Evaluation of the Use of A Laboratory Robot in a Study of Esterification Kinetics

Abstract

While the use of robots in routine quality-control and sample-preparation procedures is well established, their use in the research laboratory has not received as much attention. In order to evaluate the performance of laboratory robots in investigating problems that are non-routine and slightly more difficult, a Zymate-I robot was adapted to investigate the kinetics of two well-characterized reactions. The problems encountered and the need for verification devices in laboratory robotics are discussed.     

Simultaneous Optimization of Variables in Fia Systems by Means of the Simplex Method

Abstract

A response function (RF) in order to simultaneously optimize different variables by the SIMPLEX method in FIA systems, with the possibility of applying weights, is proposed. The optimization program developed to use this RF is assayed in the optimization of two different flow injection procedures. The obtained results are discussed.     

Development of a Tubular Sensor Based on a Polypyrrole‐Doped Membrane for the Potentiometric Determination of the Dodecylsulfate Anion in a FIA System

Potentiostatic polymerization of polypyrrole doped with dodecylsulfate anion (DS^?) was carried out in situ over a tubular composite (graphite‐epoxy resin) support in order to develop a potentiometric DS^? sensor (TISE) suitable for flow injection analysis (FIA). The sensibility of the TISE was maximized using the SIMPLEX algorithm in terms of the concentration of the pyrrole monomer, the concentration of DS^?, the potential imposed and polymerization time. Response times between 2 and 4 minutes were observed. The analytical parameters obtained with the flow system were compared with those obtained in batch studies. In both, flow and batch analysis, potential vs. DS^? concentration curves displayed two linear regions with different slopes. Flow analysis for DS^? ion brings a total linear range of 1.58×10^?5 M to 3.88×10^?3 M with a maximum sensibility of 36.4 mV/concentration decade, meanwhile in batch studies the total linear range found was of 6.31×10^?6 M to 1.0×10^?3 M with a maximum sensibility of 54.49 mV. The flow system response pH range was from 5 to 8. The reproducibility in terms of the relative error of the mean of different experiments was 1.58%. Two salient features of the system designed and built are worthy of mention: the sensor presented high selectivity to the dodecyl sulfate ion as compared to other inorganic anions including other anionic surfactants. The sensor lifetime in the FIA system by means of the sensibility changes was found to be of approximately four months.     

Direct Kinetic Determination of Bromhexine Hydrochloride in Pharmaceutical Formulations

Abstract

A very simple, automatic, fast method for the photometric determination of bromhexine hydrochloride based on the application of kinetic methodology and the stopped-flow mixing technique to the coupling reaction between the diazotized bromhexine derivative and N-(1-naphthyl)ethylenediamine is proposed. The high initial rate of this reaction allows analytical measurements to be made within only 0.5–1 s, which makes the method applicable to automatic routine analyses. The calibration graph is linear over the range 1.5–65.0 μg mL^?1 and the precision (as %RSD) is less than 2%. The presence of antibiotics such as penicillins and cephalosporins in a 100-fold excess has no effect on the analyte determination. The proposed method was satisfactorily used for direct analysis of pharmaceutical formulations containing these antibiotics.     

The Separation and Determination of Molybdenum by Electron Paramagnetic Resonance

Abstract

A procedure is described for the separation and quantitative determination of molybdenum by means of EPR. Molybdenum(VI) was precipitated from a hydrochloric acid solution (1.5 Molar) with α-benzoinoxime. The precipitate was separated by centrifugation and then the sample was dried in an oven at 105°C. Nitrogen was passed over the sample to complete the drying procedure. The precipitate was dissolved in acetonitrile which was 0.5 M in lithium perchlorate. Electrochemical reduction of the sample produced the molybdenum(V) species. The concentration of molybdenum(V) was determined directly from the intensity of the first derivative EPR signal. The range of linearity of the analytical curve was 1.00 × 10^?2 M to 1.00 × 10^?4 M, and a routine accuracy of less than 6% was obtained.     

Determination of Cefpiramide in Plasma by High-Performance Liquid Chromatographic with Internal Surface Reversed-Phase Silica Column

Abstract

We investigated the isolation of cefpiramide (CPM), cephem antibiotics, from human plasma proteins by high-performance liquid chromatography with a new column, Pinkerton^R column (Regis Chemical Co., Illinois, U.S.A.), and discussed whether the column is applicable to routine clinical determination. In condition of our studies, CPM could be analyzed without any pretreatment. The chromatograms of CPM obtained were single, sharp peaks. Proteins and endogenous compounds in plasma did not interfere with the assay. And, the precise free fraction of CPM could be obtained. The effect on the isolation by the different flow direction was also studied since the column could be used reversibly. There were significant differences (p < 0.01) between two slopes of the calibration curves by the different flow direction. It is suggested that calibration curves for both flow directions are required. The analytical procedures outlined in this study may be applicable to routine clinical use since this is a simple and rapid method.     

Synthesis of two p-methoxyphenyl substituted phosphines

Bis(m-methoxyphenyl)(p-methoxyphenyl)phosphine (1) and di(n-butyl)(p-methoxy-phenyl)-phosphine (4) were synthesized and characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy and 1 also by single crystal X-ray diffraction. The syntheses and analytical data are discussed.     

Determination of 210Pb in environmental samples

Summary Measurement of ²¹⁰Pb has gained a highly scientific attention due to its wide range of environmental applications. The most commonly used analytical techniques: gamma-spectrometry, beta-counting and alpha-spectrometry were used to measure environmental samples (geological, soil, sediment). Our paper is aiming at comparing the capabilities and limits of application of these three different analytical techniques for ²¹⁰Pb measurement in various environmental samples. In addition, analytical data of ²¹⁰Pb measurements with the three different techniques (gamma-spectrometry, beta-counting and alpha-spectrometry) are discussed to highlight the degree of comparability and the most probable sources of discrepancies and errors. Based on the demanded investigation, one analytical technique will be chosen for routine analysis, while the other techniques, if they are available, could be used for analytical quality assurance measures. It was essential to compare the analytical efficacy of each technique, which differ concerning the detection limit (MDA), sensitivity, analytical effort, the duration of analysis and waiting time before analysis.     

Analytical first derivatives of the energy for small CI expansions

Using the Z-vector formalism the analytical gradient of the energy in small CI expansions is derived and implemented for semiempirical MNDO-type methods. The computation time is shown to scale as O(N ³) with the size of the system, with the memory requirements growing as O(N ²). The evaluation of the analytical gradient is significantly faster than the underlying SCF and CI calculations, so that routine full geometry optimizations at the semiempirical CI level become possible for large systems. Received: 24 April 1997 / Accepted: 10 June 1997     

Feasibility study of an analytical method for detecting <Superscript>90</Superscript>Sr in soil using DGA resin and Sr resin

This study investigated an analytical method for detecting ⁹⁰Sr in soil samples for the routine monitoring of environmental radioactivity. Mineral acid leaching and fusion methods were first used to digest the soil sample, and the analytical results were compared. DGA resin was employed to separate ⁹⁰Y, being a daughter of ⁹⁰Sr. Then, ⁹⁰Y was analyzed by liquid scintillation counter (LSC). These analytical results were compared with those obtained using Sr resin, which is a well-known, simple and reliable separation method. With the DGA resin approach a minimum detectable activity of ~0.28 Bq kg^?1 was detected in a 50 g sample, with 180 min of counting time, 70% recovery and ~97% counting efficiency using a LSC.     

Biamperometric Determination of Tetracycline in Pharmaceuticals

Abstract

A fast, reliable, and low cost biamperometric flow‐injection method, with an error of 1.3% and an analytical throughput of 55 samples h^?1, for determination of tetracycline hydrochloride in pharmaceuticals capsules is proposed. The analytical curve was linear (r=0.998) in the range 10 to 50 mg l^?1 using Fe(CN)₆ ^3? and NaOH solutions as reagent and carrier stream/supporting electrolyte, respectively. A relative standard deviation of 1.6% (10 sequential injections of 30.0 mg l^?1) was verified with detection and quantification limits of 0.6 and 3.4 mg l^?1, respectively.     

Immobilized Enzyme Modules for Use in Analytical Microcalorimetry

Abstract

Immobilized enzyme modules designed for use in a conduction type analytical microcalorimeter were fabricated from cellulose acetate tubes and from cellulose filter paper. Catalase was bound to the modules after cyanogen bromide activation. Repetitive substrate determinations were made over a range of 0.015–1.2 mg of H₂O₂/ml of analytical solution. This was possible in spite of qualitative response differences relative to soluble enzyme reactions. The enzyme modules demonstrated excellent long term stability after repeated use and storage promising significant advantage for routine calorimetry using enzyme reagents.     

The Stereoselective Synthesis of Conjugated Allylsilanes

2-trimethylsilylethylidenetriphenylphosphorane (5) (Seyferth–Wittig reagent) reacts stereoselectively with the carbonyl compounds 6a–f to give the conjugated allylsilanes 7a–f, each as a mixture of E-and Z-isomers. The stereoselectivity of reactions of E-cinnamaldehyde (6c) with 5 has been investigated at different temperatures. A successful E-stereoselective synthesis of 7c was achieved by reacting 5 with E-cinnamaldehyde (6c) under the conditions of a Wittig–Schlosser modification reaction. Structures of the allylsilanes 7a–f were deduced by compatible analytical and spectroscopic (IR, ¹H NMR, ¹³C NMR, and GC/MS) measurements. An assignment of the E:Z ratios of 7a–f is based on their ¹H NMR spectral data.     

Biomimetic Artificial Inorganic Enzyme‐Free Self‐Propelled Microfish Robot for Selective Detection of Pb2+ in Water

The availability of drinking water is of utmost importance for the world population. Anthropogenic pollutants of water, such as heavy‐metal ions, are major problems in water contamination. The toxicity assays used range from cell assays to animal tests. Herein, we replace biological toxicity assays, which use higher organisms, with artificial inorganic self‐propelled microtubular robots. The viability and activity of these robots are negatively influenced by heavy metals, such as Pb²⁺, in a similar manner to that of live fish models. This allows the establishment of a lethal dose (LD₅₀) of heavy metal for artificial inorganic microfish robots. The self‐propelled microfish robots show specific response to Pb²⁺ compared to other heavy metals, such as Cd²⁺, and can be used for selective determination of Pb²⁺ in water. It is a first step towards replacing the biological toxicity assays with biomimetic inorganic autonomous robotic systems.     

Facile one-pot synthesis of new [1,2,4]triazolo[1,5-a]pyridine derivatives by ultrasonic irradiation

Herein, we report an ultrasonic promoted facile and convenient “one-pot” procedure for the synthesis of new [1,2,4]triazolo[1,5-a]pyridine derivatives 3, 4 and 5, using Amberlite IRA-400, in short reaction times and high yields and its comparison with classical reaction conditions. The structures of new compounds were assigned with the help of analytical ¹H, ¹³C NMR, and mass spectral studies.     

The Determination of Impurities in 233UO2 by Spark Source Mass Spectrometry

Abstract

A method for the determination of impurities in ²³³UO₂ has been developed and applied to the analysis of a product stream of ceramic grade ²³³UO₂ powder. The analytical method has combined isotope dilution and internal standard methods to permit the determination of impurities at concentrations between 0.1 and 500 ppm in a single sample.     

A Simple Coulometric Method for Determining Cu[II] and Cu[I] Contents in Various Solid Samples

Abstract

Determination of copper individual oxidation states (Cu[II] and Cu[I] in various solid samples is a rather difficult problem. Results are here presented to demonstrate that constant current coulametric techniques are useful to realize these determinations with good analytical characteristics. The analytical equivalence points obtained are based on the reversible electron transfer mechanisms: Cu[II] + 3 HC1 + 2 e CuCl^2? ₃ + 2H⁺ and : CuCl^2? ₃ +e = Cu(O) + 3 Cl^?, respectively, after quantitative dissolution in aqueous HC1 6 M. Cyclic voltammetric measurements with a carbon paste electrode are made to characterize the electron transfers involved and to investigate the analytical utility of the technique in various media. Analytical determinations are given, e.g., in the analysis of the CuO/Cu₂ O content of various samples.     

NaF-catalyzed efficient one-pot synthesis of dihydropyrano[2,3-c]pyrazoles under ultrasonic irradiation via MCR approach

Sodium fluoride was identified as an efficient catalyst for the preparation of series of dihydropyrano [2,3-c]pyrazoles (4a–l) by the three-component condensation of 3-Methyl-1-phenyl-2-pyrazoline-5-one (1), aromatic aldehydes (2) and malononitrile (3) in aqueous methanol at ambient temperature under ultrasonication. The cost and efficacy of the catalyst, mild reaction conditions, simple workup procedure, less reaction time and higher yields of the product with analytical purity keeping this protocol superior to the previously reported ones. Structures of all the compounds were in agreement with their spectroscopic data (¹H NMR, ¹³C NMR) and elemental (CHN) analyses.     

Recent Development on Determination of Low-Level 90Sr in Environmental and Biological Samples: A Review

In the context of the rapid development of the world’s nuclear power industry, it is vital to establish reliable and efficient radioanalytical methods to support sound environment and food radioactivity monitoring programs and a cost-effective waste management strategy. As one of the most import fission products generated during human nuclear activities, ⁹⁰Sr has been widely determined based on different analytical techniques for routine radioactivity monitoring, emergency preparedness and radioactive waste management. Herein, we summarize and critically review analytical methods developed over the last few decades for the determination of ⁹⁰Sr in environmental and biological samples. Approaches applied in different steps of the analysis including sample preparation, chemical separation and detection are systematically discussed. The recent development of modern materials for ⁹⁰Sr concentration and advanced instruments for rapid ⁹⁰Sr measurement are also addressed.     

The One Step Synthesis of 2-(2-Bromo-5- methoxyphenyl)-5-(3-arylidene)-1,3-thiazolo[3,2-b]- 1,2,4-triazol-6-(5H)-ones and the Evaluation of the Anticonvulsant Activity

A smooth one-step synthesis of 2-(2-bromo-5-methoxyphenyl)-5-(3-arylidene)-1,3-thiazolo[3,2-b]-1,2,4-triazol-6-(5H)-ones (4a–n) is described. The newly prepared compounds are characterized by analytical and IR, ¹ H NMR, ¹³ C NMR, and FABMS spectral analysis. A few compounds are screened for anticonvulsant activity. Compounds 4i and 4n exhibit promising anticonvulsant activity and are recommended for further studies.