Showing papers in "Analyst in 1968"
TL;DR: An enzymatic inhibition method sufficiently sensitive and reproducible for detecting ten organophosphorus pesticides and carbaryl resolved by thin-layer chromatography is described, with results satisfactory with 1-naphthyl acetate as substrate, and with bovine and sheep sera as sources of esterase.
Abstract: An enzymatic inhibition method sufficiently sensitive and reproducible for detecting ten organophosphorus pesticides and carbaryl resolved by thin-layer chromatography is described. Reproducible detection of nanogram amounts of these pesticides is achieved with a 450-µ thick gel layer, steer-liver homogenate as source of esterase, and indoxyl or substituted indoxyl acetates (5-bromoindoxyl, 5-bromo-4-chloroindoxyl and 5-bromo-6-chloroindoxyl acetates) as substrates, the esterase and substrate spray solutions being used at a pH of about 8. The coloured products of enzymatic hydrolysis of these substrates are stable and intense; white spots indicated the sites of pesticides that inhibited the enzyme.Spots persist for days when the amounts present are 1 ng of parathion; 2ng of carbophenothion; 5ng of azinphos-methyl, diazinon, ethion, malathion and parathion-methyl; 20 ng of carbaryl, Trithion®-methyl and mevinphos; and 100ng of disulfoton. Carbophenothion and disulfoton are also detected at the 1 ng level and carbaryl, at 5 ng; however, the spots produced disappear within a few hours.Unsatisfactory results are obtained with 1-naphthyl acetate as substrate, and with bovine and sheep sera as sources of esterase.
64 citations
TL;DR: The electrode is shown to be less susceptible than the colorimetric methods to interference from other ions in solution, and it gives theoretical recoveries of fluoride added to several drinking water supplies.
Abstract: Five spectrophotometric procedures for the determination of fluoride in water have been evaluated with respect to reproducibility, sensitivity, range, stability of coloured products and of reagents, specificity and effect of temperature. The thorium nitrate titration is briefly discussed, and the use of the Orion fluoride-ion electrode for pF measurement has also been investigated. Various samples of water containing natural or added fluoride have been analysed by four of the spectrophotometric methods, and the results compared with those obtained by titration and with the electrode. The electrode is shown to be less susceptible than the colorimetric methods to interference from other ions in solution, and it gives theoretical recoveries of fluoride added to several drinking water supplies.
62 citations
TL;DR: In this paper, a sensitive and selective molecular emission method for the determination of phosphorus is described, in which the intense green emission obtained by nebulising orthophosphoric acid solution into a cool, nitrogen-hydrogen diffusion flame is measured at 528 mµ.
Abstract: A sensitive and selective molecular-emission method for the determination of phosphorus is described, in which the intense green emission obtained by nebulising orthophosphoric acid solution into a cool, nitrogen-hydrogen diffusion flame is measured at 528 mµ. The limit of detection in aqueous solution under the conditions of measurement is 0.1 p.p.m. of phosphorus.Most cations produce a depressive matrix effect that can be readily overcome by a preliminary ion-exchange separation. Fifty-fold molar excesses of acetic, hydrobromic, hydrochloric, nitric, oxalic, sulphuric and tartaric acids do not interfere.
46 citations
TL;DR: Improvements are proposed for the sampling and ashing of animal and plant tissues, and soil, including the use of finely ground suspensions in dilute agar solution and the effect of silica in the analysis of plants and soils for fluorine.
Abstract: The distribution of fluorine compounds found in biological materials, including soils, is outlined. Several improvements are proposed for the sampling and ashing of animal and plant tissues, and soil, including the use of finely ground suspensions in dilute agar solution. Some modifications are suggested in the separation of fluorine by diffusion as hydrofluoric acid and its subsequent determination with alizarin complexan. The effect of silica in the analysis of plants and soils for fluorine is discussed.
41 citations
TL;DR: The experimental parameters governing the application of this technique have been studied and applied to the determination of sodium diethyl-dithiocarbamate and the results obtained were compared with those from conventional d.c. polarography, a. c. polarographers and linear potential-sweep chrono-amperometry.
Abstract: Cathodic stripping analysis has been shown to be an extremely sensitive technique for the determination of compounds that form insoluble mercury salts. The experimental parameters governing the application of this technique have been studied and applied to the determination of sodium diethyl-dithiocarbamate. The results obtained were compared with those from conventional d.c. polarography, a.c. polarography and linear potential-sweep chrono-amperometry.
35 citations
TL;DR: In this article, a method is described in which this interference is prevented by prior oxidation with potassium iodate in acidic solution, which can be used directly for trace amounts of ammonia, or following distillation when other interfering substances are present.
Abstract: Hydrazine is known to interfere in the determination of ammonia with Nessler's reagent. A method is described in which this interference is prevented by prior oxidation with potassium iodate in acidic solution. The method can be used directly for trace amounts of ammonia, or following distillation when other interfering substances are present.
35 citations
TL;DR: In this paper, a solution of tin(II) chloride in hydrochloric acid is used to decompose the sulphide in soils containing sulphide and iron(III) oxide.
Abstract: Hydrogen sulphide is partially oxidised by iron(III) when soils containing sulphide and iron(III) oxide are acidified Satisfactory recoveries of hydrogen sulphide are obtained by using a solution of tin(II) chloride in hydrochloric acid to decompose the sulphide
31 citations
29 citations
TL;DR: In this article, the resonance-line emission from the SnH species in a nitrogen-hydrogen diffusion flame is used to determine the presence of ground-state tin atoms in the diffusion flame.
Abstract: Tin can be determined in the range 3 to 3000 p.p.m. by molecular-band emission from the SnH species in a nitrogen-hydrogen diffusion flame. The emission at 609·5 nm, which is almost line-like, gives a limit of detection of 1·5 p.p.m. of tin. Spectral interference from sodium is eliminated by use of a didymium filter. The presence of oxygen gives rise to a much broader spectrum, caused by tin(II) oxide formation, with a visual limit of detection of 5 p.p.m. of tin. Atomic emission can be observed only in the presence of alcohols, e.g., isopropyl alcohol, but a high concentration of ground-state tin atoms exists in the diffusion flame. Mechanisms are discussed to explain the production of tin atoms, SnH and the resonance-line emission.
28 citations
TL;DR: In this paper, a simple and rapid method was proposed for determining fluorine in micas and related aluminosilicates. But the method was not suitable for determining the fluorine contents of silicate rock standards GSP 1 and GSP 2.
Abstract: Fluorine-bearing minerals are hydrolysed at 700° to 800° C in a gasheated fused-silica tube. The hydrogen fluoride evolved is absorbed in alkali and determined by titration with thorium nitrate or absorptiometrically with cerium-alizarin complexone. Recoveries from sodium fluoride averaged 98·6 per cent., with a coefficient of variation of 3·2 per cent., and the determined fluorine contents of the silicate rock standards GSP–1 and G2 were 0·381 and 0·134 per cent. The method is simple and rapid, and is suitable for determining fluorine in micas and related aluminosilicates.
27 citations
TL;DR: A procedure is described for rapidly screening some organophosphorus pesticides in plant extracts without elaborate clean-up and indicates that the equivalent of only a few milligrams of the original sample is required for semi-quantitative analyses of residues present at, or above, their tolerance levels.
Abstract: A procedure is described for rapidly screening some organophosphorus pesticides in plant extracts without elaborate clean-up. Azinphos-methyl, carbophenothion, diazinon, ethion, malathion, mevinphos and parathion are extracted with acetonitrile and partitioned into hexane before analysis by the thin-layer chromatographic-enzyme inhibition technique. These pesticides, in the presence of apple, beet, carrot, lettuce, pea or potato extractives, are detected on thin-layer chromatographic plates coated with a silica-gel layer. The experiment indicates that the equivalent of only a few milligrams of the original sample is required for semi-quantitative analyses of residues present at, or above, their tolerance levels.
TL;DR: Methods are described for the cold solvent extraction and analysis of traces of the fumigants methyl bromide and ethylene oxide present in flour and wheat after treatment, and for determining the efficiency of extraction, in which a combination of gas-chromatographic and chemical techniques is used.
Abstract: Methods are described for the cold solvent extraction and analysis of traces of the fumigants methyl bromide and ethylene oxide present in flour and wheat after treatment, and for determining the efficiency of extraction, in which a combination of gas-chromatographic and chemical techniques is used.Results are given showing the loss of fumigant caused by reaction with cereal constituents before recovery, and a method for correcting this is described. Recoveries generally of 95 per cent., or more, were obtained with a lower detection limit of about 0·3 p.p.m. The application of the method to other volatile compounds is indicated.
TL;DR: An automatic colorimetric method for determining sulphate in natural water in the range of 5 to 400 mg per litre is presented.
Abstract: An automatic colorimetric method for determining sulphate in natural water in the range of 5 to 400 mg per litre is presented. The method is based on the precipitation of barium sulphate and the release of the coloured acid chloranilate ion. A manifold has been developed for the determination of sulphate on the Technicon AutoAnalyzer. The proposed method will run 15 samples per hour.
TL;DR: In this paper, a detailed investigation of the polarographic behaviour of these compounds, and their metal complexes that are used as pesticides, is presented, which is suitable for the analysis of pesticide preparations and residues.
Abstract: Procedures for the determination of monoalkyl-and dialkyldithiocarbamates and some of their metal complexes that are used as pesticides are described. The methods are based on a detailed investigation of the polarographic behaviour of these compounds, and are suitable for the analysis of pesticide preparations and residues.
TL;DR: In this article, the determination of beryllium by thermal emission and atomic-fluorescence spectroscopy in a separated nitrous oxide-acetylene flame has been investigated, and the optimum conditions for both techniques have been investigated and the effects of other cations and anions studied.
Abstract: The determination of beryllium by thermal-emission and atomic-fluorescence spectroscopy in a separated nitrous oxide-acetylene flame has been investigated. The high temperature, reducing nature and low background of this type of flame permit the determination of down to 0·25 and 0·03 p.p.m. of beryllium in aqueous solution by measurement of thermal emission and atomic fluorescence, respectively. A beryllium microwave-excited, electrodeless discharge tube was used for excitation of the atomic fluorescence. The optimum conditions for both techniques have been investigated, and the effects of other cations and anions studied.
TL;DR: In this paper, the metal-complexing properties of 2-hydrazinopyridine and 1,2-naphthaquinones of α-PAN and its derivatives containing sulphonic acid groups in positions 4 to 8 of the naphthalene ring were described.
Abstract: The preparation, from 2-hydrazinopyridine and the respective 1,2-naphthaquinones, of 2-(2-pyridylazo)-1-naphthol (α-PAN) and its derivatives containing sulphonic acid groups in positions 4 to 8 of the naphthalene ring, respectively, is described. The metal-complexing properties of the dyes are discussed in relationship to the position of the sulphonic acid group, and compared with those of 1-(2-pyridylazo)-2-naphthol (β-PAN). The dye with the sulphonic acid group in position 8 appears to be the most promising colorimetric reagent. All the new dyes are shown to be superior indicators to β-PAN for the complexometric titration of copper.
TL;DR: In this paper, the determination of silicon by atomic absorption spectrophotometry in silicon-containing and siliceous materials has been investigated and means by which many types of sample can be completely dissolved without loss of silicon, thus avoiding the need for fusion.
Abstract: The determination of silicon by atomic-absorption spectrophotometry in silicon-containing and siliceous materials has been investigated. Means are outlined by which many types of sample can be completely dissolved without loss of silicon, thus avoiding the need for fusion. Full operating details are given, and the results, accuracy and sensitivity of the method are discussed.
TL;DR: In this article, the eleven molybdate ions associated with each niobium atom were determined by direct atomic-absorption spectroscopy in a nitrous oxide-acetylene flame at 313·2 nm.
Abstract: Niobium in the range 5 to 50 µg is determined by an amplification procedure in which molybdoniobophosphoric acid is formed and extracted into butanol. The molybdophosphoric acid, which is also formed, is first selectively extracted away from the molybdoniobophosphoric acid into isobutyl acetate. The eleven molybdate ions associated with each niobium atom are determined by direct atomic-absorption spectroscopy in a nitrous oxide-acetylene flame at 313·2 nm. Of the twenty-eight other ions studied, only titanium causes appreciable interference, although its presence at the same concentration as niobium can be tolerated. Large amounts of tantalum do not interfere.
TL;DR: The determination of chloride by using the membrane-type chloride electrode is described in this article, where procedures are given for the analysis of chloride materials, including silver halides, both in the presence and absence of bromide and iodide.
Abstract: The determination of chloride by using the membrane-type chloride electrode is described. Procedures are given for the analysis of chloride materials, including silver halides, both in the presence and absence of bromide and iodide.
TL;DR: Di-2-pyridyl ketoxime was used for the gravimetric determination of palladium as discussed by the authors, where the chelate is precipitated over a pH range of between 3 and 11 and weighed as Pd(C11H8ON3)2.
Abstract: Di-2-pyridyl ketoxime is proposed for the gravimetric determination of palladium. The chelate is precipitated over a pH range of between 3 and 11 and weighed as Pd(C11H8ON3)2. An extensive study of foreign ions and analytical conditions for precipitation indicates the procedure to be widely applicable, rapid and simple.
TL;DR: By using this technique in combination with a recently developed sampling procedure, it has proved possible to measure variations in carbonate concentration within thin sections of dental enamel.
Abstract: A method is described for the micro determination of carbonate in 50-µg particles of human dental enamel. The technique is rapid and more sensitive than previous procedures. Amounts of carbonate from 0·5 to 3·0 µg have been determined with an accuracy of 4 to 7 per cent. (standard deviation). Carbon dioxide is liberated by dissolving enamel particles in acid. The gas forms a single bubble, flattened into a 100-µ thick disc between the parallel glass surfaces of a Neubauer haemocytometer. The area of the flattened bubble is measured and the volume of gas calculated. By using this technique in combination with a recently developed sampling procedure, it has proved possible to measure variations in carbonate concentration within thin sections of dental enamel.
TL;DR: In this article, a gas-chromatographic study of the essential oil of origanum has been carried out with both capillary and packed columns, and some new components were found by coupling preparative gas chromatographic analysis and infrared spectroscopy.
Abstract: A gas-chromatographic study of the essential oil of origanum has been carried out with both capillary and packed columns. Furthermore, some new components of the essential oil of origanum were found by coupling preparative gas-chromatographic analysis and infrared spectroscopy.
TL;DR: In this article, the authors present a review of the available information dealing with the analysis of iron and steel by atomic-absorption spectrophotometry (ABS) and present some unpublished information.
Abstract: Atomic-absorption spectrophotometry is a useful technique for the determination of many of the minor elements commonly present in iron and steel. It is rapid and relatively free from most of the troublesome inter-element effects associated with alternative techniques such as colorimetric and polarographic analysis. This paper reviews published and certain unpublished information dealing specifically with the analysis of iron and steel by atomic-absorption spectrophotometry.
TL;DR: Investigations into the separation by distillation, solvent extraction and the use of ion-exchange resins of drugs from biological materials, with particular reference to urine, are described and discussed.
Abstract: Investigations into the separation by distillation, solvent extraction and the use of ion-exchange resins of drugs from biological materials, with particular reference to urine, are described and discussed.
TL;DR: In this paper, the role of fuel flow rate for several elements (copper, silver, gold, cadmium, tin, lead, antimony, bismuth, manganese and rhodium) is studied and the results are discussed.
Abstract: Although it is known that the use of long tubes in atomic absorption brings considerable increase in sensitivity, little is known about various factors affecting the sensitivity. In this work the role of fuel flow-rate for several elements (copper, silver, gold, cadmium, tin, lead, antimony, bismuth, manganese and rhodium) is studied and the results are discussed. A heated, 45-cm long, alumina tube is used, the burner being a Beckman type fed by air and hydrogen.
TL;DR: In this paper, a test-paper was developed that can enable up to 0·10 p.p.m. v/v of tolylene di-isocyanate (TDI) vapour to be determined in a 5-litre sample of air drawn through a circle of the paper 1 cm in diameter at the rate of 1 litre per minute.
Abstract: A test-paper has been developed that will enable up to 0·10 p.p.m. v/v of tolylene di-isocyanate (TDI) vapour to be determined in a 5-litre sample of air drawn through a circle of the paper 1 cm in diameter at the rate of 1 litre per minute. In the presence of tolylene di-isocyanate a reddish grey stain is produced, development of which is complete within 15 minutes of the end of sampling. The intensity of the stain is compared with artificial standards made by coating paper with specially formulated pigment suspen sions. The 2,4-and 2,6-isomers react equally.The test-papers are produced by treating Whatman No. 1 filter-paper with a solution of sodium nitrite, 2-hydroxy-11H-benzo[a] carbazole-3-carboxy-p-anisidide (Brenthol GB), ammonium acetate and diethyl phthalate in methanol. They are stable for at least 3 months when stored in the dark.This method is simpler than existing “wet” methods and can be carried out by less skilled operators.
TL;DR: In this paper, a method for determining platinum, rhodium, palladium and gold simultaneously on a direct-reading spectrometer with a non-absorbing reference line is described.
Abstract: A method for determining platinum, rhodium, palladium and gold simultaneously on a direct-reading spectrometer with a non-absorbing reference line is described. The concentration ranges of the working curves were as follows: platinum, rhodium and palladium 0 to 20 p.p.m. and gold 0 to 5 p.p.m. The detection limit for rhodium and palladium was 0·1 p.p.m., for platinum 0·5 and for gold 0·01 p.p.m. The reproducibility of the results was satisfactory.
TL;DR: In this article, a mixture of aluminium and ammonium chlorides is suggested for general application to suppress interference by strontium, calcium, manganese and iron in metallurgical analysis.
Abstract: Earlier published work on the determination of molybdenum with an incandescent air-acetylene flame showed that aluminium could be used effectively to suppress the interferences of such elements as strontium, calcium, manganese and iron, but this has not been confirmed for manganese and iron by other workers. Indications are that this is caused by instrumental characteristics. Ammonium chloride, subsequently shown to be effective in the suppression of manganese and iron interference in metallurgical analysis, was found to suppress the interferences of alkaline earth chlorides, but to have no effect on a severe interference by calcium ion, sulphate and phosphate in combination. As aluminium ion was found to suppress this interference, a mixture of aluminium and ammonium chlorides is suggested for general application.
TL;DR: In this paper, the X-ray properties of gypsum in soils containing large amounts of sodium sulphate have been determined satisfactorily by an Xray technique using an internal standard of potassium chloride.
Abstract: Gypsum in soils containing large amounts of sodium sulphate has been determined satisfactorily by an X-ray technique. Potassium chloride is used as an internal standard. Ratios of counts on diffraction peaks of maximum intensity for gypsum and potassium chloride are used for the quantitative determination of gypsum in soil.
TL;DR: In this paper, a 1:3 complex with 2-mercaptobenzoic acid was used for the determination of selenium in the presence of a wide range of elements.
Abstract: Selenium(IV) forms a 1:3 complex with 2-mercaptobenzoic acid that shows maximal absorption at 268 nm in the pH range 0·5 to 2·5. The formation of the complex provides the basis of a rapid and sensitive method for the determination of selenium in the presence of a wide range of elements. When the complex is extracted into ethyl acetate, 22 of 36 other ions investigated do not interfere, even at 200-fold excess. The interference of the others, including tellurium, is readily overcome by a simple technique of total-ion exchange, by masking or by solvent extraction. Of the ions examined only mercury(II) still interferes.The molar absorptivity of the complex at 268 nm is 15,600 and the sensitivity index 5 × 10–3µg per cm2. The complex is formed instantaneously and maintains an unchanging absorbance for over 2 hours. The method is suitable for the determination of selenium in the range 0·008 to 1·5 p.p.m. in aqueous solution.