Showing papers in "Analyst in 1984"
TL;DR: In this article, a procedure for the measurement and characterisation of total non-starch polysaccharides in plant foods by gas-liquid chromatography of individual sugars as alditol acetates is described.
Abstract: A procedure is described for the measurement and characterisation of total non-starch polysaccharides in plant foods by gas-liquid chromatography of individual sugars as alditol acetates. Starch, including that resistant to gelatinisation in boiling water, is dispersed with dimethyl sulphoxide and then hydrolysed with α-amylase and pullulanase. Starch-free material is hydrolysed with sulphuric acid and the released neutral sugars are measured as alditol acetates by using N-methylimidazole in order to catalyse the acetylation. Uronic acids are measured by a spectrophotometric method. The procedure is a modification of a more comprehensive method reported previously. It is relatively rapid and simple compared with gravimetric procedures, is applicable to a wide range of foodstuffs, can be carried out without special expertise in carbohydrate chemistry and is suitable for routine laboratory use.
1,007 citations
839 citations
TL;DR: A method, based on high-performance liquid chromatography, is described for the determination of chlorogenic acid isomers in instant coffee using a wide range of commercially available instant coffees.
Abstract: A method, based on high-performance liquid chromatography, is described for the determination of chlorogenic acid isomers in instant coffee. Identification of the individual components was assisted by the preparation of isomeric mixtures by the isomerisation of available compounds and quantification based on published ultraviolet molar absorptivities. A number of extraction and clearing techniques were studied to determine the optimum conditions for the recovery of all the isomers present. The developed method was applied to a wide range of commercially available instant coffees.
176 citations
TL;DR: In this article, transition metal interferences in the determination of selenium using the hydride generation AAS technique were investigated in a system in which the seenium hydrides is generated in pure acid solution and comes into contact with the metal ions only in a second flask.
Abstract: Transition metal interferences in the determination of selenium using the hydride generation AAS technique were investigated in a system in which the selenium hydride is generated in pure acid solution and comes into contact with the metal ions only in a second flask. All investigated elements interfere in the ionic form with selenium when they are present in sufficiently high concentrations. Whenever a precipitation of the metallic species occurs, however, capture and decomposition of the selenium hydride by the finely dispersed metal appear to be the predominant mechanism of interference. In addition, this solid-gas reaction occurs typically at considerably lower interferent concentrations than the liquid-gas reaction of the ionic species. A substantial increase in the range of interference-free determination of selenium can be achieved by increasing the acid concentration of the solution for measurement because of the increased solubility of the reduced metal in the strong acid.
135 citations
TL;DR: In this paper, the construction of a pH sensor, having the configuration of a probe, is described, which utilises a plastic-fibre bundle at the end of which is fabricated a sensitive tip consisting of a styrene-divinylbenzene copolymer supporting an adsorbed colorimetric pH indicator, which is retained in position by a membrane of polytetrafluoroethylene (PTFE).
Abstract: The construction of a pH sensor, having the configuration of a probe, is described. The probe utilises a plastic-fibre bundle at the end of which is fabricated a sensitive tip consisting of a styrene-divinylbenzene copolymer supporting an adsorbed colorimetric pH indicator, which is retained in position by a membrane of polytetrafluoroethylene (PTFE). Changes in pH in the vicinity of the sensitive tip cause a variation in the attenuation of specific reflected visible radiation bands. Initial results and performance specifications using bromothymol blue as the colorimetric indicator are presented.
135 citations
108 citations
TL;DR: In this paper, a haute performance des reactifs fluorigenes suivants for amines primaires, secondaires: o-phtalaldehyde, fluorexamine, chlorure de dansyle, halogenonitrobenzofurazanne and thiols: maleimide N-substitues, dansylaziridine, bimanes and halogenosulfonylbenz ofurazannes
Abstract: Revue bibliographique (263 references) de la reactivite, selectivite, stabilite, caracteristiques de fluorescence et application a la chromatographie liquide a haute performance des reactifs fluorigenes suivants pour amines primaires, secondaires: o-phtalaldehyde, fluorexamine, chlorure de dansyle, halogenonitrobenzofurazanne et pour thiols: maleimide N-substitues, dansylaziridine, bimanes et halogenosulfonylbenzofurazannes
101 citations
TL;DR: In this article, the acquisition and manipulation of contour spectra and the problems and benefits of generally available corrected fluorescence spectra are discussed and some probable future developments in these areas are indicated.
Abstract: Recent developments in photoluminescence and chemiluminescence spectroscopy are summarised, with particular reference to methods for improving the selectivity of luminescence analyses. The acquisition and manipulation of contour spectra and the problems and benefits of generally available corrected fluorescence spectra are discussed. Fluorescence and chemiluminescence immunoassays are evaluated and some probable future developments in these areas are indicated.
97 citations
TL;DR: In this article, a significant influence of the valency state of arsenic was found on the degree of signal depression owing to transition metals in hydride generation AAS, which supports the theory that the interferences are due to a gassolid reaction.
Abstract: A significant influence of the valency state of arsenic was found on the degree of the signal depression owing to transition metals in hydride generation AAS. This phenomenon can be explained by the slower evolution of arsine from As(V) in comparison with As(III) and the more complete precipitation of the interfering metals by the time the hydride is formed. This observation supports the theory that the interferences are due to a gassolid reaction.
82 citations
79 citations
TL;DR: Results of studies using a flow-cell and immobilised indicator dye reagents for the development of a chemically sensitive fibre-optic system for measurement of pH are presented.
Abstract: Results of studies using a flow-cell and immobilised indicator dye reagents for the development of a chemically sensitive fibre-optic system for measurement of pH are presented. The indicator dye reagents are immobilised on a cross-linked styrene-divinylbenzene polymer matrix and reflectance measurements are made as a function of pH using a bifurcated fibre-optic system.
TL;DR: Human serum albumin has been labelled with a terbium complex by means of a reagent prepared from the bis-cyclic anhydride of diethylenetriamine pentaacetic acid and p-aminosalicylic acid, which combines high fluorescent intensity with stability at high dilution.
Abstract: Human serum albumin has been labelled with a terbium complex by means of a reagent prepared from the bis-cyclic anhydride of diethylenetriamine pentaacetic acid and p-aminosalicylic acid. This reagent combines high fluorescent intensity with stability at high dilution (10–9M). The fluorescent conjugate so produced has been used in a simple fluoroimmunoassay, using human serum albumin as a model analyte.
TL;DR: In this article, a preferential reduction of Fe(III) to Fe(II), which inhibits the precipitation of the interfering nickel as the metal, is proposed mechanism of reaction, which can extend the range of interference-free determination for these elements by three orders of magnitude.
Abstract: Iron(III) has a releasing effect on the interference due to nickel on the determination of arsenic and selenium. Together with an increase in the acid concentration of the solution for measurement, this effect can extend the range of interference-free determination for these elements by three orders of magnitude. A preferential reduction of Fe(III) to Fe(II), which inhibits the precipitation of the interfering nickel as the metal, is the proposed mechanism of reaction.
TL;DR: The construction and performance characteristics of ion-selective membrane electrodes for phenothiazine drugs based on their ion-pair complexes with tetraphenylborate and dinonylnaphthalene sulphonate in a poly(vinyl chloride) matrix are described.
Abstract: The construction and performance characteristics of ion-selective membrane electrodes for phenothiazine drugs based on their ion-pair complexes with tetraphenylborate and dinonylnaphthalene sulphonate in a poly(vinyl chloride) matrix are described. The electrodes show a near-Nernstian response over various ranges depending on the nature of the phenothiazine drug. The selectivity of these electrodes to a number of amino acids, alkaloids, neurotransmitters, quaternary ammonium compounds and other drugs or pharmaceutical excipients is reported. The standard additions method and potentiometric titrations are used to determine the phenothiazine drugs in pharmaceutical preparations with satisfactory results.
TL;DR: In this paper, a spectrophotometric detection system was proposed for determinations of transition and rare earth metal ions by post-column mixing with the colour-forming reagents PAR and Arsenazo I, respectively, measuring the absorbance at 498 and 600 nm.
Abstract: Conventional ion chromatography excludes the analyses of anionic species with pK > 7, and transition metals that can form hydroxide precipitates at neutral pH. These limitations come from the combined characteristics of the suppressor column and the electrical conductivity detector. By suitable selection of the detection system, an extension of analytical limits can be achieved. For fast and accurate analyses of cyanide and sulphide ions, with an electrochemical method involving a silver sulphide based ion-selective electrode and a high pH buffered eluent, the detection limit can reach the p.p.b. level. For determinations of transition and rare earth metal ions, a spectrophotometric detection system is proposed. By post-column mixing with the colour-forming reagents PAR and Arsenazo I, respectively, transition metal and rare earth metal ions can be monitored by measuring the absorbance at 498 and 600 nm. The detection limit can reach the 0.1 p.p.m. level with good precision. The working principle and reaction mechanism of the proposed methods are also discussed in detail.
TL;DR: A multi-residue method for the determination of organochlorine, organophosphorus and synthetic pyrethroid pesticides and carbaryl in grain is presented.
Abstract: A multi-residue method for the determination of organochlorine, organophosphorus and synthetic pyrethroid pesticides and carbaryl in grain is presented. After extraction with acetone-methanol, the pesticides are separated from co-extractives by a partition process with dichloromethane and chromatography on an acidic aluminium oxide column. Quantitative determinations are made by packed column gas-liquid chromatography using an electron-capture detector for the organochlorine pesticides and a flame-photometric detector for the organophosphorus pesticides. High-performance liquid chromatography using an ultraviolet spectrophotometric detector is used for the determination of synthetic pyrethroids and carbaryl. Capillary column gas-liquid chromatography is used for confirmation of identity of suspected residues of organochlorine, organophosphorus and synthetic pyrethroid pesticides.
TL;DR: In this article, a general approach to the speciation of metals present in mixed oxidation states is described, which employs the use of sequential spectrophotometric and atomic absorption detectors in a flow injection system.
Abstract: A general approach to the speciation of metals present in mixed oxidation states is described. It employs the use of sequential spectrophotometric and atomic-absorption detectors in a flow injection system.The application of this approach is illustrated by two examples. (1) The determination of chromium(VI) and total chromium in corrosion test sea water: this system can operate at up to 120 injections per hour with an injected sample volume of 30 µl. The working ranges are 1–50 p.p.m. of total chromium and 0.1–20 p.p.m. of chromium(VI). (2) The determination of iron(II) and total iron in mineral process solutions: this system can also operate at up to 120 injections per hour using either a 20-or a 100-µl sample. A 20-µl sample gave linear working ranges of 5–120 p.p.m. of total iron and 0.5–120 p.p.m. of iron(II), and a 100-µl sample gave working ranges of 0.5–25 p.p.m. of total iron and 0.2–25 p.p.m. of iron(II).Short-term repeatability and interference studies are discussed.
TL;DR: An examination of the temperature-time curves for heating in the drying stage showed that programmed ramp times for drying are rarely necessary and programme times of around 60 s have been achieved; this includes the time for automatic sampling.
Abstract: Reductions in the analysis times required in electrothermal atomic-absorption spectrometry can be achieved by a critical examination of the function and timing of the steps in the heating programme. An examination of the temperature-time curves for heating in the drying stage showed that programmed ramp times for drying are rarely necessary. For most samples, drying can be achieved in under 10 s using temperatures of 130–140 °C with standard graphite tubes. Some analyses (lead in blood and copper in urine) have been found to work well without an ashing stage. For copper in urine, the ashing stage was shown to have no influence in reducing the background absorption or in affecting interferences. Using these techniques, programme times of around 60 s have been achieved; this includes the time for automatic sampling (29 s).
TL;DR: In this paper, the number of electrons involved in anodic electroactivity has been determined at rotating disc electrodes of platinum and gold in sulphuric acid and in buffer media by single scan voltammetry.
Abstract: Anodic electroactivity, shown by clomipramine, desipramine, dibenzepin, dothiepin, imipramine, opipramol and trimipramine has been studied at rotating disc electrodes of platinum and gold in sulphuric acid and in buffer media by single scan voltammetry, and at stationary disc electrodes by cyclic voltammetry. Potentiostatic and amperostatic coulometry have been used to determine the number of electrons involved in the reactions. Rapid voltammetric determinations of the active drugs have been evaluated in the best medium, 0.1 mol l–1 sulphuric acid. Adsorption of the oxidation product on the electrodes prevents determination of clomipramine and restricts the concentration range for imipramine and trimipramine. The kinetic parameters, half-wave potentials, mass and charge-transfer rate constants and charge-transfer coefficients have been determined under a wide range of conditions. Electrode reaction mechanisms have been elucidated. Dothiepin is oxidised by a single four-electron step to the sulphone. The azepines are oxidised to a radical that dimerises rapidly before a further one-electron step produces the dimer diradical; opipramol can undergo a further four-electron oxidation of the piperazine ring in the side chain to the 1,4-dihydropyrazine derivative.
TL;DR: By immobilisation of the enzymes, mainly by chemical binding to Eupergit, a considerable increase in their stability could be achieved, and electrodes were obtained with a half-life of 8.5 d, a response time, τ½, of 3.5 min and linear responses over four orders of magnitude.
Abstract: In the context of the development of enzyme electrodes for the determination of the substrates of dehydrogenases, different systems for the oxidation of NADH were tested. In a homogeneous system with the dehydrogenase, NAD+ and phenazine methosulphate, the oxygen consumption caused by oxidation of the substrate was determined with a Clark electrode. Satisfactory sensitivity and reproducibility were obtained in the range 0.04–1 mM for several substrates, but the enzyme was rapidly denatured by the mediator. The physical entrapment of dehydrogenases together with a water-forming NADH oxidase on a Clark electrode yielded enzyme electrodes for different substrates with linear responses in the range 0.1–10 mM and a response time of 2 min. Owing to the instability of the NADH oxidase, the half-life of the electrodes was less than 5 h. The most promising systems were obtained by the coupling of the dehydrogenases to 3-β-naphthoyl-Nile Blue-modified graphite electrodes leading to oxygen-independent catalysed electrochemical NADH oxidation. The systems were optimised with regard to the NAD+ concentration in the solution and the pore size of the membranes covering the electrodes. By immobilisation of the enzymes, mainly by chemical binding to Eupergit, a considerable increase in their stability could be achieved, and electrodes were obtained with a half-life of 8.5 d, a response time, τ½, of 3.5 min and linear responses over four orders of magnitude.
TL;DR: A rapid, high-performance liquid chromatographic (HPLC) method for the determination of vitamins A and D in fortified skimmed milk powder (SMP) is described and details of recoveries of added vitamins and the precision are given.
Abstract: A rapid, high-performance liquid chromatographic (HPLC) method for the determination of vitamins A and D in fortified skimmed milk powder (SMP) is described. Either vitamin D2 or D3 is added as an internal standard, depending upon which formulation has been used for fortification, and the sample is saponified and extracted. Vitamin A can be determined directly (without further clean-up) in a portion of this extract using reversed-phase HPLC. Vitamin D is determined on the remainder of the extract after clean-up using a Sep-pak cartridge and the same HPLC system. Details of recoveries of added vitamins and the precision of the method are given.
TL;DR: Description d'une methode rapide et sensible, impliquant la conversion des groupes amines de l'hydroxylysine en derives fluorescents a l'aide du chlorure de dansyle, avant the separation par chromatographie en phase inverse.
Abstract: Description d'une methode rapide et sensible, impliquant la conversion des groupes amines de l'hydroxylysine en derives fluorescents a l'aide du chlorure de dansyle, avant la separation par chromatographie en phase inverse
TL;DR: Performance characteristics of the FIA-ICP-AES technique are documented in terms of the effects of sample injection volume and carrier stream flow-rate on sensitivity and precision.
Abstract: A rapid and precise method for the simultaneous determination of Na, K, Ca, Mg, Li, Cu, Fe, and Zn in blood serum by flow injection analysis-inductively coupled plasma atomic-emission spectrometry (FIA-ICP-AES) has been developed using aqueous synthetic multi-element solutions for calibration. Performance characteristics of the FIA-ICP-AES technique are documented in terms of the effects of sample injection volume and carrier stream flow-rate on sensitivity and precision. Matrix interference was detected for injections of undiluted serum and the effect was minimised at low injection volumes and/or by using a relatively high RF power. At dilution factors of 1 + 1 (or greater) interference was not observed and reliable data were obtained for human and bovine serum pools for sample injections of 20 µl.
TL;DR: The possibility of using a continuum primary source in atomic-absorption spectrometry, rather than separate line sources for each element as is the conventional practice, has been a recurring theme in the literature of atomic absorption for many years as discussed by the authors.
Abstract: The possibility of using a continuum primary source in atomic-absorption spectrometry, rather than separate line sources for each element as is the conventional practice, has been a recurring theme in the literature of atomic absorption for many years. Past efforts have not been particularly successful. Recent advances in optical technology and data processing techniques have made this approach much more promising. Simultaneous multi-element atomic absorption, with flame and electrothermal atomisation, is now being carried out routinely with prototype instrumentation built by researchers. This approach may offer a future path for the continued development of atomic absorption.
TL;DR: In this paper, a gas-chromatographic determination of residual sulphide, or of the produced sulphoxide, affords a quantitative evaluation of the peracid present in the mixture.
Abstract: The oxidation of organic sulphides is very fast with peracids and very slow with hydrogen peroxide. Thus, addition of an excess of methyl p-tolyl sulphide to a mixture of an organic peracid and hydrogen peroxide results in the formation of methyl p-tolyl sulphoxide equimolar with the peracid. The gas-chromatographic determination of the residual sulphide, or of the produced sulphoxide, affords a quantitative evaluation of the peracid present in the mixture. The method has been applied to the determination of m-chloroperbenzoic acid and peracetic and perpropionic acids.
TL;DR: The fact that blue shifts of the fluorophore were observed depending on the hydrophobicity of the added solvents indicated the possibility of its use for the environmental analysis of reactive thiols of macromolecules with SBD-F.
Abstract: The fluorigenic reaction of thiols with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F) and the factors that affected the fluorescence of SBD-thiols were investigated. High pH, high temperature and organic solvents increased the reaction rates. The fluorescence intensity of the fluorophore was dependent on pH. Under suitable conditions (at pH 9.5 and 60 °C for 1 h), the detection limits for thiols such as cysteine, glutathione, captopril and bovine serum albumin were in the range 43–520 pmol ml–1. The fact that blue shifts of the fluorophore were observed depending on the hydrophobicity of the added solvents indicated the possibility of its use for the environmental analysis of reactive thiols of macromolecules with SBD-F.
TL;DR: Cyclic voltammetry has been used to study the reduction of phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone) at a planar glassy-carbon electrode and the reaction was found to be quasi-reversible with adsorption of the product, but not the reactant, taking place at the electrode surface.
Abstract: Cyclic voltammetry has been used to study the reduction of phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone)(vitamin K1) at a planar glassy-carbon electrode. The reaction was found to be quasi-reversible with adsorption of the product, but not the reactant, taking place at the electrode surface. Liquid chromatography with electrochemical detection was used to determine endogenous levels of phylloquinone in human plasma. The normal range was found to be 0.08–1.24 ng ml–1; the mean value was 0.41 ng ml–1. The electrochemical assay was shown to be about three times as sensitive as the previous liquid chromatographic method in which the naphthoquinone was detected by its ultraviolet absorption. Agreement between the two methods was good when phylloquinone was added to plasma in the range 0–4.8 ng ml–1(r= 0.91; 0.001 < p <0.01).
TL;DR: In this article, the analysis of chromium in steel by atomic absorption spectrometry is discussed and the basis of the flow injection standard additions method explained, in which the novel configuration of using the sample as the carrier stream is employed.
Abstract: The determination of chromium in steel by atomic-absorption spectrometry is briefly reviewed and the basis of the flow injection standard additions method explained, in which the novel configuration of using the sample as the carrier stream is employed. The effects of iron, fuel to oxidant ratio and dissolution procedure were investigated and a procedure is described that allows a conventional instrument-optimising strategy to be used, requires no releasing agents and uses pure chromium standard solutions. The selection of appropriate flow injection conditions is discussed in the light of the single well stirred mixing chamber model for dispersion. The application of the method is demonstrated by the analysis of six British Chemical Standard steels.