Enzymatic synthesis of medium chain monoglycerides in a solvent-free system

The synthesis of monocaprin, monolaurin, and monomyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The addition of molecular sieves in the assays of monomyristin synthesis was also evaluated. The reactions were carried out for 5 to 6 h and the nonpolar phase was analyzed by gas chromatography. The best results in terms of selectivity and conversion (defined as the percentage of fatty acid consumed) were achieved when the stoichiometric amount of reagents (molar ratio=1) and 9% (w/w) commercial enzyme were used and the reaction was performed at 60°C. The addition of molecular sieves did not improve the synthesis of monomyristin. Conversions as high as 80%, with monoglycerides being the major products, were attained. After 5 h of reaction, the concentration of monoglyceride was about twice that of diglyceride, and only trace amounts of triglyceride were found. The results illustrate the technical possibility of producing medium chain monoglycerides in a solvent-free medium using a simple batch reactor.     

Determination of maize and grain herbicides and their transformation products in soil by use of soil column extraction then liquid chromatography with tandem mass spectrometry

Summary A multiresidue method has been developed for identification and quantitation of the herbicides most commonly used in cultivation of maize and grain, and of their transformation products, in soil samples. The analytes were isolated by soil column extraction (SCE) and the extracts were purified by use of a Carbograph-1 cartridge. Analysis was performed by liquid chromatography coupled with tandem mass spectrometric detection (LC-TISP-MS-MS) in negative-ion mode. To optimize the extraction conditions affecting the performance of SCE, e.g. the extracting solvent used, temperature, extracting volume, and solvent flow rate, were studied. To evaluate the matrix effect in SCE, recovery experiments were performed on soil samples, with different physical and chemical characteristics, fortified with the 100 ng g⁻¹ of the target compounds. Recovery data were satisfactory and the method detection limits were between 3 and 100 ng g⁻¹, depending on the compound.     

Hydrothermal Synthesis of Two New Transition Metal Coordination Polymers with Mixed Ligands

Hydrothermal reactions of 1, 2, 4‐benzenetricarboxylic acid, 1, 10‐phenanthroline and transition metal cations including Zn^II or Co^II, in basified aqueous solution gave rise to two complexes, [Zn₃(btrc)₂(1, 10‐phen)₂(H₂O)₂]_n ( 1 ), and [Co₃(btrc)₂(1, 10‐phen)₂(H₂O)₂]_n ( 2 ) (btrc = 1, 2, 4‐benzenetricarboxylate, and 1, 10‐phen = 1, 10‐phenanthroline). 1 2 crystalize isotypically in the triclinic space group P1¯. The btrc ligand acts as multi‐dentate bridging ligand in both compound 1 and 2 to link up transition metal atoms into lamella networks, which are further attached into three‐dimensional frameworks through complex hydrogen bonding and π‐π interactions. The photoluminescence spectrum for compound 1 has also been studied. The corresponding reaction with Cu²⁺ follows another pathway.     

离子排斥色谱法同时测定果汁中11种有机酸

 用离子排斥色谱法实现了对果汁中 11种有机酸 (草酸、柠檬酸、酒石酸、苹果酸、抗坏血酸、乳酸、琥珀酸、甲酸、乙酸、戊二酸、富马酸 )的分离测定。以 17mmol/L硫酸为淋洗液 ,样品在ICE ION 30 0离子排斥柱上分离后 ,用紫外检测器在 2 10nm处测定其中的有机酸。各组分质量浓度测定的相对标准偏差在 1.5 %～ 9.8% (n =10 )。     

高效液相色谱/安培检测法测定蜂蜜中苯酚残留量

研究了用高效液相色谱 /安培检测法测定蜂蜜中苯酚残留量。考察了试验参数对测定结果的影响。在所选试验条件下 ,苯酚保留时间约为 12min ,检出限为 2 .0ng·g- 1。三组不同水平的加样回收率为 91.6 10 1.9% ,相对标准偏差 2 .812 .8%。测定结果满意     

大亚湾沉积物中氨基酸的垂直分布棗沉积物柱样W0中的游离氨基酸

用邻苯二甲醛（OPA）－3－巯基丙酸（3－MPA）柱前衍生高效液相色谱法测定了采自大亚湾近岸海域的一个长60cm的沉积物柱样W0中15种游离氨基酸（FAA）的含量，结果表明，W0中FAA总量在0．83－2．69mmol/kg之间，15种FAA以及FAA总量均随深度而以指数曲线降低，对氨基酸组成的分析表明，天冬氨酸，甘氨酸，组氨酸和苯丙氨酸的摩尔分数随深度而上升，苏氨酸，精氨酸，缬氨酸和异亮氨酸的摩尔分数随浓度而下降，其他氨基酸的摩尔分数随深度无显著变化，甘氨酸，丙氨酸，天冬氨酸，谷氨酸，丝氨酸是W0中含量最丰富的氨基酸，其摩尔数依次为28．1％，16．0％，14．7％，10．6％和7．2％。     

5-阿维菌素B1a酯的合成及生物活性

阿维菌素B_1a(AVB_1a)与羧酸在DMAP/DCC体系中直接酯化,得到10个5-AVB_1a酯衍生物,产率50%～79%;其化学结构由IR,¹H NMR,¹³CNMR和MS谱确证.生物活性测定结果表明,部分5-阿维菌素B_1a酯衍生物具有良好的杀虫、杀螨活性.     

聚丙烯熔融接枝马来酸酐反应机理的研究

改变聚丙烯（PP）熔融接枝马来酸酐（MAH）反应中的单体和引发剂的浓度以及添加适当助剂,考察了接枝产物的接枝率和恒定剪切应力（600kPa)及温度（210℃）下的剪切粘度,验证了作先前所提出的PP熔融接枝MAH的反应机理。即：在PP熔融接枝MAH的过程中,过氧化物自由基在熔融接枝过程中直接引发MAH单体及MAH单体在聚丙烯的大分子链段发生β断裂前直接被其引发而产生的接枝反应是影响产物的接枝率和分子量的关键。在不改变单体和引发剂浓度的情况下,降低过氧化物自由基在熔融接枝过程中直接引发MAH单体反应的程度而提高聚丙烯的大分子自由基直接引发MAH单体的反应趋势,是提高接枝产物接枝率和分子量的有效途径。     

Impact of Collection Volume and DNA Extraction Method on the Detection of Biomarkers and HPV DNA in First-Void Urine

The potential of first-void (FV) urine as a non-invasive liquid biopsy for detection of human papillomavirus (HPV) DNA and other biomarkers has been increasingly recognized over the past decade. In this study, we investigated whether the volume of this initial urine stream has an impact on the analytical performance of biomarkers. In parallel, we evaluated different DNA extraction protocols and introduced an internal control in the urine preservative. Twenty-five women, diagnosed with high-risk HPV, provided three home-collected FV urine samples using three FV urine collection devices (Colli-Pee) with collector tubes that differ in volume (4, 10, 20 mL). Each collector tube was prefilled with Urine Conservation Medium spiked with phocine herpesvirus 1 (PhHV-1) DNA as internal control. Five different DNA extraction protocols were compared, followed by PCR for GAPDH and PhHV-1 (qPCR), HPV DNA, and HBB (HPV-Risk Assay), and ACTB (methylation-specific qPCR). Results showed limited effects of collection volume on human and HPV DNA endpoints. In contrast, significant variations in yield for human endpoints were observed for different DNA extraction methods (p < 0.05). Additionally, the potential of PhHV-1 as internal control to monitor FV urine collection, storage, and processing was demonstrated.     

Controlling Metallophilic Interactions in Chiral Gold(I) Double Salts towards Excitation Wavelength‐Tunable Circularly Polarized Luminescence

Materials exhibiting excitation wavelength‐dependent photoluminescence (Ex‐De PL) in the visible region have potential applications in bioimaging, optoelectronics and anti‐counterfeiting. Two multifunctional, chiral [Au(NHC)₂][Au(CN)₂] (NHC=(4R,5R)/(4S,5S)‐1,3‐dimethyl‐4,5‐diphenyl‐4,5‐dihydro‐imidazolin‐2‐ylidene) complex double salts display Ex‐De circularly polarized luminescence (CPL) in doped polymer films and in ground powder. Emission maxima can be dynamically tuned from 440 to 530 nm by changing the excitation wavelength. The continuously tunable photoluminescence is proposed to originate from multiple emissive excited states as a result of the existence of varied Au^I???Au^I distances in ground state. The steric properties of the NHC ligand are crucial to the tuning of Au^I???Au^I distances. An anti‐counterfeiting application using these two salts is demonstrated.