Novel One Pot Regioselective Multicomponent Synthesis of Highly Functionlaized Spiro Pyrrolidines Through 1,3-Dipolar Cycloaddition Approach

Abstract

One-pot multicomponent synthesis of novel highly functionalized spiro pyrrolidine oxindoles has been accomplished in good yields through 1,3-dipolar cycloaddition reaction of azomethine ylide derived from sarcosine and oxindole with various benzimdazole substituted Baylis–Hillman derivatives. The regiochemical and stereochemical outcome of the multicomponent cycloaddition reaction is ascertained by spectroscopic studies, and one of the products was characterized through x-ray crystallographic analysis.     

Analysis of Polycyclic Aromatics

Abstract

Polycyclic aromatic hydrocarbons (PAH), among them carcinogenic compounds, have been found to be widely distributed in the human environment. The formation of PAH in processes relevant to environmental pollution will be described (pyrolysis or incomplete combustion of aliphatic and aromatic material, formation in higher plants). The application of the following methods to the analysis of PAH mixtures will be discussed: gas chromatography (capillary columns, use. of liquid crystals and inorganic salts such as LiCl or Cacl₂, as stationary phases in packed columns, selective detectors); luminescence spectroscopy (use of phosphorescence in paper and thin-layer chromatography, Shpol'skii spectra, quenchofluorimetry; mass spectroscopy.     

2-Benzylideniminobenzohydroxamic and 2-Sal Iciliden-Iminobenzohydroxamic Acids as Analytical Reagents for the Spectrophotometric Determination of mo(vi)

Abstract

The complexes formed between 2-benzylideniminobenzohydroxamic acid (2-BIBHA) and 2-salicylideniminobenzohydroxanic acid (2-SIBHA) and Mo(VI), have been studied spectrophotometrically on ethanolic-water and acetonic-water media, respectively.

Two methods for the spectrophotometric determination of Mo(VI) are proposed by using these reagents.     

Modern Analytical Methods for Monitoring Workplace Atmospheres

Abstract

Since measurements of exposure to hazardous substances were made obligatory in Germany under the Hazardous Material Regulation and Regulations for Accident Prevention there has been a need for widely-applicable, economic methods for determining airborne organic substance concentrations at workplaces. The relevant limits, which are based on toxicological and industrial hygiene data, are drawn up annually by the German Science Foundation and published as “Technische Regel für gefährliche Arbeitsstoffe” (TRgA 900) by the Ministry of Employment and Welfare.

Most organic substances, that have been assigned limits can be determined by gas liquid chromatography. The system described here is based on multicomponent GLC analysis. It has been used at BASF, the chemical-manufacturing company, where since 1979 approximately fifteen thousand workplaces have been evaluated. Hazardous substances have been detected at levels down to a few micrograms per cubic meter.

The standard system encompasses:

–-personal air samplers operating for 8 h;

–-adsorption by a solid sorbent;

–-desorption by solvent;

–-simultaneous GLC-separation on two different capillary columns;

–-computer correlation of the qualitative and quantitative data of the two chromatograms (plausibility check);

–-automatic print-out of the analytical report;

–-transfer of the results to a data bank for documentation.

Details are given of the method involving adsorption on activated charcoal and desorption with carbon disulfide. Benefits, cost advantages, and limitations are discussed.

Special sampling by means of other adsorbents (e.g. silica gel) in conjunction with special desorption, formation of derivatives, headspace analysis, and adsorption by liquids are techniques used to supplement the standard method of organic trace analysis in the field of industrial hygiene.     

Silica Sulphuric Acid: An Efficient and Recyclable Catalyst for the Synthesis of β‐Acetamido Ketones in Single Pot

Abstract

An efficient method has been developed for the synthesis of β‐acetamido ketones by a multicomponent condensation route using sulphuric acid on silica gel as an inexpensive catalyst. Catalyst was recycled without loss of activity.     

Multivariate Prediction by Using Conventional and Derivative Partial Least Squares Statistics in a Complex Chemical System. Ternary Metals Mixture Resolution

Abstract

The quantitative prediction abilities of Partial Least Squares methods (type 1 and 2) for analysis of conventional and derivative absorption spectra are compared. The influence of the band width and of the spectral overlapping on the capacity of prediction of PLS in both cases are described and ternary mixtures of metals are resolved. To obtain analytes with adequate spectral characteristics the resolution of the metals has been accomplished by using the reaction with a cyclic hydroxamic acid and extraction into methyl isobutyl ketone (MIBK). Significant advantages have been found by application of differentiation techniques in combination with PLS-1 method.

     

Resolution of Overlapping Chromatographic Peaks Using a Genetic Algorithm

ABSTRACT

A genetic algorithm for resolution of overlapping chromatographic peaks (GAROCP) using real-number coding, non-uniform mutation and arithmetical crossover methods is described in this paper. It was applied to resolution of highly overlapped multicomponent high-performance liquid chromatographic peaks by fitting experimental chromatogram to the exponentially modified Gaussian (EMG) model. The genetic algorithm was used to find the minimum of fitting error to optimize the parameters in the EMG functions which determine the shape and area of each peak. The applicability of the method was investigated with both simulated signals calculated by EMG functions and experimental multicomponent overlapping chromatograms.     

In Situ Measurement of Electrode Slope and Gravimetric Multiple Standard Addition Analysis by Ion Selective Potentiometry Without Prior Calibration of Electrode

Abstract

Two methods of calculation for the determination of an unknown concentration by gravimetric multiple standard addition analysis using ion selective potentiometry without prior calibration of the electrode have been described. These are based on simple calculation procedures involving linear least square fitting to Gran's equation to evaluate first the actual electrode slope ‘in situ’, then the unknown concentration and the cell constant. One method is iterative and the other is noniterative. The applicability of the methods has been demonstrated by processing the experimental data obtained by using fluoride and uranyl ion selective electrodes.     

Quantitative molecular similarity analysis (QMSA) methods for property estimation: A comparison of property-based,arbitrary, and tailored similarity spaces

Three classes of arbitrary quantitative molecular similarity analysis (QMSA) methods have been computed using atom pairs, topological indices, and physicochemical properties. Tailored QMSA models have been developed using a selected number of TIs chosen by ridge regression. The methods have been applied to the K -nearest neighbor based estimation of log P of two sets of chemicals. Results show that the property-based and tailored QMSA methods are superior to the arbitrary similarity methods in estimating log P of both sets of chemicals     

Direct Atomic Absorption Analysis of Powdered Whole-Coal Slurries

Abstract

A procedure has been developed which permits the direct analysis of powdered whole-coal samples by atomic absorption or atomic emission methods using conventional instrumentation, thereby eliminating time-consuming ashing and sample-digestion procedures. Linear plots of the absorption signal intensity versus the elemental concentration of analyzed whole-coal samples were obtained for several elements. Preliminary results indicate this method is applicable for the estimation of both minor-level (eg., Fe and Ca) and trace-level (eg., Pb and Zn) constituents.     

Thermal analyses of synthetic high basicity sinters

The paper presents studies on synthetic sinters of given basicities (CaO/SiO₂ 1.7–2.1). These multicomponent systems include not only doped iron oxides but calcium ferrites and numerous silicate phases as well. Investigatons were carried out by complex research methods, first of all by thermal analysis. Reduction processes of the sinters were observed by the methods of polythermal analysis in CO/CO₂ atmosphere. The effect of mineral composition on physico-chemical properties of the sinters has been determined.     

Trace Analysis of Explosives by HPLC-Electron Capture Detection (HPLC-ECD)18

Abstract

HPLC-ECD and HPLC-GC-ECD instrumentation can be conveniently applied to the trace analysis of a wide variety of explosive materials in complex matrices. Limits of detection, sensitivity, and linearity plots for a number of standard explosives have been determined. These methods have now been applied to the real world analysis of explosives in post-blast residue debris, and the overall methods have been compared and confirmed via more conventional TLC approaches.     

Simultaneous Spectrophotometric Estimation and Validation of Three Component Tablet Formulation Containing Pioglitazone Hydrochloride,Metformin Hydrochloride and Glibenclamide

Abstract

Simultaneous estimation of active ingredients in multicomponent pharmaceutical products normally requires the use of separation techniques, such as HPLC, HPTLC, or GC, followed by their quantitation. Presented here are two spectrophotometric methods that do not require prior separation for simultaneous estimation of three drugs—pioglitazone HCl, metformin HCl, and glibenclamid—in a tablet formulation. Shimadzu UV 1700, capable of multicomponent analysis, was used for quantitation. In method I, absorbance of the sample solution was measured at 285 nm and 300 nm for the estimation of pioglitazone HCl and glibenclaimide, and at 237 nm for estimation of metformin hydrochloride, respectively. Method II is based on a multiwavelength spectroscopic method. Recording the absorbances of standard solutions at 237 nm, 268 nm, 280 nm, and 300 nm were processed by means of statistical calculations and results of the sample solution were obtained. All three drugs obey Beer's law in the concentration ranges used for the methods. The result of the analysis for both methods were tested and validated for various parameters according to ICH guidelines. The utility of the developed methods has been demonstrated by an analysis of commercial formulation containing all the three drugs.     

Fuzzy characterization and classification of solvents according to their polarity and selectivity. A comparison with the Snyder approach

Abstract

Advanced chemometric methods, such as fuzzy c-means, a semi-supervised clustering method, and fuzzy discriminant analysis, a robust supervised method, have been successfully applied for characterization and classification of 72 solvents according to the chemical parameters (P’ and x_i) developed by Snyder. The obtained results (fuzzy partitions) and parameters of the prototypes (robust fuzzy means) clearly demonstrated the efficiency and information power of the advanced fuzzy methods in solvent characterization and classification, and allow a rationale choice of a good solvent or an efficient mixture of solvents in chromatography and other fields. Also, this methodology generates the premises for future investigations using other different properties of solvents.     

Applications of Spectrometric Full Spectrum Quantitation (FSQ) Software for Multicomponent Analysis and Stability Studies of Pharmaceuticals

ABSTRACT

A rapid, simple, accurate and specific spectrophotometric procedure for analysis of multi-component mixtures and for assessment of drug stability in pharmaceutical products has been described. The proposed method relies on the application of the spectrophotometric full spectrum quantification (FSQ) software to overcome severe spectral overlap and to permit measurement of the individual components in mixtures with satisfactory degree of accuracy and precision. The potential of FSQ software for multicomponent analysis was elucidated by analyzing complex mixtures of highly overlapping spectra (aspirin/caffeine/salicylic acid) and mixtures of structurally similar compounds (cephalexin/ cephradine) and (ceftriaxone/ ceftazidime /cefotaxime). Furthermore, the robustness of the FSQ for stability studies was assessed by analyzing chloramphenicol in presence of its alkali-induced degradation products and famotidine in presence of its acid-induced degradation products. The validity of FSQ software for multicomponent analysis and stability studies was evaluated by comparing the results with those of HPLC methods. Statistical analysis indicated that the FSQ and HPLC data were consistent, however the FSQ method is faster, easier and more reliable.     

Determination of Dicyandiamide with Non-Aqueous Polar Eluent

Abstract

Epoxy powder paints are characterized by their dicyandiamide content. Dicyandiamide is determined on a amino bonded phase column with non-aqueous but polar eluent consisting of methanol and acetonitrile (5/95, v/v). The elution order of the components is that of normal phase but the eluent is more like reversed phase. This method is essentially faster than the previous methods in the analysis of dicyandiamide in multicomponent powder extracts.     

Trace Analysis in Industrial Research

Abstract

Public concern and legislative regulations governing environmental pollution have had a dramatic effect on chemists involved in industrial research. The need to establish both the presence and amounts of trace levels of pollutants in industrial products and wastes has become imperative. Since time and cost become important considerations in such analytical determinations, it is apparent that sensitive, rapid and reliable methods of trace analysis are required. Many experimental techniques have been employed to this end and active research programs exist to develop new techniques to make such analysis more efficient.

Techniques capable of determining many elements in a single examination of a sample are of particular interest. No single 'black box' approach is, or is likely to become, feasible for all species of interest. Nonetheless, certain multielement approaches provide adequate information on some species and also provide important guidelines on the determination of other species by more specialized techniques. Problems encountered and progress achieved by the application of various spectroscopic, chromatographic, electrochemical and chemical methods to the trace analysis of industrial materials will be discussed.     

Low and high frequency dielectric spectroscopy on a liquid crystal with the phase sequence N*-SA-S*c

Abstract

Broadband dielectric measurements on a multicomponent ferroelectric liquid crystal mixture have been performed. The alignment was homeotropic and the cell and sample holder were the same in the whole frequency range. Two relaxation processes have been observed in all liquid crystal phases with shapes given by the Havriliak-Negami and inverted Havriliak-Negami functions. Strengths and frequencies of both modes have been obtained for the different phases. The values of the latter and their activation energies allowed us to assign the low and high frequency mechanism to the molecular reorientation around the transversal axis and around the longitudinal axis, respectively. The behaviour of this high frequency mode does not show any jump in the S_A-S*_c phase transition, neither in the amplitude nor in the frequency, indicating that the appearance of the spontaneous polarization in the S*_c phase is not the consequence of the freezing of this mode.     

Comparison of Different Assay Methods for Determination of Elastase Activity

Abstract

Four different methods of pancreatic elastase (E. C. 3.4.21.11) assay have been compared: one use N-succinyl-(Ala)₃-paranitroanilide as a substrate; the three others use elastin, modified or not.

The former has been monitored either with a spectrophotometric or a conductimetric device.

All methods give a linear relationship with amounts of pancreatic elastase in the range 0–5 μg.

The conductimetric method is the only one using unmodified elastin which measures elastolysis in initial rate conditions, avoiding artificial amplification of hydrolysis if other proteases are present.     

Estimation of Performance Characteristics of an Analytical Method Using the Data Set Of The Calibration Experiment

Abstract

A model to calculate the analytical sensitivity, limit of detection, limit of determination and precision of a method of instrumental analysis through a data set obtained by calibration experiment using the statistical analysis of linear regression, is proposed. This model has been applied to spectrophotometric, spectrofluorimetric and chromatographic methods. The values obtained are independent of the instrument used and can be applied as a criterion of comparison between different methods proposed for the same analyte. Also, these characteristics have been calculated using the IUPAC suggested model and both results have been compared.