validation guidelines. The established method was used to screen 65 different matrix samples using LC-ESI-MS/MS. By comparing the calculated product ion ratios with those of standards, 2C-B in one real samples and 5F-MDMB-PICA in 20 samples were identified. For re-confirmation of detected compounds, each fragmentation pattern of each compound was compared to that of each standard using LC-QTOF-MS. In this study, LC-QTOF-MS were used to elucidate the structures and fragmentation patterns of 14 NPS. A simultaneous method was developed using LC-ESI-MS/MS, which was applied to 65 real samples. The presented method and results can assist in ensuring the safety of public health from illegal adulteration.