Rapid detection of antibiotic resistance in Salmonella with screen printed carbon electrodes

Journal of Solid State Electrochemistry - Salmonella, one of the most common foodborne pathogens, poses a serious threat to human health. In recent years, the antibiotic resistance of Salmonella...     

高效液相色谱-蒸发光散射检测法在烟用香精料液中水溶性糖及山梨醇分析中的应用

建立了高效液相色谱-蒸发光散射(HPLC-ELSD)同时检测烟用香精料液中6种水溶性糖及山梨醇的分析方法。方法选用Isolute ENV+固相萃取(SPE)小柱净化样品提取液,以Prevail Carbohydrate ES高效糖柱(250 mm×4.6 mm, 5 μm)作为分析柱,以乙腈和水(75:25, v/v)作为流动相,在1.0 mL/min流速下实现目标物的良好分离;蒸发光散射检测器漂移管温度为79 ℃,载气流速为2.0 L/min。方法针对各目标物建立双对数工作曲线,线性范围约为0.06～1.2 g/L,检出限为12～26 mg/L,样品加标回收率为88%～109%。针对蒸发光散射检测器的双对数工作曲线,通过实验进行分析对比,并结合前人的工作,指出目标物的物理化学性质及其在色谱柱上的保留状态和流动相的洗脱能力等都是影响检测信号的因素。     

DLLME-HPLC测定锡金微孔草内源激素脱落酸的含量

建立分散液液微萃取-高效液相色谱法测定锡金微孔草内源激素脱落酸含量的分析方法.分散液液微萃取条件为:100μL萃取剂(氯仿),1.0mL分散剂(乙酸乙酯),pH 3.0;方法的线性范围:0.0285-1.14μg/mL,r=0.9995,检出限0.0008μg/mL (S/N=3);锡金微孔草中脱落酸的加标回收率为90.99％-93.12％,RSD为0.99％-1.57％ (n=3).本方法具有检出限低、操作简便、环境友好等优点,适于检测微孔草中痕量的脱落酸.     

Monolithic molecularly imprinted solid-phase extraction for the selective determination of trace cytokinins in plant samples with liquid chromatography–electrospray tandem mass spectrometry

Cytokinins (CTKs) are a class of growth-regulating hormones involved in various physiological and developmental processes. More novel analytical methods for the accurate identification and quantitative determination of trace CTKs in plants have been desired to better elucidate the roles of CTKs. In this work, a novel method based on monolithic molecularly imprinted solid-phase extraction followed by liquid chromatography–electrospray tandem mass spectrometry (mMI-SPE-LC-MS/MS) was developed for accurate determination of four CTKs in plant samples. The molecularly imprinted polymer monolith was prepared by using kinetin as the template in syringes and exhibited specific recognition ability for the four CTKs in comparison with that of non-imprinted polymer monolith. Several factors affecting the extraction performance of mMI-SPE, including the pH of loading sample solution, the nature and volume of elution solvent, the flow rate of sample loading, and sample volume, were investigated, respectively. Under the optimized conditions, the proposed mMI-SPE-LC-MS/MS method was successfully applied in the selective extraction and determination of four CTKs in plant tissues, and it offers detection limits (S/N?=?3) of 104, 113, 130, and 89 pg/mL and mean recoveries of 85.9%, 79.3%, 73.5%, and 70.1% for kinetin, kinetin glucoside, trans-zeatin, and meta-topolin (mT), respectively, with the corresponding RSDs less than 15%.

An electrochemiluminescence sensor for determination of durabolin based on CdTe QD films by layer-by-layer self-assembly

This work reported for the first time the use of flow injection electrochemiluminescence (FI-ECL) sensor for the determination of durabolin in an aqueous system based on CdTe quantum dot (QD) films. Aqueous CdTe colloidal solutions were prepared using thioglycolic acid as a capping agent. Zetasizer Nano ZS (Malvern, UK) was employed to characterize the size of CdTe QDs. The UV–vis and photoluminescence spectra of samples were systematically characterized. Indium tin oxide (ITO) slide glass was modified with CdTe QDs by layer-by-layer self-assembly. CdTe QD films were packed into a homemade cell and used as a recognizer of the FI-ECL sensor to determine durabolin. The intensive anodic ECL emission was obtained at a starting potential of +1.3 V (vs. Ag/AgCl) in a carbonate bicarbonate buffer solution with a pH of 9.93 at an ITO electrode. The ECL intensity was correlated linearly with the concentration of durabolin over the range of 1.0 × 10⁻⁸–1.0 × 10⁻⁵ g mL⁻¹, and the detection limit was 2.5 × 10⁻⁹ g mL⁻¹. The relative standard deviation for the determination of 1.0 × 10⁻⁶ g mL⁻¹ durabolin was 1.04% (n = 11). This simple and sensitive sensor revealed good reproducibility for ECL analysis. As a result, the new FI-ECL sensor had been successfully applied to the determination of durabolin in food samples. This strategy could be easily realized and opened new avenues for the applications of QDs in ECL biosensing.     

金银花不同部位中绿原酸和木犀草苷含量的测定

利用HPLC法测定金银花不同部位中绿原酸和木犀草苷。采用ODS-C18色谱柱(250 mm×4.6 mm,5μm),以甲醇-水(0.03 mol/L磷酸)为流动相进行梯度洗脱,流速:1.0 mL/min,检测波长:350 nm,柱温:室温。绿原酸浓度在0~0.4 mg/mL内与峰面积呈良好线性关系(r2=0.999 6),回收率为101.9%~105.2%,相对标准偏差为3.18%(n=6)。木犀草苷浓度在0~0.1 mg/mL内与峰面积呈良好线性关系(r2=0.999 1),平均回收率为100.5%~104.0%,相对标准偏差为3.42%(n=6)。结果表明:金银花、芽等部位绿原酸和木犀草苷的含量较高。     

Separation and detection of polar cuticular components from Oriental tobacco leaf by integration of normal-phase liquid chromatography fractionation with reversed-phase liquid chromatography-mass spectrometry

Integration of normal-phase LC (NPLC) fractionation with RPLC-ESI/MS was established to detect the polar fractions of cuticular components from Oriental tobacco leaf. NPLC was selected for the fractionation of polar components of cuticular leaf extract, after being concentrated with rotary evaporator, each of the enriched fractions was further analyzed by RPLC-ESI/MS. In total, 83 compounds were finally detected including 45 cembranoids, 15 labdanoids, 20 sucrose esters, and 3 glucose esters (or fructose esters). Three cembranoids and seven labdanoids possibly are new diterpenoids. Glucose esters (or fructose esters) are also reported in Nicotiana tobacco for the first time.     

溶胶凝胶法制备超疏水二氧化硅涂膜及其表面润湿行为

采用溶胶-凝胶法以正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为前驱体制备超疏水SiO2涂层。红外光谱(FTIR)和热重分析(TGA)表征合成SiO2的化学组成,通过透射电镜(TEM)和扫描电镜(TEM)观察制备SiO2的结构形貌,扫描电镜(SEM)和原子力显微镜(AFM)观察SiO2涂膜的表面形貌,通过测试水接触角(WCA)讨论SiO2涂层的表面微观结构与其表面疏水性能的关系。结果表明以TEOS和MTES为共前驱体可以制备得到表面带-CH3基团的SiO2溶胶,SiO2溶胶在老化过程中纳米SiO2粒子由于自组装作用形成草莓状微米-纳米双微观结构,这种结构赋予SiO2涂膜表面不同等级的粗糙度,使得水滴与涂膜表面接触时能够形成高的空气捕捉率和较小的粗糙度因子,与SiO2表面疏水性的-CH3基团共同作用形成类荷叶超疏水结构。     

A Lewis acid-promoted reduction of acylsilanes to α-hydroxysilanes by diethylzinc

We report here the first example of the reduction of acylsilanes to α-hydroxysilanes, in which diethylzinc was used as a highly reactive agent in the presence of Ti(OiPr)₄ or other Lewis acids. The reduction typically proceeds to give synthetically useful α-hydroxysilanes in good yields.     

Nontrivial solutions for resonant difference systems via computations of the critical groups

In this paper, we study the existence of solutions for a class of resonant difference systems by using the minimax methods and the Morse theory. We prove that there exists at least one nontrivial solution for the systems.