Determination of Thiosemicarbazones by Means of the Induced Iodine-Azide Reaction

 The iodine-azide reaction induced by eight thiosemicarbazones was investigated. Inducing properties of thiosemicarbazones are different and depend on the parent carbonyl compound used for synthesis. The inductor coefficients of the examined thiosemicarbazones vary from 61 to 176. Optimum conditions for the determination of microamounts of thiosemicarbazones are given. The detection limit for the determination by the back-titration method depends on the inducing activity and is 0.9 μg for phenyl-thiosemicarbazones and 2 μg for diethyl-thiosemicarbazone in a 5-mL sample, and this corresponds to a concentration of 0.9 × 10⁻⁶ mol/L and , respectively. The automatic titration with the diluted iodine solution decreases the detection limit to about 50 ng in a 10-mL sample. Received October 28, 1998. Revision April 9, 1999.     

Simple,Rapid, and Sensitive Determination of Thiols by Liquid Chromatography with Fluorescence Detection

Thiol compounds are important for protecting cells from oxidative stress. One common method of quantifying thiols is liquid chromatographic separation with fluorescence detection of their derivatives. The pH and the concentration of tris (2-carboxyethyl) phosphine hydrochloride in the reaction medium were shown to have significant effects on the fluorescence intensity of five thiol compounds: cysteine, glutathione, and three phytochelatins. The optimal pH range for derivatization, as indicated by the maximum fluorescence intensities, was 7.75–8.0 for all of the evaluated thiols. The thiol derivative fluorescence increased and then decreased with the tris (2-carboxyethyl) phosphine hydrochloride concentration. In particular, the fluorescence intensities of all of the derivatives decreased by 96.5–99.9% when tris (2-carboxyethyl) phosphine hydrochloride levels were increased from 0.1 to 1?mmol L^?1. We attributed these changes to preferential interactions between tris (2-carboxyethyl) phosphine hydrochloride and the thiol-specific fluorophore, monobromobimane. We describe herein a method, based on our optimized solution pH and tris (2-carboxyethyl) phosphine hydrochloride concentration, that is rapid (12?min) and boasts excellent recovery (91.3–102%), sensitivity (limit of detections, 17.8–75.2?pmol L^?1) and precision (relative standard deviation values ≤1.03%) for the quantification of these thiol compounds in microalgal samples.     

Use of The Luminol Reaction for Metal Ion Detection in Liquid Chromatography

Abstract

The use of high performance liquid chromatography (HPLC) for the separation and quantitation of trace metals in solution has been hampered by the lack of A suitable detection system. The method generally used with classical metal ion separations - fraction collection and subsequent colorimetric detection - cannot easily be used in HPLC. To overcome this problem, A novel metal ion detection system based on the luminol reaction has been developed. Column effluent is successively mixed with luminol and then hydrogen peroxide before entering A chamber where chemiluminescence from the oxidation of the luminol is detected. The reaction is catalyzed by at least 20 different metal ions, and over A wide range the luminescence is proportional to metal ion concentration. The design of the system and some of its performance characteristics are described.     

Quantification of Intracellular Thiols by HPLC-Fluorescence Detection

Biothiols, such as cysteine and glutathione, play important roles in various intracellular reactions represented by the redox equilibrium against oxidative stress. In this study, a method for intracellular thiol quantification using HPLC-fluorescence detection was developed. Thiols were derivatized with a thiol-specific fluorescence derivatization reagent, viz. ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), followed by reversed-phase separation on an InertSustain AQ-C18 column. Six different SBD-thiols (homocysteine, cysteine, cysteinylglycine, γ-glutamylcysteine, glutathione, and N-acetylcysteine as an internal standard) were separated within 30 min using a citric buffer (pH 3.0)/MeOH mobile phase. The calibration curves of all the SBD-thiols had strong linearity (R² > 0.999). Using this developed method, the thiol concentrations of human chronic myelogenous leukemia K562 cell samples were found to be 5.5–153 pmol/1 × 10⁶ cells. The time-dependent effect of a thiol scavenger, viz. N-ethyl maleimide, on intracellular thiol concentrations was also quantified. This method is useful for elucidating the role of intracellular sulfur metabolism.     

Application of Iodine-Azide Reaction as Postcolumn Reaction in HPLC for Determination of 2-Thiobarbituric Acid

The reaction between iodine and azide ion induced by 2-thiobarbituric acid (TBA) has been utilized as a postcolumn reaction for chromatographic determination of this sulphur compound. The method is based on the separation of thiobarbituric acid on an Nova-Pak® CN HP column with an acetonitrile–aqueous solution of sodium azide mobile phase. The separation stage is followed by spectrophotometric measurement of the residual iodine (λ=350 nm) from the postcolumn iodine-azide reaction induced by thiobarbituric acid after mixing iodine solution containing iodide with the column effluent containing azide ions and the inductor. Chromatograms obtained for thiobarbituric acid showed negative peaks as a result of the decrease in absorbance of background. The detection limit (defined as S/N=3) was 0.16 pmol (22.9 pg) for thiobarbituric acid. Calibration graphs, plotted as peak heights or peak area vs. concentrations, were linear up to 1 nM.     

Determination of Plant Thiols by Liquid Chromatography Coupled with Coulometric and Amperometric Detection in Lettuce Treated by Lead(II) Ions

The main aim of this paper is to utilize high performance liquid chromatography with electrochemical detection for determination of thiols content in plants tissues of lettuce treated with lead(II) ions (0, 0.5 and 1 mM). We used two HPLC‐ED instruments: HPLC coupled with one channel amperometric detector and HPLC coupled with twelve channel coulometric detector to detect simultaneously twelve thiols. The detection limits of thiols measured by CoulArray detector were about two magnitudes lower in comparison to those measured by Coulochem III detector and were from tens to hundreds pM. Under the optimal conditions, we utilized HPLC‐CoulArray detector for analysis of tissues from lettuce plants. In addition, distribution and accumulation of lead ions with high spatial resolution was monitored using laser induced breakdown spectroscopy.     

Synthesis of Thiol Esters by the Reaction of Ricinoleic Acid with Thiols Under Solvent-Free Conditions

The synthesis of several ricinoleic acid thiol esters starting from cis-(R)-12-hydroxyoctadec-9-enoic acid and thiols in the presence of N,N′-dicyclohexylcarbodiimide (DCC) is described. The method is efficient for aromatic and aliphatic thiols, selectively affording the respective fat acid thiol esters in good yields under mild, neutral, and solvent-free conditions. The protocol is general and was extended to other carboxylic acids, furnishing the desired products in satisfactory yields. The (R,Z)-12-hydroxy-octadec-9-enylic acid benzylthiol ester 3a was successfully reduced to (R,Z)-12-hydroxyoctadec-9-enal 4.      

Reaction of Some Heterocyclic Formamidines with Trimethylsilylethynyllithium

The reaction of a 2-[(dimethylamino)methyleneamino]pteridine, two 2-[(dimethylamino)methyleneamino]pyrimidines, and a 2-[(dimethylamino)methyleneamino]pyrido[2,3-d]pyrimidine with trimethylsilylethynylithium in the presence of benzyl chloroformate leads to the corresponding 2-[bis(trimethylsilylethynyl)methylamino]-substituted heterocycles. A series of such substrates was prepared and some of the factors which permit this transformation were delineated. An X-ray crystal structure was determined of one of the products - 2-[bis(trimethylsilylethynyl)methylamino]-5,6,7,8-tetrahydro-3-(2,2-dimethylpropanoyloxymethyl)quinazolin-4-one.     

Use of the Software Processing of Scanned Chromatogram Images in Quantitative Planar Chromatography

The results of quantitative TLC analysis using the software processing of scanned chromatogram images are demonstrated by the example of the separation and determination of food dyes. The chromatograms obtained were digitized by scanning with a flatbed scanner. Quantitative analysis was performed using special-purpose software. The use of the software processing of scanned images does not require expensive analytical instruments and provides an unbiased quantitative evaluation of substances in a chromatographic peak with a minimum of time expenditure.     

Column Liquid Chromatography of Reducing Carbohydrates by Fluorometric Reaction Detection with a Pressurized Reactor Outlet

Abstract

The use of reaction detection In column liquid chromatography Is not always precluded by the limitation of the reaction time to one or two minutes. A closed pressurized reactor allows heating of the reaction mixture to temperatures that exceed the boiling point of the mixture to enhance reaction speed.     

Reaction of Thiols and Bisulfite with the Pendant Allyl Groups in Polytriallylamine

The infrared spectrum of polytriallylamine prepared by the free-radical-initiated polymerization of triallylamine indicates the presence of a substantial amount of unsaturation. The usual quantitative methods of determining unsaturation (e. g., bromide/ bromate and mercuric acetate) cannot be used on polytriallylamine because of interference from the amino group. On the other hand, bisulfite was found to react rapidly and quantitatively with the pendant allyl groups of polytriallylamine. The reaction was studied over the pH range 4 to 10 and was fastest at pH 5.2. The reaction is a free-radical reaction which is catalyzed by metal ions and oxygen. The sulfonic acid groups which result from attack of bisulfite on the pendant allyl groups of polytriallylamine form strong zwitterion structures with the amine nitrogens. The addition of thiols is also a free-radical reaction. The reaction of HSCH₂CH₂OH, HSCH₂CO₂H, CH₃SH, H₂S, HSCH₂CH₂N(C₂H₅)₂, CH₅COSH, and C₆H₅SH with polytriallylamine was studied. Of these compounds, only HSCH₂CH₂OH and HSCH₂CO₂H reacted quantitatively. Some reasons for the differences in reactivity are presented.     

Reaction of Thioxanthylium Cation with Pharmacophoric Heterocyclic Amines

Russian Journal of Organic Chemistry - Reactions of thioxanthylium tetrafluoroborate with pharmacophoric heterocyclic amines, pyrimidin-2-amine, 4,6-dimethylpyrimidin-2-amine,...     

钯催化偶合卟吩-并合杂环顺烯二炔二联体的合成

具有新颖共轭顺-烯二炔结构的天然产物可精巧地引发顺-烯二炔的闭环反应而产生双自由基,从癌细胞DNA糖磷脂骨架上夺取氢原子,促成病变细胞氧化断裂而产生强烈的抗癌功效（比阿霉素抗癌活性大4000倍）。作为保证抗肿瘤疗效的另一重要因素是提高抗癌药物对病变组织的选择性,基于用于光动力疗法（PDT）的抗癌药物卟啉类化合物识别和选择性富集于肿瘤细胞的特殊功能,     

New Procedure for Analysis of Complex Mixtures by use of Multidimensional Planar Chromatography in Combination with Diode-Array Scanning Densitometry and High-Performance Liquid Chromatography Coupled with Diode-Array Detection

JPC – Journal of Planar Chromatography – Modern TLC - The purpose of this paper is to report a new procedure for analysis of analytes in complex mixtures by combination of different...     

Evaluation of the Lipophilicity of Some 1-Arylpiperazines by Planar Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The lipophilic character of some biologically active 1-arylpiperazines has been studied. A reversed-phase planar chromatographic...     

Evaluation of the Quality of Ink-Jet Printed Paper by Planar Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Paper chromatography and thin-layer chromatography (TLC) are two efficient analytical methods that can be used to characterize...     

In Vivo Monitoring of the Thiols in Rat Striatum by Liquid Chromatography with Amperometric Detection at a Functionalized Multi‐Wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode (CME) was fabricated, which was based on the immobilization of multi‐wall carbon nanotubes fuctionalized with carboxylic group (MWNT‐COOH). The results indicated that the CME exhibited efficiently electrocatalytic oxidation for L ‐cysteine and glutathione with relatively high sensitivity, stability and long‐life. Coupled with HPLC, the MWNT‐COOH CME was utilized for amperometric detection of the thiols. The peak currents of L ‐cysteine and glutathione were linear to their concentrations ranging from 3.0×10^?7 to 1.0×10^?3 mol/L with the calculated detection limit (S/N=3) of 1.2×10^?7, 2.2×10^?7 mol/L, respectively. The method had been successfully applied to assess the contents of L ‐cysteine and glutathione in rat striatal microdialysates.     

Reaction of Thiosemicarbazones from Heterocyclic Series with Acetic Anhydride

Russian Journal of Organic Chemistry -