Isolation of Ligands of Trace Metals from Plant Samples by Immobilized Metal Affinity Chromatography

Abstract

Isolation of ligands of trace elements from plants by affinity chromatography with a metal immobilised on iminodiacetate resin has been investigated. To simulate various types of bioligands the following compounds were tested: phytic acid, peptides containing Cys and peptides containing Asp. Optimal conditions allowing isolation of the peptides with good efficiency comprise the use of Ga³⁺ ion, sample adsorption at pH = 4 and elution of the compounds by 0.3 mol/l NH₃. Phytic acid was bound too tightly and was not eluted. The procedure was used for purification of extracts of rye flour. The purified sample is suitable for analysis by MALDI-MS.     

Rubidium Determination In Mineral and Thermal Waters By Atomic-Absorption Spectrometry

Abstract

A new procedure for rubidium determination in mineral and thermal waters using flame atomic-absorption spectrometry is described. to supress ionisation interference potassium solution was added. Rubidium can be determined in presence of Ca, Mg, Sr, Li, Cs, Fe, Al, CO² ₃, F^? and S^2? at higher levels that levels of these elements in waters. the precision and accuracy of the method were also investigated. In 163 mineral and thermal waters analysed, the rubidium concentration range is between 0.08 to 0.84 μg mL^?1.     

Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

ABSTRACT

A simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na₂S₂O₃), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 µL saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 µg L^?1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 µg L^?1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.     

Separation of Free Amiimo Acids on Reverse Stationary Phases Using an Alkyl Sulfonate Salt as a Mobile Phase Additive

Abstract

Alkylsulfonate (RSO₃ ^?) salts were evaluated as mobile phase additives for the separation of free amino acids on reverse stationary phases using an acidic mobile phase where the amino acids are cations. The enhanced amino acid retention is the result of two major interactions, one being retention of the RSO₃ ^? salt on the stationary phase and the other an ion exchange selectivity between the amino acid analyte cation and the RSO₃ ^? countercation, or other countercations in the mobile phase. Major mobile phase variables are: type and concentration of RSO₃ ^? salt (the studies focused on C₈SO₃ ^? salts), presence of organic modifier, type of countercation present, and mobile phase pH and ionic strength. Alkyl modified silica and polystyrenedivinyl-benzene copolymeric reverse stationary phases were compared. A mobile phase gradient, increasing per cent organic modifier was shown to be best, is necessary for separating complex mixtures of polar and nonpolar or basic amino acids. The procedure is applicable to the identification and/or determination of amino acids in mixtures or in peptides after hydrolysis.     

A Rapid Spectrophotometric Method to Resolve Ternary Mixtures of Propyphenazone, Caffeine, and Acetaminophen in Tablets

Summary.  A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm⁻³ for 2 and 3 and 1.0–5.0 μg·cm⁻³ for 1. The method involves the extraction of the drugs from tablets with 0.1 N H₂SO₄, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform. Received April 18, 2001. Accepted (revised) June 5, 2001     

A Rapid Spectrophotometric Method to Resolve Ternary Mixtures of Propyphenazone, Caffeine, and Acetaminophen in Tablets

 A simple and rapid derivative spectrophotometric assay procedure is described for the analysis of caffeine (1), acetaminophen (2), and propyphenazone (3) in tablet formulations. The concentration range of application is 5.0–25.0 μg·cm⁻³ for 2 and 3 and 1.0–5.0 μg·cm⁻³ for 1. The method involves the extraction of the drugs from tablets with 0.1 N H₂SO₄, filtration, appropriate dilution, and measurement of the fourth derivative absorbance values at zero crossing wavelengths of 230.0, 263.2, and 256.6 nm for 1, 2, and 3. As a reference method, a reversed phase HPLC procedure was developed. Commercially available tablets were analyzed; statistical comparison of the results with those obtained from the reference method showed good agreement. The derivative spectrophotometric method has the advantage of being simple, rapid, inexpensive, and easy to perform.     

Synthesis of New Cα,α-Diarylaminomethylphosphonic Acids and their Esters

Abstract

A procedure for the preparation of N-protected 1 or unprotected C_a,a-disubstituted (diarylaminomethyl)-phosphonic acids and their esters is reported.¹ This method is a generalisation of the Kabachnik-Fields method described in the literature.²     

One-Pot,Facile, Highly Efficient,and Green Synthesis of Acridinedione Derivatives Using Vitamin B1

An efficient methodology for the synthesis of acridinedione derivatives 4a–o has been achieved by one-pot, multicomponent condensation of dimedone 1, various amines 2a–d, and substitute aromatic aldehydes 3a–k, in the presence of the easily available, inexpensive, and nontoxic catalyst vitamin B₁ (VB₁) as a versatile biodegradable. Synthesis of acridine-type compounds was performed in good yields in water as green solvent. Its high-yield efficiency; clean, ecofriendly, simple workup procedure; and easy purification are regarded as the main advantages of this method besides its green solvent. The synthesized compounds are characterized using spectroscopic analyses (FTIR, ¹H NMR, ¹³C NMR, and high-resolution mass spectrometry) techniques.     

Comparison of High Performance Liquid Chromatography with 1H Nuclear Magnetic Resonance Spectrometry for the Quantitative Analysis of Pyrrolizidine Alkaloids from Senecio Vulgaris

Abstract

A high-performance liquid chromatographic method for the analysis of pyrrolizidine alkaloids from Senecio vulgaris has been developed using narceine-HCl as an internal standard. A reversed phase procedure with a methanol/.01 M KH₂PO₄30/70 solvent system is described, and compared with a quantitative¹H Nuclear Magnetic Resonance spectrometric method. Some advantages and limitations are discussed.     

Fluorimetric Determination of Silver with Brilliant Green in Aqueous Systems and its Application in Photographic Fixing Solutions

Abstract

A fluorimetric procedure for Ag⁺ determination in aqueous solutions was developed based on the ion association complex formed from the reaction between AgI^- ₂ and the brilliant green cation and its strong fluorescence (λ_exc 256 nm, λ_em 521 nm). Silver ions could be determined satisfactorily in the range of 0-100 μgAg⁺/L. Optimum conditions for complex formation and measurement of fluorescence intensity were: pH = 3.0; concentrations of brilliant green and KI, 15 and 100 mg/L, respectively; time, within 15 min after complex formation. The method proved successful in determing Ag⁺ in photography fixing solutions and the results agreed satisfactorily with those obtained using a standard Atomic Absorption Spectrometry method.     

Solid-Phase Extraction and Capillary Gas Chromatographic Determination of Triazine Herbicides in Water

Abstract

A facile and efficient method is described for the determination of trace quantities of triazine herbicides, terbutryn, prometryn and ametryn in water. The procedure involved preconcentration of water samples by sorption on chromatographic grade silica gel particles with chemically modified surface, being covalently bonded with a nonofunctional C₈H₁₇ group. This was followed by solvent desorption with 2-propanol. The determinative step was achieved by capillary gas chromatography on Supelcowax-10 fused silica column using a nitrogen-phosphorus detector. The limit of detection was 0.1 μg-10 μgL^?1.     

Analysis of Plasma Angiotensins by Reversed Phase HPLC and Radioimmunoassay

Abstract

The analysis of biologically active angiotensin peptides in blood plasma by high performance liquid chromatography in a weakly non-polar reversed phase (C₂) chromatographic system combined with quantification of chromatographically isolated peptides by radioimmunoassay has been developed. This system is able to resolve each of seven closely-related peptides of the angiotensin group. The chromatographic system was applied to plasma samples which have been prepared for chromatographic analysis by C₁₈ cartridge extraction. Samples were reconstituted in HPLC solvent prior to injection into the HPLC system. Separated angiotensin were collected by fraction collector and the volatile components of the solvent system were blown off under an air stream. The content of several of the various angiotensin peptides in the fractions was then determined by radioimmunoassay using an appropriate antiserum. Antiserum to angiotensin II (octapeptide) was used to quantify the biologically active components angiotensin II, angiotensin III (hepta-peptide) and C-terminal hexapeptide. Recovery of angiotensin II in the C₁₈ cartridge extraction has been assessed at 85.0 ± 0.9% (mean ± SEM) using I¹²⁵-labelled angiotensin II, and 82.2 ± 4.45% using synthetic unlabelled angiotensin II. Recovery of standard preparations of angiotensin II in the HPLC system have been estimated at 67.5 ± 6.08%. The application of this technique to evaluating some components of the angiotensin in normal plasma is presented.     

Comparative Tryptic Peptide Analysis Of Rabbit Heavy Chain Allotypes By Hplc

Abstract

Reversed-phase, high pressure liquid chromatography (HPLC) in a modified TFA/H₂O-TFA/acetonitrile gradient has been successfully applied to the structural analysis of serologlcally defined rabbit immunoglobulln heavy chains. This mobile phase modification yields a relatively flat baseline at high UV sensitivity. Approximately 40 distinct tryptic pep-tides were resolved from each heavy chain, representing the V_Ha⁺ (a), a2, and a3) and V_Ha^? (y33,30 and y33,^?) immunoglobulin allotypes. About 30 peptides were shown to be derived from the Fc region (C_H2 and C_H3), and 8–10 peptides from the Fd region (V_H1 and C_H1). Seven Fd peptides were shared by all V_Ha⁺ and V_Ha^? heavy chains. The al and a2 digests each displayed one allotype-specific peptide, whereas no allotype-specific peptides were observed for the a3 heavy chain. No differences were detected between the y33,30 and y33,^? peptides; however, both expressed a common y-specific pep-tide. Amino acid analysis of purified al-specific and y-specific peptides Indicate that the two peptides are very similar in composition to the predicted first N-terminal tryptic peptides of V_Hal and V_Ha^? heavy chains, respectively.     

Determination of Strong Acid in Air-Borne Matter

Abstract

A titration variant for determination of strong acid in air-borne matter with Gran's plot method is proposed. The procedure can be applied to the titration of non sufficiently acidic samples containing weak acids as NH₄ ⁺, HSO₄ ^? and protolyzable ions. Interferences due to the presence of these species are evaluated.     

Determination of acid dissociation constants of histidine-containing peptides by proton magnetic resonance spectroscopy

The acid dissociation constant of the imidazolium ring of the decapeptide luliberin has been determined by ¹H NMR-followed titration in D₂O. The normal procedure for the analysis of the titration curve, i.e. direct use of the Henderson-Haselbalch equation, is still applicable in this case, but for more complex peptides a modified calculation procedure is proposed. Results obtained when both methods were applied to luliberin are compared. The influence of D₂O when used as the solvent in this type of determination has been studied using N^α-acetyl-L -histidine methyl ester as a model compound. The difference between the acid dissociation constant of this molecule determined in H₂O and in D₂O implies that a correction of ?.25 unit is needed for those pK_a values calculated by plotting the chemical shifts in D₂O vs the apparent pH meter readings. The pK_a found for N^α-acetyl-L-histidine methyl ester, 6.30 ± 0.04, can be taken as a standard value for histidine-containing peptides.     

Simultaneous Determination of Lonidamine, 1-(2,4-Dichlorobenzyl)-1h-indazole-3-carboxylic Acid,a New Antitumoral,and Its Impurity,N2 Substituted Isomer,by UV Derivative Spectrophotometry

Abstract

A direct and fast analytical method for the determination of Lonidamine and its impurity of synthesis, the N₂ alkylated isomer, by UV derivative spectrophotometry, is described.

The procedure was defined by regression analysis for a high number of standard solutions.

Linear relationships were obtained between mixture composition and maximum amplitude in <²D at 316 nm for Lonidamine quantitation, and peak trough ⁴D 226,234 and ⁴D 323,316 amplitudes by utilising polynomial equation for N₂ isomer quantitation.

The method, yielding accurate and precise results, was satisfactorily applied to laboratory mixtures and to a commercial formulation.     

High-Performance Liquid Chromatography of Arginine-Containing Neuropeptides by Precolumn Derivatization and Fluorimetric Detection

Abstract

A previously developed fluorescence method for determining leupeptin and the angiotensins is shown to be applicable to assaying other small arginine-containing peptides. In this procedure arginine residues are derivatized by reaction with benzoin. Femtomole sensivity is obtainable with this method. However, it cannot be used with larger arginine-containing peptides because those fragment upon derivatization.     

Opioid Peptides Determination by Tyrosinase-Modified Oxygen Electrode

Abstract

Opioid peptides morphiceptin (Tyr-Pro-Phe-Pro-NH₂), [D-Ala², D-Leu⁵]-enkephalin (Tyr-D-Ala-Gly-Phe-D-Leu, DADLE) and [D-Thr²]-Leu-enkephalin-Thr (Tyr-D-Thr-Gly-Phe-Leu-Thr, DTLET) containing tyrosine has been studied in the reaction with mushroom tyrosinase immobilized on Clark-type oxygen electrode. A 4–6-times higher response is observed for tyrosine compared to peptides. The detection limit of the tyrosinase-modified electrode for DADLE, morphiceptin and DTLET was 6 μM, 9 μM and 16 μM, respectively.     

Isoliquiritigenin extracted from licorice <Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> roots by a facile conversion technique

Isoliquiritigenin (1), one of the major constituents of licorice, is a natural pigment with a simple chalcone structure 4,2',4'-trihydroxychalcone. This study was performed to determine whether liquiritin, isoliquiritin, and liquiritigenin can be converted into isoliquiritigenin using alkaline conversion after acid hydrolysis. An orthogonal L₉ (3)⁴ test design was used in the extraction mode and used for optimization of the extract conditions, and the yield from the conventional procedure and from the optimum procedure to extract 1 was compared. The results demonstrated that the yield of the novel procedure was increased about 27 times compared with the conventional procedure, which indicated that the novel procedure is powerful in separating and purifying isoliquiritigenin.