Metformin and Moroxidine Determination With Cu (II)

Abstract

Conductometric titrations of metformin and moroxidine are reported. The procedure is based on the copper-biguanide reaction which gives a pink soluble complex. Studies at several pH values and presence of NH₃ are carried out. NaOH-NH₃ (1:15) are added to 5 ml of biguanide aqueous solution and diluted to 60 ml and titrated with copper sulphate. Concentrations of metformin in 205x10^?4-1,7x10^?3 M range are determined. Foreign species presence is studied too.     

The Titrametric Determination of Rhenium

Abstract

A spectrophotometric titration for the determination of rhenium was developed using tin(II) as the titrant. Samples containing approximately 1 × 10^?2 meq/ml were titrated with errors of approximately four percent. Titration of rhenium was investigated in the presence of glucose, ethanol, and oxalate. No significant induced reactions were shown to occur.     

Lead(II)-Selective Membrane Electrode Based on Tetraphenylporphyrin

ABSTRACT

A PVC membrane electrode for Pb² ions based on tetraphenylporphyrin was prepared. The sensor exhibits a Nernstian response for lead ions over a wide concentration range (1.0 x 10^?5-1.0 x 10^?2 M). The limit of detection is 8.5 x 10^?6M. It has a response time of 15 s and can be used for at least three months without any divergence in potential. The proposed electrode shows a fairly good discriminating ability towards Pb² ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. The electrode can be used in the pH range 5.0 to 7.5. It was used as an indicator electrode in potentiometric titration of lead ion.     

Determination of Germanium in Zinc by Differential Cathode Ray Polarography

Abstract

A differential cathode ray polarographic method is described for determining traces of germanium in zinc and its compounds. The germanium was previously extracted with carbon tetrachloride from the sample solution in hydrochloric acid. After reextraction with water the germanium content was determined polarographically in 1.4 M perchloric acid ? 5.10^?2 M pyrogallol. The detection limit was 0.0012 μg/ml, allowing to detect about 4 ppb of germanium in zinc using 5 g samples.     

Study of the Fluorescence Enhancement of Eu-Y-DEM-Dibenzoylmethane-Ammonia System

Abstract

The fluorescence enhancement and solvent effect of Eu-dibenzoylmethane-ammonia system was studied. The fluorescence intensity of the system can be greatly increased by y³⁺. The maximum fluorescence intensity was obtained at pH 8.9 – 9.5. The fluorescence intensity is a linear function of Eu²⁺ in the range of 1.0x10^?9 M -4.0x10^?8 M. The detection limit is 1.1x10^?10 M. The optimized procedure is applied to the determination of europium in lanthanide oxide samples.     

Room Temperature Phosphorescence Optosensor for Terbium

Abstract

A solid surface room temperature phosphorescence optosensing method has been developed for the determination of terbium(III) based on the adsorption of its binary complex with 1,4-bis (l'-phenyl-3′-methyl-5′-pyrazolone-4′-) butanedione-(1,4) (BPMPBD) onto the hydrogen form of a strong cation exchange resin packed in a flow cell in an aqueous flow system. The phosphorescence intensity is a linear function of the concentration of terbium in the range of 8x10^?9 M-6x10^?7 M, and the detection limit is 3x10^?9 M terbium. The response mechanism was also studied. The present optosensor has been used for the determination of trace amounts of terbium in synthetic samples with satisfactory results.     

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.     

Synthesis of 5-Thio-L-Fucose and its Inhibitory Effect on Fucosidase

ABSTRACT

5-Thio-L-fucose was synthesized for the first time from D-glucose in 16 steps and ^-found to have a remarkable inhibitory effect on fucosidases from bovine epididymis (Ki 4.2x10^?5 M) and kidney (Ki 8.4 x 10^?5 M).     

Analysis of Sub-Microgram Levels of Palladium (II) in Environmental Samples by Selective Extraction and Spectrophotometric Determination with N-p-Methoxyphenyl-2-Furylacrylohydroxamic Acid and 5-(Diethylamino)-2-(2-Pyridylazo) Phenol

Abstract

Nine new hydroxamic acids in conjunction with four pyridylazo reagents were explored for extractive separation and spectrophotometric determination of palladium in environmental samples. It was found that maximum sensitivity and selectivity was achieved by employing N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA) and 5-(diethylamino)-2-(2-pyridylazo) phenol (DEPAP). Palladium was first selectively extracted with MFHA in isoamyl alcohol at pH 2.7-3.5 and the extract was equilibrated with a mixture of 5 M HCl and 10^{? 3} M solution of DEPAP in ethanol. The resulting intensely green ternary complex was measured at 560 nm (σ 5.1 × 10⁴ l mole^?1 cm^?1). The extraction system is suitable for enrichment of palladium over 15 times without loss in recovery and enables determination of palladium at levels as low as 10^?4 ppm (0.1 ppb). The method tolerates the presence of a large number of diverse ions normally associated with palladium, including platinum metals, and was employed for the determination of palladium in standard catalysts, biological materials, and freshwaters.     

Zinc-Selective Membrane Electrode Based On 5, 6, 14, 15-Dibenzo-l, 4-Dioxa-8, 12-Diazacyclopentadecane-5, 14-Diene

ABSTRACT

A new PVC membrane for zinc ions based on DBDA15C4 as membrane carrier was prepared. The electrode shows a linear stable response over a wide concentration range (5.0 × 10^?5-1.0 × 10^?1 M) with a slope of 22 mV/decade and a limit of detection of 3.0 × 10^?5 M (2.0 μg/ml). It has a very short response time of less than 5 s and can be use for at least 11 months without any divergence in potential. The zinc ion-selective electrode exhibited very good selectivities with respect to alkali, alkaline earth and some transition and heavy metal ions and could be used in a pH range 1.5-7.0. It was successfully applied for the direct determination of zinc in a pharmaceutical sample and, as an indicator electrode, in potentiometric titration of Zn²⁺ ions.     

Electrocatalytical Oxidation and Determination of Dopamine at Redox Polymer/Nafion Modified Electrodes

ABSTRACT

The modified glassy carbon electrodes prepared by simultaneously covering with [Os(bpy)₂(PVP)₁₀Cl]⁺ redox polymer and Nafion film exhibited excellent electrocatalytic activity for the oxidation of dopamine (DA). Dual linear regions between 1.0x10^?8-1.8x10^?5 M and 1.8x10^?5-4.0x10^?4 M with correlation coefficients of 0.998 and 0.995, respectively, were obtained for log-log plots of catalytic current versus DA concentration. The detection limit for DA determination was ca. 5 nM with 3σ. The dual-film modified electrodes eliminated efficiently the interference from AA presence in a 1000-fold concentration ratio and showed excellent reproducibility for the determination of DA. The modified electrodes have been used to determine DA concentration with both cyclic voltammetric and chronoamperometric techniques. Electrocatalytic kinetics have been studied using a rotating disk electrode. Both the addition of Nafion film and an increase in DA concentration resulted in a decrease in the electrocatalytic rate constant. An apparent Michaelis-Menten constant of 1.3 mM and maximum catalytic current of 88μA were evaluated from the chronoamperometric measurements.     

Photometric Detection Inside the Stream of Sample Sheath Fluid

Abstract

Photometric detection with continuous feed of reagent into the centre of sample flow is described. Performance characteristics of this technique were tested at models without and with chemical reaction. Linear calibration curves were obtained for methylorange (5 x 10^?6 - 1 x 10^?4 M) and for ammonia reaction with the Nessler's reagent (6 x 10^?6 6 x 10^?4 M). The technique was applied for the determination of ammonia in drinking water. In this case, the preconcentration step was necessary.     

Amperometric Biosensor for Adenosine-5′-Triphosphate Based on a Platinum-Dispersed Carbon Paste Enzyme Electrode

Abstract

A new amperometric biosensor for adenosine-5′-triphosphate (ATP) was designed using a platinum-dispersed carbon paste into which glycerol kinase and glycerol-3-phosphate oxidase were incorporated. The biosensor is based on the detection of hydrogen peroxide produced by the enzymatic reaction of ATP with glycerol and the subsequent oxidation of glycerol-3-phosphate. The use of the platinum-dispersed carbon paste electrode lowered the oxidation potential for hydrogen peroxide, permitting the sensitive detection of ATP at 0.4 V vs. Ag/AgCl. A linear response to ATP was observed in the concentration range of 1 x 10^?5 to 2.5 x 10^?3 M.

     

A New Poly (Vinyl Chloride) Matrix Membrane Electrode for Manual and Flow Injection Determination of Pilocarpine in Some Pharmaceutical Preparations

Abstract

A novel pilocarpinium ion selective membrane electrode is prepared, characterized and used in pharmaceutical analysis. The electrode system incorporates a PVC membrane with pilocarpine-reineckatc ion pair complex as an electroactive material. The electrode exhibits a fast near-Nernstian response for 10^?1-4x10^?5M pilocarpine over the pH range 4-6.5. The electrode displays a good selectivity for pilocarpine with respect to a number of foreign cations. Pilocarpine in various pharmaccutical preparations is determined either by direct potentiometry or potentiometric titration with NaTPB using the proposed sensor. Pilocarpinereineckate membrane is also used in a flow through sandwich cell as a detector for flow injection determination of pilocarpine. Results with an average recovery of 99% and a relative standard deviation of ± 0.3% are obtained. The data compare favorably with those obtained by the standard US Pharmacopeia method.     

Determination of Lysine in Nutrition Sample by Adsorption Voltammetry

Abstract

Lysine can be determined by adsorptive voltammetry after derivatization with acetaldehyde in 1.3 x 10^?2mol/ L borax-NaOH buffer solution (containing 4 x 10^?3mol/ L of CH₃CHO at pH10). The Schiff's base product of the derivation can be adsorbed on a hanging mercury electrode and reduced with peak potential of about -1.33v (vs.SCE) after 120s pre-concentration time. The derivative peak height is linearly proportional to the concentration for lysine in the range 6.0 x 10^?7-1.0 x 10^?5mol/ L. The detection limit is 4.0 x 10^?7mol/ L. Using this method, we have directly determined lysine in nutrition samples without any pre-separation step.     

Kinetic-Fluorimetric Determination of Choline and Acetylcholine by Oxidation with Ce(IV)

Abstract

A kinetic fluorimetric method for the determination of choline and acetylcholine based on the oxidation of these analytes by Ce(IV) in a sulfuric acid medium yielding fluorescent Ce(III) is proposed. The calibration graph of each analyte is linear over the range 1.7x10^?5 ? 1×10^?3 M and the relative standard deviation is about 2% in both cases. The rate of appearance of Ce(III) fluorescence was found to be influenced by various processes in addition to the oxidation reaction and experiments were carried out in order to elucidate them.     

Voltammetric Monitoring and Speciation of Copper Ions in Italian “Grappa” with Platinum Microelectrodes

A linear sweep voltammetric (LSV) investigation and the anodic stripping voltammetric (ASV) detection of copper ions in ethanol‐water mixtures and grappa samples are reported. The measurements are carried out by using platinum microdisk electrodes. Ethanol‐water mixtures with ethanol content in the range 40–100 vol%, commercially available and raw grappa samples having ethanol content in the above range are examined. From LSV measurements of copper (II) ions added to the samples, the formation of intermediate copper (I) soluble species, which are stabilized mainly by the naturally occurring organic compounds present in the real samples, is observed. The analysis of LSV and ASV current responses against added Cu²⁺ ions provides linear trends over the concentration range 5×10^?5?5×10^?3 M and 5×10^?7?5×10^?5 M, respectively. The sensitivity depends on the ethanol content in the mixture and, as expected, it is the higher the lower the viscosity of the medium. In particular, it varies from 1.54 to 3.53 nA mM^?1 and from 0.114 to 0.263 nA μM^?1 for LSV and ASV measurements, respectively, upon changing the ethanol content from 40 to 100 vol%. In the same range of ethanol content, detection limits obtained by ASV vary from 0.27 to 0.15 μM, respectively. Labile or total copper contents in the grappa samples are determined by ASV measurements performed in the untreated matrices or in the samples acidified with 0.1 M HClO₄, respectively. Finally, acidification of the samples with different amounts of HClO₄ allows also some speciation investigations to be performed.     

Determination of Nitrite in Aqueous Solutions using the Linear Sweep Voltammetry Technique

ABSTRACT

An electrochemical method using linear sweep voltammetry techniques was developed to determine nitrite ion in aqueous solution in the presence of nitrate. Nitrite solutions exhibited a well-defined oxidation wave at +1.0V vs SCE at vitreous carbon, while no oxidation process was observed for nitrate solutions. The pH of the nitrite solutions varied from 2.37 to 5.60 and no change was observed in the Ep values, except for the pH 5.60 solution, where little change was verified. The potential also did not vary with change in the nitrite concentration in the 5.0 x 10^?5 to 7.0 x 10^?4 mol L^?1 range. Very good straight lines for plots of current versus nitrite concentration in the 7.0 x 10^?5 to 7.0 x 10^?4 mol L^?1 range were obtained; the correlation coefficient was never worse than 0.990. The nitrite determination was also performed in the presence of 1.0 x 10^?3 mol L^?1 of NO₃ ^? ions. The addition of NO₃ ^? did not change significantly the current values even when it was added in one hundred times molar excess.     

Synthesis and carboxylate anion binding studies on cyclic sugar-amino acid hybrids

Abstract

Here in, the condensation of boc-glycine with 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitol followed by its boc-deprotection to form 2,6-anhydro-3,4,5-tri-O-benzyl-D-gluco-heptitolyl bis-glycinate, which in turn on condensation with succinic acid/pyridine-2,6-dicarboxylic acid led to the formation of sugar-amino acid hybrid macrocyclic compounds 4, 6 and debenzylated marocyclic compound 5, having amide bonds that function as efficient host for polar, hydrogen bond acceptors and carboxylate ions. The anion inclusion capability of synthesized macrocylic hosts has been evaluated by the study of their binding with boc-GlyCOOˉ anion as guest through 1H NMR titration studies in CDCl₃. The binding constant (K_a) of boc-GlyCOOˉ guest with macrocyclic hosts 4 and 6 involving succinate and pyridine-2,6-dicarboxylate linkers was found to be 9.201?×?10³ and 1.437?×?10⁴ M^?1, respectively. The higher binding constant was observed in the complex of boc-GlyCOOˉ with pyridine-dicarboxylate containing host may be due to the extra rigidity & suitable conformation attained by the presence of rigid-aromatic dicarboxylate linker.     

A Selective Fluorimetric Method for the Determination of Some β-Lactamic AntibioticsSupported by Natural Science Foundations of China and Shandong province

Abstract

Based on the reaction between acetylacetone-formaldehyde and β-lactamic antibiotics at pH=4.0, in which product can emit strong fluorescence, a selective simple fluorimetric method is described for the determination of both α-aminocephalosporins (namely cepharadine and cefalexin) and 6-aminopenicillanic acid (6-APA) in pure form and in pharmaceutical form. Other β-lactamic antibiotics free from α-amino group do not interfere with the assay. The linear ranges are 1.0×10^?4-8.0×10^?2 mg/ml, 2.0×10^?4-3.0×10^?2 mg/ml and 3.0×10^?4-2.0×10^?2mg/ml for cepharadine, cefalexin and 6-APA, respectively. Their detection limits (S/N=3) are 3.0×10^?5mg/ml, 4.0×10^?5mg/ml and 6.0×10^?5mg/ml.