Xiaohong Hou

Ultrasound-assisted dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet followed by gas chromatography for the determination of eight pyrethroid pesticides in tea samples

A novel ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet method (UA-DLLME-SFO) combined with gas chromatography (GC) was developed for the determination of eight pyrethroid pesticides in tea for the first time. After ultrasound and centrifugation, 1-dodecanol and ethanol was used as the extraction and dispersive solvent, respectively. A series of parameters, including extraction solvent and volume, dispersive solvent and volume, extraction time, pH, and ultrasonic time influencing the microextraction efficiency were systematically investigated. Under the optimal conditions, the enrichment factors (EFs) were from 292 to 883 for the eight analytes. The linear ranges for the analytes were from 5 to 100μg/kg. The method recoveries ranged from 92.1% to 99.6%, with the corresponding RSDs less than 6.0%. The developed method was considered to be simple, fast, and precise to satisfy the requirements of the residual analysis of pyrethroid pesticides.

A combined experimental/computational study on metal-organic framework MIL-101(Cr) as a SPE sorbent for the determination of sulphonamides in environmental water samples coupling with UPLC-MS/MS

As a novel kind of materials, metal-organic frameworks (MOFs) have great potential for the preconcentration of trace analytes. In our work, MIL-101(Cr) was prepared and applied as a solid phase extraction (SPE) sorbent for the pretreatment of sulfadiazine (SDA), sulfamethazine (SMZ), sulfachloropyridazine (SCP) and sulfamethoxazole (SMX) in different environmental water samples coupling with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection. Experimental parameters, such as SPE materials, pH of water sample, volume of sample, flow rate, and type and volume of elution solvent, were properly optimized. Under the optimum conditions, good sensitivity levels were achieved with the detection limits of 0.03-0.08μg/L and the quantitation limits of 0.11-0.27μg/L. The linear ranges were from 0.2-40 or 0.5-100μg/L (r(2)>0.996) for the analytes, and the relative recoveries were in the range from 83.5% to 107.3% with the relative standard deviations (RSD) between 0.2% and 8.0% (n=6). In addition, computational simulation was primarily used to predict the adsorption of MIL-101(Cr) toward sulphonamides (SAs), and also demonstrated the molecular interactions and free binding energies with the molecular modeling method. The results revealed that the combination of experimental and computational study not only accurately recognized the adsorption of MIL-101(Cr) on SAs, but also provided a new strategy on the trace contaminant analysis.

A novel metal-organic framework composite MIL-101(Cr)@GO as an efficient sorbent in dispersive micro-solid phase extraction coupling with UHPLC-MS/MS for the determination of sulfonamides in milk samples

As a novel material, metal-organic framework/graphite oxide (MIL-101(Cr)@GO) has great potential for the pretreatment of trace analytes. In the present study, MIL-101(Cr)@GO was synthesized using a solvothermal synthesis method at the nanoscale and was applied as sorbent in the dispersive micro-solid phase extraction (DMSPE) for the enrichment of the trace sulfonamides (SAs) from milk samples for the first time. Several experimental parameters including kinds of sorbents, the effect of pH, the amount of MIL-101(Cr)@GO, ionic strength, adsorption time, desorption solvent and desorption time were investigated. Under the optimal conditions, the linear ranges were from 0.1 to 10μg/L, 0.2-20μg/L or 0.5-50μg/L for the analytes with regression coefficients (r) from 0.9942 to 0.9999. The limits of detection were between 0.012 and 0.145μg/L. The recoveries ranged from 79.83% to 103.8% with relative standard deviations (RSDs)<10% (n=3). MIL-101(Cr)@GO exhibited remarkable advantages compared to MIL-101(Cr), MIL-100(Fe), activated carbon and other sorbent materials used in pretreatment methods. A simple, rapid, sensitive, inexpensive and less solvent consuming method of DMSPE-ultra-high performance liquid chromatography-tandem mass spectrometry (DMSPE-UHPLC-MS/MS) was successfully applied to the pre-concentration and determination of twelve SAs in milk samples.

Characterization of chemical constituents in Zhi–Zi–Da–Huang decoction by ultra high performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

A sensitive and reliable ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was established to separate and identify the chemical constituents of Zhi-Zi-Da-Huang decoction, a classic traditional Chinese medicine formula. The chromatographic separation was achieved on a Shim-pack XR-ODS C18 column (75 × 3.0 mm, 2.2 μm) using a gradient elution program. The detection was performed on a Waters Xevo G2 Q-TOF mass spectrometer equipped with electrospray ionization source in both positive and negative modes. With the optimized conditions, a total of 82 compounds were identified or tentatively characterized. Of the 82 compounds, 21 compounds were identified by comparing the retention time and MS data with reference standards, the rest were characterized by analyzing MS data and retrieving the reference literature. In addition, 31 compounds were identified from Gardenia jasminoides Ellis, ten compounds were identified from Rheum palmatum L., 33 compounds were identified from Citrus aurantium L., and eight compounds were identified from Sojae Semen Praeparatum. Results indicated that iridoids, anthraquinones, flavonoids, isoflavonoids, coumarins, glycosides of crocetin, monoterpenoids, and organic acids were major constituents in Zhi-Zi-Da-Huang decoction. It is concluded that the developed ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method with high sensitivity and resolution is suitable for identifying and characterizing the chemical constituents of Zhi-Zi-Da-Huang decoction, and the analysis provides a helpful chemical basis for further research on Zhi-Zi-Da-Huang decoction.

Trace determination of antibacterial pharmaceuticals in fishes by microwave-assisted extraction and solid-phase purification combined with dispersive liquid-liquid microextraction followed by ultra-high performance liquid chromatography-tandem mass spectrometry.

A novel pretreatment method involving microwave-assisted extraction and solid-phase purification combined with dispersive liquid-liquid microextraction (MAE-SPP-DLLME) followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was established for the simultaneous determination of six antibacterial pharmaceuticals including metronidazole, tinidazole, chloramphenicol, thiamphenicol, malachite green and crystal violet. The conditions of MAE were optimized using an orthogonal design and the optimal conditions were found to be 8mL for acetonitrile, 50°C for 5min. Then, neutral alumina column was employed in the solid-phase purification. Finally, the critical parameters affecting DLLME, including selection of extraction and dispersive solvent, adjustment of pH, salt concentration, extraction time, were investigated by single factor study. Under optimum conditions, good linearities (r>0.9991) and satisfied recoveries (Recoveries>87.0%, relative standard deviation (RSD)<6.3%) were observed for all of the target analytes. The limits of detection and quantification were 4.54-101.3pgkg(-1) and 18.02-349.1pgkg(-1), respectively. Intra-day and inter-day RSDs were all lower than 3.6%. An obvious reduction in matrix effect was observed by this method compared with microwave assisted extraction followed by purification. The established method was sensitive, rapid, accurate and employable to simultaneously determine target analytes in farmed fish, river fish and marine fish.

The metal-organic framework MIL-101(Cr) as efficient adsorbent in a vortex-assisted dispersive solid-phase extraction of imatinib mesylate in rat plasma coupled with ultra-performance liquid chromatography/mass spectrometry: Application to a pharmacokinetic study ☆

Metal-organic framework MIL-101(Cr) was successfully used as an efficient sorbent in a vortex-assisted dispersive solid-phase extraction (VA-DSPE) and applied for the determination and the pharmacokinetic of imatinib mesylate in rat plasma by UPLC-MS/MS. In the enrichment of imatinib from rat plasma, the analyte was efficiently adsorbed on MIL-101(Cr) and simply recovered by using initial mobile phase (0.1% formic acid-methanol (6:4 v/v)) as elution solvent. Meanwhile, the protein in the plasma samples was excluded from the porous structure of MIL-101(Cr), leading to direct extraction of drug molecule from protein-rich biological samples without any other pretreatment procedure. After being removed, the supernatant was filtered and directly injected into the UPLC-MS/MS for the analysis of the target. The experimental parameters, including nature of MOFs, amount of MIL-101(Cr), pH value of aqueous solution, extraction time, type and volume of elution solvent, were systematically optimized. After VA-DSPE, chromatographic separation was performed on an ACQUITY UPLC(®) BEH C18 column (2.1mm×100mm, 1.7μm) with a 3min gradient elution using 0.1% formic acid and methanol as mobile phase at a flow rate of 0.3mL/min. The detection was accomplished on a tandem mass spectrometer via an electrospray ionization (ESI) source by multiple reaction monitoring (MRM) in the positive ionization mode. The lower limit of quantification of 1ng/mL was achieved and the mean recovery of the analyte was higher than 81.2%. Moreover, computational simulation was primarily applied to predict the adsorption behavior and revealed the molecular interactions and free binding energies between MIL-101(Cr) and imatinib with the molecular modeling method, providing certain explanation of the adsorption mechanism. The originally established pretreatment and detection method has some merits, such as less solvent consumption, easy operation, higher sensitivity and lower matrix effect. And the MIL-101(Cr) exhibited a potential as an efficient sorbent in the enrichment of the analyte from complex biosamples.

Identification of the absorbed components and metabolites of Zhi-Zi-Da-Huang decoction in rat plasma by ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry

Zhi-Zi-Da-Huang decoction (ZZDHD), consisting of Gardenia jasminoides Ellis, Rheum palmatum L., Citrus aurantium L. and Sojae Semen Praeparatum, is a widely used traditional Chinese medicine preparation for the treatment of acute or chronic hepatic diseases. In the present study, a sensitive and selective ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) method was developed to separate and identify the absorbed components and metabolites in rat plasma after oral administration of ZZDHD. The plasma samples were pretreated by protein precipitation and separated on a Shim-pack XR-ODS C18 column (75 mm × 3.0 mm, 2.2 μm) using a gradient elution program. Mass spectrometric detection was performed on an Agilent 6520 Q-TOF mass spectrometer equipped with electrospray ionization (ESI) source in positive and negative ion modes. By comparing the retention time, high resolution mass data of blank plasma and dosed plasma, a total of 43 constituents, including 21 prototype compounds and 22 metabolites were identified or tentatively characterized. Results indicated that glucuronidation and sulfation were the main metabolic pathways of iridoid glycosides and anthraquinones, glucuronidation was the main metabolic pathways of flavanone-related compounds. It is concluded the developed UHPLC-Q-TOF-MS method with high sensitivity and resolution is suitable for identifying and characterizing the absorbed components and metabolites of ZZDHD, and the results will provide essential data for further studying the relationship between the chemical components and pharmacological activity of ZZDHD.

A UHPLC-MS/MS method for simultaneous determination of six flavonoids, gallic acid and 5,8-dihydroxy-1,4-naphthoquinone in rat plasma and its application to a pharmacokinetic study of Cortex Juglandis Mandshuricae extract.

Cortex Juglandis Mandshuricae is used as a folk remedy for treating cancer, diarrhea and dysentery in traditional Chinese medicine for many years. Six flavonoids (myricitrin, quercitrin, taxifolin, myricetin, quercetin and naringenin), gallic acid and 5,8-dihydroxy-1,4-naphthoquinone are major bioactive components in Cortex Juglandis Mandshuricae extract. In this study, an ultrahigh performance liquid chromatography and tandem mass spectrometry method was developed for simultaneous determination of eight ingredients in rat plasma using chloromycetin as an internal standard. Plasma samples added vitamin C (antioxygen) were acidified with hydrochloric acid and extracted by liquid-liquid extraction with ethyl acetate. Eight ingredients were separated on a Venusil ASB C18 column and detected by multiple reaction monitoring mode using electrospray ionization in the negative ion mode. The method was linear for all analytes over investigated range with all correlation coefficients greater than 0.9900. The validated lower limit of quantification was 20ng/mL for gallic acid, 5ng/mL for myricitrin, 3ng/mL for quercitrin, 10ng/mL for taxifolin, 6ng/mL for myricetin, 3ng/mL for quercetin, 2ng/mL for naringenin and 1μg/mL for 5,8-dihydroxy-1,4-naphthoquinone, respectively. Intra- and inter-day precisions (RSD%) were less than 15% and accuracy (RE%) ranged from -6.9% to 6.9%. The validated method was successfully applied to investigate the pharmacokinetics of the eight analytes after oral administration of Cortex Juglandis Mandshuricae extract to rats.

Simultaneous determination of two iridoid glycosides, two anthraquinones and four flavonoid glycosides of Zhi-Zi-Da-Huang decoction in rat plasma by UFLC-MS/MS: Application to a comparative pharmacokinetic study in normal and cholestatic liver injury rats

A selective, sensitive and reliable ultra fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method has been developed for the simultaneous determination of two iridoid glycosides (geniposide and genipin gentiobioside), two anthraquinones (rhein and emodin) and four flavonoid glycosides (isonaringin, naringin, hesperidin and neohesperidin), the major active ingredients of Zhi-Zi-Da-Huang decoction (ZZDHD), in rat plasma using paeoniflorin as internal standard (IS). After liquid-liquid extraction with ethyl acetate-isopropanol (1:1, v/v), separation was achieved on a Shim-pack XR-ODS C18 column (75 mm×3.0 mm, 2.2 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.4 mL/min. Detection was performed on 4000 QTRAP mass spectrometry equipped with turbo ion spray source in the negative ionization and multiple reaction monitoring (MRM) mode. The intra- and inter-day precisions (as relative standard deviation) were less than 11.4%, and accuracy (as relative error) was within ± 10.0%. The lower limits of quantification (LLOQ) were 4.0, 0.5, 2.0, 0.1, 1.0, 2.0, 1.0, 2.0 ng/mL for geniposide, genipin gentiobioside, rhein, emodin, isonaringin, naringin, hesperidin and neohesperidin, respectively. The extraction recoveries of the analytes and IS from rat plasma were all more than 86.0%. The method was fully validated and applied to compare the pharmacokinetic profiles of the analytes in normal and cholestatic liver injury (CLI) rats after oral administration of ZZDHD. Results showed that there were remarkable differences in pharmacokinetic properties of the analytes between normal and CLI group.

A dispersive liquid–liquid microextraction method based on the solidification of a floating organic drop combined with HPLC for the determination of lovastatin and simvastatin in rat urine

A dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with HPLC was developed for the determination of lovastatin and simvastatin in rat urine for the first time. 1-Dodecanol and methanol were used as the extraction and disperser solvents, respectively. Several important parameters influencing the micro-extraction efficiency were studied and systematically optimized, including the type and volume of extraction solvent and disperser solvent, extraction time, pH and salt concentration. The analytes were separated on a Kromasil C18 column at 30°C with a mobile phase of methanol and 0.2% acetic acid in water (83:17, v/v) and detected at 238 nm. Under the optimal conditions, the maximum number of enrichment factors for both analytes was 27. The linear ranges were 20.08-1004 and 20.00-1000 µg/L with the correlation coefficients ranging from 0.9990 to 0.9994 for lovastatin and simvastatin, respectively. The volume of organic solvent consumed in extraction was <0.3 mL, and the extraction time was 10 min. The newly developed environment-friendly sample pretreatment method will be a good alternative to conventional techniques, such as solid-phase extraction, liquid-liquid extraction and protein precipitation, for the HPLC determination of lovastatin and simvastatin in biological samples.