Simultaneous determination of amino acids in different teas using supercritical fluid chromatography coupled with single quadrupole mass spectrometry

Tea is a widely consumed beverage and has many important physiological properties and potential health benefits. In this study, a novel method based on supercritical fluid chromatography coupled with mass spectrometry (SFC-MS) was developed to simultaneously determine 11 amino acids in different types of tea (green teas, Oolong tea, black tea and Pu-erh tea). The separation conditions for the analysis of the selected amino acids including the column type, temperature and backpressure as well as the type of additive, were carefully optimized. The best separation of the 11 amino acids was obtained by adding water (5%, v/v) and trifluoroacetic acid (0.4%, v/v) to the organic modifier (methanol). Finally, the developed SFC-MS method was fully validated and successfully applied to the determination of these amino acids in six different tea samples. Good linearity (r ≥ 0.993), precision (RSDs≤ 2.99%), accuracy (91.95%-107.09%) as well as good sample stability were observed. The limits of detection ranged from 1.42 to 14.69 ng/mL, while the limits of quantification were between 4.53 and 47.0 ng/mL. The results indicate that the contents of the 11 amino acids in the six different tea samples are greatly influenced by the degree of fermentation. The proposed SFC-MS method shows a great potential for further investigation of tea varieties.

Terminal Effect of Drop Coalescence on Single Drop Mass Transfer Measurements and Its Minimization

For the mass transfer to single drops during the stage of steady buoyancy-driven motion, experimental measurement is complicated with the terminal effect of additional mass transfer during drop formation and coalescence at the drop collector. Analysis reveals that consistent operating conditions and experimental procedure are of critical significance for minimizing the terminal effect of drop coalescence on the accuracy of mass transfer measurements. The novel design of a totally-closed extraction column is proposed for this purpose, which guarantees that the volumetric rate of drop phase injection is exactly equal to that of withdrawal of drops. Tests in two extraction systems demonstrate that the experimental repeatability is improved greatly and the terminal effect of mass transfer during drop coalescence is brought well under control.

Experimental and Numerical Investigations of Single Drop Mass Transfer in Solvent Extraction Systems with Resistance in Both Phases

Numerical simulation of transient mass transfer to a single dropcontrolled by the internal resistance or by the resistance in bothphases was mathematically formulated and simulated in aboundary-fitted orthogonal coordinate system. The simulated resultson the transient mass transfer dominated by the internal resistanceare in good agreement with the Newman and Kronig-Brink models fordrops with low Reynolds number. When the drop Reynolds number is upto 200, the mass transfer coefficient from numerical simulation isvery low as compared with The Handlos-Baron model.

A review on single bubble gas–liquid mass transfer

It is common to empirically correlate volumetric mass transfer coefficient kLa for predicting gas–liquid mass transfer in industrial applications,and the investigation of single bubble mass transfer is crucial for a detailed understanding of mass transfer mechanism.In this work,experiments,models and simulations based on the experimental results were highlighted to elucidate the mass transfer between single bubbles and ambient liquid.The experimental setups,measurement methods,the mass transfer of single bubbles in the Newtonian and the nonNewtonian liquid,models derived from the concept of eddy diffusion,the extension of Whitman’s,Higbie’s and Danckwerts’models,or dimensionless numbers,and simulation methods on turbulence,gas–liquid partition methods and mass transfer source term determination are introduced and commented on.Although people have a great knowledge on mass transfer between single bubbles and ambient liquid in single conditions,it is still insufficient when facing complex liquid conditions or some phenomena such as turbulence,contamination or non-Newtonian behavior.Additional studies on single bubbles are required for experiments and models in various liquid conditions in future.

Analysis of Single Nucleotide Polymorphism in Human Paraoxonase 1 Gene(Q192R) with Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

Introduction Single nucleotide polymorphisms （SNPs） are the most abundant DNA markers in the human genome occurring at a frequency of one in every 500--1000 nucleotides. A variety of methods have been used for the analysis of single nucleotide polymorphisms, including restriction fragment length polymorphism （RFLP）, direct sequencing by using laser-induced fluorescence detectionTM, fluorescence energy transfer, MALDI-TOF MS combined with primer extension or invasive cleavage, and fluorescence polarization. During the past two decades, mass spectrometry has become a very popular tool in the analysis of biomolecules and is perfectly suited to the analysis of single nucleotide polymorphisms （SNPs） due to its speed, low cost, and accuracy. In this work, we used MALDI TOF mass spectrometry to detect the fragments of restriction endonuclease hydrolysis of PCR products flanking a SNP located at paraoxonase 1（Q192R）. Compared with electrophoresis, this method requires less time of analysis and possess a higher accuracy.

Influence of Isothermal Treatment on Superelastic Behavior of Cu-13.8Al-4.0Ni(mass fraction) Single Crystals

The superelastic behaviors of different isothermal treated Cu-13.SAl-4.ONi (mass fraction) single crystals were studied by applying tensile stress along <001> of the d phase. The different isothermal specimens have different superelastic behavior due to the change of the ratio of stress-induced r1 and β1. The superelasticity of r1 phase tends to that of g; phase with cycling. Typical stabilization of stress-induced martensite above Ap results in residual deformation. Due to the reverse transformation of 7I, there is a deviation of pseudo-yield stress from linear relation with temperature at relatively low stress.

Simulated and Experimental Study of Single Particle Measurement Using Inductively Coupled Plasma Mass Spectrometry

A droplet carrying particle is desolvation, vaporization, ionization, and diffusion in an inductively coupled plasma (ICP) to form a cloud of ions. It then is detected as a mass-spectrum peak of individual particle. The diameter of the particle is derived from its mass, which is calibrated using the peak area. This is the basic principle of measuring single particles using inductively coupled plasma mass spectrometry (ICP-MS). In this paper, a mathematical model describing single particles in plasma is investigated. This makes it possible to investigate the process and contributing factors of single particles measurement by ICP-MS. A series of processes are investigated, which include increasing the droplet temperature to the boiling point, desolvation of the droplets, increasing the particle temperature to the melting point, the particles are melted from a solid to the liquid, increasing the particle temperature to the boiling point, and particle vaporization. The simulation shows that both the atomic (ion) diffusion in the plasma and the incomplete vaporization of the particles are two important factors that limit the signal intensity of the particle’s mass spectrum. The experiment reveals that ICP-MS is very linear for Ag nanoparticles below 100 nm and SiO2 particles below 1000 nm. Both the simulation and experiment reveal the measurement deviation for large particles and that an increase of sampling depth can extend the diffusion time and cause signal suppression. The model can be used to study the mechanisms of monodispersed droplet or single-particle mass spectrometry, analyze the contributing parameters for single particle measurements by ICP-MS and provide a theoretical base for the optimization of single particle measurements in the practical application, such as nanoparticle devices, magnetic materials, biomedical materials additives and consumer products.

Analytical Solution of Vibration Analysis on Fixed-Free Single-Walled Carbon Nanotube-Based Mass Sensor

Fixed-free single-walled carbon nanotubes (SWCNTs) have attracted a lot of interest in recent years due to their suitability for a wide range of applications, such as field emission and vacuum microelectronic devices, nanosensors, and nanoactuators. Based on a cantilever beam-bending model with a rigid mass at the free end and mode analysis, an analytical solution is developed in the present study to deal with the resonant frequency and mode shapes of a SWCNT- based mass sensor. The resonant frequency shift and mode shape of the fixed-free SWCNTs caused by the addition of a nanoscale particle to the beam tip are examined in order to explore the suitability of SWCNTs as a mass detector device. The simulation results reveal that the volume of the added particle has little effect on the first resonant frequency. In contrast, the second resonant frequency decreases with increasing the volume of the added particle. Furthermore, the resonant frequency shift of the first mode is very obvious for the amount of added mass, and the second resonant frequency decreases rapidly with increasing volume of added particle. Therefore, the first and second resonant frequencies can be used in the measurement of the mass of added particle and its volume, respectively.

Association between low molecular polypeptide 7 single nucleotide polymorphism and response to therapy in hepatitis C virus infection

AIM: To investigate the relationship between low molecular polypeptide-7 (LMP-7) gene polymorphism and response to interferon (IFN) therapy in chronic hepatitis C virus (HCV) patients. METHODS: LMP-7 polymorphism at codon 49 with nucleotide substitution from A to C was amplified in 104 chronic HCV patients of genotype 4. The amplicons were digested with restriction endonuclease Bsm I and the produced restriction fragment length polymorphism was analyzed. Patients received IFN + regional blood volume therapy for 48 wk and the frequency of thissingle nucleotide polymorphism (SNP) was statistically correlated with treatment response. The exclusion criteria for these patients were stated by the national health program for treating viral hepatitis. Main exclusion criteria included co-infection with hepatitis B virus or schistosomiasis, thyroid dysfunction, uncontrolled diabetes mellitus, history of long term drug or alcohol intake and autoimmune hepatitis. Multivariate analyses were done to correlate LMP-7 SNP plus several factors such as age, gender, weight, serum alpha-fetoprotein (AFP) and alanine aminotransferase levels, liver activity, fibrosis score and viral load with response to therapy. RESULTS: The data presented in this study clearly demonstrated statistically significant differences between sustained virological response (SVR) (defined as the absence of HCV RNA levels in the patient's sera at least 6 mo after discontinuation of treatment) and non-response (NR) (where HCV RNA levels in the patient's sera never become undetectable for 6 mo during or after treatment). Variables were described as odds ratio with 95%CI. The data were considered significant if P values were ≤ 0.05; highly significant if P < 0.01 and very highly significant if P < 0.001. Current data showed that 91.7% of patients carrying LMP-7 C/C allele were associated with SVR, while the other two genotypes C/A and A/A were associated with NR patients, 83.3% and 64.3% respectively, showing that genotype CC was strongly associated with response to interferon (95%CI: 12.0719-134.6572, P = 0.0001). The majority of parameters recorded in SVR and NR patients included higher values of mean age (P = 0.004), alanine aminotransferase (P = 0.001), AFP (P = 0.001), body weight (P = 0.025), viral load (P = 0.025), higher fibrosis and histological activity index indices among NR vs SVR patients. Also, the multivariate statistical analysis of the different factors of fibro-sis score, liver activity grade, genotypes and alleles of LMP-7 gene polymorphism in responders and NRs of HCV patients in this study showed that HCV patients with A allele had a very highly significant association with the NRs, high fibrosis and higher liver activity, while the C allele had a very highly significant association with the responders, low fibrosis and lower liver activity (95%CI: 3.5800-13.2519, P = 0.0001).CONCLUSION: LMP-7 SNP is a candidate gene that should be considered when designing a mathematical model for predicting response to therapy and disease progression in HCV patients.

A state-of-the-art review on single drop study in liquid–liquid extraction:Experiments and simulations

The experimental and numerical investigations of single drop in liquid/liquid extraction system have been reviewed with particular focus on experimental techniques and computational fluid dynamic simulation approaches.Comprehensive surveys of available experimental techniques and numerical approaches for single drop rising and falling were given.Subsequently,single drop mass transfer was also reviewed both experimentally and numerically.Additionally,single drop breakage and coalescence process and the influencing factors were summarized and compared,so as to establish sub-models for population balance model.Future directions on single drop mass transfer,drop breakage and coalescence were suggested.It is believed that the single drop is a powerful tool to assist extraction process design from lab-scale to pilot-scale.

Kinetics of Forward Extraction of Boric Acid from Salt Lake Brine by2-Ethyl-1,3-hexanediol in Toluene Using Single Drop Technique

The kinetics of forward extraction of boric acid from salt lake brine by 2-ethyl-1,3-hexanediol in toluene was investigated using the single drop technique. The factors affecting the extraction rate include interfacial area between aqueous phase and organic phase, initial concentration of boric acid in aqueous phase, initial concentration of 2-ethyl-1,3-hexanediol in organic phase, and extraction temperature. The experimental results show that the extraction rate increases with the increase of the initial concentration of boric acid and2-ethyl-1,3-hexanediol, interfacial area of two phases, and temperature. With the temperature-dependence study, it is showed that the extraction is a diffusion-controlled process. The kinetic equation is presented for pH 1.0 in the aqueous phase and temperature of 318 K.

Laparoendoscopic single site,laparoscopic or open surgery for adrenal tumors:Selecting the optimal approach

Numerous surgical modalities are available to treat adrenal lesions. Minimally-invasive approaches for adrenalectomy are indicated in most circumstances, and new evidence continues to be accumulated. In this context, current indications for open surgical adrenalectomy(OS-A), minimally-invasive adrenalectomy(MI-A), and laparoendoscopic single-site adrenalectomy(LESS-A) remain unclear. A comprehensive Englishlanguage literature review was performed using MEDLINE/Pub MED to identify articles and guidelines pertinent to the surgical management of adrenal tumors. A comprehensive chart review was performed for three illustrative cases. Clinical recommendations were generated based on relevant literature and the expertise of the investigator group. MI-A offers advantages over OS-A in properly selected patients, who experience fewer complications, lower blood loss, and shorter hospital stays. Robot-assisted laparoscopic and retroperitoneoscopic adrenalectomy may offer advantages over transperitoneal surgery, and LESS-A may be an even less-invasive option that will require further evaluation. MI-A remains the surgical treatment of choice for most adrenal lesions. Tumor size and stage are the primary indications for selecting alternative treatment modalities. OS-A remains the gold standard for large tumors(> 10 cm) and suspected or known advanced stage malignancy. LESS-A appears to be an appropriate initial approach for small tumors(< 4-5 cm), including pheochromocytoma and isolated adrenal metastases.

大气压固体分析探针结合单四极杆质谱仪快速检测18种合成大麻素

本研究建立了一种大气压固体分析探针结合单四极杆质谱仪(ASAP-MS)快速检测18种合成大麻素(SCs)的方法。通过优化ASAP-MS锥孔电压,确定4种优化电压为15、25、35和50 V,以提供化合物全面的质谱信息。在优化条件下对一系列SCs标准溶液进行分析,建立了18种SCs的质谱库,并对本方法进行方法学验证,得到18种SCs的检出限为10~20 mg/L。应用该方法对缴获的15批次未知样品进行检测,9批次呈阳性。该方法具有前处理简单、分析速度快、匹配高效精准、定性准确的优势,可用于基层公安禁毒部门的分析检测。

基于常时微动的单结构面危岩体损伤识别实验

危岩体的动力学参数能够表征危岩体与基岩之间结构面的损伤,实际工程中人工激励危岩体较为困难,因此,如何根据场地常时微动特征识别危岩体动力学参数仍是亟需解决的问题.本文将常时微动激励下的危岩体振动问题归为欠阻尼条件单自由度结构受迫振动问题,将危岩体频谱幅值与基岩频谱幅值之比作为相对幅值谱,通过相对幅值K>1的最大峰值点对应的频率得到危岩体的一阶固有频率.以宏观裂缝控制型危岩体(悬臂式和错断式危岩体)及微观裂隙控制型危岩体(滑移式危岩体)为研究对象,通过模型实验验证了常时微动条件下测量危岩体一阶固有频率的可行性,通过切割裂缝模拟悬臂式危岩体和错断式危岩体结构面损伤弱化,发现随着损伤程度加剧,一阶固有频率呈明显下降趋势;通过水溶胶冻结融化模拟滑移式危岩体结构面损伤弱化,随着损伤程度加剧,其一阶固有频率无明显变化,高频段的重心频率发生明显变化.实验结果表明对于宏观裂缝控制型危岩体结构面损伤可通过危岩体的一阶固有频率进行识别,对于微观裂隙控制型危岩体结构面损伤可通过危岩体高频段的重心频率变化进行识别,将两者综合起来对危岩体结构面损伤进行识别将更加有效.

再造烟叶烟气中刺激性气味的关键化学组分研究

为研究再造烟叶烟气中刺激性气味的关键化学组分,本工作利用元素分析仪(EA)与电感耦合等离子体质谱(ICP-MS)表征天然烟叶、再造烟叶以及基片,解析3种原料的化学组成差异。利用U型固定床热解反应器对3种原料进行热解实验,产生的气态产物先通过与固定床反应器出口相连的光电离质谱(SPI-MS)进行实时在线检测,同时结合气相色谱-质谱(GC-MS)的离线定性分析结果确定热解产物的具体组成。随后,采用主成分分析(PCA)法对谱图进行统计学分析,以区分3种原料热解后特征产物的质荷比(m/z),选择含量显著差异的产物作为模型化合物,开展嗅辨实验。结果表明,再造烟叶烟气中刺激性气味的关键化学组分主要为环戊酮、环己酮和4-乙基苯酚。此外,根据产物随温度的实时变化谱,能够准确了解上述模型化合物在热解过程中的温度释放范围。该研究可为后续减少再造烟叶中刺激性气味提供数据支撑。

CD45^(+)CD326^(+)双阳性细胞的特征及其在膀胱癌预后预测中的作用

目的探讨CD45^(+)CD326^(+)双阳性细胞(double positive cells,DPCs)对膀胱癌预后的影响,并构建膀胱癌DPCs相关基因评分系统,探究不同DPCs评分膀胱癌患者肿瘤微环境的特征。方法采用单细胞测序技术分析DPCs的分子特征,质谱流式技术分析DPCs高比例组和低比例组患者的肿瘤微环境异质性。基于TCGA‐BLCA队列,根据DPCs的特征基因构建评分系统,并在GSE13507队列及GSE32894队列中进行验证。结果膀胱癌患者中DPCs高比例组患者的预后较低比例组患者的预后差(P=0.0158),且高、低比例组患者的肿瘤微环境存在异质性,高比例组患者较低比例患者的免疫细胞和肿瘤细胞有更高的免疫检查点、共抑制因子和共激活因子的表达水平(均P<0.05);基于TCGA‐BLCA队列构建了9个基因(APOBEC3G、CD96、CLEC2D、GNG2、GNLY、IL32、PSMB9、RORA、SKAP1)的膀胱癌DPCs相关基因评分系统。TCGA‐BLCA队列、GSE13507队列和GSE32894队列分析结果显示,高风险评分组膀胱癌患者的总生存期明显比低DPCs评分组短(均P<0.01)。免疫抑制、雌激素等信号通路在高风险评分组中显著富集。结论DPCs与膀胱癌不良预后密切相关,基于DPCs特征基因构建的模型可较准确地预测膀胱癌患者的临床预后。

两样本孟德尔随机化分析身体质量指数与前列腺癌发病风险的因果关系

目的通过孟德尔随机化(MR)分析基因预测的身体质量指数(BMI)与前列腺癌(PCa)发病风险之间的因果关系,以期探索PCa的潜在风险因素,制定预防策略。方法汇总统计339224个样本的BMI全基因组关联研究(GWAS)数据和463010个样本的PCa GWAS数据进行两样本MR。使用BMI的69个单核苷酸多态性(SNP)作为工具变量对PCa进行MR分析。采用逆方差加权法(IVW)、MR-Egger法、加权中位数法(WME)、简单众数法(SM)和加权众数法(WM)进行MR分析。采用异质性检验、多效性检验和留一法敏感性检验验证数据的稳定性和可靠性。结果IVW分析发现BMI与PCa发病风险存在关联(OR:0.997,95%CI:0.995~0.999,P=0.001);在WME(OR:0.996,95%CI:0.994~0.999,P=0.009)和WM(OR:0.995,95%CI:0.991~1.000,P=0.045)中得到相同的结果。而在MR-Egger法(OR:0.996,95%CI:0.991~1.002,P=0.205)和SM法中(OR:0.995,95%CI:0.990~1.000,P=0.079),差异无统计学意义。结论两样本MR分析基因预测的BMI较高与较低的PCa患病风险之间存在因果关系,这一发现可为探究PCa的潜在风险因素及制定预防策略提供参考。

基于质谱的单细胞分析技术研究新进展

细胞是生物体最基本的结构和功能单位。近年来,人们对细胞异质性的关注越来越多。为了分析细胞的这种异质性,避免单细胞信息被群体细胞的平均值所淹没,单细胞分析技术不断发展起来。由于单细胞的体积小,内含物质含量低且种类繁多,某些物质在细胞内的变化迅速,分析过程中不同物质之间相互干扰,造成了单细胞分析极具挑战性。基于质谱的单细胞分析技术具有通用性强、无需标记、高灵敏度、高分辨率、高选择性的优点,已逐渐在单细胞分析技术中脱颖而出,成为单细胞分析的理想工具。本文系统地总结了近5年来基于质谱的单细胞分析技术的最新进展,包括电喷雾电离质谱、激光解吸电离质谱、二次离子质谱、电感耦合等离子体质谱,并对未来的研究和技术方向进行展望,希望为单细胞质谱分析技术的研究提供参考。

基于参数标准化的单样本定标方法在微波等离子体炬水泥快速分析中的应用

流程工业颗粒物成分的在线检测具有低延时、安全可靠及低成本等要求,目前没有适合的技术手段.微波等离子炬(Microwave plasma torch,MPT)原子发射光谱法具有直接进样、成本低及装置安全可靠等优点,有潜力成为工业在线检测的重要手段.本文基于MPT装置对水泥样品进行直接进样分析,并针对工业应用场景中标准样品受限的问题,采用单样本定标技术(Single sample calibration,SSC)进行定量分析.SSC法中的线性假设容易受到等离子体参数波动的影响,导致精度下降.为此,提出了一种基于参数标准化的SSC算法PS-SSC(SSC based on parameter standardization),通过激发温度和电子数密度对谱线强度进行修正以提高SSC的定量精度.为了评估MPT和PS-SSC方法联用在水泥成分快速分析中的有效性,将GSB 08-2985-2013标准水泥粉末气溶胶直接引入MPT中进行定量分析,并将PS-SSC与现有定量方法进行比较.与传统SSC方法相比,PS-SSC方法的决定系数R2由‒0.81~0.81提高到0.39~0.88,平均相对误差由4.39%~10.33%提高到1.55%~5.83%,平均相对标准偏差由2.89%~9.40%提高到2.28%~6.50%,展现了该方法在工业在线成分检测中的应用潜力.