Hydrothermal Transformations of Ascorbic Acid

Hydrothermal treatment of aqueous solution of ascorbic acid has resulted in the formation of soluble and insoluble products. The soluble product (carbon quantum dots) has exhibited pronounced fluorescent properties. The insoluble product consists of densely aggregated 1–2 μm particles. The increase in the hydrothermal treatment duration has resulted in continuous transformation of carbon quantum dots into the microparticles.     

On-line solution stability determination of pharmaceuticals by capillary electrophoresis

Summary Good agreement between the impurity levels in a batch of a related impurity of ranitidine were obtained by CE and HPLC. A solution of the impurity was positioned on the CE autosampler and analysed sequentially. The extent of degradation was monitored by loss of main peak and the formation of two principal degradation products. It was found that after 9.25 hours only 2% area/area of the original impurity remained. Buffering of the sample solution to pH 7 was shown to minimise this degradation.Unattended in-situ stability testing of an solution of the impurity in water was performed by CE.     

Shape-controlled production of biodegradable calcium alginate gel microparticles using a novel microfluidic device

In this paper we describe a novel method of manufacturing shape-controlled calcium alginate gel microparticles in a microfluidic device. Both manufacturing shape-controlled microparticles and synthesizing hydrogel microparticles could be performed simultaneously in the microfluidic device. The novel microfluidic device comprised of two individual flow-focusing channels and a synthesizing channel was successfully applied as a continuous microfluidic reactor to synthesize gel microparticles with size and shape control. By passive control based on the microchannel geometric confinement and liquid-phase flow rates, we succeeded in producing monodisperse sodium alginate microparticles with diverse shapes (such as plugs, disks, microspheres, rods, and threads) in the flow-focusing channels of the microfluidic device. The shape and size of the sodium alginate microparticles could be tuned by adjusting the flow rates of the various streams. Further stages of the chemical reaction could be initiated by mixing sodium alginate microparticles and calcium chloride (CaCl2) solution in the synthesizing channel. The shapes of the sodium alginate microparticles could be permanently preserved by the synthesis of calcium alginate gel microparticles. The preparation conditions of size- and shape-controlled calcium alginate microparticles and influence factors were studied.     

pH-dependent release from ethylcellulose microparticles containing alginate and calcium carbonate

Ethylcellulose microparticles containing alginate and calcium carbonate nanoparticles were prepared by spray drying water-in-oil emulsion. Alginate solution (3%) in distilled water was used as an aqueous phase, ethylcellulose solution (5%) in dichloromethane as an oil phase, and sorbitan sesquioleate as an emulsifier. The nanoparticles of calcium carbonate were dispersed into the emulsion. By spray-drying the emulsion, ethylcellulose microparticles containing alginate and calcium carbonate were obtained. When the ratios of alginate to calcium carbonate were 4:1 and 2:1, the pH dependency of the release was marked and the degree of release was suppressed in acidic conditions. When the ratio increased to 1:2, the degree of release increased while the pH-dependent release profiles were maintained. Cavities created by the dissolution of calcium carbonate could account for the increased release.     

EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

二氧化碳沉淀法去除苯扎贝特中主要杂质

在苯扎贝特合成的后处理过程中,利用苯扎贝特及其主要杂质在酸性上的差异,在反应物的碱性水溶液中通入CO₂,将杂质从产物中沉淀去除。 以苯扎贝特的收率和含量为指标,对该纯化工艺和传统的重结晶工艺进行了比较。 结果显示,该纯化工艺可以使合格品的收率从原工艺的62.5%提高到70.9%。 该法克服了常规重结晶带来的大量溶剂消耗和产品损失,有效提高了杂质去除率,降低了分离成本。     

Analysis of human parathyroid hormone (1-84) products. Separation of a major impurity in synthetic products by ion-pairing reversed-phase high-performance liquid chromatography

Human parathyroid hormone (1-84) is a naturally occurring polypeptide that acts as the major regulator of calcium ion homeostasis. It can be efficiently produced through both synthetic and biosynthetic routes and, as such, highly selective analytical methods are required for the detection of a wide range of impurities. Herein we report on the development of an ion-pairing reversed-phase HPLC method for the analysis of human parathyroid hormone and the separation of impurities including a major, unidentified impurity detected in synthetic preparations. This impurity could not be resolved using trifluoroacetic acid-based methods generally used for monitoring purity levels in commercial products. Separation conditions consisted of a gradient elution of 0.155 M sodium chloride containing 0.037 M sodium pentanesulfonate, pH 5.6, as mobile phase A and acetonitrile as mobile phase B. Separations were carried out on an octadecylsilyl silica column maintained at 50 degrees C. Both column temperature and pH of mobile phase A significantly affected the separation of the major impurity. The major impurity eluted after the main human parathyroid peak and was detected in the two commercial synthetic products analyzed. Several minor impurities eluting before and after the main peak were also detected. Purity levels measured by the developed HPLC method (method C) were similar to those previously measured by capillary electrophoresis. Analysis of purified recombinant human parathyroid hormone did not show the presence of this impurity. This method offers a significant advantage for the purity assessment of human parathyroid hormone.     

Hydrogel-shelled biodegradable microspheres for sustained release of encapsulants

Biodegradable microparticles are promising for the sustained release of encapsulated lipophilic drugs. In particular, the microparticles with uniform size show excellent linearity of cumulated release over time with minimized initial burst. Here, we encapsulate the biodegradable microparticles with a hydrogel shell to improve the controllability over the sustained release and suspension stability. With a capillary microfluidic device, monodisperse oil-in-water-in-oil (O/W/O) double-emulsion droplets are produced to have a toluene solution of polylactic acid (PLA) in the core and sodium alginate and calcium-ethylenediaminetetraacetic acid (EDTA) complex in the shell, whereas the continuous oil phase contains acetic acid. As the toluene evaporates, PLA consolidates to form a microsphere in the core. At the same time, acetic acid diffuses from the continuous phase to the water layer, which causes the dissociation of the Ca-EDTA complex and the gelation of alginate. The hydrogel-shelled PLA microspheres are transferred from the oil to an aqueous solution of calcium chloride, which further tightens the gel shell. The resulting core-shell microspheres show sustained release of encapsulants for extended periods as the hydrogel shell serves as a diffusion barrier. Moreover, the hydrogel shells prevent interparticle agglomeration and adhesion to the solid walls, securing high suspension stability during the injection.     

抗癌药顺铂对照品制备及其纯度测定

提出了抗癌药顺铂对照品的新制备方法并进行其纯度测定。该方法涉及在二甲基甲酰胺中用18-冠醚-6选择沉淀trans-[Pt(NH3)2Cl2],然后用NaCl溶液反析顺铂、分离K[Pt(NH3)Cl3]。采用HPLC和TLC法测定制备出的顺铂。结果表明所制备的顺铂纯度大于99.5%,有关杂质均小于0.1%,满足作为对照品的要求。     

Voltammetry of Immobilized Particles of Cannabinoids

A new electrochemical method for the detection of cannabinoids in food products is proposed. The method is based on the voltammetry of microparticles at a paraffin‐impregnated graphite electrode. In square‐wave voltammetry, in 0.1 M KNO₃ at pH 7, the responses of delta‐9‐tetrahydrocannabinol, cannabinol and cannabidiol consist of a single peak with the maximum at 0.55 V±0.01 V. This peak is ascribed to the electrooxidation of the phenol group to phenoxy radical. In microparticles of hemp and marijuana cannabinoids can be detected in pure drug as well as in the mixture with foreign insoluble powders.     

Tandem on-line dialysis with a double and single dialyser in flow injection dialysis — Simultaneous determination of calcium and high chloride in industrial effluents

The on-line double membrane dialyser described previously was coupled in series to a single dialyser in the manifold of a flow injection system to include the determination of samples with a high chloride content simultaneously with calcium in industrial effluents from a single sample injection. 50 μl of industrial effluent samples are injected into a carrier stream and are simultaneously dialysed in the double on-line dialyser for chloride and calcium. The dialysed chloride sample zones are further directed to a second dialyser that is incorporated in series with the first dialyser. This enables laboratories to determine samples with a very high chloride content up to 60 g/l simultaneously with calcium by using an automated tandem on-line dialysis technique. The fast and reliable fully automated two-component flow injection procedure operated at a sampling frequency of 90 samples per hour and the results obtained for chloride and calcium in industrial effluents compared well with those obtained by standard methods.     

Zn2+ release from zinc and zinc oxide particles in simulated uterine solution

Zn²⁺ release from Zn and ZnO particles with different sizes in simulated uterine solution were investigated by absorbance measurements. The effects of pH and human serum albumin (HSA) on Zn²⁺ release were also studied. The morphology of Zn and ZnO particles was observed by scanning electron microscopy, and the corrosion products of zinc nanoparticles were analyzed by XRD. The results indicate that the maximum release ratios of Zn²⁺ from Zn and ZnO nanoparticles are higher than those from Zn and ZnO microparticles. Zn²⁺ release ratio depends not only on the pH of the simulated uterine solution but also the presence of human serum albumin. It decreases as the pH of the uterine solution increases. The trends of Zn²⁺ release ratios are almost the opposite for solutions with and without HSA. XRD analysis results indicate that zinc oxide is the main corrosion product of zinc particles.     

Electrochemical dissolution of chalcopyrite studied by voltammetry of immobilized microparticles

The characteristics of anodic electrochemical dissolution of chalcopyrite (CuFeS₂) powder in hydrochloric acid medium with sodium chloride have been studied. Cyclic voltammetry and chronopotentiometry of immobilized microparticles using paraffin-impregnated graphite electrode was employed. Present work is focused on electrochemical identification of chalcopyrite cathodic and anodic reaction products within the potential range of −0.7 to +0.8 V (vs. SCE) in hydrochloric acid solution containing sodium chloride and/or copper(II) chloride.     

Composite phospholipid-calcium carbonate microparticles: influence of anionic phospholipids on the crystallization of calcium carbonate

The synthesis and characterization of calcium carbonate microparticles by reaction of calcium chloride and ammonium bicarbonate in the presence of negatively charged phospholipid mixtures of negative and zwitterionic phospholipids has been reported. Negatively charged phospholipids influence the crystal morphology of calcium carbonate and induce the formation of thermodynamically less stable veterite polymorph as opposed to calcite polymorph. The phospholipids are entrapped in the calcium carbonate microparticles during the crystallization process, with a uniform distribution of phospholipids in the interior of the microparticles. This phenomenon was exploited to encapsulate a model hydrophobic fluorophore, the tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride complex, to simulate encapsulation of hydrophobic drug molecules. Thermogravimetric analysis reveals that, in these microparticles, the calcium carbonate and the phospholipid exhibit strong interactions.     

A convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions

A mild method for the facile removal of phosphine oxide from the crude products of Wittig and Appel reactions is described. Work-up with oxalyl chloride to generate insoluble chlorophosphonium salt (CPS) yields phosphorus-free products for a wide variety of these reactions. The CPS product can be further converted into phosphine.     

Monitoring the removal of carbonate from alkali metal hydroxide solutions using gas diffusion flow injection

Monitoring the removal of carbonate from alkali metal hydroxide (MOH, M = K, Na) solutions with calcium oxide (CaO) was studied using a newly developed method for the determination of trace amounts of total carbonate (TC) in alkaline solutions based on a flow injection (FI) technique coupled with a gas diffusion system. The optimized conditions of the FI system were as follows: the flow rate of each carrier, reaction solution (H2SO4) and receptor solution (Cresol Red, pH 8.9) was 0.25 ml min(-1), the sample size was 0.1 ml and the concentration of H2SO4 in the reaction solution was 0.09 M. The limit of detection of TC by the proposed method was 4 x 10(-7) M. The removal efficiency of carbonate was affected by the amount of CaO added, the shaking time of the solutions and the concentration of MOH. For 1 M NaOH and KOH solution, the removal efficiency of carbonate was about 99% and the concentration of residual carbonate was 4 x 10(-5) and 1.2 X 10(-4) M, respectively, when the amount of CaO added was 2 g l(-1) and the shaking time was 16 h.     

浓硫酸脱水实验中蔗糖炭化产物对Pb~(2+)的吸附性能研究

将《人教版必修1》浓硫酸脱水实验中蔗糖炭化废弃物经洗涤、水煮、干燥等处理后制得蔗糖炭产物,将处理后的炭产物用于铅离子的吸附实验,探讨了炭产物的用量、浸泡温度、溶液p H值等单因素对吸附铅离子的影响;并将炭产物的吸附效果与一些已经商业化的吸附剂进行对比,实验取得良好的实验结果,表明该废弃炭产物可以有效除去溶液中的铅离子。     

In Situ Amperometric Detection of Vesicles and Microgel Phases in an Aggregating System: Calcium Alginate

In situ amperometric characterization of an aggregating system in terms of molecular adsorption and single microparticle interactions at the electrode interface is demonstrated using a model system: alginate/Ca(II) in an aqueous electrolyte solution. Recording of chronoamperometric curves of oxygen reduction at the dropping mercury electrode is designed for detection of dip‐shaped signals of individual gel microparticles. By addition of Ca(II) decrease of alginate adsorption is accompanied by appearance of signals indicating vesicle type association of alginate molecules and microparticles of gel phase. AFM imaging provided evidence of initial stage in calcium alginate gel formation.     

酶法动力学拆分制备光学活性γ-内酯

研究了脂肪酶对桃醛和γ-癸内酯的水解动力学拆分反应,考察了温度、pH值、酶的用量等因素对酶催化水解拆分过程的影响.选择氯化钙-阿拉伯胶水溶液作为反应介质,使γ-内酯拆分产物取得较高的ee值.回收拆分中产生的γ-羟基酸,外消旋化后再内酯化,投入下一批反应,提高了光学活性γ-内酯的总得率.