Clinical observation of Otitis Media Secretory during Covid-19.

OBJECTIVE: This study aims to analyze the onset of otitis media secretory, the peak period of infection with the Omicron strain of SARS-CoV-2 virus, and the time of transmigration during a pandemic of the Omicron strain. Additionally, the study aims to investigate to study the presence of SARS-CoV-2 virus in the middle ear cavity of patients with otitis media secretory and the survival time through a new method for detecting SARS-CoV-2 virus antigen in middle ear effusion. METHODS: Retrospective comparison of the incidence of otitis media secretory during infection with SARS-CoV-2 virus Omicron strain from December 15, 2022, to January 15, 2023, versus the noninfection period from December 15, 2021, to January 15, 2022. We used a questionnaire star application to investigate the demographic and epidemiological characteristics of the 40 patients with otitis media secretory who participated in this study were investigated. A novel coronavirus (2019-nCoV) antigen detection kit (colloidal gold method) was used to detect middle ear effusion in patients with otitis media secretory. The data were statistically analyzed using SPSS 29.0 software. The measurement data are expressed as x ± s , the count data are expressed as the number of cases (%), and the data were compared using the χ 2 test. p < 0.05 indicated a statistically significant difference. RESULTS: During the SARS-CoV-2 virus Omicron strain pandemic, the incidence of otitis media secretory increased by 15% compared with the noninfection period. The peak infection period for the SARS-CoV-2 virus Omicron strain was December 25, 2022, and December 15, 2022, and the peak time of conversion was 7 to 9 days after the infection. Middle ear effusion SARS-CoV-2 virus antigen testing was performed in patients with otitis media secretory after conversion; 5 patients (12%) were positive, and 35 patients (88%) were negative. The disease duration in patients with negative results was more than 3 weeks. CONCLUSIONS: Otitis media secretory is one of the most common ear complications after infection with the Omicron strain of SARS-CoV-2 virus, and the significantly higher incidence is associated with middle ear viral infection. Middle ear effusion SARS-CoV-2 virus antigen test detected the virus, which survived longer in the middle ear effusion than in the nasal cavity. The middle ear effusion test can detect SARS-CoV-2 virus antigen and determine whether the organism contains virus residue.

A Simple and Low-cost Preliminary Quantification of Target Membrane Protein in Single Cells.

To study the heterogeneity of target membrane proteins in single cells with cellular integrity, we proposed a simple and low-cost method to obtain the copy number of the membrane proteins. HeLa cells were labeled by FITC affinity bodies specifically targeting HER2 membrane proteins. The immunolabeled HeLa cells were quantified by a laboratory-built laser induced fluorescence detector. A series of fluorescent microspheres with known number of FITC molecules on the surface were used to establish the calibration curve, instead of the standard fluorescent solutions, because the morphology of the microspheres was similar to the cells, and the distribution of FITC on the spheres were similar to the distribution of HER2 on the HeLa. The fluorescence intensity of the cells was converted to the molecule number of HER2 by the calibration curve. A capillary electrophoresis system was used to drive the microspheres and cells through the detection window. The copy number of HER2 in HeLa cells ranged from 4,036 to 1,224,920 ± 100 (2.5-97.5%), and the median of copy numbers were 104,438 ± 100 per cell. This method for measuring low-abundance membrane proteins can be utilized for the initial exploration of proteomics in ordinary laboratories.

A 96-well plate UV fluorometer based on micro fluorescence detector array and dynamic zero correction algorithm.

A 96-well plate UV fluorometer was developed and evaluated. Eight micro fluorescence detectors close to each other were used as detector array for 8 channels. Each detector employed an UV light emitting diode (LED) as light source and a photodiode (PD) with an amplifier circuit as optoelectronic detector. The optical paths of the detectors were designed by ray tracing method to avoid crosstalk between wells. Simultaneously scanning and detecting of 8 channels saves scanning time and improves detection efficiency. The scanning time of the 96-well plate was about 80 s. A dynamic zero correction algorithm was proposed to solve the problem of measurement accuracy reduction caused by the background fluorescence differences between plates and wells under irradiation of UV light. The measurement repeatability (RSD) for 1 µg/L 7-Diethylamino-4-methylcoumarin sample was 2.25%. Compared with the fixed zero correction method, the limit of detection (LOD), measurement repeatability, and average relative error were improved by 3.3, 2.7, and 4.5 times, respectively. The proposed method is robust and can be applied to different analysis systems. The developed fluorometer has great potential in high-throughput rapid detection of food safety and life sciences.

A miniaturized hydrogen flame ionization detector based on integrated nozzle assembly and embedded sealing structure.

A modified miniaturized hydrogen flame ionization detector (m-FID) was developed and evaluated. An integrated nozzle assembly was constructed to solve the gas leakage caused by adhesive crack during repeated high-low temperature processes or vibration. An embedded sealing structure was designed to realize the face sealing, thus improving the sealing stability and reliability of the m-FID. Polyimide was employed as seal and insulation material to ensure the detector can be used at 300 °C for a long term. The hydrogen and air consumption of the m-FID was 12 mL/min and 110 mL/min, which is about 1/3 of the FID gas consumption of commercial laboratory instruments. The limit of detection (LOD) for n-hexadecane was 3.2 × 10-12 g/s, with a linear response range of nearly 5 orders of magnitude. Finally, it was installed onto an on-site gas chromatograph to detect drug samples with wide boiling point range from room temperature up to 535 °C.

Online micro solid phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry for trace analysis of endogenous plant hormones in Ulva linza.

OBJECTIVE: Ulva linza (L.) is a species of green algae widely distributed in China. We aimed to establish a sensitive online analytical method for quantification of endogenous phytohormones in fresh minute seaweed samples. METHOD: The method for quantification of endogenous plant hormones in fresh minute samples was developed based on a homemade online micro solid phase extraction (m-SPE) system coupled with an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) platform. The online m-SPE instrument injected the eluent of m-SPE directly onto the LC separation column, improving the utilization of samples and saving time. The m-SPE column, of which the effective size was 9.6 × 2 mm i.d., was filled with 19 mg of C18 (10 µm). RESULTS: Under optimized conditions, the limits of detection were 0.002-0.060 ng ml-1 for five plant hormones. The actual sample recoveries of phytohormones were 76.4-103.4% and the coefficients of variance were below 14.1%. The temporal distribution of these endogenous plant hormones of U. linza during different growth periods is described. CONCLUSION: The proposed online m-SPE method was successfully applied to quantification of endogenous acidic and alkaline plant hormones in U. linza. It provides important information for the further study of the physiological and ecological effects of plant hormones in lower algal species.

Construction of the prognostic signature of alternative splicing revealed the prognostic predictor and immune microenvironment in head and neck squamous cell carcinoma.

Background: Head and neck squamous cell carcinoma (HNSC) is a prevalent and heterogeneous malignancy with poor prognosis and high mortality rates. There is significant evidence of alternative splicing (AS) contributing to tumor development, suggesting its potential in predicting prognosis and therapeutic efficacy. This study aims to establish an AS-based prognostic signature in HNSC patients. Methods: The expression profiles and clinical information of 486 HNSC patients were downloaded from the TCGA database, and the AS data were downloaded from the TCGA SpliceSeq database. The survival-associated AS events were identified by conducting a Cox regression analysis and utilized to develop a prognostic signature by fitting into a LASSO-regularized Cox regression model. Survival analysis, univariate and multivariate Cox regression analysis, and receiver operating characteristic (ROC) curve analysis were performed to evaluate the signature and an independent cohort was used for validation. The immune cell function and infiltration were analyzed by CIBERSORT and the ssGSEA algorithm. Results: Univariate Cox regression analysis identified 2726 survival-associated AS events from 1714 genes. The correlation network reported DDX39B, PRPF39, and ARGLU1 as key splicing factors (SF) regulating these AS events. Eight survival-associated AS events were selected and validated by LASSO regression to develop a prognostic signature. It was confirmed that this signature could predict HNSC outcomes independent of other variables via multivariate Cox regression analysis. The risk score AUC was more than 0.75 for 3 years, highlighting the signature's prediction capability. Immune infiltration analysis reported different immune cell distributions between the two risk groups. The immune cell content was higher in the high-risk group than in the low-risk group. The correlation analysis revealed a significant correlation between risk score, immune cell subsets, and immune checkpoint expression. Conclusion: The prognostic signature developed from survival-associated AS events could predict the prognosis of HNSC patients and their clinical response to immunotherapy. However, this signature requires further research and validation in larger cohort studies.

Peltier thermoelectric cooler improves both the signal-to-noise ratio and warm-up time of high-power LED induced fluorescence detector and application to aflatoxins.

High-power LED induced fluorescence detector (HP-LED-IF) suffers from problems of large noise and poor baseline stability. In this study, a Peltier thermoelectric cooler (PTC) was utilized to stabilize the HP-LED junction temperature of a HP-LED-IF to reduce the baseline noise for the first time. Compared with traditional fan cooling, the signal-to-noise ratio was improved to 3.8 times, and the warm-up time was shortened by 64.4%. For application, a 365/450 nm HP-LED-IF was constructed and coupled with HPLC for detection of aflatoxins. The limits of detections (LODs, 3 times peak-to-peak noise) for aflatoxin G2 and B2 were 1.2 and 1.0 pg/mL, respectively. In-situ photochemical derivatization reaction of G1 and B1 in 28 µL detection cell within 2.1 s flow time was found surprisingly for the first time, which enhanced the fluorescence signal by about 10 times. The LODs for aflatoxin G1 and B1 were 3.4 and 2.4 pg/mL, respectively. These LODs are among the lowest values that have been reported. This study provides a key technique to improve both the signal-to-noise ratio and warm-up time of HP-LED-IFs and a novel in-situ derivatization method for aflatoxins G1 and B1.

Efficacy and Durability of Intratympanic Gentamicin Treatment for Meniere's Disease.

Objective: To study the success of intratympanic gentamicin (ITG) treatment in reducing vertigo attacks in Meniere's disease (MD) and the value of the Halmagyi head thrust test (HTT) in predicting treatment durability. Study Design: Retrospective cohort study. Setting: Tertiary care vestibular clinic. Patients: Unilateral MD patients treated with ITG from 2006-2019 with ≥6 months follow-up. Main Outcome Measures: Demographics, audiometric data, subjective symptomatology, and HTT results were collected. Treatment success was defined as sufficient symptom relief. Treatment failure indicated vertigo control of less than 6 months duration. Treatment relapse indicated vertigo recurrence after 6 months. Results: Of 255 patients, treatment success, failure, and relapse occurred in 226 (88.6%), 29 (11.4%), and 121 (47.1%) patients, respectively. 48 (18.8%) patients who failed to respond or relapsed underwent labyrinthectomy. Mean follow-up time was 3.7 yrs (range 0.5-12.8). After ITG treatment, 25% patients reported worse hearing; mean pure tone average (PTA) increased by 18.6 ± 11.3 dB and mean word recognition score (WRS) decreased by 33 ± 21%. Of the 148 patients with negative pre-treatment HHT, 103 (69.6%) converted to positive after ITG treatment. Mean time-to-relapse in the converted and non-converted HTT cohorts was significantly different (49.7 vs. 27.0 months, p = 0.009) even after adjusting for gender, age, laterality, duration of symptoms, and number of ITG treatments. There were no significant differences between the two groups in hearing outcomes or subjective symptoms (e.g. lingering disequilibrium). Conclusions: ITG treatment effectively reduces the number of vertigo attacks in MD. HTT is valuable in predicting durability of treatment benefit.

Enhancement of Chemiluminescence Intensity of S2* in Non-premixed Hydrogen Microjet Flame in the Photometric Detector for Sulfur Detection.

A transparent quartz rod (q) placed vertically on top of a non-premixed hydrogen microjet flame in a flame photometric detector (qFPD) was developed and evaluated for sulfur detection. The microjet flame burned around the quartz rod because of Coanda effect, forming an extended downstream flame zone with a relatively low temperature between 550 and 650 °C, which is favorable to the formation of S2*. The emission intensity of S2* and the signal-to-noise ratio (SNR) of sulfur response were enhanced 2.6- and 2.1-fold, respectively. It was found that the quartz rod of diameter 4 mm with a tip shape of semicircle placed 6 mm above the nozzle yielded the highest SNR. The limits of detection (LOD) for seven kinds of tested sulfur-containing compounds of qFPD were 0.3-0.5 pg S s-1, which is 5-7 times better than that of commercially available FPD detectors (LOD: 1.6-2.8 pg S s-1). The selectivity of sulfur over carbon was 105 on qFPD when the SNR for the mass flow rate of S and C atoms was ∼3 times. It was the first time that a quartz rod was used vertically on top of a microjet hydrogen-rich flame in FPD to enhance the chemiluminescence of S2* and improve the LOD down to 0.3-0.5 pg S s-1.

Spherical Dichroic Reflector Improves Limit of Detection in Laser-Induced Fluorescence Detection.

A miniature laser-induced fluorescence (mLIF) detector utilizing a novel spherical dichroic reflector (SDR), an unconventional long working distance high magnification objective, an uncommon broadband emission-matched excitation filter pair, and a silicon-based photodiode detector assembly instead of a photomultiplier tube was developed and evaluated. The detection cell was placed at the spherical center of the SDR instead of the regular focus, yielding a 1.8× signal-to-noise ratio (SNR) improvement. Different from previous works, the use of a 40× objective with a long working distance of 5.38 mm and a broadband BP 527-70 nm emission filter with matched BP 450-30 nm excitation filter improved SNR to 4.6× and 1.9×, respectively. By flow injection analysis (FIA) evaluation, the limit of detection (LOD; 3σ method) for fluorescein sodium was 1.5 × 10-13 M or 8.9 fluorescein molecules in 98 pL detection volume, which was the lowest level of LIFs evaluated by FIA mode. The analysis of three kinds of amino acids with LODs at sub pM to fM level (the lowest levels, hundreds of times lower than previous works using normal capillary) demonstrated the potential of the mLIF in ultratrace analysis of biological and environmental samples, including low copy molecules in a single cell.

Cationic metal-organic frameworks as an efficient adsorbent for the removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions.

Metal-organic frameworks (MOFs) material with high surface area, good chemical stability and multi-functionality, has become an emerging adsorbent for water treatment. A novel kind of quaternary amine anionic-exchange MOFs UiO-66 namely UiO-66-NMe3+ was firstly synthesized for adsorptive removal of a widely used toxic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions. The well-prepared UiO-66-NMe3+ MOFs were fully characterized, and then the main parameters affecting the adsorption process including solution pH, adsorbent dosage and coexisting anions were systematically investigated. The maximum adsorption capacity of UiO-66-NMe3+ toward 2,4-D reached as high as 279 mg g-1, much higher than that of pristine UiO-66 and aminated UiO-66. The adsorption mechanism could be attributed to the electrostatic interactions efficiently enhanced by the functionalization of quaternary amine groups, combining with the π-π conjugations between the linkers in MOFs and 2,4-D molecules, leading to the better adsorption performance of UiO-66-NMe3+. Additionally, the UiO-66-NMe3+ could be well regenerated by simple solvent washing and exhibited a slight decline of adsorption capacity after seven successive recycle. Furthermore, satisfactory adsorption capacity and reusability of the MOFs in environmental water samples were attained. Comparing with reported activated carbon and resin materials, the UiO-66-NMe3+ MOFs possessed higher adsorption capacity and shorter equilibrium time, as well as good reusability and practicality. The developed ion-exchange functionalized MOFs provided an ideal alternative for efficient adsorptive-removal of 2,4-D from complicated aqueous environment.

Cationic metal-organic framework based mixed-matrix membrane for extraction of phenoxy carboxylic acid (PCA) herbicides from water samples followed by UHPLC-MS/MS determination.

A novel kind of cationic metal-organic framework(MOF) based mixed-matrix membrane(MMM) namely cationic MOF-MMM was firstly designed and used for simultaneous dispersive membrane extraction(DME) of six phenoxy carboxylic acid(PCA) herbicides from water samples followed by determination using ultrahigh-performance liquid chromatography tandem mass spectrometry. The cationic MOF-MMM was synthesized by soaking the zirconium-based MOFs in a polyvinylidene fluoride(PVDF) solution and further functionalization with quaternary amine groups, viz., UiO-66-NMe3+ MMM. The well-prepared UiO-66-NMe3+ MMM was characterized by FT-IR, SEM, XRD, XPS, NMR and etc. Several main variables influencing the MMM based DME efficiency were investigated and optimized in detail, such as dosage ratio of MOF/PVDF, solution pH, extraction time, coexistent anions and ionic strength. Electrostatic interactions dominated adsorption mechanism between anionic PCAs and cationic UiO-66-NMe3+ MMM, along with ππ conjugation and cation-π bonding, leading to better adsorption performance. Low limits of detection in the range of 0.03-0.59 ng/L and satisfactory recoveries within 80.06-117.40 % for all the PCAs are a reliable witness to demonstrate supreme sensitivity and the applicability of the developed method. By relying on the obtained results, the present work implied cationic MOF-MMM based DME can be a versatile and worthy utility for extraction of pollutants from different water samples with high throughput.

Aqueous extraction followed by dispersive solid phase extraction with in situ derivatization for the determination of aflatoxins in traditional Chinese medicines.

A green sample preparation method based on aqueous extraction followed by dispersive solid phase extraction (d-SPE) with in situ derivatization (ISD) was developed for the determination of aflatoxins (AFs) in traditional Chinese medicines (TCMs). AFs in TCMs were extracted by alkaline aqueous solution and converted to substituted coumaric acids. Then, mixed-mode anion exchange (MAX) sorbent was used to isolate and enrich the substituted coumaric acids. During the elution by acetonitrile/trifluoroacetic acid solution, AFs were reconstructed and in situ derivatized. Several parameters affecting the procedure were evaluated. The developed preparation method coupled with high performance liquid chromatography-fluorescence detection was successfully applied for AFs determination in TCMs. The limit of detection (LOD) reached 10 pg/mL for AFs. Good linearity was obtained in three orders of magnitude with correlation coefficients ranging from 0.9996 to 0.9999. The relative recoveries of the method were between 72.7% and 114.5% with intra- and inter-day relative standard deviations (RSDs) less than 9.5% and 10.1%, respectively. The method was successfully applied to determine AFs in 15 kinds of TCMs in China, with the results verified by IAC standard method.

A miniaturized and high sensitive dual channel fluorimeter based on compact collinear optical arrangement.

A miniaturized and high sensitive dual channel fluorimeter was developed and evaluated. It employed collinear optical arrangement, a 365 nm and a 470 nm light emitting diodes (LEDs) as light sources, two photodiodes (PDs) integrated with pre-amplifiers as optoelectronic detectors, and a 12.5 mm × 12.5 mm × 45 mm (width × length × height) quartz cuvette as detection cell. The optical parameters such as spectrum compatibility of dual channel, reshaping lens, the common optical path length (COPL), the common focus lens (CFL), as well as working distance of the cuvette were optimized carefully. It was found that the use of shortened optical path and common focal lens could improve the sensitivity of the dual channel fluorimeter significantly. The limits of detection (LODs) for coumarin, aflatoxin B1, fluorescein sodium, and vitamin B2 were 0.002 µg L-1, 0.006 µg L-1, 0.008 µg L-1, and 0.03 µg L-1, respectively. The dual channel fluorimeter can be used for detection of several categories of substance, such as mycotoxins, polycyclic aromatic hydrocarbons, fluorescein, vitamins, and pathogenic microorganisms etc. As a key component, it can also find application in different disciplines such as fluorescent PCR instruments and 96-well plate fluorescence analyzer.

A flame photometric detector with a silicon photodiode assembly for sulfur detection.

A flame photometric detector with a silicon photodiode assembly instead of a photomultiplier tube for sulfur detection was developed and evaluated. The photosensitive area of photodiode, the optical design, and band-pass filters, were optimized. It was found that the optimal photosensitive area of the photodiode was 100 (mm)2, and three focus lenses combined with a broad band-pass filter of 378/52 nm and a QB21 glass yielded the best result. This design fully utilized the wide emission spectrum of S2*, the response characteristics of silicon photodiode, and effective absorption of strong emission spectrums of OH* at wavelength around 310 nm by QB21 glass. The limits of detection for nine kinds of sulfur containing compounds were between 5.8 × 10-12 to 9.5 × 10-12 g s-1. This mode provided a linear response of 3 orders of magnitude for compounds being tested and a selectivity of sulfur over carbon of 105. It is demonstrated for the first time that the overall performance of the flame photometric detector integrated with a silicon photodiode assembly work at room temperature was comparable to a conventional detector coupled with a photomultiplier tube, with advantages of short equilibration time, robust to electromagnetic interference and vibration, and low cost. The new detector can find wide application in gas chromatography and on-line monitoring instruments for sulfur measurement.

Facile synthesis of zirconia-coated mesoporous silica particles by hydrothermal strategy under low potential of hydrogen conditions and functionalization with dodecylphosphonic acid for high-performance liquid chromatography.

In this work, multilayer zirconia-coated silica (ZrO2/SiO2-n) microspheres were successfully produced by a straightforward hydrothermal procedure with a low concentration of Zr4+ (5 mM) under low potential of hydrogen (pH) conditions (pH = =2). The obtained ZrO2/SiO2-n materials exhibited favorable characteristics for high-performance liquid chromatography (HPLC) separation, including high surface area and pore volume, good pore structure, narrow particle size, and pore size distribution. In addition, the zirconia coverage in the mesopores was confirmed by soaking the material in 1 M NaOH solution, with the particles showing strong resistance to the basic solution. The obtained ZrO2/SiO2-n stationary phases were packed into a fused-silica capillary tubing for the separation of alkaloids in hydrophilic interaction chromatography (HILIC) mode, and a column efficiency of 47,800 plates/m was obtained for berberine on a ZrO2/SiO2-6 micro column. The ZrO2/SiO2-6 microspheres were further modified by dodecylphosphonic acid (C12P-2-ZrO2/SiO2-6); the C12P-2-ZrO2/SiO2-6 material showed great potential for application in reversed-phase liquid chromatography (RPLC) mode. The C12P-2-ZrO2/SiO2-6 micro column showed a column efficiency of 55,000 plates/m for naphthalene and 51,300 plates/m for benzene.

[Recent advances in spatio-temporal distribution of endogenous phytohormones].

Endogenous phytohormone is a kind of trace organic small molecule compound synthesized in plants. It plays important roles in regulating the growth and development of plants throughout their life cycles, and responding to external stimuli. With the development of analytical methods for the detection of phytohormone, the amount of analytical samples is gradually reduced. Moreover, the differences in the types and contents of phytohormones in different plant tissues (or organs) are constantly presented. These developments greatly promote the study of the physiological effects of plant hormones. In recent years, the temporal and spatial distribution of endogenous phytohormones in several plant samples has attracted more and more attention in plant hormone analysis. This review summarizes the research progress made in the study of the spatial and temporal distribution of endogenous phytohormones in the last five years. Mainly, the review summarizes and discusses the difficulties associated with analysis, the development of analytical methods, and the spatial and temporal distribution of major plant hormones. The sampling methods, sample preparation and detection methods for spatial and temporal distribution studies are discussed in detail with a special focus on our work in plant hormone detection. Finally, the future development of the plant hormone analysis research field analysis is prospected.

Quantification of Low Copy Number Proteins in Single Cells.

We have developed an ultrasensitive and highly selective method to quantify low copy number intracellular proteins in a single cell using a low-cost laser-induced fluorescence (LIF) detector and a BV605 fluorescent probe. Active caspase3 proteins in cells were labeled by corresponding antibody-BV605 fluorescent binding, and a cell was injected into a 20 cm × 50 µm i.d. capillary column, followed by in situ lysis and capillary electrophoresis (CE)-LIF analysis. About seven active caspase3 protein molecules in a detection volume of 91 pL could be detected. In our method, cross-bounding proteins other than active caspase3 could be separated and distinguished by differences of retention time. By using Si photodiode assembly as a fluorescent detector instead of PMT, the dynamic range of the LIF is over 4 orders of magnitude. In this experiment, we found that the number of active caspase3 molecules in 98 single Jurkat cells were from 629 to 12171, reflecting significant heterogeneity among the cells although they were from the same batch. For extended application, it could also be applied to quantify other types of low copy number proteins in a single cell as long as the corresponding antibodies are provided. This high-sensitive method could also be a promising tool for earlier cancer diagnosis and related disease pathway research which is relevant to low copy number proteins. In addition, this low-cost system could also be easily expanded to an array system for high-throughput quantitation of low copy proteins in single cells.

Dispersive Matrix Solid-Phase Extraction Method Coupled with High Performance Liquid Chromatography-Tandem Mass Spectrometry for Ultrasensitive Quantification of Endogenous Brassinosteroids in Minute Plants and Its Application for Geographical Distribution Study.

An ultrasensitive analysis method for quantification of endogenous brassinosteroids in fresh minute plants was developed based on dispersive matrix solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry. During the dispersive matrix solid-phase extraction, plant samples were first ground with solid sorbent (dispersant) in one microcentrifuge tube and then centrifuged after adding extraction solvent and cleanup materials (another type of sorbent). Three protocols based on dispersive matrix solid-phase extraction were compared and discussed for plant samples with different matrix complexity. The choice of any protocol was a compromise of increasing purification efficiency and decreasing sample loss. Under optimized conditions, the limits of detection were 1.38-6.75 pg mL-1 for five brassinosteroids in the oilseed rape samples. The intraday and interday precisions were in the range of 0.8%-9.8% and 4.6%-17.3%, respectively. The proposed method was successfully applied to detection of endogenous brassinosteroids in milligram oilseed rape (2.0 mg) and submilligram Arabidopsis thaliana seedlings (0.5 mg). Finally, the geographical distribution of five endogenous brassinosteroids of Brassica napus L. oilseed rape in different provinces of origin in the Yangtze River basin was described.

One step rapid dispersive liquid-liquid micro-extraction with in-situ derivatization for determination of aflatoxins in vegetable oils based on high performance liquid chromatography fluorescence detection.

A rapid dispersive liquid-liquid micro-extraction (DLLME) with in-situ derivatization method for extraction and purification of aflatoxins (AFs) in vegetable oils was developed and evaluated. Oil extract, dichloromethane and trifluoroacetic acid were mixed and injected into water to form a cloudy solution. AFs in the oil were extracted into the numerous liquid droplets (with diameters from a few microns to dozens of microns) of extractant, where derivatization was carried out in situ. The proposed sample preparation method was coupled with high performance liquid chromatography with fluorescence detection (HPLC-FLD) for determination of four AFs in vegetable oils. The method showed excellent linearity in three orders of magnitude, good relative recoveries, good repeatability and high sensitivity with limits of detection in range of 0.005-0.03 ng/mL. The accuracy of the method was also verified by certified reference sample. Finally, different kinds of vegetable oils from the local supermarket were analyzed.