Ultrasound assisted crystallization of cephalexin monohydrate:Nucleation mechanism and crystal habit control

With the high-quality requirements for cephalexin monohydrate,developing a robust and practical crys-tallization process to produce cephalexin monohydrate with good crystal habit,appropriate aspect ratio and high bulk density as well as suitable flowability is urgently needed.This research has explored the influence of ultrasound on crystallization of cephalexin monohydrate in terms of nucleation mechanism and crystal habit control.The results of metastable zone width and induction time measurement showed the presence of ultrasound irradiation can narrow the metastable zone and shorten induction time.Cavitation phenomena generated by ultrasound were used to qualitatively explain the mechanism of ultrasound promoting nucleation of cephalexin monohydrate.Furthermore,on the basis of classical nucleation theory and induction time data,a series of nucleation-related parameters (such as crystal-liquid interfacial tension,radius of the critical nucleus and etc.) were calculated and showed a decreasing trend under ultrasound irradiation.The diffusion coefficient of the studied system was also determined to increase by 72.73％ under ultrasound.The changes in these parameters have quantitatively confirmed the mechanism of ultrasound influence on the nucleation process.In further,the calculated surface entropy factor has confirmed that the growth of cephalexin monohydrate follows continuous growth mechanism under the research conditions of this work.Through the exploration of crystallization conditions,it is found that suitable ultrasonic treatment,seeding,supersaturation control and removal of fine crystals are conducive to improving the quality of cephalexin monohydrate product.Optimizing the crystalliza-tion process coupled continuous ultrasound irradiation with fine-crystal dissolution policy has achieved the controllable production of monodisperse cephalexin monohydrate crystal with good performance.     

便携式光谱仪检测白酒中乙偶姻含量

目的 建立一种便携式光谱仪快速检测白酒中乙偶姻含量的分析方法。 方法 首先利用AS7341光谱传感器搭建便携式光谱仪,结合肌酸比色法,构建一种检测白酒中乙偶姻含量的即时检测方法。接下来对肌酸比色法反应的温度和时间条件进行优化,反应结果与酶标仪进行对比。最后通过检测7种白酒样本中乙偶姻的含量,来评价本装置的准确性和实用性。 结果 优化后肌酸比色法的最佳反应条件为40℃反应30 min,利用该装置检测到乙偶姻在510 nm波长下吸光度与其浓度呈正相关关系。乙偶姻的线性检测范围为0.25~20.00 mg/L,检出限为0.049 mg/L。该装置检测结果与酶标仪检测结果具有很好的一致性,相关系数为0.9899。最后利用该装置对7种白酒样本中乙偶姻含量进行检测,加标回收率为96.90%~103.32%。 结论 该装置具有准确、快速、便捷等特点,适用于白酒中乙偶姻含量的即时检测。     

碳源对LiFePO_4/C正极材料性能的影响

以FePO_4·2H_2O、Li_2CO_3和柠檬酸/酒石酸/抗坏血酸为原料,经机械球磨后在惰性气氛中高温煅烧合成LiFePO_4/C正极材料.研究了不同碳源对LiFePO_4结构、形貌及电化学性能的影响.重点考察了碳源为酒石酸时,不同合成温度对材料性能的影响.采用XRD、SEM以及电化学测试等手段对目标产物进行了结构表征和性能测试.结果表明,以酒石酸做碳源时,合成的正极材料物相单一,颗粒细小,粒度均匀,并且具有优良的电化学性能.在室温下以0.1C倍率充放电,首次放电比容量可达155mAh/g,1.0C首次放电比容量为120mAh/g,经过100次循环以后容量仍有109mAh/g.     

Parallelogram-like microparticles of calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) obtained by a rapid precipitation route in aqueous and acetone media

Calcium dihydrogenphosphate monohydrate (Ca(H₂PO₄)₂·H₂O) was prepared by a rapid and simple precipitation method using CaCO₃ and H₃PO₄ in aqueous and acetone media at ambient temperature. The thermal transformation of the synthesized Ca(H₂PO₄)₂·H₂O at 500 °C was obtained to be CaP₂O₆ occurred through the dehydration and the phosphate condensation reactions, as revealed by thermoanalytical techniques (TG/DTG/DTA). The synthesized Ca(H₂PO₄)₂·H₂O and its decomposition product CaP₂O₆ were characterized by X-ray powder diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy and scanning electron microscope (SEM). Thermal behavior and the morphology of the synthesized Ca(H₂PO₄)₂·H₂O in aqueous and acetone media are compared with those of other works. The SEM micrograph of Ca(H₂PO₄)₂·H₂O show parallelogram-like microparticles containing small and large grain sizes. The aqueous and acetone media are proposed to play an important role in the synthetic process of calcium phosphates in exhibiting different physical properties, which are important for specific applications.     

掺烧废硫酸亚铁制硫酸技术经济的讨论

硫酸法钛白配有废酸浓缩工序,废酸浓缩产生的废硫酸亚铁,绝大部分企业采用石灰中和处理,既造成资源浪费,又增加处理费用。介绍了采用掺烧新途径能使废硫酸亚铁中硫铁资源得到充分利用,并且取得显著的经济效益,以10万t/a钛白匹配30万t/a硫酸为例,年节省硫铁矿4.69万t,创产值2 292万元。     

强化蒸发技术在天然碱加工中的应用研究

提高一水碱结晶质量是提高 (一水碱法 )重质纯碱质量的关键。笔者对河南桐柏安棚天然碱卤水进行了添加活性剂的蒸发试验。试验表明 :添加适宜的活性剂 ,可使一水碱结晶颗粒增大、粒度分布均匀、含水量降低、沉降时间缩短 ;不仅明显提高了重质纯碱的质量 ,而且增加了产量。强化蒸发技术是一水碱法生产重质纯碱企业提高产品质量和产量的有效、可行途径。     

Micronization of creatine monohydrate via Rapid Expansion of Supercritical Solution (RESS)

In the pharmaceutical industry, an even greater number of products are in the form of particulate solids. In the case of pharmaceutical substances the particle size is quite important since it can limit the bioavailability of poorly water soluble drugs. Since the mid-1980s, a new method of powder generation has appeared involving crystallization with supercritical fluids. In this study, RESS was used to micronize the creatine monohydrate particles. The RESS process consists in solvating the product in the fluid and rapidly depressurizing this solution through an adequate nozzle, causing an extremely rapid nucleation of the product into a highly dispersed material. In addition, the effect of six different RESS parameters including, extraction temperature (313-333 K), extraction pressure (140-220 bar), nozzle length (2-15 mm), effective nozzle diameter (450-1700 μm), spraying distance (1-7 cm) and pre-expansion temperature (353-393 K) were investigated on the size and morphology of the precipitated particles of creatine monohydrate. The characterization (size and morphology) of the precipitated particles of creatine monohydrate was determined by scanning electron microscopy (SEM). The results show great reduction in the size of the precipitated particles of creatine monohydrate (0.36-9.06 μm) compared with the original particles of creatine monohydrate. Moreover, a slight change into spherical form was observed for the precipitated particles of creatine monohydrate while the original particles were irregular in shape.     

Levels of creatine,organic contaminants and heavy metals in creatine dietary supplements

High performance liquid chromatography (HPLC) has been optimised for the analysis of the creatine content and possible organic contaminants in 33 samples of creatine supplements from the market. Creatinine resulted to be the major organic contaminant (44% of the samples over 100 mg/kg). About 15% of the samples had dihydro-1,3,5-triazine concentrations exceeding the detection limit of 4.5 mg/kg (maximum 8.0 mg/kg) and a dicyandiamide concentration over 50 mg/kg, while none of the samples were contaminated with thiourea. The heavy metals (arsenic, cadmium, mercury and lead) content was also assessed by means of inductively coupled plasma mass spectrometry (ICP-MS). Only mercury was present in detectable amounts (at levels lower than 1 mg/kg).     

脂肪醇聚氧乙烯醚(5)磺酸盐的合成与耐温耐盐性能

以脂肪醇聚氧乙烯醚(5)(AEO-5)为原料,先与金属钠反应生成醇钠,再与氯乙基磺酸钠反应生成脂肪醇聚氧乙烯醚(5)磺酸钠(AESO),考察了反应温度、反应时间以及氯乙基磺酸钠与醇钠摩尔比对合成AESO反应的影响,并对提纯产物进行红外光谱表征,同时考察了其表面及耐温耐盐性能。结果表明,在64℃、氯乙基磺酸钠与醇钠摩尔比为1.2的条件下反应5h,AESO收率最高;AESO的表面及耐温耐盐性能均优于醇醚硫酸盐(AES),可适用于高温高矿化度油藏的三次采油。     

硫酸氢钠催化合成草酸二丁酯

用硫酸氢钠作催化剂,环己烷作带水剂,以草酸与正丁醇为原料合成了草酸二丁酯。考察了醇酸摩尔比、催化剂用量、带水剂用量、反应时间对草酸二丁酯收率的影响,结果表明,硫酸氢钠有着良好的催化活性,在草酸用量0．1mol、醇酸摩尔比3．0：1、催化剂用量为反应物总质量的1．0％、环己烷用量32mL条件下回流反应30min,草酸二丁酯收率可达87．0％,且催化剂重复使用5次仍保持较高活性。