Modified QuEChERS combined with ultra high performance liquid chromatography tandem mass spectrometry to determine seven biogenic amines in Chinese traditional condiment soy sauce

Simultaneous analysis of 2-methylimidazole, 4-methylimidazole, and 5-hydroxymethylfurfural potentially formed in fermented soy sauce by "quick, easy, cheap, effective, rugged, and safe" purification and UHPLC with tandem mass spectrometry

2-Methylimidazole, 4-methylimidazole and 5-hydroxymethylfurfural are harmful by-products potentially formed via Maillard reaction in fermented soy sauce. The present study proposed a new method based on "quick, easy, cheap, effective, rugged, and safe" purification and ultra high performance liquid chromatography with tandem mass spectrometry for the simultaneous analysis of 2-methylimidazole, 4-methylimidazole and 5-hydroxymethylfurfural in fermented soy sauce. The sample was dissolved in water after addition of internal standard 4-methylimidazole-d₆ and extracted with acetonitrile. After dehydration, it was centrifuged and the supernatant was subsequently purified using two sorbents namely primary-secondary amine and multi-walled carbon nanotube. Three target analytes were separated by gradient elution and determined under multiple reactions monitoring mode. The limit of detection, matrix effect, recovery and precision of the developed method were investigated. Results found that three target analytes displayed excellent linearity in concentration range of 1-250 μg/L. Limit of detection was in the range of 0.3-1 μg/kg for three target analytes. The mean recoveries for fermented soy sauce samples at three spiked concentrations were in the range of 91.2-112.5%, and the intra- and interday precision were in the ranges of 3.6-9.2 and 7.1-10.8%, respectively. This validated method was successfully applied to determine 2-methylimidazole, 4-methylimidazole and 5-hydroxymethylfurfural concentrations in fermented soy sauce.

Analysis of the dissipation kinetics of thiophanate-methyl and its metabolite carbendazim in apple leaves using a modified QuEChERS-UPLC-MS/MS method

As one of the main fungicides for the apple leaf disease control, thiophanate-methyl (TM) mainly exerts its fungicidal activity in the form of its metabolite carbendazim (MBC), whose dissipation kinetics is very distinct from that of its parent but has been paid little attention. The aim of this work was to investigate the dissipation kinetics of TM and its active metabolite MBC in apple leaves using a modified QuEChERS-UPLC-MS/MS method. The results showed that TM and MBC could be quickly extracted by this modified QuEChERS procedure with recoveries of 81.7-96.5%. The method linearity was in the range of 0.01-50.0 mg kg^-1 with the quantification limit of 0.01 mg kg^-1 . Then this method was applied to the analysis of fungicide dissipation kinetics in apple leaves. The results showed that the dissipation kinetics of TM for the test in 3 months can be described by a first-order kinetics model with a DT₅₀ (dissipation half-life) range of 5.23-6.03 days and the kinetics for MBC can be described by a first-order absorption-dissipation model with the T_max (time needed to reach peak concentration) range of 4.78-7.09 days. These models can scientifically describe the behavior of TM and MBC in apple leaves, which provides necessary data for scientific application.

Hexafluoroisopropanol-based hydrophobic deep eutectic solvents for dispersive liquid-liquid microextraction of pyrethroids in tea beverages and fruit juices

A series of new hydrophobic deep eutectic solvents (DESs), which are liquid at room temperature and have high density (>1.4 g mL^-1), were synthesized using hexafluoroisopropanol (HFIP) as hydrogen-bond donor and l-carnitine/betaine as hydrogen-bond acceptor. Then these hydrophobic DESs were used as extraction solvents to establish dispersive liquid-liquid microextraction (DLLME) method for extraction of pyrethroids. The DES extraction phase was in the bottom after DLLME, being easy to be collected for analysis. After optimization by one-variable-at-a-time and response surface methodology, the enrichment factors of 265-360 were achieved for five pyrethroids. The proposed DLLME method coupled with HPLC has good performance: linear ranges of 0.25/0.5/1-100/200/400 ng/mL (r ≥ 0.9990), limits of detection of 0.06-0.17 ng mL^-1, relative recoveries of 85.1-109.4%, intra-day and inter-day RSDs below 7.5%. The novel DLLME method is simple, rapid, highly efficient and eco-friendly for extraction of pyrethroids in real tea beverages and fruit juices.

Development and comparison of single-step solid phase extraction and QuEChERS clean-up for the analysis of 7 mycotoxins in fruits and vegetables during storage by UHPLC-MS/MS

A robust and sensitive UHPLC-MS/MS method was developed for the analysis of seven mycotoxins in fruits and vegetables. The variations of seven mycotoxins concentrations during storage were also determined for the first time. Solid phase extraction (SPE) and QuEChERS clean-up were compared, and extraction was finally performed with acetonitrile under acidic conditions followed by HLB SPE purification. Seven mycotoxins were separated on a C18 column by gradient elution, scanned by ESI⁺ and ESI^- dynamic switching and detected with MRM mode. LOD and LOQ, matrix effect, accuracy and precision of the developed method were investigated. Results were linear in their concentration ranges for all mycotoxins with R² being greater than 0.999. LODs and LOQs were ranged from 0.05 to 3.0 μg/kg and 0.2 to 10.0 μg/kg, respectively. Average recoveries were between 81.1% and 116% with intraday- and interday-precision being in the ranges of 3.0-6.2% and 4.2-6.1%, respectively. The validated method provides sufficient selectivity, sensitivity and accuracy to screen for seven mycotoxins at trace levels, without using standard addition or matrix-matched calibration to compensate for matrix effects. The method was successfully applied for mycotoxins analysis in fruits and vegetables. None were detected in fresh samples, but AOH and AME were detected in strawberry, and TeA was detected in tomato fruits during long-term storage. Their concentrations were in the range of 3.6-165.3 μg/kg from 3 days to 60 days and significantly increased along with storage time.

Rapid Evaluation of Spermidine from 12 Bean Cultivars by Direct Real-Time Mass Spectrometry Analysis

The routine spermidine (SPD) detection method is time-consuming and laborious due to the lengthy chromatographic separation and/or tedious sample derivatization pretreatment. In this study, direct analysis in real-time ionization mode coupled with mass spectrometry (DART-MS) was developed to rapidly determine the SPD content of 12 bean cultivars. The results were compared in detail with those of the classical UHPLC-ESI-QTOF method. After conducting a series of optimizations, a simple sample extraction procedure employing 80% aqueous methanol, was followed by determination of sample extracts directly without any chromatographic separation or prior derivatization. The validated method showed excellent performance with low limits of detection (LOD of 0.025 mg·kg⁻¹) and good recovery rates (102.79–148.44%). The investigation highlighted that the DART-MS method (~1.3 min per three samples) could be used as a high-throughput alternative to the classic UHPLC-ESI-QTOF method (~15 min per three samples).

Rapid determination of hexavalent chromium in textiles by a novel ammonium pyrrolidine dithiocarbamate derivatization combined with UHPLC-MS/MS

Hexavalent chromium is mainly determined by traditional spectrophotometry, atomic absorption spectrometry, and ion chromatography methods. In the present work, a reliable ultra high performance liquid chromatography with tandem mass spectrometry method was firstly developed for the determination of hexavalent chromium in textiles. The sample was extracted by acetic acid/sodium acetate buffer solution and followed by derivatization with ammonium pyrrolidine dithiocarbamate. The resulting derivative product was extracted by ethyl acetate, separated on a C18 column, and detected through electrospray ionization source in the positive mode with multiple reaction monitoring conditions. The derivatization reaction conditions were investigated and optimized. The developed method was validated in terms of the sensitivity, linearity range, matrix effects, recovery, accuracy, intra- and interday precision. Results showed that the calibration curves of pure solvent and matrix were linear over the selected concentration ranges of 0.1-20.0 μg/L. The achieved instrument and method limit of quantification were 0.1 and 40.0 μg/kg, respectively. Recoveries were calculated at three spiked concentrations and the values were between 92.2 and 103% with relative standard deviation values of 2.7-4.9% for intra-day precision and 6.1% for inter-day precision. Successful analysis of hexavalent chromium in practical textiles indicated that there was hexavalent chromium contamination in textiles.

Determination of halquinol residual levels in animal-derived food products using liquid chromatography-tandem mass spectrometry

A reliable and highly sensitive detection method based on liquid chromatography coupled with triple quadrupole electrospray tandem mass spectrometry (LC-MS/MS) analysis has been developed for determination and quantification of halquinol, including 5,7-dichloroquinolin-8-ol and 5-chloroquinolin-8-ol. The target analytes were extracted from porcine muscle, egg, milk, eel, flatfish and shrimp using a mixture of acetonitrile and ethyl acetate followed by liquid-liquid purification with n-hexane. The analytes were separated on an Agilent Eclipse XDB-C₁₈ reversed-phase analytical column using 0.05% formic acid in distilled water and acetonitrile as mobile phases. Good linearity from six-point matrix-matched calibration was obtained with correlation coefficients (R² ) ≥ 0.9904. Recoveries from three spiking levels (5, 10 and 20 μg/kg) ranged between 70.6 and 101.7% in various matrices with relative standard deviations ≤8.6%. Samples acquired from markets located in Seoul, Republic of Korea, tested negative for the target analytes. In conclusion, the proposed method is versatile and precise for the routine detection of halquinol residual levels in animal-derived food products intended for human consumption.

Quantitative determination of doxorubicin in the exosomes of A549/MCF-7 cancer cells and human plasma using ultra performance liquid chromatography-tandem mass spectrometry

In cancer therapy, exosomes efflux enhances resistance of cancer cells toward anticancer agents through mediating the transport of anticancer drugs outside the cells. In this study, a rapid, simple and highly sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the determination of Doxorubicin (DOX) in exosomes of cancer cells and human plasma using Ketotifen as an internal standard (IS). Plasma samples spiked with DOX and two cancer cell lines (A549 & MCF-7) were incubated with different concentrations of DOX and IS. The analytes were then extracted with methanol after protein precipitation and the chromatographic separation was carried out using a C18 column, with a mixture of acetonitrile–water- formic acid (85:15:0.1%, v/v/v) as mobile phase. Multiple reaction monitoring (MRM) was utilized to monitor the protonated precursor to product ion transitions of m/z 544.25 > 397.16 and m/z 310.08 > 96.97 for the quantification of DOX and IS, respectively. The method was linear over ranges of 1–1000 ng/mL for DOX in plasma and 2–1000 ng/mL for DOX in exosome samples. The lower limit of quantification of this method was 1 ng/mL, 2 ng/mL and 2 ng/mL in human plasma, A549 & MCF-7 cells respectively. Intra- and inter day precision of all quality control concentrations were less than 10.33% and the accuracy values ranged from −4.82 to 12.60%. The optimized UPLC-MS/MS method proved to be fast, specific, simple and highly sensitive and was successfully applied for the estimation of DOX in the exosomes of cancer cells and plasma.

Physicochemical characterization and in vitro hypoglycemic activities of polysaccharides from Sargassum pallidum by microwave-assisted aqueous two-phase extraction

Microwave-assisted aqueous two-phase extraction (MAATPE) was applied for simultaneous extraction and separation of polysaccharides from Sargassum pallidum (SPPs). The optimal extraction parameters, physicochemical properties, and hypoglycemic activities in vitro of SPPs were investigated. The results revealed that the optimal extraction conditions were as follows: 21.0% ethanol (w/w) and 22.0% ammonium sulfate (w/w) for ATPS, ratio of material to liquid 1:60 (g/mL), extraction time 15 min, microwave power 830 W, and extraction temperature 95 °C. Under the optimal these conditions, the maximum yields of SPPs were 0.75 ± 0.04% of the top phase (SPP-1) and 6.81 ± 0.33% of the bottom phase (SPP-2). SPP-1 and SPP-2 were homogeneous with molecular weights of 1518.6 and 50.6 kDa, respectively. SPP-1 mainly consisted of fucose, galactose, mannose, and glucuronic acid with a molar ratio of 4.97:9.75:6.44:6.07, whereas SPP-2 was mainly composed of fucose, galactose, glucose, and mannose with a molar ratio of 4.20:2.88:18.05:7.83. SPP-1 and SPP-2 exhibited favorable α-amylase and α-glucosidase inhibitory activities, and could remarkably improve glucose consumption in insulin resistance (IR) model cells. Notably, SPP-1 exhibited stronger α-glucosidase inhibitory activity than SPP-2, and even was comparable with acarbose.

Solid phase extraction with high polarity Carb/PSA as composite fillers prior to UPLC-MS/MS to determine six bisphenols and alkylphenols in trace level hotpot seasoning

The present study reports an ultra high-performance liquid chromatography tandem mass spectrometry method for the simultaneous determination of six bisphenols (bisphenol A, bisphenol B and bisphenol F) and alkylphenols (4-nonylphenol, 4-n-nonylphenol and octylphenol) in hotpot seasoning. Samples were dispersed in n-hexane after addition of internal standards bisphenol A-d₄ and 4-n-nonylphenol-d₄. Sample solutions were then centrifuged, and the supernatants purified using solid phase extraction with high polarity Carb/PSA composite fillers. Six target analytes were separated on a Waters ACQUITY BEH C18 column by gradient elution with methanol and 0.05% ammonium hydroxide in water as the mobile phase, and determined under multiple reactions monitoring mode. The limits of detection and quantitation, matrix effect, recovery and precision of the method were investigated. Results were linear in the concentration range 0.1-250 µg/L for all compounds of interest, with R² > 0.9950. Limits of detection were in the range 0.1-0.4 μg/kg, and limits of quantitation were between 0.5 μg/kg and 1.0 μg/kg. The mean recoveries for negative samples at three spiked concentrations were in the range 87.9%-102.4%, and the intra-day precision and inter-day precision were in the ranges 2.1-8.2% and 4.8-11.2%, respectively. This method is accurate and sensitive, and had good clean-up characteristics, which might apply to screening and quantitation of target bisphenols and alkylphenols in hotpot seasoning.

Enhanced antioxidant activity, antibacterial activity and hypoglycemic effect of luteolin by complexation with manganese(ii) and its inhibition kinetics on xanthine oxidase

A coordination compound with enhanced biological activities was synthesized with luteolin and manganese(ii) cation. The inhibition effect assay found that the complex reversibly inhibited xanthine oxidase in a competitive manner.