Automated determination of sugar in molasses

The importance of determining sugars in molasses is emphasized, and a short critical review of the methods available is presented. The difficulties and sources of errors in determining total sugar levels in molasses and sugar mixtures are discussed. A continuous automated procedure based on the hexacyanoferrate(III)/(II) redox reaction has been optimized by reducing the errors and interferences to a minimum. With this technique, sugar concentrations of 0–10 gl^-1 can be determined directly.     

Methodology for determining degree of hydrolysis of proteins in Hydrolysates: a review

Degree of hydrolysis (DH) is defined as the proportion of cleaved peptide bonds in a protein hydrolysate. Several methods exist for determining DH; the most commonly used of these include the pH-stat, trinitrobenzenesulfonic acid (TNBS), o-phthaldialdehyde (OPA), trichloroacetic acid soluble nitrogen (SN-TCA), and formol titration methods. The pH-stat method is based on the number of protons released during hydrolysis; the TNBS, OPA, and formol titration methods are based on the measurement of amino groups generated from hydrolysis. The SN-TCA method measures the amount of TCA-soluble nitrogen, rather than DH. The pH-stat is the simplest and most commonly used method, but does not determine peptide bonds directly. In addition, the accuracy of the method depends on the type of hydrolytic enzymes used, the size of the hydrolyzed peptides, and the reaction temperature. Generally, the TNBS and OPA methods compare well and do directly determine DH. However, the assumption that the response factor for all derivatized N-terminal amino acids is similar may lead to inaccuracies. In conclusion, there is no consensus as to the best method for determining the DH of protein hydrolysates; consequently, there is a need for a standardized approach if interstudy comparisons are to be made.     

Simultaneous determination of furaltadone and chloramphenicol in pharmaceuticals by derivative spectrophotometry and the derivative of the ratio spectra

Two methods for determining furaltadone and chloramphenicol in mixtures by first derivative spectrophotometry and the derivative of the ratio spectra are described. The procedures do not require any separation step. By both methods lower determination and detection limits are obtained. The methods were applied for determining the two compounds in two pharmaceutical products.     

Review of separation methods for the determination of ammonium/ammonia in natural water

Ammonium (NH₄⁺) and ammonia (NH₃) in aquatic ecosystems are of great interest to environmental scientists because they can be used to study the nitrogen cycle and as water quality indicators. Analytical separation methods developed in recent decades have been used widely to determine NH₄⁺ and NH₃ in aqueous solutions. This review presents an overview of state-of-the-art separation methods and analytical techniques for determining NH₃/NH₄⁺ in natural water, including chromatographic methods, electrophoretic methods, extraction methods, membrane-based gas diffusion methods, membraneless gas diffusion methods, passive sampling methods, and paper-based analytical methods. Common detection techniques that can be used in conjunction with particular separation methods are described, phase-transfer strategies (liquid-liquid, liquid-solid, liquid-membrane-liquid, and liquid-gas-liquid methods) are highlighted, and the strengths and weaknesses of the separation methods are discussed. The outlook, challenges, and expected future developments in the field of separation methods for determining NH₄⁺ and NH₃ in natural water are presented.     

Nichtchelatierende Farbstoffe als Basis empfindlicher spektrophotometrischer Methoden zur Bestimmung von Elementen

Zusammenfassung Zu den empfindlichsten, zur Spurenanalyse besonders geeigneten spektrophotometrischen Methoden gehören extraktions- und flotationsspektrophotometrische Methoden auf der Basis von lonenassoziaten unter Mitwirkung nichtchelatierender Farbstoffe. Eine Systematisierung der angewandten Gruppen basischer und saurer Farbstoffe wurde vorgenommen. Die Möglichkeiten der Bestimmung einzelner Elemente mit entsprechenden, nichtchelatierenden Farbstoffen wurden in erschöpfender Weise gezeigt. Anorganische und organische Liganden wurden angeführt, die die zu bestimmenden Elemente in die zur Assoziation mit Farbstoffen geeigneten Komplexanionen bzw.-kationen überführen. Probleme der Extraktion sowie der Extraktionsmittel wurden erörtert. Die Rolle sehr empfindlicher, zur Bestimmung kleiner Spurenmengen vieler Elemente geeigneter flotationsspektrophotometrischer Methoden wurde hervorgehoben.

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Non-chelating dyestuffs as basis for sensitive spectrophotometric methods for determining elements

Summary Extraction and flotation Spectrophotometric methods based on ion associates with participation of non-chelating dyestuffs are among the most sensitive Spectrophotometric methods and especially suitable for trace analysis. A systematization of the groups of basic and acid dyestuffs employed was undertaken. The possibilities of determining individual elements with appropriate non-chelating dyes were shown exhaustively. Inorganic and organic ligands were cited which convert the elements to be determined into complex anions or cations suitable for association with dyestuffs. Problems of extraction and the extractants were discussed. The role of very sensitive flotation Spectrophotometric methods suitable for determining small trace amounts of many elements was emphasized.

     

Determination of the molecular weight of polyoxypropylenepolyols by <Superscript>1</Superscript>H NMR spectroscopy

Commercial and laboratory samples of polyoxypropylenepolyols were studied by ¹H NMR spectroscopy at operating frequencies of 100 and 500 MHz. Various methods depending on the solvent used were suggested for determining the equivalent weight (molecular weight of the polyether per terminal hydroxy group). The ¹H NMR data are compared to the data obtained by chemical methods and gel permeation chromatography.     

Modification of the titrimetric method of analyzing pectin substances

A potentiometric variant of the titrimetric method of analyzing pectin substances has been developed which is distinguished by adequate accuracy and good reproducibility. The modified method has been tested on methyl (methyl 2,3-di-O-methyl-α,β-galactopyranosid)uronate and has been used for determining the free (K_f) and esterified (K_e) carboxy groups of the pectin substances of mint. The methods of isolating, purifying, and fractionating the pectin substances and determining their K_f and K_e values are given. Formulas are presented for calculating the percentage values of K_f and K_e.     

Determination of Silicon, Phosphorous, Arsenic, and Germanium as Heteropoly Acids

Data reported in the literature on the methods for determining silicon, phosphorous, arsenic, and germanium as molybdenum, tungsten, and mixed heteropoly acids are systematized. The analytical methods and their potentialities are compared. Special attention is paid to preconcentration methods and the chromatographic determination of heteropoly acids.     

Using gold nanoparticles in spectrophotometry

Published data on the use of gold nanoparticles in spectrophotometry are summarized. Data on methods for preparing gold nanoparticles and their optical properties are presented. The main approaches on which spectrophotometic methods of substance determination using gold nanoparticles are based are discussed. Examples of determining of metal ions, anions, and organic compounds are presented.     

Theoretical methods in thermodynamics of condensed phases

Theoretical possibilities of determining energetic and thermodynamic characteristics of chemical entities in gaseous and condensed (solid and liquid) phases are briefly reviewed. The considerations include quantum chemistry methods which enable evaluation of energetic quantities and statistical thermodynamics dependencies necessary for determining other thermodynamic characteristics. The possible applications of these methods are also discussed in brief.     

Electron energy levels in semiconductor electrochemistry

The significance of the flat-band potential and the energetic position of the band edges at the semiconductor/electrolyte interface in semiconductor electrochemistry and photoelectrochemistry is pointed out. Different methods for determining these parameters experimentally are discussed, such as methods based on the measurement of the photovoltage or photocurrent, as well as the method for determining the flat-band potential from interfacial capacitance measurements. The capacitance-voltage relationship of the ideal semiconductor/electrolyte Schottky barrier is described. Subsequently, possible complications of the capacitance behavior are discussed, and conditions indicated under which the determination of the flat-band potential from non-ideal capacitance results is still possible. A critical survey is then given of flat-band data for some selected semiconductor electrodes (ZnO, CdS, GaP, GaAs, TiO₂, SrTiO₃), comprising a discussion of problems encountere, factors on which the flat-band potential depends and discrepancies between different results. Attempts to predict the flat-band potential and the position of the band edges from atomic electronegativity data are reviewed. The relationship between flat-band potential or band-edge position and electrochemical behaviour is considered, i.e., as far as the magnitude of the photovoltage as well as the electrochemical and photoelectrochemical reactivity are concerned.     

Comparative study of solvent extraction and thermal desorption methods for determining a wide range of volatile organic compounds in ambient air

This paper compares two analytical methods for determining levels of 90 volatile organic compounds (VOCs) commonly found in industrial and urban atmospheres. Both methods are based on two official methods for determining benzene levels and involve collecting samples by active adsorptive enrichment on solid sorbents. The first method involves solvent extraction and uses activated charcoal as a sorbent. After sampling, the sorbent is extracted with 1 mL of carbon disulfide and then 1 μL of the extract is analysed in a GC-MS. The second method involves thermal desorption (TD) and uses Tenax TA and Carbograph 1TD as sorbents, which allows the whole sample to be analysed. In general, the thermal desorption method showed the best repetitivity and recovery and the lowest limit of detection and quantification for all target compounds. Because of its lower sensitivity, the solvent extraction method needs the preconcentration of large sample volumes of air (720 L vs. 2.64 L for the thermal desorption method) to yield similar limits of detection.The performance of both methods in real samples was tested in a location near to a petrochemical complex. The results of the 24-h samples for the solvent extraction method were compared with the average of 12 2-h samples for the TD method. In some cases, both methods found differences in the VOC concentrations, especially in those compounds whose concentrations fluctuate significantly during the day.     

The 125th Anniversary of the Griess Reagent

The creation of the Griess reagent for nitrites is an example of the first directed synthesis of an organic reagent in analytical chemistry. In connection with the jubilee of the reagent, some aspects of the use of diazotization and azo coupling reactions for determining nitrites and nitrates are considered. It is shown that the Griess reaction is widely used at present; however, the components of this reaction and the methods for determining nitrites are continuously improved.     

Spectrophotometric determination of rosmarinic acid in plant cell cultures by complexation with Fe2+ ions

A spectrophotometric method for determining rosmarinic acid (α-O-caffeoyl-3,4-dihydroxyphenyllactic acid) in unpurified methanolic extracts from Lavandula cell cultures is reported. It is based on a complexation reaction of rosmarinic acid with Fe²⁺ to give a blue-dark product with λ_max=572 nm and ?₅₇₃=3.82×10³ l mol^?1 cm^?1. The stoichiometry of the reaction and the optimal conditions for colour development are checked. The sensitivity and accuracy of this spectrophotometric method are compared with UV-spectral and HPLC methods for determining rosmarinic acid in plant cell cultures; similar results are obtained.     

Determining the independent parameters in stationary kinetic equations for linear mechanisms

Coloring methods in graph theory are used in estimating the number of parameters to be determined in a kinetic model corresponding to a linear mechanism. The estimates are based on determining the numbers of differently colored frameworks. Examples are discussed of isomerization and an enzymatic reaction catalyzed by ammonoacyl-MRNA synthetase.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 2, pp. 187–191, March–April, 1987.     

Analysis of insect chemosterilants.

Background information concerning the concept of insect chemosterilization and analytical methods for determining trace levels of 19 P- and/or S- containing chemicals of current interest are presented. GC retention times of the compounds on 6 different columns and their p-values in 11 solvent systems are tabulated. The utility of the flame photometric detector for determining subnanogram levels of the sterilants in biological substrates is illustrated.     

Electrochemical biosensors based on nucleic acids and their use in bioaffinity assays for determining DNA and and its effectors

The analytical capabilities of electrochemical biosensors based on nucleic acids are systematized. Immobilization methods that retain the biological activity of nucleic acids and provide an opportunity to use them as multipurpose analytical reagents are described. The use of the above sensors in bioaffinity assays for determining DNA and its effectors in biochemical analysis and environmental monitoring and for determining the nucleotide composition of DNA is demonstrated in many examples.     

Study of the structural and electronic origin of the sandalwood odor of some terpenylcyclohexanols

Abstract  

The correlation between structural and electronic features and the sandalwood odor of some terpenylcyclohexanols is established on the basis of quantum chemical calculation methods. A definite structural fragment with electronic properties determining the origin of the odor is revealed. The effects of HOMO–LUMO energy gaps and total energies of some terpenylcyclohexanols on their odor intensity are investigated.     

Fluorimetric determination of pyrene:protein association ratios

Two fluorimetric methods for determining pyrene:protein association ratios are described. The methods are useful for measuring the uptake by proteins of small, fluorescent molecules with limited aqueous solubility (10^-6 M or less). The association ratios (moles pyrene per mole protein) determined by the two methods were found to be:bovine β-lactoglobulin (0.32, 0.33), human serum albumin (0.44, 0.42), bovine γ-globulin (0.23, 0.20), and human γ-globulin (0.04, 0.00).     

Using solid-phase microextraction combined with gas chromatography-mass spectrometry for the study of the volatile products of biosynthesis released by plants and microorganisms

Published data on the methods and results of study of profiles of volatile biologically active compounds are summarized and discussed. The leading role of gas chromatography-mass spectrometry combined with headspace solid-phase microextraction as an optimum analytical method for determining the qualitative and quantitative composition of volatile organic compounds in in vivo experiments is substantiated. The results of investigation of volatile organic compounds produced by micromycetes of the genus Fusarium are reviewed.