Raman Spectroscopic Studies on the Complexation and Adsorbed Behaviour of Thiourea

Raman spectroscopic studies on thiourea (TU) in highly acidic media (e. g. >3 mol/L HC1O4) show that TU as a solution species is protonated through its sulphur atom and forms complex with anions. However, as an adsorbed species, TU is protonated via the nitrogen atom and adsorbed at the silver electrode surface through the sulphur atom. The distinct effects of pH and anions of the solution on the surface enhanced Raman (SER) spectra of TU were investigated. In acidic and neutral solutions, TU is coadsorbed with anions through its NH3 and - NH2 groups respectively.     

Investigation of the interaction of DNA and neutral red by fluorescence spectroscopic analysis

The binding characteristics of neutral red (NR) with DNA were investigated by fluorescence spectrometry. Chemometrics approach as singular value decomposition (SVD) was used to evaluate the number of spectral species in the drug-DNA binding process, and then the intrinsic binding constant of 1.6 × 104 in base pairs and the binding site number of 0.97 were obtained from the Scatchard plot.     

Study of the Complexation Behavior of Calixarene with Transition Metal Cations by UV—vis and Fluorescent Spectra

A new fluorescent compound based on calix[4] arene skeleton was synthesized.Its complexation ability with transition metal ions,such as Fe^3 ,Co^2 ,Ni^2 ,Cu^2 ,Zn^2 and Ag^ ,Was investigated by UV-vis and fluorescent spectra.     

Investigation of the Interaction between Isoflavonoids and Bovine Serum Albumin by Fluorescence Spectroscopy

The interactions of bovine serum albumin （BSA） with three structurally related isoflavonoids, genistein, puerarin and daidzein, were studied under physiological conditions by fluorescence spectroscopic technique. The quenching mechanism of these compounds with BSA was suggested as static quenching and the binding constants were determined at different temperatures based on the fluorescence quenching results. The transfer efficiency of energy and distance between the acceptor and BSA were investigated on the basis of the mechanism of the Forster energy transference. According to the thermodynamic parameters it has been suggested that the acting force be mainly hydrophobic force. The comparison of binding potency of the three isoflavonoids to BSA showed that the substitution by 5-OH and 8-Glc could enhance the binding affinity. All these obtained in the work can make us better understand the mode of the action and pharmacological activities of the isoflavonoids.     

Investigation of the Effect of Inclusion of Eriochrome Black T with β-Cyclodextrin on Its Complexation Reaction with Ca2+ and Mg2+ Using Rank Annihilation Factor Analysis

Rank annihilation factor analysis (RAFA) was used to investigate the effects of inclusion of eriochrome black T (EBT) on its complexation reaction with Ca²⁺ and Mg²⁺ at different pH values. Addition of β-cyclodextrin (β-CD) to Ca-EBT or Mg-EBT caused decomposition of the 1:1 metal complex and increase in EBT concentration in solution due to the formation of EBT-β-CD inclusion complex. In order to perform RAFA, concentration profiles were calculated by optimizing the value of the conditional stability constant and inclusion constant. The rank of original data matrix reduces by one by removing the information from the complex form (Ca-EBT or Mg-EBT). The performance of the method was evaluated by using synthetic data as well as experimental data and good results were obtained. The proposed method is capable of the simultaneous spectrophotometric determination of formation constant of a complex and the equilibrium constant of the competing reaction in solution.     

Investigation on the Complexation of Dioxovanadium (V) with D-(-)-Quinic Acid in Water + 1-Butyl-3-Methylimidazolium Tetrafluoroborate and Water + Methanol Mixed Solvents Using the KAT Model

The complex formation reaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} at T = 298 K, I = 0.1 mol·dm^?3 of sodium chloride in various aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF₄, and methanol were studied by using potentiometric and UV spectrophotometric techniques. As far as we know, the calculated stability constants data presented in the current work are the first reported values for [bmim]BF₄ and methanol mixed solvents. The Kamlet–Abboud–Taft solvatochromic equation enabled us to interpret the UV data and the stability constants values. The Redlich–Kister equation was applied for the calculation of solvatochromic parameters in the binary water + [bmim]BF₄ mixtures. Hydrogen bonding is important for the dissociation constant in both media. In these systems the solvent polarizability and hydrogen-bond donor ability are the main interactions for the stability constants in the aqueous ionic liquid and methanol solutions, respectively.     

4-Aminoantipyrine as an Analytical Reagent for the Colorimetric Determination of Tetracycline and Oxytetracycline

Abstract

A spectrophotometric method is proposed for the determination of tetracycline and oxytetracycline and their dosage forms. The suggested method depends on the reaction with 4-aminoantipyrine in the presence of an alkaline oxidising agent. A red antipyrine dye is produced. The reaction ratio has been determined. Variables such as pH, temperature, reagent concentration, stability of the colour produced have been evaluated to permit selection of the most advantageous technique. Beer's law was obeyed over the concentration range 0.04 - 0.12 mg/ml and 0.04 - 0.16 mg/ml for tetracycline and oxytetracycline respectively.     

Kinetic Method of Tetracycline and Oxytetracycline Assay Using Spect-Rophotometric Measurements

Abstract

A Kinetic method is based on the degradation rate of tetracycline (TC) or oxytetracycline (OTC) to their anhydro derivatives with subsequent spectrophotometric measurements. With optimized degradation rate parameters, calibration curves relating decrease in absorbance difference (of alkaline solution versus acid solution) as a funotion of concentration in a range of 0.8-4.0 mg% are linear with negligible interecept. The method is applicable for powder and capsule assays and gives results within the pharmacopoeial limits.     

钐、铕-四环素类抗生素络合物荧光性能的研究及其在荧光分析中的应用

本文探讨了钐、铕-四环素、强力霉素、土霉素、金霉素络合物的荧光性能及利用该体系以荧光分析光度法测定痕量钐和铕的可能性与最佳测定条件.结果表明:在高碱度条件下(pH12～1.0mol/L NaOH),以四环素体系的稳定性、灵敏性最好,钐和铕的检测限分别为38.2和0.09ng/mL.     

用钼（铕）络合物法测定四环素类抗生素的研究

利用四环素与钼、土霉素与铕的络合反应，建立了用钼、铕络和物法测定药物的新方法。检出限分别为０．５μｇ／ｍＬ，０．６μｇ／ｍＬ，线性范围分别为０．５～５０μｇ／ｍＬ和０．６～５０μｇ／ｍＬ。方法快速、简便。应用于尿中四环素的测定，结果较为满意。     

Analysis of Tetracycline,Oxytetracycline and Chlortetracycline in Plasma Extracts by Electrospray Tandem Mass-Spectrometry and by Liquid Chromatography

Abstract

Pure standards of tetracyclines (tetracycline, oxytetracycline and chlortetracycline) have been analyzed on a triple quadrupole mass spectrometer with Atmospheric Pressure Chemical Ionization (APCI) and Electrospray Ionization (ESI). ESI appeared to be considerably more sensitive than APCI. Collisional activation of the MH⁺ ions gave fragment ions at m/z values equal to MH⁺ - 35 which corresponds to loss of both H₂O and NH₃. The collisionally induced loss of 35 from MH⁺ was used in developing a mass spectrometric method based on loop injection and selected reaction monitoring (SRM) as the final analytical step. The method was tested on extracts from fortified plasma and the measurements from the MS-MS analysis were compared with results from High Performance Liquid Chromatography (HPLC) analysis of the same samples. The fortified plasma (from pig) samples were purified by chelate affinity chromatography (amberlite XAD columns). After filtration and evaporation of the solvent the redissolved residues were analyzed by HPLC and by MS-MS with ESI. The HPLC eluates (gradient of 0.01 M aqueous oxalic acid and CH₃CN) were monitored at 356 and 369 nm. The signal to noise ratio in the analyses of extracts from plasma fortified to 20 ppb suggests a detection limit for the MS-MS method below 10 ppb of tetracylines in plasma.     

基于四环素荧光熄灭测定碘的研究

基于碘对荧光试剂四环素的荧光熄灭,建立了测定微量碘的荧光分析方法。在pH10的碱性介质中,最大激发/发射波长分别为400.0nm/509.0nm,四环素的荧光强度与碘浓度的对数呈良好的线性关系,测定碘浓度的线性范围为3.20×10^-7～1.00×10^-4mol/L,检出限为1.30×10^-8mol/L,常见的共存离子不干扰测定。该方法适用于食盐中微量碘含量的测定。     

钙对钐、铕-四环素类体系荧光法测定钐和铕的增敏作用及其机理探讨

本文研究了常见金属离子（Cr3+、Mn2+、Fe3+、Ni2+、Cu2+、Ca2+、Sr2+、Ba2+、Sn2+、Al3+、Zn2+、Li+、Ms2+）对钐、铕-四环素（TC）、土霉素（OTC）、强力霉素（DOTC）、金霉素（CTC）体系荧光的影响，并从电子自旋磁性和多核络合物的形成等方面对其作用机理进行了探讨。进一步探讨了Ca2增敏TC类体系恻定Sm3+、Eu3+的最佳测定条件。由于钙的加入，可使钐、铕的荧光强度分别增敏3～5和6～30倍。以TC体系为最佳，加入钙，可分别使钐、铕的检测限由38.2和0.09μg／L降低到7.9和0.015μg／L。成功地对样品进行了分析测定。     

玻片表面上四环素毛细流自组装环的荧光特性及其应用

基于溶剂毛细流效应的自组装，提出一种测定四环素的分析方法。四环素的六氢吡啶液滴在聚乙烯醇—124存在下，能在憎水性玻璃表面形成一个自组装环(SOR)，环直径为1.14mm，环线宽为0.025mm。通过测定环线上荧光强度，实现了对四环素的定量分析，方法的检出限为8.5fmol(0.2μL液滴)，方法成功地应用于样品及合成样分析。     

流动注射化学发光测定盐酸土霉素

水浴加热后的盐酸土霉素在磷酸介质中,过氧化氢存在下与高碘酸钠反应产生强烈的化学发光。结合流动注射技术建立了一种测定盐酸土霉纱的化学发光新方法。方法的线性范围为１．０＊１０＾－８－６．０＊１０＾－６ｇ／ｍＬ盐酸土霉素。检出限为４．３＊１０＾－９ｇ／ｍＬ,ＲＳＤ为２．５％（Ｃｓ＝２．０＊１０＾－６ｇ／ｍＬ;ｎ＝１１）。     

高效液相色谱法测定四环素类抗生药物中土霉素、强力霉素、四环素和金霉素

利用高效液相色谱,发展了一种快速、灵敏、同时测定土霉素、强力霉素、四环素和金霉素的方法。在反相C18柱上进行梯度洗脱分离,流动相由甲醇和乙酸钠缓冲溶液组成(内含EDTA和氯化钙,pH 8.10),紫外检测波长为386 nm。四环素类药物的质量浓度在8~4 000μg.L-1范围内呈线性关系,回收率为95%~102%,相对标准偏差为1.2%~3.6%,检出限分别为6,13,6和7μg.L-1,方法应用于四环素类抗生药物的分析。