Positive Ion Detection Research Articles

Detection of Sugar Syrups in Honey Using Untargeted Liquid Chromatography-Mass Spectrometry and Chemometrics.

Background: Honey is one of the most adulterated foods worldwide, and several analytical methods have been developed over the last decade to detect syrup additions to honey. These include approaches based on stable isotopes and the specific detection of individual marker compounds or foreign enzymes. Proton nuclear magnetic resonance (1H-NMR) spectroscopy is applied as a rapid and comprehensive screening method, which also enables the detection of quality parameters and the analysis of the geographical and botanical origin. However, especially for the detection of foreign sugars, 1H-NMR has insufficient sensitivity. Methods: Since untargeted liquid chromatography-mass spectrometry (LC-MS) is more sensitive, we used this approach for the detection of positive and negative ions in combination with a recently developed data processing workflow for routine laboratories based on bucketing and random forest for the detection of rice, beet and high-fructose corn syrup in honey. Results: We show that the distinction between pure and adulterated honey is possible for all three syrups, with classification accuracies ranging from 98 to 100%, while the accuracy of the syrup content estimation depends on the respective syrup. For rice and beet syrup, the deviations from the true proportion were in the single-digit percentage range, while for high-fructose corn syrup they were much higher, in some cases exceeding 20%. Conclusions: The approach presented here is very promising for the robust and sensitive detection of syrup in honey applied in routine laboratories.

B-166 Differentiation of Aziridine Functionality from Related Functional Groups in Protonated Analytes by Using Selective Ion-Molecule Reactions

Abstract Background The development of better methods for the rapid and reliable identification of unknown compounds in mixtures is urgently needed in drug development. Aziridines, in particular, are used for drug synthesis but are potentially mutagenic and carcinogenic compounds. However, the detection and identification of these compounds pose challenges for many analytical methods, such as Nuclear Magnetic Resonance (NMR) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and X-ray crystallography. These techniques are time-consuming and often require large quantities of highly pure compounds. Methods Therefore, this study demonstrates that selective gas-phase ion-molecule reactions of protonated analytes with neutral tris(dimethylamino)borane (TDMAB), followed by diagnostic collision-activated dissociation (CAD), can be used to differentiate aziridines from structurally related compounds in a modified linear quadrupole ion trap (LQIT) mass spectrometer. The experiments were performed using an atmospheric pressure chemical ionization (APCI) source in positive ion detection mode. TDMAB was purchased from Sigma-Aldrich and used without purification. It was introduced into the ion trap (2 mtorr of helium buffer gas) via an external reagent mixing manifold through a syringe pump at a flow rate of 10 μL h-1 and diluted with helium before entering the ion trap through a variable leak valve. All analytes were prepared at a concentration of 1 mM in methanol. The protonated analytes were transferred into the ion trap, isolated, and allowed to react with TDMAB (MS2 experiments). Results Product ions formed upon reactions of the analyte ions with TDMAB were subjected to a collision-activated dissociation (CAD) experiment (MS3 experiments). CAD on product ions produced diagnostic fragment ions with 25- and 43 m/z-units lower m/z values than the adduct - DMA product ions. Quantum chemical calculations were employed using the Gaussian 16 program calculated at the M06-2X/6-311++G(d,p) level of theory to provide theoretical foundation and to explore the underlying mechanisms of the observed gas-phase reactions. None of the tested structurally related analytes produced a similar fragmentation pattern Conclusions The innovative approach presented in this study offers a promising avenue for enhancing efficiency and accuracy in drug development. The successful differentiation of aziridine is an alternative method in overcoming the limitation of traditional techniques. The findings from the research contributes to the advancement of analytical techniques, addressing critical issues in identifying impurities in drug products. The versatility of the methods extends beyond drug developments, making it applicable in various other fields such as in molecular diagnostics, metabolism and laboratory medicines.

UPLC-MS/MS analysis of axitinib and pharmacokinetic application in beagle dogs

ObjectiveTo develop a method for determining the concentration of axitinib in beagle dog plasma and utilize this method to investigate the pharmacokinetics of orally administered axitinib in beagle dogs. MethodsPlasma samples were processed using acetonitrile precipitation and analyzed by UPLC-MS/MS with sunitinib as an internal standard (IS). Chromatographic separation was achieved on a Waters Acquisition UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 μm) with a gradient elution of acetonitrile and 0.1 % formic acid. Mass spectrometry uses an electrospray ion source for positive ion detection in a multiple reaction monitoring mode. The monitored ion transitions for axitinib and sunitinib were m/z 387 → 355.96 and m/z 399.3 → 282.96, respectively. Six beagle dogs were administered 0.33 mg/kg of axitinib orally, and venous blood samples were collected at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 h post-dose for pharmacokinetic analysis. ResultsThe assay demonstrated a linear range of 0.5–100 ng/mL (r2 = 0.9992), and the lower limit of quantification was up to 0.5 ng/mL. Precision, as assessed by relative standard deviation (RSD), was within 8.64 % for both intraday and interday variability. The relative error (RE) for precision from −2.77 %–1.20 %. The recovery rate of the analytes exceeded 85.28 % and the matrix effect was approximately 100 %. Plasma samples maintained stability under various conditions, including room temperature storage for 12 h, processed on an automatic sampler at 4 °C for 6 h, three freeze-thaw cycles, and long-term storage at −80 °C for 60 days. Pharmacokinetic parameters were determined using DAS 2.0 software, revealing a half-life (T1/2) of 6.05 h and an area under the curve (AUC (0 →∞)) of 97.13 ng h/mL for axitinib. ConclusionsThe UPLC-MS/MS method developed in this study offers high specificity, rapid analysis, high recovery, excellent linearity, and minimal plasma volume requirements, making it well-suited for pharmacokinetic and drug interaction studies in beagles dogs.

Assessing the matrix effects on MALDI-MS in the positive and negative ion mode detection for protein-protected metal nanoclusters

Protein-protected metal nanoclusters (MNCs) represent a new class of highly photoluminescent nanomaterials that have wide applications. Suitable reaction conditions combining protein and metal precursors can produce a vast range of different NC sizes (i.e. different number of metal atoms). The average number of metal atoms per protein can be determined by mass spectrometry (MS). MS coupled with matrix-assisted laser desorption ionization (MALDI) presents a number of advantages such as detection with high sensitivity of nanoclusters with high molecular weights. Although many protein-protected MNCs have been characterized by MALDI-MS, a large dispersion in the number of metal atoms has been reported mainly due to sample preparation. In this work, we optimized the protocols for negative and positive ion detection mode as a general MALDI-MS sample preparation method for protein-protected MNCs (bovine serum albumin and lysozyme and with gold and silver). Negative and positive ion mode detection was compared, showing that negative ion mode detection in MALDI-MS can also be used with acidic matrices. Obvious matrix effects on ion signals and peak positions by MALDI-MS were observed. The average metal numbers of MNCs embedded in proteins are different depending on the MALDI matrix. The matrix effects give a warning for more serious consideration on MALDI-MS measurement and spectra analysis of MNCs.

Advanced UPLC-MS/MS Method for the Quantification of SIPI6398 in Rat Plasma and Its Pharmacokinetic Characterization.

SIPI6398 is a novel anti-schizophrenia agent with a new mechanism of action and demonstrates better target selectivity and safety compared to its competitors. However, few in vivo studies on the pharmacokinetics and bioavailability of SIPI6398 have been performed. A rapid and simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) approach was developed for accurate quantification of SIPI6398 in rat plasma. A simple protein precipitation of acetonitrile-methanol (9 : 1, v/v) was used to treat plasma. Chromatography was performed on a UPLC HSS T3 column (50 mm × 2.1 mm, 1.8 μm) at a flow rate of 0.4 ml/min. The mobile phase consisted of acetonitrile-water (with 0.1% formic acid) and gradient elution was used, and the elution time was 4 minutes. Quantitative analysis was performed using electrospray ionization (ESI) in positive ion detection mode with multiple reaction monitoring (MRM) mode. To evaluate the pharmacokinetics and bioavailability, SIPI6398 was administered to rats in two different ways: oral (4 mg/kg) and intravenous (2 mg/kg) administration. The calibration curve for the UPLC-MS/MS approach shows excellent linearity in the range of 1-2000 ng/mL with an r value above 0.99. The precision, accuracy, recovery, matrix effect, and stability results all meet the criteria established for biological analytical methods. The UPLC-MS/MS method was successfully applied it to pharmacokinetics study of SIPI6398. The bioavailability of SIPI6398 was calculated to be 13.2%. These studies have the potential to contribute towards a more comprehensive comprehension of the pharmacokinetics and bioavailability of SIPI6398.

Determination of nine cardiovascular drugs in human plasma by QuEChERS-UPLC-MS/MS

ObjectiveTo determine the concentrations of nine drugs used in the treatment of cardiovascular diseases in human plasma through QuEChERS pre-treatment combined with ultra-performance liquid chromatography-tandem mass spectrometry. Plasma samples were extracted with 3 mL of acetonitrile, 400 mg of anhydrous magnesium sulfate as a salting agent, and 20 mg of C18 as a sorbent. An Agilent Poroshell 120 EC-C18 column (4.6 × 100 mm, 2.7 μm) was selected and methanol-0.1 % water was used as the mobile phase, and ESI positive ion detection mode was selected. Results: The plasma concentrations of nisoldipine, metoprolol, and prazosin exhibited good linearity within the range of 0.05–4.0 ng/mL (r > 0.99), while atenolol, bisoprolol, propranolol, rosuvastatin, and atorvastatin showed linearity within the range of 0.5–40 ng/mL (r > 0.99). Fluvastatin showed good linearity within the range of 5.0–400 ng/mL. The accuracy of the method ranged from 94.15 to 110.62 %, while the recovery levels were in the range of 85.23 %–115.13 %. The matrix effects were observed between-6.54 % and 12.43 %. The intra-day and inter-day RSD was <15 % for the three concentrations of low, medium, and high. Conclusion The proposed method is rapid, accurate, specific, simple, reproducible, and suitable for the simultaneous measurement of the concentrations of nine drugs used in the treatment of cardiovascular diseases in human plasma.

Simultaneous determination of maltol and maltol glucuronide in human plasma and urine by HPLC–MS/MS: Application in clinical study in patients with iron deficiency

Ferric maltol has been used as an oral drug for iron deficiency. This study developed and fully validated the novel HPLC–MS/MS methods to determine maltol and maltol glucuronide simultaneously in plasma and urine. The protein precipitation was performed by addition of acetonitrile in the plasma samples. The dilution was performed for the urine samples to reach the suitable concentrations for injection. The multiple reaction monitoring (MRM) with an electrospray ionization (ESI) positive ion detection mode was used for the quantification. The maltol concentration linear ranges were 6.00–150 ng/mL and 0.100–10.0 μg/mL for the plasma and urine samples, respectively. The maltol glucuronide concentration linear ranges were 50.0–15000 ng/mL and 2.00–2000 μg/mL for the plasma and urine samples, respectively. These methods were applied to a single dose clinical study at a dose of 60 mg ferric maltol capsule in the patients with iron deficiency. The half-lives of maltol and maltol glucuronide were 0.90 ± 0.40 h and 1.02 ± 0.25 h in the iron deficiency patients, respectively. 39.52 ± 7.11 % maltol were excreted in urine in the form of maltol glucuronide.

Major benznidazole metabolites in patients treated for Chagas disease: Mass spectrometry-based identification, structural analysis and detoxification pathways

Benznidazole is the drug of choice for the treatment of Chagas disease, but its metabolism in humans is unclear. Here, we identified and characterized the major benznidazole metabolites and their biosynthetic mechanisms in humans by analyzing the ionic profiles of urine samples from patients and untreated donors through reversed-phase UHPLC-ESI-QTOF-MS and UHPLC-ESI-QqLIT-MS. A strategy for simultaneous detection and fragmentation of characteristic positive and negative ions was employed using information-dependent acquisitions (IDA). Selected precursor ions, neutral losses, and MS3 experiments complemented the study. A total of six phase-I and ten phase-II metabolites were identified and structurally characterized in urine of benznidazole-treated patients. Based on creatinine-corrected ion intensities, nitroreduction to amino-benznidazole (M1) and its subsequent N-glucuronidation to M5 were the main metabolic pathways, followed by imidazole-ring cleavage, oxidations, and cysteine conjugations. This extensive exploration of benznidazole metabolites revealed potentially toxic structures in the form of glucuronides and glutathione derivatives, which may be associated with recurrent treatment adverse events; this possibility warrants further exploration in future clinical trials. Incorporation of this knowledge of the benznidazole metabolic profile into clinical pharmacology trials could lead to improved treatments, facilitate the study of possible drug-drug interactions, and even mitigation of adverse drug reactions.

Evaluating the “wrong-way-round” electrospray ionization of antiretroviral drugs for improved detection sensitivity

The presence of antiretroviral drugs (ARVDs) in the aquatic environment poses a significant health risk to the ecosystem. The dilution of these compounds during wastewater treatment processes, followed by discharge into the environment, results in extremely low concentrations in the range of ng/L. Therefore, to enable detection of these low concentrations, it is important to determine the most efficient electrospray ionization (ESI) mode using the right mobile phase modifier and to establish a selective extraction procedure. In this study, we compared the ESI intensity in the positive and negative mode using both formic acid (FA) and ammonium hydroxide (NH4OH) as mobile phase modifiers. The results revealed a phenomenon known as the “wrong-way-round” (WWR) ESI in which high intensity [M + H]+ ions were detected under basic conditions using NH4OH as modifier and, similarly, high intensity [M-H]− ions were detected under acidic conditions using FA as modifier. Furthermore, mixed-mode strong cation (MCX) and mixed-mode strong anion (MAX) exchange sorbents were evaluated for extraction recoveries, which yielded extraction recoveries between 60 and 100%. Finally, the recoveries obtained using mixed-mode ion exchange sorbents compared to ion production during the ESI process provide evidence that ions produced in solution do not necessarily reflect the ions that are produced during the ESI process. Based on the results of this study, it is recommended to evaluate the optimal ionization mode under basic and acidic conditions, instead of defaulting to the use of acidic modifiers with positive ion detection.

Synthesis, structure and characterisation of late transition metal complexes with 2-(tetrazol-1-yl)pyridine

Complexes [MII(2-pytz)Cl2] (M(II) = Pt, Pd; 2-pytz = 2-(tetrazol-1-yl)pyridine) were synthesised via direct interaction of the corresponding metal chlorides (K2PtCl4 or PdCl2) with 2-pytz under ambient conditions. RuCl3 does not react with 2-pytz under reflux in the protic media, while under reflux in N, N-dimethylformamide in the presence of LiCl, decomposition of the tetrazole cycle occurred leading to the formation of Ru(III)-coordinated N, N-dimethyl-N ′-(pyridin-2-yl)formimidamide derivative Li[RuIII(Py — N =C — NMe2)2Cl2]. The complex [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH, where DMSO is dimethyl sulfoxide, was synthesised by reacting a specially prepared precursor cis-[Ru(DMSO)4Cl2] with 2-pytz in methanol under reflux conditions. The complex [Ru(2-pytz)(DMSO)2Cl2] was synthesised by reacting cis-[Ru(DMSO)4Cl2] with 2-pytz in ethanol under reflux conditions. The resulting complexes were characterised by elemental analyses, electrospray ionisation mass-spectrometry with detection of positive and negative ions, infrared spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and simultaneous thermal analysis. The structures of complexes [Pd(2-pytz)Cl2] and [Ru(2-pytz)(DMSO)3Cl2] ⋅ MeOH were investigated by single-crystal X-ray analysis. In the former, 2-pytz shows a N,N-chelating coordination via the pyridine ring N and the tetrazole ring N2 atoms. In the latter, 2-pytz coordinates as a monodentate ligand via the tetrazole ring N4 atom. According to 1H NMR spectroscopy data, in complex [Ru(2-pytz)(DMSO)2Cl2], 2-pytz coordinates as a N, N-chelating ligand via the pyridine ring N and the tetrazole ring N2 atoms.

Equilibration for Electrospray Ionization Mass Spectrometry in Quantitative Analysis.

Electrospray ionization mass spectrometry (ESI-MS) is widely used in drug development, therapeutic drug monitoring, and other fields. However, unstable mass spectral signals, especially during the initial stages of instrument operation, plague analysts. Generally, in quantitative experiments, the stability of response can be achieved by running the analytical system for some time. However, the equilibration time required for the responses of different compounds to stabilize has been elusive. To investigate the response stability of the ESI-MS system, 72 compounds with different physicochemical properties were employed on three systems, and flow injection analysis was performed in positive ion mode. With the use of 5.00% (response stable factor, RSF) as the stability limit, about 80% of the compounds were stable within 60 min. Under a 2.00% criterion, the stabilization time was significantly longer. The stabilization time varies with different instruments and physicochemical properties of the compounds. When positive ion detection is performed in an acidic mobile phase, the octanol-water partition coefficient (Log P), molecular weight, and molar volume can all affect the time required to stabilize the response. In general, it is necessary to balance the ESI-MS system for an appropriate time before sample detection, especially for the analysis of compounds with strong hydrophilicity, small molecular weight, or small molar volume under the conditions above.

Rapid screening of low-quality cooking oil by extractive electrospray ionization mass spectrometry

• Methodology of direct analysis of crude extract of edible vegetable oil and illegal cooking oil using extractive electrospray ionization (EESI) was established. • Characterized differences of each kind of quality oil mass fingerprint in the positive and negative ion detection mode. • Combined with principal component analysis (PCA), 20 different brands of cooking oil and five kinds of illegal cooking oil samples are successfully distinguished. Edible oils, an important raw material in food processing and the main sources for people to intake energy and nutrients in daily life, is too complex to rapid analyze due to its complicated chemical mixtures. Herein, methodology of direct analysis of crude extract of edible vegetable oil and illegal cooking oil using extractive electrospray ionization (EESI) was established. Fatty acids and other substances were directly identified, as well as differences of each kind of quality oil mass fingerprint were characterized in the positive and negative ion detection mode. Combined with principal component analysis (PCA), 20 different brands of cooking oil and five kinds of illegal cooking oil samples were successfully distinguished. Thus this method could distinguish sources of edible oil with high specificity, good accuracy, low false positives (∼ 0%) and rapid analysis (about 2 min), which was expected to be used for fast, effective high-throughput analysis of low-grade cooking oil.

The pharmacokinetic study on compound diphenhydramine hydrochloride and caffeine in rats

Objective To establish an assay method for diphenhydramine hydrochloride and caffeine in rat plasma by UPLC-MS/MS for pharmacokinetic study. Methods The chromatographic separation was performed on an ACE 3 C18-PFP (3.0 mm×150 mm, 3 μm) by isocratic elution with the mobile phase of water containing 0.1% formic acid and acetonitrile (62:38, V/V). MS condition was optimized in the positive ion detection mode by multiple reaction monitoring (MRM), along with the Agilent JetStream electrospray source interface (AJS-ESI). The precursors to the product ion transitions were 256.2→167.0 (m/z) for diphenhydramine hydrochloride, 262.0→167.0 (m/z) for the internal standard (IS) diphenhydramine-D6, 195.0→138.0 (m/z) for caffeine and 204.0→116.2 (m/z) for the IS caffeine-D9. Results The calibration curve was linear in the range of 1-1×103 ng/ml for diphenhydramine hydrochloride in rat plasma (r=0.999 6), and in the range of 15-1.5×105 ng/ml for caffeine in rat plasma, (r=0.999 9). The intra-day and inter-day precision and accuracy were good (RSD Conclusion This method is accurate, rapid and sensitive. It can be used for the determination of diphenhydramine hydrochloride and caffeine in rat plasma collected for pharmacokinetic study. The results of pharmacokinetic studies in rats provide reliable data support for the clinical application of the compound preparation.

Regional Lipid Expression Abnormalities Identified Using MALDI IMS Correspond to MRI-Defined White Matter Hyperintensities within Post-mortem Human Brain Tissues.

Periventricular white matter hyperintensities (pvWMHs) are a neurological feature detected with magnetic resonance imaging that are clinically associated with an increased risk of stroke and dementia. pvWMHs represent white matter lesions characterized by regions of myelin and axon rarefaction and as such likely involve changes in lipid composition; however, these alterations remain unknown. Lipids are critical in determining cell function and survival. Perturbations in lipid expression have previously been associated with neurological disorders. Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) is an emerging technique for untargeted, high-throughput investigation of lipid expression and spatial distribution in situ; however, the use of MALDI IMS has been previously been limited by the need for non-embedded, non-fixed, fresh-frozen samples. In the current study, we demonstrate the novel use of MALDI IMS to distinguish regional lipid abnormalities that correlate with magnetic resonance imaging (MRI) defined pvWMHs within ammonium formate washed, formalin-fixed human archival samples. MALDI IMS scans were conducted in positive or negative ion detection mode on tissues sublimated with 2,5-dihydroxybenzoic acid or 1,5-diaminonaphthalene matrices, respectively. Using a broad, untargeted approach to lipid analysis, we consistently detected 116 lipid ion species in 21 tissue blocks from 11 different post-mortem formalin-fixed human brains. Comparing the monoisotopic mass peaks of these lipid ions elucidated significant differences in lipid expression between pvWMHs and NAWM for 31 lipid ion species. Expanding our understanding of alterations in lipid composition will provide greater knowledge of molecular mechanisms underpinning ischemic white matter lesions and provides the potential for novel therapeutic interventions targeting lipid composition abnormalities.

Development of p-Coumaric Acid Analysis in Human Plasma and Its Clinical Application to PK/PD Study.

It has been recognized that p-Coumaric acid (p-CA) has protective effects as an antioxidant, anti-inflammatory agent. A sensitive and efficient Liquid Chromatography-Mass Spectrometry (LC-MS) method for maximum determination of p-CA in human plasma has been established using Ultra-performance liquid Chromatography-tandem mass Spectrometry (UPLC-MS/MS). This study provides the developed analysis of p-CA extracted from Bambusae Caulis in Taeniam (BC) to examine the improvement of the treatment p-CA, IGF-1 and Osteocalcin level in human children which are important factors on the growth of children’s height through Pharmacokinetics/Pharmacodynamics (PK/PD) model. p-CA and internal standard in a plasma sample were detected by the Multiple Reaction Monitoring (MRM) scan mode with positive ion detection. The sample participating in the study was made of 34 subjects (placebo = 18, treatment = 16). The subjects were enrolled to be randomized to the control group and BC group. Randomized subjects took tested treatment twice a day, three capsules with oral administration (258 mg/capsule) each time after a meal. Standard calibration curves (reproducibility) were constructed and the lower limit of quantitation (LLOQ) for p-CA was found to be 0.2 ng/mL on injection of the sample into the UPLC-MS/MS system. Accuracy and precision were evaluated and the intra-accuracy was 99.2–103.8% with precision of 1.0–5.6% and inter-accuracy was 99.6–108.4% and precision of 1.3–6.4% for p-CA. The method has been successfully applied to PK/PD studies of p-CA in human plasma. The p-CA, BC in Taeniam extract increased the level of IGF-1 and Osteocalcin, and changed the height from baseline, which suggested that the p-CA could play an important role in longitudinal bone growth. Therefore, the p-CA extracted from BC in Taeniam might be a good alternative medicine to growth hormone (GH) therapy.

Direct infusion nano-electrospray ionization mass spectrometry for therapeutic drug monitoring of ciprofloxacin and its metabolites in human saliva

A rapid and sensitive method based on direct infusion-nano-electrospray ionization mass spectrometry (DI-nESI-MS) has been developed for the detection and quantification of ciprofloxacin and its metabolites in human saliva. Saliva samples were collected after the oral administration of 500 mg ciprofloxacin tablets. Internal standard (IS), tamoxifen, was added to the collected samples, and then diluted with the ionization solvent, centrifuged and filtered. An aliquot of 4 μL of the filtrate was loaded into a nanospray (NS) capillary. The NS capillary was then fitted into an off-line ion source and the instrument was operated to acquire a two-minute run by applying a voltage of 1000 V (positive-ion detection mode). Quantification of ciprofloxacin relied on the ratio of its peak intensity to the IS peak intensity. The DI-nESI-MS method was validated and provided satisfactory precision with relative standard deviation ranging from 0.39 to 7.48 % and accuracy with relative error ranging from -2.12 to 9.72 %. The calibration curve showed good linearity (r2) > 0.999 over the concentration range of 10−4000 ng/mL. These results verify the effectiveness of the DI-nESI-MS method for monitoring of ciprofloxacin and its metabolites in human saliva samples.

Metabolomic Profiles of Curcuma longa L and Cosmos caudatus Extracts and Their In-Silico Anti-cancer Activity

The current work intends to analyze Curcuma longa L and Cosmos caudatus extracts using LC-HRMS study, their prospective anti-cancer activity was determined through in silico molecular-docking. Extraction of Curcuma longa L and C. caudatus was carried out first. The resulted extracts were analyzed using LC-HRMS, in the positive ion detection. Using LC-HRMS analysis, many compounds were identified in the both extracts. The target compounds for Curcuma longa L extract was curcumin, and lutein was the target compound for Cosmos caudatus. The 3D molecular structures of curcumin and lutein were downloaded from PubChem database. The protein target was caspase-8 and was retrieved from Protein Data Bank. Caspase-8 protein were docked to curcumin and lutein, performing at HEX 8.0 program and visualized using Discovery Studio v19.1.0.18287. Interaction of curcumin and lutein on caspase-8 showed different patterns. Hydrophobic interactions, formation of hydrogen bonds, and van der Waals forces were shown in the interactions between protein and ligands. The interaction between curcumin, lutein, and the mixture of lutein-curcumin resulted in the LD50 values of 2000 mg/kg, 10 mg/kg, and 2000 mg/kg, respectively. These suggest that not only curcumin and lutein, but also complex of curcumin-lutein might possess capacity as anti-cancer agents.

Analysis of hydroxylated phenylalkylamine stimulants in urine by GC-APPI-HRMS.

A gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry (GC-APPI-HRMS) method was developed for the determination of eight phenylalkylamine stimulants in urine samples. Spiked urine samples were hydrolyzed, processed by solid-phase extraction, and derivatized before analysis. Two derivatization reactions were studied: the formation of trimethylsilyl (TMS) derivatives with N-methyl-N-trimethylsilyl trifluoroacetamide (MSTFA) and trimethylsilyl/trifluoroacetyl (TMS/TFA) derivatives with MSTFA and N-methyl-bis (trifluoroacetamide) (MBTFA) as derivatization reagents. Gas chromatography of both derivatives was performed with a 100% dimethylsiloxane column and a good separation of all isomeric compounds was achieved. To maximize the signal of the protonated molecule [M+H]+, the APPI most critical parameters were optimized. Three solvents were tested as dopant agents, with acetone yielding the lower in-source collision-induced dissociation (CID) fragmentation. The acquisition was performed in full scan and product ion scan (parallel reaction monitoring, PRM) using a quadrupole-Orbitrap mass analyzer (35,000 FWHM at m/z 200) in positive ion detection mode. At the optimal working conditions, the full scan method was evaluated for the fulfillment of identification requirements in doping analysis. Selectivity, limits of detection, matrix effect, and precision were estimated to validate the method for confirmation purposes and its applicability was tested by the analysis of spiked samples as well as by the analysis of samples obtained after the administration of some of the compounds to healthy volunteers. Results were compared with those obtained by GC-electron ionization-MS, demonstrating that the GC-APPI-HRMS method improved selectivity and sensibility, achieving lower limits of detection and satisfactory reproducibility.

In situ detection and imaging of lysophospholipids in zebrafish using matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

In this paper, a matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) (MALDI-FTICR-MS) imaging method was developed to rapid and in situ detect the spatial distribution of lysophospholipids (LPLs) in zebrafish. The combination of MALDI with ultrahigh-resolution FTICR-MS achieves the MS imaging of LPLs with a mass resolution up to 50 000, which allows accurate identification and clear spatial visualization of LPLs in complex biological tissues. A series of lysophosphatidylcholines (LPCs) was detected using positive ion detection mode, and their concentration differences and spatial distributions were clearly visualized in different parts of zebrafish tissue. The method is rapid, simple, and efficient, being a desirable way to understand the spatial distribution of LPLs in biosome.

Investigation of Organic Acids in Saffron Stigmas (Crocus sativus L.) Extract by Derivatization Method and Determination by GC/MS

The beneficial health properties of organic acids make them target compounds in multiple studies. This is the reason why developing a simple and sensitive determination and investigation method of organic acids is a priority. In this study, an effective method has been established for the determination of organic (lactic, glycolic, and malic) acids in saffron stigmas. N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA) was used as a derivatization reagent in gas chromatography combined with mass spectrometric detection (GC/MS). The saffron stigmas extract was evaporated to dryness with a stream of nitrogen gas. The derivatization procedure: 0.1 g of dried extract was diluted into 0.1 mL of tetrahydrofuran, then 0.1 mL MTBSTFA was orderly and successively added into a vial. Two different techniques were used to obtain the highest amount of organic acid derivatives from saffron stigmas. To the best of our knowledge, this is the first report of the quantitative and qualitative GC/MS detection of organic acids in saffron stigmas using MTBSTFA reagent, also comparing different derivatization conditions, such as time, temperature and the effect of reagent amount on derivatization process. The identification of these derivatives was performed via GC-electron impact ionization mass spectrometry in positive-ion detection mode. Under optimal conditions, excellent linearity for all organic acids was obtained with determination coefficients of R2 > 0.9955. The detection limits (LODs) and quantitation limits (LOQs) ranged from 0.317 to 0.410 µg/mL and 0.085 to 1.53 µg/mL, respectively. The results showed that the highest yield of organic acids was conducted by using 0.1 mL of MTBSTFA and derivatization method with a conventional heating process at 130 °C for 90 min. This method has been successfully applied to the quantitative analysis of organic acids in saffron stigmas.