HPLC法测定阿奇霉素在水溶液中的降解动力学

目的研究阿奇霉素在水溶液中的降解动力学,为阿奇霉素液体制剂的开发提供参考。方法通过经典恒温试验,应用HPLC法测定阿奇霉素在不同pH值、不同温度、不同离子强度、不同缓冲液条件下的降解动力学参数。结果阿奇霉素在水溶液中的降解呈现一级动力学特征,其最稳定pH值(pHm)为6.41;随着离子强度和温度的增加,阿奇霉素的降解加快;阿奇霉素在磷酸盐缓冲液中比在醋酸盐、枸橼酸盐缓冲液中相对稳定。结论阿奇霉素降解速率与溶液pH值、缓冲液种类、离子强度以及温度有关;溶液pH值与温度对阿奇霉素降解作用的影响较为明显。     

阿立哌唑在酸性溶液中的降解动力学研究

目的研究阿立哌唑在酸性溶液中的降解动力学。方法通过经典恒温实验,采用HPLC法测定阿立哌唑在不同温度、pH值、缓冲液种类及质量浓度的降解动力学参数,用Arrhenius公式预测其活化能。结果阿立哌唑在酸性溶液中最稳定的pH值为4.0。随着温度增加,阿立哌唑的降解加快,其活化能Ea=117.60kJ·mol~(-1)。阿立哌唑在枸橼酸盐中的降解速率最快,在磷酸盐及醋酸盐中相对较慢。结论阿立哌唑在酸性溶液中的降解近似一级动力学过程,与温度和缓冲盐质量浓度呈正相关,pH值对其降解速率影响显著,缓冲盐种类的不同对其降解速率影响较明显。本研究为该制剂的研究开发提供了必要的数据支持。     

盐酸地尔硫[艹卓]溶液的稳定性考察

目的：研究盐酸地尔硫[艹卓]溶液在不同条件下的稳定性。方法：采用经典恒温法考察了盐酸地尔硫[艹卓]在不同pH值的磷酸盐缓冲液、相同pH值的不同缓冲盐溶液及多种有机溶剂中的稳定性。结果：盐酸地尔硫[艹卓]在pH4时最为稳定；枸橼酸盐缓冲液和酒石酸盐缓冲液能延缓其水解；其在乙醇和甲醇中较稳定。结论：盐酸地尔硫[艹卓]溶液在不同条件下稳定性不同，该结果为盐酸地尔硫[艹卓]的分析及相关制剂的研究提供了参考。     

盐酸地尔硫芯溶液的稳定性考察

目的:研究盐酸地尔硫芯溶液在不同条件下的稳定性。方法:采用经典恒温法考察了盐酸地尔硫芯在不同pH值的磷酸盐缓冲液、相同pH值的不同缓冲盐溶液及多种有机溶剂中的稳定性。结果:盐酸地尔硫芯在pH4时最为稳定;枸橼酸盐缓冲液和酒石酸盐缓冲液能延缓其水解;其在乙醇和甲醇中较稳定。结论:盐酸地尔硫芯溶液在不同条件下稳定性不同,该结果为盐酸地尔硫芯的分析及相关制剂的研究提供了参考。     

盐酸地尔硫(卄卓)溶液的稳定性考察

目的:研究盐酸地尔硫(卄卓)溶液在不同条件下的稳定性.方法:采用经典恒温法考察了盐酸地尔硫(卄卓)在不同pH值的磷酸盐缓冲液、相同pH值的不同缓冲盐溶液及多种有机溶剂中的稳定性.结果:盐酸地尔硫(卄卓)在pH 4时最为稳定;枸橼酸盐缓冲液和酒石酸盐缓冲液能延缓其水解;其在乙醇和甲醇中较稳定.结论:盐酸地尔硫(卄卓)溶液在不同条件下稳定性不同,该结果为盐酸地尔硫(卄卓)的分析及相关制剂的研究提供了参考.     

人工合成胸腺五肽在水溶液中的稳定性-pH及缓冲溶液对降解的影响

目的利用高效液相色谱法研究不同的pH值和各种缓冲盐(醋酸盐、硼酸盐、柠檬酸盐及磷酸盐)的水溶液(50℃时)对胸腺五肽的影响。方法高效液相色谱柱采用u-Bondapak C18柱(0μm,250×3.9mm),流动相:0.02M磷酸二氢钾溶液(pH3.0)-甲醇(90∶10),流速:1.0ml.min-1,检测波长:210nm。结果及结论胸腺五肽溶液浓度在50~200μg.ml-1时有良好的线性关系,相关系数大于0.999。胸腺五肽的降解速率符合表观一级动力学方程。水溶液中最佳的pH值很难确定。缩氨酸在pH大约5.5~8.0时相对较稳定。这些稳定状态在其他的缓冲体系都可以观察到;不同的缓冲体系产生不同影响,醋酸盐可以起到很好的稳定作用而磷酸盐则会产生很强的降解。     

不同因素对水溶液中鱼腥草素钠降解速率的影响

目的:考察溶液pH、缓冲液浓度、亚硫酸氢钠和温度对水溶液中鱼腥草素钠降解速率的影响。方法:乙腈-0.01mol·L-1四丁基溴化铵溶液-三乙胺(43∶57∶0.3)为流动相,HPLC法测定不同条件下鱼腥草素钠水溶液浓度变化。结果:鱼腥草素钠的降解反应符合二级动力学方程,pH 7条件下降解速度常数K最大。磷酸盐缓冲液浓度越高,鱼腥草素钠降解速率越快;溶液中加入亚硫酸氢钠和低温储存有利于溶液的稳定。结论:鱼腥草素钠水溶液不稳定,降解速率与溶液pH值、磷酸盐溶液浓度、亚硫酸氢钠和温度等因素均有关。     

盐酸阿莫罗芬在水溶液中的降解动力学研究

目的：研究盐酸阿莫罗芬在水溶液中的降解动力学。方法：建立HPLC法,测定盐酸阿莫罗芬在不同pH值、不同温度、不同离子强度的缓冲液中的降解动力学参数。结果：盐酸阿莫罗芬在水溶液中的降解呈现伪一级动力学特征,随着温度的增加,其降解速率增大;在37和60℃时,随着PH的增加,盐酸阿莫罗芬的降解速率明显增大（P〈0．05）,其半衰期和有效期明显减小（P〈0．05）,而随着离子强度的增大,其降解速率有所减小（P〉0．05）;在4和25℃时,盐酸阿莫罗芬在不同pH和不同离子强度的缓冲液中相对稳定;盐酸阿莫罗芬降解活化能随着pH的增大而增大。结论：盐酸阿莫罗芬在水溶液中的降解速率与温度、pH值和离子强度有关,其中温度对盐酸阿莫罗芬降解的影响较为明显。     

河豚毒素处方前初步研究

目的 考察河豚毒素（TTX）在不同溶剂中的溶解性及稳定性，以及温度和pH值对稳定性的影响。方法 配制TTX不同介质的溶液，采用高效液相色谱法（HPLC）测定其在不同温度、不同pH缓冲液中的浓度，分析计算其溶解度及稳定性。结果 TTX在pH值为3.5时溶解度最大，随着pH值增加其溶解度逐渐降低。TTX在强碱条件下降解最为迅速，在70 ℃条件下、0.1 mol/L的氢氧化钠溶液中，20 min即完全降解。稳定性试验结果同样证明TTX在碱性条件下的稳定性最差，在37 ℃、pH值=7.4的磷酸缓冲盐溶液（PBS）中，TTX浓度在1~10 h时开始持续降低，28天降解率为88.07±0.27%。结论 TTX易溶于pH值=3.5的酸性水溶液，几乎不溶于碱性水溶液。其稳定性与温度、介质pH值密切相关，在酸性水溶液中较为稳定，在碱性条件下易降解，温度升高会加速其降解过程。     

pH及不同缓冲盐对阿莫西林化学稳定性的影响

根据化学动力学的原理,采用经典法及单测点法,考察了ｐＨ对阿莫西林化学稳定性的影响,同时,对不同种类的缓冲盐对其降解作用也进行了考察．结果表明阿莫西林的最稳定（ｐＨ）ｍ为６２～７２,在醋酸盐及磷酸盐缓冲液中较稳定．     

Degradation kinetics of indocyanine green in aqueous solution

The degradation kinetics of a near-infrared fluorescent, diagnostic, and photodynamic agent, indocyanine green (ICG), was investigated in aqueous solution by steady-state fluorescence technique. The influence of ICG concentration on its fluorescence spectrum was determined. The degradation kinetics of ICG in aqueous solution was studied as a function of light exposure, type of light exposed, temperature, and ICG concentration. The degradation of ICG was found to follow first-order kinetics. Exposure to light and high temperatures caused acceleration in the degradation. The type and intensity of exposed light also affected degradation. ICG aqueous solutions were found to be more stable in dark, at low temperatures, and at higher ICG concentrations.     

Mechanism and kinetics of secretion degradation in aqueous solutions

In order to clarify the mechanism of secretin degradation in aqueous solutions, the formation of degradation products from secretin, aspartoyl3 secretin and beta-aspartyl3 secretin was investigated; the stabilities of these three peptides were investigated as well. Aspartoyl3 secretion and beta-aspartyl3 secretin, degradation peptides produced during the storage of secretin in aqueous solutions, were isolated by preparative reversed-phase HPLC (RP-HPLC). The amounts of secretin and its two degradation peptides resulting from storage of secretin in various buffer solutions (pH 2.3 to 10.0, mu = 0.5 M, 60 degrees C) were determined by analytical RP-HPLC. Secretin and the isolated degradation peptides were stored separately in various aqueous buffer solutions resulting in the degradation of each peptide. A mixture of secretin and its degradation or cleavage peptides was formed in each solution. The observed degradation rates for each peptide approximately followed first-order kinetics. The pH-rate profiles for conversion of secretin and beta-aspartyl3 secretin were similar, while that for aspartoyl3 secretin was different from these two. Aspartoyl3 secretin was more stable than the others at pH 2.3 to 4.0, but it was easily degraded between pH 5.0 and 10.0. Investigation of aspartoyl3 secretin degradation showed that its degradation was related to the pH value of the solution, and that hydroxide ion catalyzes the ring opening of the aspartoyl peptide. Secretin was most stable in pH 7.0 buffer solution and more stable in acidic solutions than in alkaline solutions. Secretion was mainly degraded through the following pathways: cleavage peptides reversible secretin in equilibrium aspartoyl peptide in equilibrium beta-aspartyl peptide vector cleavage peptides.     

穿琥宁体外稳定性研究

目的:研究穿琥宁的体外酸碱及酶稳定性。方法:将穿琥宁溶解于不同pH值(2.0～9.0)的磷酸缓冲液、人工肠液和不同浓度的肝组织匀浆液中,37℃恒温水浴,于不同时间取样,高效液相色谱法测定穿琥宁的浓度,考察其降解情况或降解动力学。结果:穿琥宁在酸性(pH2.0～5.0)条件下迅速降解(温孵1h后残余量低于10%);在pH7.0磷酸溶液、人工肠液中相对稳定,2h内各取样点的穿琥宁含量均高于95%;37℃下,在50%肝匀浆液中温孵24h后,降解23%;在25%肝匀浆液中温孵24h后,降解15%,且随肝匀浆液浓度的增大而降解加快。结论:穿琥宁在pH<5.0的环境下极不稳定;而胰酶对其几无影响;在肝匀浆液(pH7.0)中不稳定,肝微粒体酶对其有一定影响。     

盐酸青藤碱水溶液的降解动力学研究

目的:研究盐酸青藤碱水溶液的降解动力学特征。方法:应用比色法确定盐酸青藤碱在不同pH值、不同离子强度、不同介电常数水溶液中经80℃恒温加速试验所得的降解动力学参数。结果:经过线性拟合对比分析,盐酸青藤碱水溶液的降解反应级数为n=1。降解速率常数(k)值随pH值的上升而增高,在pH<3的低pH值区域降解十分缓慢;而进入pH3.9～5的区域趋于稳定,出现一个较低的平台;当pH>5时,k值随pH值的上升而迅速增高。盐酸青藤碱水溶液随离子强度的增加,降解速率增加;溶液的介电常数增加,其降解速率也增加。结论:盐酸青藤碱水溶液的降解属于近似1级动力学过程,降解速率受溶液pH影响显著;降解速率与溶液离子强度成正相关,与溶液介电常数亦成正相关。     

Stability of Gonadorelin and Triptorelin in Aqueous Solution

The influence of pH, temperature, various buffer species at different concentrations, and ionic strength on the stability of gonadorelin and triptorelin in aqueous solution has been studied using stability-indicating high-performance liquid chromatographic methods. The degradation behavior of both peptides is similar. The maximum stability of both peptides was shown to be at an approximate pH of 5.0. Acetate has the most favorable effect on stability, while phosphate causes higher degradation. Varying the concentration of acetate buffer does not affect the degradation behavior of the peptides. A higher phosphate concentration in buffer solutions causes higher degradation, however. The ionic strength of buffer solutions has no significant influence on stability. Solutions of gonadorelin and triptorelin, respectively, buffered with acetate (0.1 M, pH 5.0) with 3% (w/v) mannitol as an additive show a predicted t _90% of 9.0 years and 7.7 years at 20°C, respectively.     

Hydrolysis of nicotinyl 6-aminonicotinate

The degradation kinetics of nicotinyl 6-aminonicotinate in aqueous buffer solutions were studied over the pH range from 4.0 to 10.0. In all cases, pseudo-first-order kinetics were observed at constant hydronium ion concentration. The pH-rate profile indicated that the hydrolysis of nicotinyl 6-aminonicotinate may be described by at least two catalytic terms. In alkaline solution the hydrolysis is catalyzed primarily by hydroxyl ions. In acidic solution the hydrolysis may be attributed to either the water-catalyzed reaction of the protonated species or the hydronium ion catalyzed reaction of the free base. The resulting catalytic profile afforded a sharp pH minimum of approximately 5.90 at 65 degrees C. An activation energy of 16 Kcal/mol was obtained in a phosphate buffer solution at a pH of approximately 5.90 +/- 0.2. The first- and second-order reaction constants for water and hydroxyl ion catalysis were determined, and the temperature dependency of the reaction was studied. The buffer effect and solvent effect on the hydronium and hydroxyl ion catalysis was also investigated.     

A systematic study on the chemical stability of the novel indoloquinone antitumour agent EO9

The chemical stability of the new anticancer drug EO9 in aqueous solution has been investigated utilizing a stability-indicating reversed-phase high-performance liquid Chromatographie assay with ultraviolet detection and ultraviolet spectrophotornetry. The degradation kinetics of EO9 have been studied as a function of pH, buffer composition, ionic strength and temperature. A pH-rate profile, using rate constants extrapolated to zero buffer concentration, was constructed demonstrating that EO9 is most stable in the pH region 8–9. The degradation mechanism of EO9 in aqueous solution is discussed.