Identification and determination of triterpenoids in Hieracium pilosella L

Fractions of triterpenoids have been isolated from herb, inflorescences, and rhizomes with roots of Hieracium pilosella by typical extraction with petroleum ether. The fraction from inflorescences was investigated using GC-MS techniques. The occurrence of alpha- and beta-amyrin, taraxerol, taraxasterol, and fern-7en-3beta-ol has been observed. Quantitative analysis was also performed and taraxasterol is distinctly predominant in this triterpenoid fraction. Thin-layer chromatography on silica gel was performed on all the investigated fractions and additionally revealed the occurrence of lupeol and psi-taraxasterol in vestigial quantities. All of the triterpenoid components are reported for the first time in the investigated plant.     

Separation and evaluation of free radical-scavenging activity of phenol components of Emblica officinalis extract by using an HPTLC-DPPH* method

A new procedure has been developed to separate and quantify the free radical-scavenging activity of individual compounds from an Emblica officinalis extract based on the combination of HPTLC with a diode array detector (DAD) and postchromatographic DPPH* radical derivatization. Free gallic and ellagic acids and emblicanins A and B in the E. officinalis extract were separated by TLC and identified. All the compounds of the extract were capable of scavenging of DPPH* radicals. It was established that the DPPH* scavenging activity of emblicanins A and B was 7.86 and 11.20 times more than that of ascorbic acid and 1.25 and 1.78 times more than gallic acid, respectively. From the estimated ID50 values, it can be seen that the increasing order of activity was emblicanin B > emblicanin A > gallic acid > ellagic acid > ascorbic acid. Probably, the antioxidant activity of E. officinalis extract is associated with the presence of hydrolyzable tannins having ascorbic acid-like action.     

薄层层析法在表面活性剂检测和分析中的应用

薄层层析（ＴＬＣ）是一种简便的分离分析方法。适用于许多有机化合物的分离,精制,定性和定量分析,也是表面活性剂分析中的重要手段之一。文中简述了薄层层析的测试方法、条件选择和发展趋势,并对ＴＬＣ在表面活性剂检测和分析中的应用作了具体阐述。     

发酵液中泰乐菌素测定方法的研究

对发酵液中泰乐菌素含量的两种测定方法（即薄层层析法和高效液相色谱法）进行了比较研究,结果表明,这两种方法都具有较好的分离效果和较高的回收率,回收率分别为９５．９％和９０．３％。说明除了高效液相色谱法外,薄层层析法是一种简易又实用的测定方法     

AC发泡剂中一种助发泡剂的鉴定

目前国内外通过在AC发泡剂中添加各种促进剂进而获得改性AC的方法已成为一种趋势。添加何种改性剂无疑是研究改性AC的关键。因此定性分析AC中的改性剂,对改性AC的研发将有极大的帮助。文章应用由作者在Vibrational Spectroscopy上首次提出的薄层色谱显微傅里叶红外联用的方法,鉴定出某改性AC中一种罕见添加剂的官能团,结合元素分析及化学物性分析等,推测出此添加剂的结构。通过对推测物质碎裂机理的解释和未知添加剂质谱图的分析,进一部验证了该添加剂为所推测的物质。这种鉴定方法同样适用于AC中其他无标准图谱的改性剂分析。     

仙方玉容膏中黄芪甲苷含量的测定

目的:建立仙方玉容膏中黄芪甲苷含量的高效薄层色谱测定方法。方法:以氯仿-甲醇-水(13∶6∶2)为展开剂,扫描波长λS=530nm,λR=700nm。结果:线性范围0 25～4ug,回收率97 6～103 4%,RSD2 84%(n=5)。结论:本法简便、灵敏、重线性好,可用于测定仙方玉容膏中黄芪甲苷含量和质量标准的控制。     

Densitometric determination of (+)-catechin and (−)-epicatechin by 4-dimethylaminocinnamaldehyde reagent

We report the optimization of a sensitive, selective and robust derivatization method using 4-dimethylaminocinnamaldehyde (DMACA) for densitometric determination of (+)-catechin and (−)-epicatechin. The separation of these compounds was achieved by thin-layer chromatography (TLC) on cellulose plates developed with water. With DMACA in HCl, both compounds gave blue bands, while under the same conditions, vanillin produced a fast fading red coloration of bands. Quantitation at 655 nm showed that for both compounds the calibration curve was linear from 2 to 12 ng and polynomial from 2 to 30 ng, and the repeatability of chromatography of 20 ng was 3.5% (RSD, n = 6). The visible limit of detection of both standards was 1 ng, but the densitometric limit of detection was lower (0.2 ng). The optimized DMACA reagent is superior to the more frequently used vanillin reagent and is applicable also for determination of mixtures containing other catechins ((−)-catechin, (−)-epicatechin gallate, (−)-epigallocatechin gallate, procyanidin A2, procyanidin B1 and procyanidin B2).     

Development and Validation of HPLC,TLC and Derivative Spectrophotometric Methods for the Analysis of Ezetimibe in the Presence of Alkaline Induced Degradation Products

Reversed phase‐high performance liquid chromatography (RP‐HPLC), thin layer chromatography (TLC) densitometry and first derivative spectrophotometry (1D) techniques are developed and validated as a stability‐indicating assay of ezetimibe in the presence of alkaline induced degradation products. RP‐HPLC method involves an isocratic elution on a Phenomenex Luna 5μ C₁₈ column using acetonitrile: water: glacial acetic acid (50:50:0.1 v/v/v) as a mobile phase at a flow rate of 1.5 mL/min. and a UV detector at 235 nm. TLC densitometric method is based on the difference in Rf‐values between the intact drug and its degradation products on aluminum‐packed silica gel 60 F₂₅₄ TLC plates as stationary phase with isopropanol: ammonia 33% (9:1 v/v) as a developing mobile phase. On the fluorescent plates, the spots were located by fluorescence quenching and the densitometric analysis was carried out at 250 nm. Derivative spectrophotometry, the zero‐crossing method, ezetimibe was determined using first derivative at 261 nm in the presence of its degradation products. Calibration graphs of the three suggested methods are linear in the concentration ranges 1–10 mcg/mL, 0.1–1 mg/mL and 1–16 mcg/mL with a mean percentage accuracy of 99.05 ± 0.54%, 99.46 ± 0.63% and 99.24 ± 0.82% of bulk powder, respectively. The three proposed methods were successfully applied for the determination of ezetimibe in raw material and pharmaceutical dosage form; the results were statistically analyzed and compared with those obtained by the reported method. Validation parameters were determined for linearity, accuracy and precision; selectivity and robustness and were assessed by applying the standard addition technique.     

致癌性多环芳烃萘、蒽、芘的分析方法比较

利用薄层色谱（TLC）、紫外光谱（UV）、反相高效液相色谱（RPHPLC）对多环芳烃（PAHs）萘、蒽、芘的分析方法进行了研究。TLC中使用环己烷：氯仿（5：4,V／V）作为展开剂时,三者的R,值分别为0．78、0．65和0．72;用UV法在溶液中测定了三者的最大吸收波长分别为303、380、338nm;当流动相为甲醇：水（9：1,V／V）时三者在RP—HPLC中的保留时间为4．179、5．190、6．178min,5次重复RSD分别为1．1％、1．8％、0．91％,并用于实际水样中萘、蒽、芘的分析。     

安全驾驶的横向安全预警报警阈值的确定

为减少车道偏离事故的发生,基于车辆将要横越车道边界的时间标准（TLC）,提出一种新的横向安全报警算法。该算法根据车辆运行状态判断驾驶人意图,基于实车试验数据,分析车辆的车轮轨迹曲线与TLC曲线,设定不同路况、不同类型驾驶人的报警阈值;利用驾驶人分类结果中最激进和最保守驾驶人的实车数据,分别验证不同路况下的报警阈值。结果表明：在不同路况下,报警算法给性格保守的驾驶人留出了1s左右的反应时间,给性格激进的驾驶人留出了0.5s左右的反应时间。