Quality assessment and traceability study of Angelicae Sinensis Radix via binary chromatography, triple quadrupole tandem mass spectrometry, and multivariate statistical analysis.

Angelicae Sinensis Radix is a world-renowned herbal medicine originating in China. Owing to many environmental and geographical factors, Angelicae Sinensis Radix from various origins may have a difference in the content of ingredients, which made the confusion in the clinical practice and market. Herein, a binary chromatographic fingerprinting analysis method is developed via hydrophilic interaction chromatography and reversed-phase liquid chromatography to obtain more chemical information. Following that, an ultra-performance liquid chromatography with a triple quadrupole mass spectrometry method is furnished to simultaneously detect 17 ingredients of Angelicae Sinensis Radix gathered from six geographic zones in China. Eventually, the principal component analysis is successfully carried out to classify and differentiate the Angelicae Sinensis Radix from different origins, meanwhile the quantitative volcano plots was used to observe the changes of ingredient trends vividly. Accordingly, the proposed binary chromatography and triple quadrupole tandem mass spectrometry coupled with multivariate statistical analysis can be utilized as a facile and reliable method for origin tracing and quality control of Angelicae Sinensis Radix.

Qualitative and quantitative analysis of chemical components in Eupatorium lindleyanum DC. by ultra-performance liquid chromatography-mass spectrometry integrated with anti-inflammatory activity research.

As a traditional Chinese medicine, Eupatorium lindleyanum DC. has an effect on resolving phlegm, relieving cough, and relieving asthma. In this study, an ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry method was established for qualitative analysis of Eupatorium lindleyanum. Besides, we developed an ultra high performance liquid chromatography with triple quadrupole tandem mass spectrometry method in positive and negative multiple reaction monitor modes for the quantitative analysis of 27 chemical constituents from 19 different batches of Eupatorium lindleyanum. The methodology validated linearity, intraday and interday precision, stability, repeatability, and recovery. The results showed that there were some differences in different batches of Eupatorium lindleyanum, which might be attributed to the influence of different growth environments and climatic conditions on the accumulation of compounds. The variable importance of projection value of orthogonal partial least square discriminant analysis and anti-inflammatory activity test showed that eupalinolide A, B, C, and K have high content and strong activity, which could provide a reference for the follow-up study of the quality markers of Eupatorium lindleyanum. Collectively, we developed a rapid and efficient method for the qualitative analysis and simultaneous quantification of Eupatorium lindleyanum, which was beneficial for the comprehensive utilization and development of resources.

ZIF-8@SiO2 core-shell microsphere extraction coupled with liquid chromatography and triple quadrupole tandem mass spectrometry for the quantitative analysis of four plant growth regulators in navel oranges.

Monodisperse silica spheres that comprised a rhombic-dodecahedral zeolitic imidazolate framework core-shell microsphere were applied in the sample pretreatment of navel orange. A rapid and efficient liquid chromatography with triple quadrupole tandem mass spectrometry method was established for simultaneously quantifying four plant growth regulators, 6-benzylaminopurin, indole-3-acetic acid, indolepropionic acid, 3-indolebutyric acid, in navel oranges. A satisfactory result was obtained, i.e., the peak area of the four plant growth regulators against concentration was linear with good correlation coefficients of 0.99987-0.99991. Under optimized conditions, the limits of detection were 3.0-59.4 µg/L for the four plant growth regulators. This method was applied to the simultaneous analysis of the four plant growth regulators in commercial samples, and all the detections were confirmed by acquiring transitions for each pesticide in the samples.

Determination of polycyclic aromatic hydrocarbons in water samples by gas chromatography coupled to triple quadrupole tandem mass spectrometry using macroporous resin solid-phase extraction.

A method for the determination of 16 polycyclic aromatic hydrocarbons in water has been developed. First, we made a solid-phase extraction column. After this, the parameters affecting the efficacy of the experimental method were optimized, including appropriate selection of a solid-phase extraction column and cleanup conditions on columns. The separation was achieved by gas chromatography and detection with triple quadrupole tandem mass spectrometry. The method showed satisfactory linearity (R2  > 0.999) over the range assayed (0.01-1 µg/mL), and limits of quantification ranging from 0.0011 to 0.0199 µg/L. The recoveries ranged from 83 to 113%. The relative standard deviation is in the range 0.86-3.1%. The results indicated that this method had high selectivity and precision that was suitable for the simultaneous determination of 16 polycyclic aromatic hydrocarbons in water.

Novel approach to integrated DNA adductomics for the assessment of in vitro and in vivo environmental exposures.

Adductomics is expected to be useful in the characterization of the exposome, which is a new paradigm for studying the sum of environmental causes of diseases. DNA adductomics is emerging as a powerful method for detecting DNA adducts, but reliable assays for its widespread, routine use are currently lacking. We propose a novel integrated strategy for the establishment of a DNA adductomic approach, using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS/MS), operating in constant neutral loss scan mode, screening for both known and unknown DNA adducts in a single injection. The LC-QqQ-MS/MS was optimized using a representative sample of 23 modified 2'-deoxyribonucleosides reflecting a range of biologically relevant DNA lesions. Six internal standards (ISTDs) were evaluated for their ability to normalize, and hence correct, possible variation in peak intensities arising from matrix effects, and the quantities of DNA injected. The results revealed that, with appropriate ISTDs adjustment, any bias can be dramatically reduced from 370 to 8.4%. Identification of the informative DNA adducts was achieved by triggering fragmentation spectra of target ions. The LC-QqQ-MS/MS method was successfully applied to in vitro and in vivo studies to screen for DNA adducts formed following representative environmental exposures: methyl methanesulfonate (MMS) and five N-nitrosamines. Interestingly, five new DNA adducts, induced by MMS, were discovered using our adductomic approach-an added strength. The proposed integrated strategy provides a path forward for DNA adductomics to become a standard method to discover differences in DNA adduct fingerprints between populations exposed to genotoxins, and facilitate the field of exposomics.

Determination of acidic non-steroidal anti-inflammatory drugs in aquatic samples by liquid chromatography-triple quadrupole mass spectrometry combined with carbon nanotubes-based solid-phase extraction.

A solid-phase extraction (SPE) method based on multi-walled carbon nanotubes (CNT) was developed for the determination of 12 acidic non-steroidal anti-inflammatory drugs (NSAIDs) in surface waters and tap water. Pristine and functionalised CNTs were evaluated as sorbent materials. Batch experiments were used to optimise sorption and desorption conditions (sorbent type and amount, adsorption time, pH). The adsorption equilibrium was reached after 8 to 48 h duration, which increased with the pH of solution. Non-agglomerated pristine CNTs (20 mg) showed the most optimal adsorption (94 to 100%) for all of the analytes after a 30-min contact period in acidified water solutions (100 mL). The compounds retained at those conditions were recovered by 40 to 95% by using 5% ammonium hydroxide in methanol as the desorbing solution at ambient conditions. A comprehensive liquid chromatography coupled to triple quadrupole mass spectrometry (LC-QqQ-MS/MS) was used for the analysis of real water samples. The method showed sufficient recovery (65-125%) and good precision (2-14% relative standard deviation (RSD)). The limits of detection and quantification ranged between 0.01 and 1.3 ng L-1 and 0.04 and 3.9 ng L-1. Only diclofenac and ibuprofen were found in the analysed surface water samples from Latvia (n = 10) and Norway (n = 14). Diclofenac was found at 1.7-8.4 ng L-1 concentration in two samples of surface waters, whereas the concentrations of ibuprofen ranged between 1.0 and 9.2 ng L-1 in seven samples collected in Norway and 3.9-17 ng L-1 in three samples from Latvia.

Determination of residual levels of naloxone, yohimbine, thiophanate, and altrenogest in porcine muscle using QuEChERS with liquid chromatography and triple quadrupole mass spectrometry.

A quick, easy, cheap, effective, rugged, and safe QuEChERS (method) was used for the simultaneous detection of four veterinary drug residues, namely naloxone, yohimbine, thiophanate, and altrenogest, in porcine muscle, using liquid chromatography with electrospray ionization triple quadrupole tandem mass spectrometry. Because of the unavailability of a suitable internal standard, matrix-matched calibrations were used for quantification, with determination coefficients ≥ 0.9542. The accuracy (expressed as recovery %) ranged from 60.53 to 83.25%, and the intra- and interday precisions (expressed as relative standard deviations) were <12%. The limits of quantification were 5, 0.5, 2, and 5 ng/g for naloxone, yohimbine, thiophanate, and altrenogest, respectively. Samples purchased from local markets in Seoul, Republic of Korea, revealed no traces of the target analytes. The developed method described herein is sensitive and reliable and can be applied to quantify the tested veterinary drugs in animal tissues.

Structure analysis of depsides, dibenzofuran and sugar derivatives from Cladia aggregata (SW) Nyl using ultra-performance liquid chromatography-tandem mass spectrometry.

Cladia aggregate (SW) Nyl is a lichenized fungi in the family Cladoniaceae producing characteristic secondary metabolites of interest. There are only limited chemical studies relating to the genus Cladia. A chemical study of the lichen C. aggregata was conducted and their chemical constituents were elucidated by ultra-performance liquid chromatography-electrospray ionization/triple-quadrupole tandem-mass spectrometry analysis. It is the first time report of structure analysis of its metabolite by liquid chromatography-mass spectrometry/mass spectrometry. The molecular masses for 20 compounds were detected from different fractions. Seven compounds were elucidated with mass spectrometry/mass spectrometry fragmentation pattern analysis. Barbatic acid (12) was identified as the major compound being common to all fractions. The identified compounds belong to depsides (2, 11, 12 and 20), dibenzofurans (13, 18) and sugar derivatives (1) which are usually distributed in lichens.

Cross-sectional, commercial testing, and chromatographic study of the occurrence of antibiotic residues throughout an artisanal raw milk cheese production chain.

This study investigated antibiotic utilization in artisanal dairies and residue occurrence throughout the raw milk cheese production chain using commercial testing (Charm KIS and Eclipse Farm3G) and UHPLC-QqQ-MS/MS and LC-QqQ-MS/MS. The cross-sectional survey results revealed gaps in the producers' knowledge of antibiotic use. Commercial testing detected antibiotic levels close to the LOD in 12.5 % of the samples, mainly in raw milk and whey, with 10.0 % testing positive, specifically in fresh and ripened cheeses, indicating that antibiotics are concentrated during cheese-making. Chromatographically, several antibiotics were identified in the faeces of healthy animals, with chlortetracycline (15.7 ± 34.5 µg/kg) and sulfamethazine (7.69 ± 16.5 µg/kg) predominating. However, only tylosin was identified in raw milk (3.28 ± 7.44 µg/kg) and whey (2.91 ± 6.55 µg/kg), and none were found in fresh or ripened cheeses. The discrepancy between commercial and analytical approaches is attributed to compounds or metabolites not covered chromatographically.

Organotin compounds in seafood by ultrasonic assisted extraction and gas chromatography-triple quadrupole tandem mass spectrometry.

Although restricting environmental quality values for organotin compounds (OTs) are set by Directive 2013/39/EU of the European Parliament, marine environment remains being affected due to maritime circulation at global scale. Fish and seafood accumulate OTs, making fish and seafood consumption the main source of OTs in humans. Because of the fish and seafood matrices complexity and the required low limits of detection, a robust and fast procedure for the quantification of OTs in fish and seafood, using ultrasound-assisted extraction and gas chromatography-tandem mass spectrometry, was validated and applied. Detection (2.7 µg Sn kg-1) and quantification (8.0 µg Sn kg-1) limits, repeatability and intermediate precision (<10%), accuracy by analysing ERM®-CE477 Mussel Tissue and analytical recoveries (65-122%) were assessed. Multivariate analysis shown that the matrix effect for some OTs displayed good negative correlation with the fat and protein content. Health risk assessment of OTs intake revealed no serious risk for human consumption.

Detection of Leachable Components from Conventional and Dental Bulk-Fill Resin Composites (High and Low Viscosity) Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method.

The aim of this study was to investigate leachable components (monomers) in high and low viscosity dental bulk-fill resin composites and conventional resin composite materials after polymerization. Six bulk-fill and six conventional dental resin composite materials were used in this study. The samples of each material (three sets of triplicates) were cured for 20 s with irradiance of 1200 mW/cm2 with a LED curing unit and immersed in a 75% ethanol solution at 37 °C. The eluates from each triplicate set were analyzed after 24 h, 7 days or 28 days using liquid chromatography coupled with triple quadrupole tandem mass spectrometry (LC-MS/MS). Detectable amounts of 2-Hydroxyethyl methacrylate (HEMA) were found in both Gradia materials and the amount observed across different time points was statistically different (p ˂ 0.05), with the amount in solution increasing for Gradia and decreasing for Gradia Direct flo. Bisphenol A diglycidildimethacrylate (BIS GMA) was found in Filtek and Tetric materials. Triethylene glycol dimethacrylate (TEGDMA) was detected in all materials. On the other hand, there were no statistically significant differences in the amounts of TEGDMA detected across different time points in either of the tested materials. Monomers HEMA, TEGDMA, 4-dimethylaminobenzoic acid ethyl ester (DMA BEE) and BIS GMA in bulk-fill and conventional composites (high and low viscosity) can be eluted after polymerization. The good selection of composite material and proper handling, the following of the manufacturer's instructions for polymerization and the use of finishing and polishing procedures may reduce the elution of the unpolymerized monomers> responsible for the possible allergic and genotoxic potential of dental resin composites.

Magnetic ionic liquid-based liquid-liquid microextraction followed by ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry for simultaneous determination of neurotransmitters in human cerebrospinal fluid and plasma.

A green, efficient and easy sample pretreatment method of magnetic ionic liquid-based liquid-liquid microextraction (MIL-based LLME) combined with a sensitive, rapid and precise analytical method of ultra-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UPLC-QqQ/MS2) was developed to simultaneously - determining of neurotransmitters (NTs) in biosamples. Two magnetic ionic liquids (MILs), [P6,6,6,14]3[GdCl6] and [P6,6,6,14]2[CoCl4] tested, and the latter was selected as the extraction solvent due to its advantages of visual recognition, paramagnetic behavior and higher extraction efficiency. Facile magnetic separation of MIL containing analytes from matrix was realized by applying external magnetic field without rather than centrifugation. Experimental parameters that would influence the extraction efficiency, including type and amount of MIL, extraction time, speed of the vortex process, salt concentration, and environmental pH, were optimized obtained. The proposed method was successfully applied to the simultaneous extraction and determination of 20 NTs in human cerebrospinal fluid and plasma samples. Excellent analytical performance indicates the broad potential of this method for clinical diagnosis and therapy of neurological diseases.

Establishment of Residual Methods for Matrine in Quinoa Plants and Soil and the Effect on Soil Bacterial Community and Composition.

A method was developed for the determination of matrine residues in quinoa (Chenopodium quinoa Willd.) plants and soil by liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS) with QuEChERS clean-up. Matrine from soil, quinoa roots, stems, leaves and seeds was extracted with 25% ammonia, 20 mL acetonitrile/methanol, salted with sodium chloride (NaCl) and purified with anhydrous magnesium sulfate (MgSO4), N-propyl ethylenediamine (PSA) and graphitized carbon black (GCB). Then a chromatographic separation was performed on a Shim-pack XR-ODS II (75 mm × 2.0 mm, i. d., 2.2 µm) column with a gradient elution of 5 mmol/L ammonium formate-methanol as the mobile phase and monitored in multiple reaction monitoring modes (MRM) in electrospray positive ionization mode. The results showed that in the range of 0.005~1 mg/L, the linear correlation coefficients of matrine in the five matrices were all above 0.999. The LOQs for soil, quinoa roots, stems, leaves and seeds were 0.005, 0.005, 0.01, 0.01 and 0.005 mg/kg, respectively. The mean recoveries ranged from 74.42% to 98.37%, with RSDs of 1.25-6.84% at the three concentration addition levels. The average intra-day and inter-day recoveries were 73.92-92.36% and 78.56-90.18%, respectively, with RSDs below 8.72% and 9.43%. The recoveries and reproducibility of the method were superior. The method was used to determine the actual samples, which indicated that the half-lives of matrine in quinoa seeds, leaves, stems and soil were 1.28-1.32, 1.03-1.21, 0.81-0.92 and 0.93-0.97 d. It has a half-life below 30 d, which is an easily dissipated pesticide. The method is simple, sensitive, accurate, reliable and applicable to a wide range of applications, and it can achieve the rapid multi-residue determination of matrine to a certain extent. Next Generation Sequencing was used to explore the effects of exposure to high and low doses of matrine on soil bacterial communities and the composition of the three soils in the Qinghai Province (Haixi, Haidong and Haibei). The results showed that the number of ASVs increased significantly after treatment with matrine at an effective dose of 0.1 mg/kg than after treatment with matrine at an effective dose of 5.0 mg/kg. Similarly, bacterial abundance was higher after 0.1 mg/kg of matrine treatment than after 5.0 mg/kg of matrine treatment. The inhibitory effect on some bacterial flora was enhanced with an increase in matrine application, while the inhibitory effect on bacterial flora was weakened with time. Applying a certain dose of matrine e changed the relative abundance of the dominant bacterial genera of the soil bacteria.

A facile molecularly imprinted column coupled to GC-MS/MS for sensitive and selective determination of polycyclic aromatic hydrocarbons and study on their migration in takeaway meal boxes.

The analysis of toxic and harmful substances in food has attracted significant attention. In this work, a molecularly imprinted column coupled to gas chromatography-triple quadrupole tandem mass spectrometry method (MIC-GC-MS/MS) method for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in takeaway meal boxes was established by comparing the extraction results of 16 PAHs with 5 different sample pretreatment techniques, and the effects of food types and storage conditions on the migration of PAHs was studied by migration test. The conditions of extraction and chromatography-mass spectrometry were optimized. The results showed that the linear ranges were in the wide range of 1-100 ng mL-1 for 16 PAHs, with the correlation coefficients (R) higher than 0.9983; the detection limits (LODs) and the limits of quantification (LOQs) were in the range of 0.08-0.42 µg kg-1 and 0.24-1.26 µg kg -1, respectively; the spiked recoveries at three levels of 10, 20, 30 µg kg-1 were in the range of 86.2%-107.7% with the relative standard deviation (RSD) less than 7.8%. Therefore, this method had high sensitivity and good reproducibility and was suitable for the determination of 16 PAHs in food contact materials. The migration test of PAHs showed that the migration amount of PAHs in takeaway meal boxes was closely related to food types, and the migration amount was positively correlated with contact temperature and contact time in a certain range.

Monitoring Lipophilic Toxins in Seawater Using Dispersive Liquid-Liquid Microextraction and Liquid Chromatography with Triple Quadrupole Mass Spectrometry.

The use of dispersive liquid-liquid microextraction (DLLME) is proposed for the preconcentration of thirteen lipophilic marine toxins in seawater samples. For this purpose, 0.5 mL of methanol and 440 µL of chloroform were injected into 12 mL of sample. The enriched organic phase, once evaporated and reconstituted in methanol, was analyzed by reversed-phase liquid chromatography with triple-quadrupole tandem mass spectrometry. A central composite design multivariate method was used to optimize the interrelated parameters affecting DLLME efficiency. The absence of any matrix effect in the samples allowed them to be quantified against aqueous standards. The optimized procedure was validated by recovery studies, which provided values in the 82-123% range. The detection limits varied between 0.2 and 5.7 ng L-1, depending on the analyte, and the intraday precision values were in the 0.1-7.5% range in terms of relative standard deviation. Ten water samples taken from different points of the Mar Menor lagoon were analyzed and were found to be free of the studied toxins.

Quantitative analysis of the relationship of derivatization reagents and detection sensitivity of electrospray ionization-triple quadrupole tandem mass spectrometry: Hydrazines as prototypes.

Chemical derivatization-assisted electrospray ionization-triple quadrupole mass spectrometry (ESI-QqQ-MS) has become an efficient tool for the quantification of low-molecular-weight molecules. Many studies found that the derivatives of the same analytes derivatized by different derivatization reagents with the same reaction group had different detection sensitivity, even under the same conditions of electrospray ionization-mass spectrometry (ESI-MS). This phenomenon was suggested to be caused by the different modifying groups in the derivatization reagents. However, there is still a lack of systematic study on how modifying groups in the derivatization reagents affect the detection sensitivity of their corresponding derivatives of analytes, especially theoretical investigations. In this study, we employed a quantitative structure-activity relationship (QSAR) modeling approach to explore the relationship between modifying group structures and the detection sensitivity of derivatization reagents and their derivatives during ESI-MS detection. A total of 110 derivatization reagents of the hydrazine family and their hexanal derivatives (substituted hydrazones) were selected as the prototypes to construct QSAR models. The established models suggested that several molecular descriptors, related to hydrophobicity, electronegativity, and molecular shape, were related to the detection sensitivity of hexanal derivatives induced by different modifying groups in the derivatization reagents. Besides, we found that the detection sensitivity of compounds detected in selected ion mode (SIM) showed a positive correlation with that obtained in multiple reaction monitoring mode (MRM), and the ionization efficiency was the key factor on the detection sensitivity in both modes.

Uptake and Translocation of Triflumezopyrim in Rice Plants.

A new type of mesoionic insecticide triflumezopyrim is mainly used to control rice planthoppers, leafhoppers, etc. In order to study the uptake and translocation characteristics of this new insecticide in rice (Oryza sativa), a method for the detection of triflumezopyrim in rice, soil, and water was established using liquid-liquid extraction and QuEChERS sample pretreatment combined with liquid chromatography-triple quadrupole tandem mass spectrometry. The distribution of triflumezopyrim in rice was investigated after hydroponic treatment and foliar treatment at the concentrations of 2.5 and 5 mg·L-1 within the ranges of 24, 48, and 72 h. The results showed that triflumezopyrim could be absorbed by roots and form a systematic distribution in rice by hydroponic treatment; meanwhile, it could also be absorbed by leaves and transported to the bottom leaves under foliar treatment, but no triflumezopyrim was detected in the roots. Thus, triflumezopyrim exhibited high acropetal translocation within the rice plant. This study provides an important scientific basis for the development of an application strategy of triflumezopyrim to control planthoppers and leafhoppers as well as for the residue detection method and safety evaluation.

Determination of exogenous prohibited flavour compounds added in coffee using gas chromatography triple quadrupole tandem massspectrometry and gas chromatography/combustion/isotope ratio mass spectrometry.

An analytical method based on gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed for the simultaneous determination of exogenous prohibited flavour compounds in coffee samples. In addition, gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) was developed to determine the origin of the founded prohibited flavour compound, N-methylpyrrole-2-carboxaldehyde (NMPCA). The good selectivity and sensitivity achieved in multiple reactions monitoring (MRM) mode allowed satisfactory confirmation and quantitation for the flavour compounds. The limits of detection (LODs) and limits of quantitation (LOQs) of these compounds were in the range of 0.0005-5.0 µg/kg and 0.002-16.0 µg/kg, respectively. The coffee samples were extracted with simultaneous distillation extraction (SDE) and NMPCA was analysed on a GC/C/IRMS system. The δ13C values of endogenous NMPCA in coffee beans were within a range of -35.0‰ to -31.1‰, whereas exogenous NMPCA was the range from -27.9‰ to -23.9‰. The validation results revealed that the GC-MS/MS method was sensitive and reliable, and the origin of NMPCA can be distinguished by GC/C/IRMS. Finally, this method was successfully applied to coffee samples analysis and NMPCA was found in coffee samples.

Quantitation of pyrazines in roasted green tea by infrared-assisted extraction coupled to headspace solid-phase microextraction in combination with GC-QqQ-MS/MS.

Pyrazines play an important role in the characteristic flavor of roasted green tea due to powerful strong odours and low sensory thresholds. It is important to analyze these compounds reliably and rapidly in roasted green tea. In this study, infrared-assisted extraction coupled to headspace solid-phase microextraction (IRAE-HS-SPME) and gas chromatography-triple quadrupole-tandem mass spectrometry (GC-QqQ-MS/MS) were developed and validated to determine the pyrazines in roasted green tea. Good linear correlation coefficients (0.9955-0.9996) were obtained over the concentration ranges of 10-5000 ng/mL. The limits of detection (LODs) and limits of quantification (LOQs) for the pyrazines were in the range of 1.46-3.27 ng/mL and 4.89-10.90 ng/mL, respectively. The average recoveries varied from 84% to 119%. The method was used to analyze the pyrazines in roasted green tea manufactured by different final firing methods, the results revealed that microwave final firing method had maximum contents of pyrazines, and significantly improved the aroma quality. In addition, there were great disparities of pyrazines in flatten-shaped green tea and strip-shaped green tea according to the appearance. The result is expected to better understand the role of pyrazines related to aroma quality of roasted green tea and improve processing technology.

Qualitative and quantitative analysis on the chemical constituents in Orthosiphon stamineus Benth. using ultra high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

A sensitive and efficient method was established and validated for qualitative and quantitative analysis on the chemical constituents in Orthosiphon stamineus Benth. (O. stamineus) using ultra high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Based on the retention time and MS spectra, 61 compounds were detected by using ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry. 52 chemical structures in the O. stamineus extracts including 26 phenolic acids, 11 flavonoids, 6 diterpenoids, 4 fatty acids and 5 tanshinones were tentatively identified without the time-consuming process of isolation. Moreover, five chemical constituents (Danshensu, Caffeic acid, Rosmarinic acid, Sinensetin and Eupatorin) were quantified in three different batches of O. stamineus samples by the developed ultra high-performance liquid chromatography coupled with electrospray ionization triple-quadrupole mass spectrometry method in 10 min. The method validation of the five compounds was performed with acceptable linearity (R2, 0.9930-0.9997), precision (RSD, 1.87-10.36%), repeatability (RSD, 0.59-4.87%) and recovery (105.30-110.53%, RSD ≤ 13.90%).