Showing papers in "Analyst in 1980"
TL;DR: In this paper, a simple and rapid method for the spectrophotometric determination of hydrogen peroxide using potassium titanium(IV) oxalate is described, which can be used to measure peroxide concentrations down to about 10 µM (0.3 mg kg-1) under the most favourable conditions.
Abstract: A simple and rapid method for the spectrophotometric determination of hydrogen peroxide using potassium titanium(IV) oxalate is described. The method can be used to measure peroxide concentrations down to about 10 µM(0.3 mg kg–1) under the most favourable conditions. A variety of complexing and reducing agents, and catalysts of peroxide decomposition, known to interfere with the alternative iodide method for peroxide determination, had no effect. Fluoride was found to interfere.
783 citations
TL;DR: In this article, a reaction scheme for the spectrophotometric determination of ammonia by means of a modified Berthelot reaction is proposed, in which salicylate, dichloroisocyanurate and complex cyanides are the principal reagents.
Abstract: A reaction scheme for the spectrophotometric determination of ammonia by means of a modified Berthelot reaction is proposed, in which salicylate, dichloroisocyanurate and complex cyanides are the principal reagents. The experimental results presented are consistent with, and support, the reaction scheme proposed. It is suggested that the complex cyanides act on two stages of the reaction, firstly to stabilise monochloramine at pH values (12–13) at which it is normally unstable and hence facilitate the formation of 5-aminosalicylate from salicylate (this step is the rate determining step of the reaction), and secondly, to accelerate the oxidative coupling of 5-aminosalicylate with salicylate to form the indophenol dye [possibly via a hexacyanoferrate(III) intermediate]. It is shown that the optimum pH of reaction is a result of a complex inter-relationship of a number of equilibria and it thus remains necessary to optimise the pH value for each combination of reagents used. The implications of this study on the choice of reagents for the determination of ammonia by the Berthelot reaction are noted.
619 citations
103 citations
TL;DR: A simple method for the determination of total iodine in food, based on the catalytic destruction of thiocyanate by nitrite in the presence of iodide, has been evaluated and the colorimetric finish technique automated.
Abstract: A simple method for the determination of total iodine in food, based on the catalytic destruction of thiocyanate by nitrite in the presence of iodide, has been evaluated and the colorimetric finish technique automated. Optimum conditions for the destruction of organic matter and the liberation of iodine have been investigated and a set of conditions applicable to the automated finish technique developed. The method, when applied to 160 foods, had a precision of about 10%, a detection limit for iodine of 1 µg per 100 g of food, a mean recovery of added iodide of 90% and an output of about 70 samples per week. The effect of storage conditions on the iodine content of fish and eggs has also been examined, and the effect of some possible interfering substances, such as chloride, bromide and mercury, investigated.
91 citations
87 citations
TL;DR: In this article, the effects of some matrix and concomitant elements on the determination of cadmium and arsenic by optical emission spectrometry with an inductively coupled plasma using sample introduction with a graphite rod electrothermal vaporization device have been investigated.
Abstract: The effects of some matrix and concomitant elements on the determination of cadmium and arsenic by optical emission spectrometry with an inductively coupled plasma using sample introduction with a graphite rod electrothermal vaporisation device have been investigated. These effects are shown to be caused by variations in pre-vaporisation loss of analyte and analyte transport efficiency to the plasma. Selenium (VI) is shown to effect matrix stabilisation and to improve sample transport efficiency via experiments utilising radio-active cadmium-115m as a tracer.
80 citations
TL;DR: A procedure for the determination of nitrate and nitrite in meat products by a direct potentiometric method with a nitrate ion-selective electrode and results obtained were compared with those obtained by recommended spectrophotometric methods.
Abstract: A procedure for the determination of nitrate and nitrite in meat products by a direct potentiometric method with a nitrate ion-selective electrode is presented. The soluble nitrate and nitrite were extracted from the meat products with a Soxhlet extractor using borax buffer solution (pH 9). The effect of pH on the recovery of nitrite and nitrate was studied. Results obtained by the proposed method were compared with those obtained by recommended spectrophotometric methods. Storage of samples before analysis was also studied.
77 citations
TL;DR: The ease, rapidity and safety by which samples can be processed by this method make it suitable for the routine preparation of a large number of samples simultaneously.
Abstract: A simple and rapid digestion method is reported for the simultaneous acid extraction of chromium, copper, zinc, cadmium, nickel and lead from high-fat fish tissue. Samples are digested with nitric and sulphuric acids at 150 °C in a modified aluminium hot-block. The method is specially set up for fish sample sizes of up to 5 g, for low level detection of these elements. After digestion, acid extracts of the sample are analysed by direct flame atomic-absorption spectrometry for copper, zinc and chromium. The other three elements, cadmium, nickel and lead, are concentrated by chelation with ammonium tetramethylene dithiocarbamate followed by solvent extraction with isobutyl methyl ketone and determined by flame atomic-absorption spectrometry. The ease, rapidity and safety by which samples can be processed by this method make it suitable for the routine preparation of a large number of samples simultaneously.
59 citations
TL;DR: In this paper, the evolution of inorganic arsenic(III) by hydride evolution directly into an atomic-absorption system was found to be subject to error when organic forms of arsenic (such as dimethylarsinic acid) were present.
Abstract: Speciation of inorganic arsenic(III) by hydride evolution directly into an atomic-absorption system was found to be subject to error when organic forms of arsenic (such as dimethylarsinic acid) were present Organic forms of arsenic can produce an underestimation of total arsenic when the hydride response from concentrated acid is quantitated against inorganic arsenic Hydride responses from solutions of various acidities are reported for dimethylarsinic acid, monomethylarsonic acid, inorganic arsenic(III) and inorganic arsenic(V) Even simultaneous equations did not provide a means of resolving mixtures of the four arsenic species investigated by using direct analysis of the evolved hydrides
52 citations
TL;DR: An automated procedure for the determination of soluble arsenic, using hydride generation atomic absorption spectroscopy, is described and optimised operating conditions are derived in this article, where the detection limit (based on twice the standard deviation for 15 blank measurements) is 0.90 ng ml-1 of arsenic for arsenic(III), arsenic(V) and methylarsenic species.
Abstract: An automated procedure for the determination of soluble arsenic, using hydride generation atomic-absorption spectroscopy, is described and optimised operating conditions are derived. Interferences are observed in the presence of silver(I), gold(III), iron(III), platinum(IV), antimony(III), strontium(II), fluoride and sulphide but can be overcome by suitable pretreatment procedures. The detection limit (based on twice the standard deviation for 15 blank measurements) is 0.90 ng ml–1 of arsenic for arsenic(III), arsenic(V) and methylarsenic species. A 10% negative bias of results is observed in the determination of dimethylarsenic species.
50 citations
TL;DR: In this paper, an inductively coupled plasma-volatile hydride method was used to detect trace amounts of arsenic, antimony and bismuth in soils and sediments.
Abstract: Trace amounts of arsenic, antimony and bismuth in soils and sediments are determined simultaneously by an inductively coupled plasma-volatile hydride method after rapid attack with concentrated hydrochloric acid in sealed tubes. The samples are treated with the acid at 150 °C for 2 h in capped test-tubes. After addition of potassium iodide solution, the hydrides are formed by mixing the solution with sodium tetrahydroborate(III) solution in a continuous-flow system, and are swept into the plasma by a stream of argon for determination by atomic-emission spectrometry. Acceptable precision and accuracy are obtained, and the detection limits for all three analytes are about 0.1 µg g–1. Approximately 200 samples can be analysed by one person in a 2-d cycle.
TL;DR: In this paper, the luminescence of petroleum derivatives is discussed with reference to a standard technique for their differentiation based on synchronous fluorescence spectroscopy, and various spectral features that differ between samples are defined.
Abstract: The luminescence of petroleum derivatives is discussed with reference to a standard technique for their differentiation based on synchronous fluorescence spectroscopy. The spectra are highly sensitive to quenching by oxygen and by halogenated compounds; for general-purpose use, solutions of samples (in hydrocarbon solvents) must be deoxygenated. Although the quantum yield of the fluorescence is of the order of 0.15, the fluorescence is distributed over a wide wavelength range and, at the sample concentrations usually required in order to obtain satisfactory spectra, significant inner filter effects are often present and corrections must be made for these. Various spectral features that differ between samples are defined. After correction for instrumental and inner filter effects, the features are expressed numerically for evaluation and use in the pattern recognition study that will be described elsewhere in Part II. Examples of other types of spectra are considered in relation to the standard technique. These are synchronous and conventional fluorescence contour diagrams, synchronous derivative spectra, low-temperature synchronous fluorescence spectra and phosphorescence spectra.
TL;DR: The compositions of the samples obtained by using thin-layer chromatography, gas-liquid chromatography and high-performance liquid chromatography were compared and the relative merits of each method are discussed.
Abstract: Samples of the sulphates of polymyxin B and polymyxin E (colistin) have been assayed microbiologically. The content of phenylalanine was determined in the samples of polymyxin B. The compositions of the samples obtained by using thin-layer chromatography, gas-liquid chromatography and high-performance liquid chromatography were compared. The relative merits of each method are discussed.
TL;DR: In this paper, the authors examined the widely held view that the frequency distribution of analytical error is log-normal at concentrations of analyte near the detection limit, and argued that there is no theoretical reason why such distributions should be lognormal and there is abundant evidence that they are not.
Abstract: The widely held view that the frequency distribution of analytical error is log-normal at concentrations of analyte near the detection limit is examined in detail. It is argued that (a) there is no theoretical reason why such distributions should be log-normal and there is abundant evidence that they are not; (b) quasi-log-normal distributions can be produced as artifacts by data recording practices; and (c) inordinately large numbers of analytical results would be needed to distinguish a log-normal distribution from a normal distribution.
TL;DR: In this article, a preservation study was carried out to determine the stability of inorganic species of arsenic as arsenic(III) and arsenic(V) in distilled and natural waters for a duration of 125 d. Various conditions of storage, such as pH, level of arsenic, type of container material and size of container, were studied.
Abstract: A preservation study was carried out to determine the stability of inorganic species of arsenic as arsenic(III) and arsenic(V) in distilled and natural waters for a duration of 125 d. Various conditions of storage, such as pH, level of arsenic, type of container material and size of container, were studied. It was found that arsenic(III) and arsenic(V) are satisfactorily preserved for this time in both distilled and natural water samples at 1 and 10 µg l–1 levels at room temperature if they are stored in polyethylene or Pyrex bottles with 0.2%V/V sulphuric acid.
TL;DR: In this article, the conditions for the sorption of certain metal cations by polyether-type polyurethane foam have been studied, and the results showed that foam-supported material can support various solvent extractants, such as 1-(2-pyridylazo)-2-naphthol (PAN) and α-dinonyl phthalate.
Abstract: The conditions for the sorption of certain metal cations by polyether-type polyurethane foam have been studied. Cobalt(II), iron(III), zinc and cadmium sorb from aqueous thiocyanate solution, whereas nickel(II) is not extracted to any significant extent. Considerable amounts of hydrochloric acid are needed to reduce the uptake of iron(III) by the foam. The metal thiocyanato complexes can be desorbed with hot 0.1 M nitric acid.Polyurethane foam can support various solvent extractants, and the sorption and separation elution of bismuth and nickel(II) from thiourea (3%m/V)-sodium perchlorate (1%m/V)-perchloric acid (0.1 M) by tributyl phosphate supported on the foam is described. Amberlite LA-2 supported on the foam sorbs iron(III), tin(IV), cadmium, mercury(II) and zinc from appropriate hydrochloric acid solutions, especially at about 3 M hydrochloric acid, but there is little or no sorption of cobalt(II), copper(II), nickel(II) and lead(II) up to 10 M hydrochloric acid.The chelating extractant, 1-(2-pyridylazo)-2-naphthol (PAN), is readily supported on unplasticised polyurethane foam and, when plasticised with α-dinonyl phthalate, the foam-supported material will extract zinc, mercury(II) and copper(II) from aqueous solution at pH 8–9, and less effectively at lower pH.
TL;DR: In this paper, a method based on the extraction of potassium picrate active substances (PPAS) has been investigated in the determination of non-ionics with R = dodecyl by considering both mono- and polydisperse surfactants.
Abstract: Non-ionic surfactants of the type R(OCH2CH2)nOH, where R represents an n-alkyl group and n is the degree of polymerisation, are widely used in house-hold detergent formulations and are found at trace levels (0.01–1 mg l–1) in waters receiving untreated urban liquid sewage. A method based on the extraction of potassium picrate active substances (PPAS) has been investigated in the determination of non-ionics with R = dodecyl by considering both mono- and polydisperse surfactants.The reactivity of monodisperse surfactants (4 ⩽n⩽ 14) as PPAS is explained qualitatively by considering the equilibria involved in the extraction. Commercial polydisperse surfactants with 3.8 ⩽text-decoration:overlinen⩽ 28 (where text-decoration:overlinen is the number-average degree of polymerisation) are also considered and compared with other polydisperse surfactants in which R =p-tert-nonylphenyl. In both surfactant series the proposed method allows the absolute determination of the polydisperse surfactants in the range of text-decoration:overlinen from 13 to at least 28.
TL;DR: Trace amounts of selenium(VI) and total seenium in human blood and plasma were determined with a practical detection limit of 2 ng.
Abstract: Selenium(IV) reacts with 1,2-diamino-3,5-dibromobenzene to form 4,6-dibromopiazselenol, which is detected by means of a gas chromatograph equipped with an electron-capture detector. Trace amounts of selenium(VI) and total selenium in human blood and plasma were determined with a practical detection limit of 2 ng.
TL;DR: In this paper, the silver diethyldithiocarbamate spectrophotometric procedure for the determination of arsenic has been modified to perform the differential determination of inorganic arsenic(III) and arsenic(V) species.
Abstract: The silver diethyldithiocarbamate spectrophotometric procedure for the determination of arsenic has been modified to perform the differential determination of inorganic arsenic(III) and arsenic(V) species. Based on pH control of the reduction characteristics of the borohydride ion, arsine is generated at pH 6 from arsenic(III); following acidification, arsine is then generated and trapped from arsenic(V) species. The procedure is appropriate to the determination of 2–40 µg of each arsenic species. Antimony(III), bismuth(III), chromium(VI), copper(II), gold(III), nickel(II), platinum(IV), silver(I), tellurium(IV) and tin(II) interfere in the determination of arsenic(III) and “methylarsenic” and “dimethylarsenic” species, platinum(IV) and silver(I) interfere in the determination of arsenic(V). Interference effects due to platinum can be masked by the addition of 1,10-phenanthroline to the reductant mixture. Interference due to bismuth, copper, gold, nickel, silver, tellurium and tin can be overcome by preliminary extraction of the interferents from the sample as their dithizonates.
TL;DR: In this article, the polarographic behavior of the azo dyes CI Direct Orange 34, Acid Red 73, Direct Blue 84 and Direct Red 80 over the pH range 1−13 was studied.
Abstract: The polarographic behaviour of the azo dyes CI Direct Orange 34, Acid Red 73, Direct Blue 84 and Direct Red 80 over the pH range 1–13 was studied. Mechanisms of reduction are postulated, the optimum pH ranges for the determination of the dyes by differential-pulse polarography are selected and the appropriate linear ranges deduced from calibration graphs.
TL;DR: In this article, a poly(methyl acrylate) ion-selective polyvinyl chloride (PMA) support matrix was used with divalent sensor arrays to measure divalent character with respect to calcium and magnesium in standard analates.
Abstract: Poly(methyl acrylate)(PMA) provides an alternative support matrix to poly(vinyl chloride) but the usual 0.17 g of polymer established for functional poly(vinyl chloride) ion-selective electrodes must be increased to 0.3 g to produce master membranes of sufficient mechanical strength. The best membrane compositions were: PMA (0.3 g), calcium bis(didecylphosphate)(0.02 g), didecylphosphoric acid (0.02 g) with either 0.09 or 0.18 g of decanl-ol. Electrodes with such sensor membranes showed near-Nerstian response to calcium and magnesium and functioned for about 10 days. Selectivity coefficients for divalent character with respect to calcium and magnesium measured by separate and mixed solution techniques were close to unity in many instances. The useful pH range lay between approximately 2.7 and approximately 7.2 in solutions of either 10–1M calcium chloride or 10–1M magnesium chloride levels and at their 10–3M levels.Neither the PMA electrode nor two others based on PVC matrix membranes with divalent sensor systems permitted accurate assays of total calcium and magnesium in standard analates. However, a PVC calcium ion-selective electrode based on calcium bis{di[4-(1,1,3,3-tetramethylbutyl)phenyl]-phosphate} and dioctyl phenylphosphonate facilitated the accurate assay of calcium in the presence of three times its amount of magnesium.
TL;DR: The porosity of compacts of magnesium trisilicate has been determined by low temperature nitrogen adsorption and mercury intrusion methods as discussed by the authors, and the results are in agreement with the porosity-compaction relationship put forward by Bockstiegel.
Abstract: The porosity of compacts of magnesium trisilicate has been determined by low temperature nitrogen adsorption and mercury intrusion methods. An insight into the compaction mechanism has been obtained because the total porosity of the compacts decreases rapidly as the compaction pressure is initially increased, and then becomes progressively slower. The results are in agreement with the porosity-compaction relationship put forward by Bockstiegel.
TL;DR: A method is described for the determination of total chromium, cobalt and silver in foodstuffs by chelation with diethylammonium diethyldithiocarbamate and extraction into 4-methylpentan-2-one.
Abstract: A method is described for the determination of total chromium, cobalt and silver in foodstuffs. Organic matter is destroyed by a wet-digestion procedure and the cobalt and silver are concentrated by chelation with diethylammonium diethyldithiocarbamate and extraction into 4-methylpentan-2-one. Chromium is then chelated with pentane-2,4-dione and separately extracted into 4-methylpentan-2-one. The concentrations of the three elements in the extracts are measured by flame atomic-absorption spectrophotometry.
TL;DR: The infrared and electron spin resonance spectra of these coloured compounds showed that the molybdoarsenic acid oxidises phenothiazines to a radical cation with which it subsequently forms the coloured compound.
Abstract: A method for the spectrophotometric determination of four phenothiazines (promazine hydrochloride, mepazine hydrochloride, chlorpromazine hydrochloride and prochlorperazine maleate), based on the coloured compounds formed between the phenothiazines and molybdoarsenic acid, is described. The infrared and electron spin resonance spectra of these coloured compounds showed that the molybdoarsenic acid oxidises phenothiazines to a radical cation with which it subsequently forms the coloured compound. The method is simple and rapid. The influence of the substrates commonly employed as excipients with phenothiazine drugs was studied. The proposed method has been applied to the analysis of commercial phenothiazine-containing preparations, the results of which are in good agreement with those obtained by the official method of the British Pharmacopoeia.