An efficient synthesis of 3,4-dihydropyrimidin-2(1H)-ones catalyzed by thiamine hydrochloride in water under ultrasound irradiation

An environmentally benign aqueous Biginelli protocol for the synthesis of substituted 3,4-dihydropyrimidin-2(1H)-ones using thiamine hydrochloride as a catalyst has been achieved. These ultrasound-assisted reactions proceed efficiently in water in the absence of organic solvent. Utilization of ultrasound irradiation, simple reaction conditions, isolation, and purification makes this manipulation very interesting from an economic and environmental perspective.     

Determination of phenylephrine hydrochloride and chlorpheniramine maleate in binary mixture using chemometric-assisted spectrophotometric and high-performance liquid chromatographic-UV methods

Four methods have been developed for the simultaneous determination of phenylephrine hydrochloride and chlorpheniramine maleate without previous separation. In the first method both drugs are determined using first derivative UV spectrophotometry, with zero-crossing measurement. The second method depends on first derivative of the ratios spectra. The third method describes the use of multivariate spectrophotometric calibration for the simultaneous determination of the analyzed binary mixture where the resolution is accomplished by using partial least squares (PLS) regression analysis. In the fourth method (HPLC), a reversed-phase column and a mobile phase of methanol:water:acetonitrile (80:12:8 v/v/v/) at 0.9 ml/min flow rate have been used to separate both drugs with a UV detection at 270 nm. All the proposed methods are extensively validated. They have the advantage to be economic and time saving. All the described methods can be readily utilized for analysis of pharmaceutical formulations. The results obtained using the proposed methods are statistically analyzed and compared with some reported methods.     

Spectrofluorimetric determination of fexofenadine hydrochloride in pharmaceutical preparation using silver nanoparticles

A novel sensitive fluorimetric method was investigated for the assay of fexofenadine hydrochloride (FEX) using silver nanoparticles (NPs) as a fluorescence probe. The NPs, which were prepared by chemical reduction of silver nitrate with sodium borohydride (reducing agent) in aqueous solution (without organic stabilizers) were water soluble, stable and had narrow emission band. The addition of drug to NPs solution caused considerable quenching of the emission band of silver NPs, which was likely due to the complexation of the drug to silver NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the concentration of FEX in the range of 1 × 10^?7 to 2.5 × 10^?5 mol L^?1 (0.9985) with a detection limit of 1.2 × 10^?8 mol L^?1. The quenching mechanism of the studied drug on the emission band of silver NPs was explained by Stern–Volmer law. The developed method was applied to FEX determination in a pharmaceutical formulation (allegra tablets) and biological fluids (human serum and urine).     

盐酸氨溴索在碳糊电极上阳极伏安法的研究

在０．５ ｍｏｌ／Ｌ Ｈ２ＳＯ４底液中，用碳糊电极阳极伏安法测定盐酸氨溴索，被测的阳极峰电位为１．１０Ｖ（ｖｓ．ＳＣＥ），另外，在０．４６Ｖ处还产生一对可逆的氧化还原峰。１．１０ Ｖ处的峰电流与盐酸氨溴索的浓度在３．９８×１０~（－７）～６．３４ × １０~（－５）ｍｏｌ／Ｌ范围内呈良好的线性关系，该方法的检出下限为３．０ × １０~（－８）ｍｏｌ／Ｌ。用标准加入法测得回收率范围为９２．８％～１０２％，ＲＳＤ为２．９％（ｎ＝１０）。对电极响应机理进行了初步探讨，氨溴索在１．１０ Ｖ处的氧化为不可逆过程，其氧化产物在０．４６０Ｖ处产生一对２电子２质子受扩散控制的可逆波，用该波也可进行定量测定并且干扰较少，但灵敏度略低。     

L-卡尼丁分子压印聚合物作为手性分离色谱固定相的研究

以L－卡尼丁为模板分子，分别以α－甲基丙烯酸和丙烯酰胺为功能单体，乙二醇二甲基丙烯酸酯为 剂，采用分子压印技术合成了对L－卡尼丁具有高选择性的分子压印聚合物。将所得聚合物用作高效液相色谱固定相，研究了它们对外消旋卡尼丁盐酸盐的拆分能力，分析结果表明，α－甲基丙烯酸作为功能单体所得聚合物对外消旋卡尼丁盐酸盐具有良好的拆分作用，其分离因子α为1．89。     

硅钨酸与盐酸巴马汀相互作用光谱研究及其分析应用

在pH 为0.91 的HCl-NaOAc 缓冲介质中, 盐酸巴马汀与硅钨酸通过静电相互作用导致共振光散射信号显著增强,最大散射波长为297 nm, 增强的散射信号强度与盐酸巴马汀浓度在0.09～3.2 μg/mL 范围内呈线性关系, 据此建立了盐酸巴马汀的共振光散射分析方法, 检测限为9.1 ng/mL. 实验考察了pH、离子强度对体系的影响, 研究了体系紫外吸收光谱及荧光光谱, 讨论了共振光散射增强机理. 该方法用于黄藤素片、黄藤素胶囊及血清样品中盐酸巴马汀含量测定,RSD≤4.2%.     

七、八元瓜环对盐酸雷尼替丁的包合作用及缓释性能

研究了七元瓜环(Q[7])和八元瓜环(Q[8])与盐酸雷尼替丁(RH)的包合作用及包合物的体外药物缓释性能.采用紫外-可见光谱法测定了体系的包合比、包合稳定常数和药物累积释放度;用1H NMR技术考察了体系主-客体的包合作用.结果表明,Q[7]和Q[8]与RH在酸性及中性条件下均能发生1∶1包合作用,包合稳定常数分别为1.21×104和2.06×104 L/mol;在碱性条件下则不发生包合作用.原药RH,Q[7]-RH及Q[8]-RH包合物在人工胃液(pH=1.2)中的60 min累积释放度分别为89.1%,56.6%和38.4%;而在人工肠液(pH=6.8)中三者的60 min累积释放度分别为90.2%,58.7%和38.0%.实验结果表明,Q[7]及Q[8]包合对RH有明显的体外缓释作用.     

Investigation of a liquid-liquid extraction system based on non-ionic surfactant-salt-H2O and mechanism of drug extraction

Based on the investigation of a non-ionic surfactant-salt-H₂O liquid-liquid extraction system, general rules concerning salt selection are concluded and the mechanism of phase separation is explained. The extraction behavior of chlorpromazine hydrochloride (CPZ) and procaine hydrochloride (PCN) in such a system is studied. Research shows that the extraction efficiency of CPZ can amount to 96% by twice extraction, which means that quantitative extraction is realized, while that of PCN is 77%. This system produces distribution coefficients (K_D) of 12.3 and 2.6, respectively, for CPZ and PCN. Extraction mechanism is deduced according to ultraviolet absorbance; and molecular fluorescence spectra change of the drugs in the system studied.     

The electrochemistry and determination of Ligustrazine hydrochloride

Ligustrazine is one of the active ingredients contained in Ligusticum chuanxiong Hort. (Umbelliferae), which is widely used in traditional Chinese medicine for the treatment of cardiovascular problems. In this work, the electrochemistry of Ligustrazine hydrochloride (LZC) and its determination are investigated. The detection limit is estimated to be 8.0×10^–8 M, with three linear ranges from 1.0×10^–6 to 1.0×10^–4 M, 1.0×10^–4 to 5.0×10^–4 M, and 6.5×10^–4 to 1.6×10^–3 M. The method has been proved to be highly sensitive, selective, and stable, and has been successfully applied to determining LZC in LZC injections.     

Flow Injection Chemiluminescence Determination of Difenidol Hydrochloride Using N-Chlorosuccinimide-Dichlorofluorescein Reaction

Abstract

A flow injection method combined with chemiluminescence detection was described for the determination of difenidol hydrochloride. Strong chemiluminescence was recorded when difenidol hydrochloride was added into the reaction mixture of N-chlorosuccinimide with dichlorofluorescein in alkaline medium. The experimental conditions that affected the chemiluminescence signal, including the concentrations of reactants, the reaction medium, and the instrumental parameters, were carefully optimized. Under the optimum experimental conditions, the enhanced chemiluminescence intensity was linear related to the concentration of difenidol hydrochloride in the range of 4.0 × 10^?9 to 4.0 × 10^?7 g/ml. The detection limit for difenidol hydrochloride was 7 × 10^?10 g/ml, and the sample throughput was 90/h. The relative standard deviation was 2.5% for 5.0 × 10^?8 g/ml difenidol hydrochloride solution (n = 11). The interference of common inorganic ions, excipients, and additives used in pharmaceutical preparation was studied, which showed the method has higher tolerance limit for these substances and has good selectivity. As a preliminary application, the method was applied to the determination of difenidol hydrochloride in tablets, and the satisfactory results were achieved.