Lower Limit Of Quantitation Research Articles

Development and validation of a simple, fast and sensitive liquid chromatography-tandem mass spectrometry method to establish reference intervals for 24-h urinary free normetanephrine, metanephrine and methoxytyramine

ObjectiveTo develop and validate a rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to detect urinary free metanephrines and methoxytyramine, establishing reference intervals. MethodsUrine samples were diluted with isotope internal standard solution, then analyzed directly using tandem mass spectrometry with multiple reaction monitoring measurement and electrospray ionization source in positive ion mode. Analytical parameters including linearity, lower limit of quantitation, imprecision and accuracy of the method were evaluated. The reference intervals for urinary catecholamine metabolites were established by analyzing 24-h urine samples collected from 81 apparently healthy volunteers. ResultsThe analytical times for MN, NMN, and 3-MT were at 2.79, 2.80, and 2.74 min, respectively. The method displayed excellent linearity (r > 0.99) in the range of 1-1000 ng/mL, with lower limits of quantification (LLOQ) at 0.50 ng/mL for MN and NMN, and 0.25 ng/mL for 3-MT. The method's intra-day and inter-day imprecisions were less than 8 %. The method recovery ranged from 96.8% to 105.8 % for MN, 89.7%–106.4 % for NMN, and 93.5%–106.2 % for 3-MT. No carry-over was observed during the analysis of all analytes. The LC-MS/MS method was used to establish reference intervals in 24-h urine samples from 81 apparently healthy volunteers. There was no association of sex with urinary free metabolites. ConclusionThis study established a novel, fast and sensitive LC-MS/MS method for determining urinary free catecholamine metabolites, which could facilitate screening and diagnosis for catecholamine-related tumors more conveniently and quickly.

Quantitative determination of Hexavalent chromium using a microtiter plate: Analytical performance, operational efficiency, and fixation of a colorimetric reagent in the plate wells

Efficient and sensitive trace determination of Cr(VI) in small sample volumes is an important issue for environmental protection and the sustainable development of industries. A microtiter plate and a microplate reader have been applied to the colorimetric determination of Cr(VI) using 1,5-diphenylcarbazide (DPC) as indicator, to realize an efficient method with low detection limits. The DPC reagent was fixed on the plate well and the time for color development was significantly reduced (<1 min) compared to conventional methods by using small volume reaction vessel which made it possible to perform determinations of Cr(VI) in a short period of time. The lower limit of quantification of 0.021 mg/L obtained with this method is better than that of the microplate method reported previously, and is comparable to general analytical methods with large sample volumes. In addition, when the chromogenic reagent is fixed to the plate with a water-soluble polymer, the lower limit of quantitation is comparable as that of the unfixed reagent. This results in improved instrument portability and more efficient analytical operations.

High-Throughput Quantitative Analysis of Amino Acids in Freeze-Dried Drops Using Time-of-Flight Secondary Ion Mass Spectrometry.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a promising analytical tool for molecular profiling in biological applications. However, its ultrahigh vacuum environment and matrix effects hamper the absolute quantitation of solution samples. Herein, we present a rapid high-throughput platform for quantitative ToF-SIMS analysis of amino acids in matrix deposits formed from freeze-dried solution drops through ice sublimation on a parylene film microarray substrate. Droplets of the amino acid solutions, which were mixed with stable isotope-labeled phenylalanine (F*) of high concentration (10 mM), were loaded on wells of the microarray, then frozen and evaporated slowly below the freezing point, forming continuous solid-phase F* matrix deposits. The amino acids (≤500 μM), adequately well dispersed throughout the F* matrix deposits on each well, were quantitatively analyzed by ToF-SIMS in a rapid and high-throughput fashion. The lower limit of quantitation reached below 10 μM.

Determination of Perchloroethylene in blood by headspace gas chromatography-mass spectrometry

Objective: To establish a method for determination of Perchloroethylene (PCE) in blood by headspace gas chromatography-mass spectrometry (HS/GC-MS) . Methods: From Dctober to December 2021, A total of 3 mL blood samples were taken into a 10 mL headspace bottle, after heated at 60 ℃ for 30 mins, PCE in the top air was separated by VF-WAXms capillary column and detected by GC-MS. The retention time and external standard method were used for qualitative and quantitative analysis of PCE in samples, respectively. Results: There was good linear relationship in the range of 5.09-200.17 μg/L. The linear correlation coefficient was 0.9993.The detection limit was 0.21 μg/L and the lower limit of quantitation was 0.70 μg/L. The recovery rates of samples with different concentrations were 95.3%-103.8%. The intra-batch relative standard deviations (RSD) were 3.2%-4.6%, and inter-batch RSD was 4.0%-6.1%. The samples can be stored at 4 ℃ for three days and at -20 ℃ for seven days. Conclusion: This method is proved to be simple, practical and highly sensitive, which is suitable for the determination of PCE in blood.

Semistable emulsion assisted dispersive liquid–liquid microextraction for the determination of fungicide residues via HPLC

Fungicide residues in food can pose serious hazards to humans. The aim of this study was to establish a new method of semistable emulsion assisted dispersive liquid–liquid microextraction (DLLME) for the preconcentration and determination of fungicide residues in juice samples. In this study, Gum Acacia (GA) was selected as the dispersive agent and decanoic acid was adopted as the extractant in aqueous sample. Based on that, a semistable emulsion was induced to facilitate the extraction of target analytes and automatic phase separation. The mechanistic analysis results revealed that the formation of the semistable emulsion was attributed to the mild emulsification of GA with a high molecular weight. Besides, the semistable emulsiont allowed the automatic phase separation in DLLME for the first time. Moreover, the novel method was optimized for detecting fungicide residues and exhibited good linearity (R2 ≥ 0.995), precision (≤16.2 %), matrix effect (≤9.8 %), method recovery (84.0–103.6 %), as well as a low limit of detection (0.5–2.5 μg·L−1) and quantitation (1–5 μg·L−1). In conclusion, this method can be employed to effectively measure fungicide residues in juice samples (orange, grape, carrot and peach). Furthermore, this method can be considered as an effective DLLME alternative for the automatic pretreatment of samples, exhibiting a promising application prospect in food safety.

Magnetic solid-phase extraction coupled with LC-MS/MS methods for the simple extraction and rapid determination of sugammadex in human plasma.

Sugammadex (SUG) is a novel antagonist of neuromuscular blocking agents (NMBAs). The NMBA rocuronium is usually employed to obtain better surgical conditions in kidney transplant. Nevertheless, rocuronium has several disadvantages, such as an increased risk of pulmonary complications. Thus, SUG is vital to kidney-transplant surgery. However, because SUG is excreted by the kidneys in prototypes, the pharmacokinetics (PK) may be affected in patients with renal impairment. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to monitor SUG in plasma samples to investigate the PK of SUG in kidney-transplant patients. Due to the complexity and limitation of other methods of sample preparation, magnetic solid-phase extraction (MSPE) was adopted to purify samples. Chromatographic separation was obtained using a reversed-phase Polaris® C18 column and gradient elution with 0.1% formic acid (FA) in water as phase A and in methanol (MeOH) as phase B as mobile phases. The transitions 999.7 → 963.9 (m/z) and 1055.7 → 1012.2 (m/z) were used to quantify SUG and ORG26265, respectively, under negative electrospray ionization. A linear calibration curve was achieved in concentrations varying from 100 to 10 000 ng mL-1. The acceptable accuracy varied from 95.7% to 106.4%, and intra- and inter-precision did not exceed 15% (20% at the lower limit of quantitation (LLOQ)). The matrix effect, stability, dilution integrity, and carry-over were validated. This method was applied successfully for the PK study of 13 recipients and 12 donors of kidney transplant after intravenous injection of SUG (2 mL per kg bodyweight).

Development and validation of a multiplexed LC-MS/MS ketone body assay for clinical diagnostics

ObjectivesKetone bodies (KBs) serve as important energy sources that spare glucose, providing the primary energy for cardiac muscle, skeletal muscle during aerobic exercise, and the brain during periods of catabolism. The levels and relationships between the KBs are critical indicators of metabolic health and disease. However, challenges in separating isomeric KBs and concerns about sample stability have previously limited their clinical measurement. MethodsA novel 6.5-minute liquid chromatography-mass spectrometry-based assay was developed, enabling the precise measurement of alpha-, beta- and gamma-hydroxybutyrate, beta-hydroxyisobutyrate, and acetoacetate. This method was fully validated for human serum and plasma samples by investigating extraction efficiency, matrix effects, accuracy, recovery, intra- and inter-precision, linearity, lower limit of quantitation (LLOQ), carryover, specificity, stability, and more. From 107 normal samples, reference ranges were established for all analytes and the beta-hydroxybutyrate/acetoacetate ratio. ResultsAll five analytes were adequately separated chromatographically. An extraction efficiency between 80 and 120 % was observed for all KBs. Accuracy was evaluated through spike and recovery using 10 random patient samples, with an average recovery of 85–115 % for all KBs and a coefficient of variation of ≤ 3 %. Coefficients of variation for intra- and inter-day imprecision were < 5 %, and the total imprecision was < 10 %. No significant interferences were observed. Specimens remained stable for up to 6 h on ice or 2 h at room temperature. ConclusionsThe developed method is highly sensitive and robust. It has been validated for use with human serum and plasma, overcoming stability concerns and providing a reliable and efficient quantitative estimation of ketone bodies.

Real-world safety and effectiveness of tenofovir alafenamide for 144 weeks in Japanese patients with chronic hepatitis B.

Tenofovir alafenamide (TAF), a prodrug of tenofovir, delivers high levels of active drug to hepatocytes and is given in a lower dose than tenofovir disoproxil fumarate (TDF). TAF reduces viral replication in patients with chronic hepatitis B (CHB) similar to TDF and has shown a lower risk of the renal and bone toxicities associated with TDF use. This post-marketing surveillance study examined the safety and effectiveness of TAF in treatment-naïve and -experienced CHB patients who received TAF for 144 weeks at real-world clinical sites in Japan. Safety assessments included the incidence of adverse drug reactions (ADRs), renal and bone events, and changes in selected laboratory parameters. Effectiveness was based on the proportion of patients with HBV DNA levels below the lower limit of quantitation or <29 IU/mL. This analysis included 580 patients; 18.4% of whom were treatment-naïve. The cumulative incidence of ADRs was 0.21 per 100 person-months, and the incidence of serious ADRs was 0.01 (95% CI, 0.00-0.04) per 100 person-months. There were no ADRs of declines in estimated glomerular filtration rates, renal failure or proximal tubulopathy. The most common ADR was hypophosphataemia in seven (1.2%) patients. Two (0.4%) patients each had decreased blood phosphorus, bone mineral density decreased, dizziness and alopecia. Overall, the proportion of virologically suppressed patients increased from 68.8% at baseline to 97.5% at Week 144. These results confirm the real-world safety and effectiveness of TAF in Japanese patients with CHB and are consistent with the findings of other evaluations of the safety and efficacy of TAF in CHB.

Determination of Tyrosine Kinase Inhibitor Icotinib in Rat Plasma using UPLC-MS/MS and its Application In vivo Pharmacokinetic

Objective: The purpose of this study was to develop a UPLC-MS/MS method for the determination of icotinib concentrations in blood plasma. Methods: For plasma sample preparation, protein precipitation with acetonitrile was utilized. Analytes were separated on a Kinetex C18 column using 10 mM ammonium acetate containing 0.2% formic acid and methanol (30:70) as the mobile phase, with a gradient flow rate ranging from 0.2 ml·min-1 to 0.4 ml·min-1. The total chromatographic analysis duration was 4.5 minutes. The UPLC system was connected to a mass spectrometer via an electrospray ionization (ESI) interface operated in positive ion mode. Mass monitoring was conducted in multiple reaction monitoring (MRM) modes, with precursor-to-product transitions being m/z 392.06→304.07 for icotinib and m/z 248.00→120.09 for the internal standard, tinidazole. This method has been used for a pharmacokinetic study in rats that were orally administered a single dose of 30 mg/kg icotinib. Results: The assay showed good linearity over concentration ranges of 1-1000 ng/ml for icotinib, with the correlation coefficient exceeding 0.99. The lower limit of quantitation (LLOQ) was established at 1 ng/ml. Both intra- and inter-day precisions (RSD, %) were below 8.23%. The results demonstrated that stability, matrix effect, extraction recovery, carryover effect and dilution stability were all within the acceptable conditions. The primary pharmacokinetic parameters in SD rats after oral administration of icotinib (30 mg·kg-1 ) were as follows: t1/2 = (2.92 ± 0.87)h, Cmax = (2168.65 ± 268.72)ng/ml, Tmax = (0.70 ± 0.27)h, AUC=(9.69 ± 1.95)ug/mL•h, Vd = (14.51 ± 5.60)L, and CL = (3.19 ± 0.59)L/h. Conclusion: A simple and sensitive UPLC-MS/MS method was developed and validated for the determination of icotinib in pharmacokinetic studies.

Effective extraction and determination of 24 quinolones in water and egg samples using a novel magnetic covalent organic framework combined with UPLC-MS/MS.

The excessive use of quinolones (QNs) has seriously threatened human health. In this study, a novel functionalized magnetic covalent organic framework Fe3O4@SiO2@Ah-COF was fabricated with biphenyl-3,3',5,5'-tetracarbaldehyde and hydrazine hydrate (85%) as monomers and was used as a magnetic solid-phase extraction (MSPE) absorbent for the determination of 24 QNs in water and egg samples through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The extraction parameters of MSPE were optimized, including pH, adsorbent dosage, adsorption time, and eluent type. An effective and rapid detection method was then established, which showed good linearity (R2 ≥ 0.9990), low limits of detection (0.003-0.036 μg L-1) and low limits of quantitation (0.008-0.110 μg L-1) for QNs. The good recoveries of 24 QNs in water and egg samples were in the range of 70.3-106.1% and 70.4-119.7%, respectively, with relative standard deviations lower than 10% (n = 5). As a result, Fe3O4@SiO2@Ah-COF is a promising magnetic adsorbent, and the established method was successfully applied for the determination of 24 QNs in water and egg samples.

An innovative electrochemical sensor for brinzolamide detection in athletes' urine using a mercury-phen complex: a step forward in anti-doping.

Brinzolamide (BRZ) is an antiglaucoma drug also used by athletes for doping purposes; therefore, it is prohibited by the World Anti-Doping Agency. Consequently, the presence of BRZ or its metabolites in athletes' urine constitutes a violation of anti-doping rules. The current work presents a novel electrochemical method that assesses the effectiveness of mercury oxide nanoparticles (HgO-NPs) and a mercuric chloride-1,10-phenanthroline complex (HgCl2-Phen complex) as sensors for BRZ analysis. A comparative analysis revealed that the synthesized HgCl2-Phen complex exhibited superior sensitivity and efficiency in determining BRZ levels. The properties of the modifiers were extensively characterized using elemental analysis, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM). Furthermore, electrochemical characterization was conducted using square wave voltammetry (SWV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The electrode showed a good response for SWV evaluations of BRZ in a concentration range of 0.1 to 6.0 μmol L-1, with very low limits of detection (0.01 μmol L-1) and quantitation (0.031 μmol L-1). The method's applicability was validated by detecting BRZ in urine samples from healthy human volunteers and in pharmaceutical eye drops. Additionally, the practical effectiveness of the method was assessed using the blue applicability grade index (BAGI). The key advantages of this sensor include its simple manufacturing process, as well as its remarkable sensitivity and selectivity.

Contactless conductivity detector as a tool for improving universality and sensitivity of capillary electrophoresis-frontal analysis: Proof of concept.

Drug binding to plasma proteins influences processes such as liberation, adsorption, disposition, metabolism, and elimination of drugs, which are thus one of the key steps of a new drug development. As a result, the characterization of drug-protein interactions is an essential part of these time- and money-consuming processes. It is important to determine not only the binding strength and the stoichiometry of interaction, but also the binding site of a drug on a protein molecule, because two drugs with the same binding site can mutually affect free drug concentration. Capillary electrophoresis-frontal analysis with mobility shift affinity capillary electrophoresis is one of the most used affinity capillary electrophoresis methods for the characterization of these interactions. In this study, awell-known sensitivity problem of most capillary electrophoresis-frontal analyses using ultraviolet detection is solved by its combination with contactless conductivity detection, which provided sixfold lower limits of quantitation and detection. Binding parameters of the human serum albumin-salicylic acid model affinity pair were evaluated by this newly developed approach and by the classical approach with ultravioletdetection primarily used for their mutual comparison. The results of both approaches agreed well and are also in agreement with literature data obtained using different techniques.

Simultaneous quantification of co-administered trastuzumab and pertuzumab in serum based on nano-surface and molecular-orientation limited (nSMOL) proteolysis.

Monoclonal antibodies (mAbs) are pivotal therapeutic agents for various diseases, and effective treatment hinges on attaining a specific threshold concentration of mAbs in patients. With the rising adoption of combination therapy involving multiple mAbs, there arises a clinical demand for multiplexing assays capable of measuring the concentrations of these mAbs. However, minimizing the complexity of serum samples while achieving rapid and accurate quantification is difficult. In this work, we introduced a novel method termed nano-surface and molecular orientation limited (nSMOL) proteolysis for the fragment of antigen binding (Fab) region-selective proteolysis of co-administered trastuzumab and pertuzumab based on the pore size difference between the protease nanoparticles (∼200 nm) and the resin-captured antibody (∼100 nm). The hydrolyzed peptide fragments were then quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this process, the digestion time is shortened, and the produced digestive peptides are greatly reduced, thereby minimizing sample complexity and increasing detection accuracy. Assay linearity was confirmed within the ranges of 0.200-200 μg mL-1 for trastuzumab and 0.300-200 μg mL-1 for pertuzumab. The intra- and inter-day precision was within 9.52% and 8.32%, except for 12.5% and 10.8% for the lower limit of quantitation, and the accuracy (bias%) was within 6.3%. Additionally, other validation parameters were evaluated, and all the results met the acceptance criteria of the guiding principles. Our method demonstrated accuracy and selectivity for the simultaneous determination of trastuzumab and pertuzumab in clinical samples, addressing the limitation of ligand binding assays incapable of simultaneously quantifying mAbs targeting the same receptor. This proposed assay provides a promising technical approach for realizing clinical individualized precise treatment, especially for co-administered mAbs.

Amplifying the electrochemical footprint of

The ability of analytical strategies to detect and positively identify molecules under extremely dilute conditions is important for the growth and expansion of analytical techniques and instrumentation. At present, few measurement science techniques can robustly approach the measurement of just a few thousand molecules. Here, we present an electrochemical platform for the detection and positive identification of fewer than 1000 molecules of decamethylferrocene ((Cp*)2FeII). We achieve this remarkable detection threshold by trapping (Cp*)2FeII in a 1,2-dichloroethane microdroplet, which is allowed to dissolve into an aqueous continuous phase while on a gold microelectrode (radius ∼6.25 μm). Because electrochemistry is not sensitive enough to observe the charge of less than 1000 molecules, we dissolved μM amounts hexacyanoferrate(III) in the aqueous continuous phase. The biphasic reaction between hexacyanoferrate(III) and Cp2*(Fe)II allows for a feedback loop when the microelectrode is biased sufficiently negative to reduce Cp2*(Fe)III. This feedback loop, a typical EC' catalytic mechanism, amplifies the electrochemical signal of Cp2*(Fe)II when the droplet is of small enough dimensions for feedback to occur. Our results demonstrate that clever biphasic reactions can be coupled with dissolving microdroplets to access extremely low limits of quantitation in electroanalysis.

Biomass waste-derived magnetic material coated with dual-dummy-template molecularly imprinted polymer for simultaneous extraction of organophosphorus and carbamate pesticides

An eco-friendly biomass waste-derived magnetic material coated with a dual-dummy-template molecularly imprinted polymer was fabricated using aqueous ethanol as a green porogen, lower amounts of toxic compounds as template molecules, and tyrosine and tryptophan as biocompatible binary monomers. The binding characteristics and selectivity of the material toward pesticides were assessed. High adsorption capacities ranging from 150.11 to 509.09 mg g−1 and imprinting factors reaching 2.2 were achieved within just 30 s. The material was applied for extraction of organophosphorus and carbamate pesticides prior to HPLC analysis. Under the optimum conditions, low limits of detection and quantitation were achieved, with ranges of 0.05–1.49 μg/L and 0.18–5.00 μg/L, respectively. The established approach enables efficient analysis of vegetable and fruit samples, yielding satisfactory recoveries ranging between 80 and 110 %. The method showed promise as an analytical method for the sensitive enrichment of pesticide residues in vegetable and fruit samples.

A rapid, sensitive method for clinical monitoring of ketamine and norketamine by ultra-high-performance reverse-phase liquid chromatography tandem mass spectrometry.

Ketamine is an NMDAR antagonist with aggregating use across many areas of medicine. P450 enzymes heavily metabolise ketamine, where norketamine is a first pass formed metabolite following initial N-demethylation. Serum ketamine monitoring is becoming increasingly important, requiring a sensitive method with a robust lower limit of quantitation. Samples were prepared using protein precipitation or solid phase extraction. Ion suppression was investigated to optimise sample preparation technique, followed by reverse-phase chromatography coupled with tandem mass spectrometry to analyse extractions using a Waters Xevo TQ-S Micro and associated Acquity chromatography systems. Performance characteristics were analysed to validate the assay. Ketamine and norketamine retention times were 1.28 and 1.23min, respectively. Ketamine and norketamine precursor ions fragmented into 2 distinguishable product ions (238.14 > 207.18/125.06 and 224.1 > 178.96/124.86). Performance characteristics include an assay recovery of 103.7% (ketamine) and 96.3% (norketamine), lower limit of quantitation 36.2µg/L (ketamine) and 38.9µg/L (norketamine), and intra-assay imprecision ≤ 7.04% on average. A robust and reproducible assay with limited sample preparation has been designed and validated. The linearity of the assay covers all ranges of interest reported in the literature. Ion suppression was clearly reduced via use of solid phase extraction. The method will form the basis of ketamine monitoring and providing valuable patient information on tolerance and metabolism.

Development and validation of a bioanalytical method for the quantification of methotrexate from serum and capillary blood using volumetric absorptive microsampling (VAMS) and on-line solid phase extraction (SPE) LC-MS

High-dose methotrexate is part of the polychemotherapy protocols for the treatment of Acute lymphoblastic leukaemia (ALL) with therapeutic drug monitoring (TDM) to adjust leucovorin rescue. An immunoassay is commonly used to analyse serum samples collected via venous blood sampling. However, immunoassays cannot distinguish between the parent drug and its metabolites. Besides, the blood volume required by venous blood sampling is high. Therefore, the aim of this project was to develop a fast, simple, reliable and cost-efficient micro sampling bioanalytical method using capillary blood to minimize the harm of children and to analyse both methotrexate and its metabolites. To achieve this aim, a LC-MS method with on-line solid phase extraction (SPE) for the simultaneous detection of methotrexate and its metabolites from capillary blood using volumetric-absorptive-microsampling (VAMS) technology was developed and fully validated. Besides, the method was also validated and modified for serum samples to compare the results with the immunoassay. A single-quadrupole MS detector was used for detection. Through the use of on-line SPE technology, a lower limit of quantitation of 0.03 µM for MTX and 7-OH-MTX and of 0.05 µM for DAMPA from a 10 μL capillary blood sample was achieved. The accuracy is between 90.0 and 104% and the precision between 4.7 and 12% for methotrexate and its metabolites, respectively. Because of the cross reactivity of the immunoassay a cross-validation was not successful. Besides, a correlation factor of 0.46 for MTX between plasma and whole-blood was found.A fast, simple, reliable and cost-efficient extraction and analysis LC-MS method could be developed and validated, which is applicable in ambulatory and clinical care.

Theory and protocol of dual mode unity solid-phase microextraction

The solid-phase microextraction (SPME) bias problem limits comprehensive analysis of volatile compounds in real samples. The study introduces dual mode unity solid-phase microextraction (DMU-SPME) as a novel SPME mode to achieve balanced extraction of both volatile and low-volatile compounds. The DMU-SPME method exhibits excellent linearity (R2 ≥ 0.994), low quantitation limits (0.12–240 μg/L), and notable stability (relative standard deviations below 20 % for both intra-day and inter-day analyses). In practical application to soy sauce, the DMU-SPME method identified a total of 107 compounds, encompassing all those detected by both headspace solid-phase microextraction (HS-SPME) and direct immersion solid-phase microextraction (DI-SPME). Theoretical insights indicate that DMU-SPME is less influenced by Kfs0 and Kfs in comparison to HS/DI-SPME, rendering it suitable for complex matrices containing both volatile and low-volatile compounds. In conclusion, DMU-SPME emerges as a highly effective extraction mode for analyzing volatile and low-volatile compounds in food, medical, and environmental samples.

Development of simultaneous quantitative analytical method for three active components of Korean mint (Agastache rugosa (Fisch. & C.A.Mey.) Kuntze) extract in human plasma using ultra-high-performance liquid chromatography–tandem mass spectrometry

Agastache rugosa contains phenolic compounds and flavonoids, and has been extensively used as a traditional herbal medicine. The major components in Agastache rugosa extract (ARE) are rosmarinic acid, tilianin, and acacetin, for which several analytical techniques have been reported. However, these substances have yet to be simultaneously quantified in human plasma. In this study, we aimed to simultaneously determine the three active components of ARE in human plasma by developing a reliable quantitative analytical method using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Chromatographic separation of the plasma samples was achieved using an ACQUITY UPLC® BEH C18 column with a gradient mobile phase of water and acetonitrile containing 0.1 % formic acid. Mass spectrometric detection was performed using a triple quadrupole tandem mass spectrometer in negative electrospray ionization (ESI−) and multiple reaction monitoring (MRM) modes. The developed quantitative method was validated for the three active components. All three analytes exhibited a linear response over the ranges of 0.5–50 ng/mL for rosmarinic acid, 0.1–20 ng/mL for acacetin, and 0.5–20 ng/mL for tilianin with a weighting factor of 1/x (where x is the concentration). At three quality control (QC) concentration levels (low, medium, and high), including the lower limit of quantitation (LLOQ), acceptable accuracy (±15 %) was achieved in the intra- and interday validations. The concentration of rosmarinic acid was highest in plasma. Tilianin and acacetin appeared and were eliminated earlier in the plasma than rosmarinic acid. This study provides a successfully validated method that can be used in further clinical applications of Agastache rugosa extracts.

Improving fluorescence emission of cyproheptadine by hindering its intramolecular photoinduced electron transfer (PET): Application to content uniformity testing and human plasma

The ability to determine antihistaminic drugs in biological matrices is critical for the medication adherence assessment. Among these antihistaminic medications, cyproheptadine (CPD); that is acting as a potent first-generation antihistaminic drug that has been extensively prescribed for allergic patients. Most of the established approaches for CPD detection are not appropriate for this purpose owing to their weak sensitivity, lack of rapidity, and complicated experimental procedures. Herein, we present a very fast, highly sensitive, and reproducible approach for the detection of CPD in its pure form, tablet formulation, and spiked human plasma. The photoluminescence approach depends on hindering the intramolecular photoinduced electron transfer (PET) effect of the lone pair of the N-atom present on the piperidine ring of CPD by making the surrounding medium acidic using 1.0 M acetic acid. Based on blocking PET, the target CPD drug has been sensitively detected from 5.0 to 500 ng mL−1 with a very low detection and quantitation limit of 7.01 and 21.25 ng mL−1, respectively. Moreover, the established approach was used for checking the tablet content uniformity testing for each tablet and spiked human plasma, and noteworthy, the matrices interference was insignificant.