Showing papers in "Analyst in 1975"
TL;DR: In this article, the determination of arsenic, bismuth, germanium, antimony, selenium, tin and tellurium by reaction with sodium borohydride in dilute hydrochloric acid followed by measurement with atomic-absorption spectrophotometry in an argon-hydrogen flame was made.
Abstract: A study has been made of the determination of arsenic, bismuth, germanium, antimony, selenium, tin and tellurium by conversion into the hydrides by reaction with sodium borohydride in dilute hydrochloric acid followed by measurement with atomic-absorption spectrophotometry in an argon-hydrogen flame. A general study, involving 48 elements, of interferences has been carried out and it has been shown that significant interference occurs in many instances but that the procedure is simple to carry out and gives a considerable increases in sensitivity and detection limits for the elements listed, with the exception of tin, for which high blank values were obtained owing to the presence of tin in the sodium borohydride reagent.
237 citations
TL;DR: A method for the determination of Iron(II) in water in the presence of iron(III) with 1,10-phenanthroline is described, in which the interfering effect of iron (III) ions is suppressed by masking with complexones.
Abstract: A method for the determination of iron(II) in water in the presence of iron(III) with 1,10-phenanthroline is described, in which the interfering effect of iron(III) ions is suppressed by masking with complexones. In the absence of a chelating agent for iron(III) the colour intensity of samples being analysed is unstable, owing to redox processes induced by the effect of 1,10-phenanthroline on the iron(II)-iron(III) system, causing reduction of iron(III) and formation of the corresponding coloured iron(II) chelate compound in a stoicheiometrically proportional concentration. The advantages of complexones, especially nitrilotriacetic acid, over other chelating agents are discussed.
150 citations
106 citations
TL;DR: In this article, the use of an atmospheric pressure d.c. plasma as an ion source has been explored for the direct analysis of solutions introduced into it from a nebuliser.
Abstract: The use of an atmospheric pressure d.c. plasma as an ion source has been explored for the direct analysis of solutions introduced into it from a nebuliser. Ions are extracted from the plasma into a vacuum system and are focused into a quadrupole mass analyser. A high yield of singly charged ions with a small energy spread is obtained and clear spectra of the constituents of the solution are observed.The method is described and the results observed on simple solutions are given. The sensitivity of the method for a number of elements is indicated and appears to be comparable with other trace-analysis methods.
88 citations
TL;DR: In this paper, the method of determination of antimony, arsenic, selenium, and tellurium using a sodium borohydride reduction with subsequent atomic fluorescence was found to be very sensitive.
Abstract: The method of determination of antimony, arsenic, selenium and tellurium, by using a sodium borohydride reduction with subsequent atomic fluorescence, was found to be very sensitive.The calibration graphs were linear over a wide range of concentrations and the method was 5–30 times more sensitive than the corresponding atomic-absorption technique.
67 citations
TL;DR: The construction and performance of gas-sensing membrane probes are described and discussed in this article, where the effects of temperature and osmotic pressure were examined, the response speeds of the probes were determined and their use in continuous analysis was investigated.
Abstract: The construction and performance of gas-sensing membrane probes are described and discussed. Experimentally, probes to measure ammonia, sulphur dioxide and nitrogen oxide in aqueous solution have been studied. In particular, the effects of temperature and osmotic pressure were examined, the response speeds of the probes were determined and their use in continuous analysis was investigated. Selectivity is discussed. Consideration is given to the development of new methods of analysis and current applications of the probes are mentioned.
56 citations
TL;DR: A fundamental re-appraisal of the conditions leading to the formation of α- and β-molybdosilicic acids has been made in this paper, where the classification of these conditions recommended by Strickland has been rejected and replaced with a rigorous system involving pH and molybdate concentration in the reaction mixtures.
Abstract: A fundamental re-appraisal of the conditions leading to the formation of α- and β-molybdosilicic acids has been made. The classification of these conditions recommended by Strickland has been rejected and replaced with the rigorous system involving pH and molybdate concentration in the reaction mixtures. The α-molybdosilicic acid is formed at pH between 3·8 and 4·8 (possibly slightly higher) and the β-acid at pH between 1·0 and 1·8. The yield of both α- and β-acids (at pH 4·0 and 1·2) is independent of molybdate concentrations between 0·015 and 0·100 mol l–1. The rate of formation of each compound at various known pH and molybdate concentrations is discussed. A number of hitherto unexplained complications reported by other workers are now resolved.
55 citations
TL;DR: In this paper, a catalytic procedure, in which a Technicon AutoAnalyzer(I) is used, for determining iodide or iodate (50 µg l-1) added to river water (during river-flow gauging operations by the dilution method) is described.
Abstract: A catalytic procedure, in which a Technicon AutoAnalyzer(I) is used, for determining iodide or iodate (50 µg l–1) added to river water (during river-flow gauging operations by the dilution method) is described. The maximum error of the analytical procedure, as determined by replicate analysis of six sets of eleven samples, is ± 0·36 per cent. in the range 20–100 µg l–1. The setting up of the procedure is described in detail, according to Mark's (1973) recommendations. The shape of the most appropriate calibration graph is considered. Also, the effects of changes in temperature, reaction period and spectrophotometric variables are discussed. This information could be used directly in the development of methods for determining iodine in other types of sample, e.g., protein-bound iodine in blood or urine and iodate or iodide in sea water, etc. Further, it could also be used in developing other automatic procedures that rely upon catalytic reactions that follow a pseudo-first-order behaviour.
53 citations
TL;DR: A procedure is given in which dialkyllead species are preferentially extracted as dithizonates from the buffered sample solution in the presence of ethylene-diaminetetraacetic acid, which complexes any inorganic lead compounds that may be present.
Abstract: A method is described for the specific determination of tetraalkyllead vapour in air. The atmosphere under test is passed through a solution of iodine monochloride in hydrochloric acid, which converts the tetraalkyllead compounds into their dialkyllead ionic forms.A procedure is given in which dialkyllead species are preferentially extracted as dithizonates from the buffered sample solution in the presence of ethylene-diaminetetraacetic acid, which complexes any inorganic lead compounds that may be present. The dialkyllead dithizonates are then decomposed by shaking with a nitric acid-hydrogen peroxide solution and the concentration of lead in the resulting solution is determined by atomic-absorption spectrophotometry, using a carbon furnace for atomisation.The method has a limit of detection of 7 ng of lead in the sample. When expressed as a concentration of tetraalkyllead in air the detection limit is 0·2 µg m–3 for a 10-min sampling period and 0·04 µg m–3 for 1-h sampling period.
49 citations
TL;DR: Modifications to a cold-vapour, mercury-fluorescence detector have resulted in a large increase in sensitivity and the time required for each measurement and a 2σ detection limit of 0·02 ng was achieved.
Abstract: Relatively simple modifications to a cold-vapour, mercury-fluorescence detector have resulted in a large increase in sensitivity and have decreased the time required for each measurement. A 2σ detection limit of 0·02 ng was achieved.
47 citations
TL;DR: An analytical method is established in which the over-all recovery of added nicotine has been increased from 55 to over 80 per cent and the identity of the nicotine peak has been confirmed by mass spectrometry.
Abstract: An analytical method for the determination of nicotine has been established. It is a modification of an earlier reported method in which the over-all recovery of added nicotine has been increased from 55 to over 80 per cent. The determination is carried out by gas-liquid chromatography and the identity of the nicotine peak has been confirmed by mass spectrometry. The method has been applied to the determination of nicotine in the blood of cigarette smokers, and concentrations at the level of 1 ng ml–1 can be measured.
TL;DR: A flow-through cell packed with silica gel is used for the spectrofluorimetric examination of adsorbed states and as a detector in high-pressure liquid chromatography.
Abstract: A flow-through cell packed with silica gel is used for the spectrofluorimetric examination of adsorbed states and as a detector in high-pressure liquid chromatography. The intensified fluorescence of adsorbed benzo homologues of quinoline and acridine is found to be caused by protonation of the electronically excited states by the gel. Sub-nanogram amounts of such compounds can therefore be analysed by high-pressure liquid chromatography.In the presence of silica gel the fluorescence of polynuclear hydrocarbons is enhanced proportionally to their radiative lifetimes. The effect is disfavoured by adsorbate formation, and can therefore be employed in both adsorption and reversed-phase liquid chromatography in order to improve selectivity and sensitivity towards readily quenched fluorescences.Microcolumns (90 × 1 mm) exhibit a ten-fold reduction in theoretical plate height compared with conventional high-pressure columns of the same adsorbent. Separations in such columns mounted on a microscope stage can be monitored by spectrofluorimetric microscopy of a silica gel particle located at the end of the column.The techniques described are applied to heterocycles in creosotes, polynuclear hydrocarbons in gasolines and sump oil, and wood splinters, soot particles and trace amounts of pitch.
TL;DR: A fast and simple method for the determination of pyridoxine in pharmaceutical preparations is given and a comparison of the proposed method with a colorimetric method has also been made; the voltammetric method has a better relative standard deviation.
Abstract: The oxidation of pyridoxine and related compounds in ammonia buffer solutions is described and a fast and simple method for the determination of pyridoxine in pharmaceutical preparations is given. The only interferences are from ascorbic acid and iron(II), both of which can be removed by ion-exchange chromatography. A comparison of the proposed method with a colorimetric method has also been made; the voltammetric method has a better relative standard deviation.
TL;DR: A very sensitive method for the determination ofxylose in plasma has been developed, which involves condensation of phloroglucinol with the furfural released from xylose by the action of hot hydrochloric acid-acetic acid.
Abstract: A very sensitive method for the determination of xylose in plasma has been developed, which involves condensation of phloroglucinol with the furfural released from xylose by the action of hot hydrochloric acid-acetic acid. In the standard method duplicate analyses of plasma samples containing 0·667–2·667 mmol l–1 of xylose can be achieved by using 0·2-ml samples. A modified method using 0·1 ml of whole blood can also be used. The absorbance obtained on analysing solutions containing 1·333 nmol l–1 of xylose is 0·372 at 554 nm using cuvettes of 10-mm light path. This value corresponds to a molar absorption of approximately 33 000. By using hydrobromic acid-acetic acid an even higher molar absorption of approximately 39 000 is obtained. Glucose gives only a weak reaction under the test conditions, 417 nmol of glucose giving an absorbance equivalent to 7·6 nmol of xylose.
TL;DR: In this paper, a preliminary separation of molybdenum as its benzoin α-monoxime complex is recommended, based on its catalytic effect on the liberation of iodine from the reaction between potassium iodide and hydrogen peroxide.
Abstract: Molybdenum is determined by its catalytic effect on the liberation of iodine from the reaction between potassium iodide and hydrogen peroxide. The detection limit is 0·003 µg ml–1 of molybdenum. Interference from iron and tungsten can be overcome by addition of ammonium fluoride, but for the greatest precision and accuracy a preliminary separation of molybdenum as its benzoin α-monoxime complex is recommended. Molybdenum concentrations determined by the proposed method in some reference plant materials are presented.
TL;DR: A comparative determination of vitamin B2 and nicotinamide in three complex multivitamin preparations showed that differential pulse polarography is more selective than d.c.p. polarography.
Abstract: The determination of low concentrations of the vitamins B2, nicotinic acid, nicotinamide, ascorbic acid, K1 and K3 in pure solutions by use of differential pulse polarography has been studied. The approximate limits of detection achieved for the different vitamins varied from 0·01 to 1 p.p.m., which is 10 to 100 times better than for d.c. polarography. A comparative determination of vitamin B2 and nicotinamide in three complex multivitamin preparations showed that differential pulse polarography is more selective than d.c. polarography. With the former method the nicotinamide can be determined directly, i.e., without prior separation of interfering substances.
TL;DR: In this paper, atomic emission signals obtained from sodium, potassium, magnesium, chromium, lithium, and aluminium using a standard carbon furnace atomic-absorption spectrometer are reported.
Abstract: Atomic-emission signals obtained from sodium, potassium, magnesium, chromium, lithium and aluminium by using a standard carbon furnace atomic-absorption spectrometer are reported. Optimisation of the instrument for emission measurements is discussed and detection limits are compared with those obtained by flame emission and carbon furnace atomic absorption using the same instrument.
TL;DR: In this paper, the authors derived quantitatively pre-atomisation heating losses, the advantages to be gained from operating under stopped gas flow conditions and the relative merits of signal peak height and signal integration measurements.
Abstract: Kinetic information for the atomisation of copper in a heated graphite furnace has been used to derive analytical parameters that are encountered in atomic-absorption determinations. Equations have been derived to describe quantitatively pre-atomisation heating losses, the advantages to be gained from operating under stopped gas flow conditions and the relative merits of signal peak height and signal integration measurements.
TL;DR: The spontaneous oxidation of alkaline mixtures of p-aminophenol and phenol with molecular oxygen to form indophenol has been made the basis of a colorimetric procedure for the determination of paracetamol via its hydrolysis product, p-aminsophenol.
Abstract: The spontaneous oxidation of alkaline mixtures of p-aminophenol and phenol with molecular oxygen to form indophenol has been made the basis of a colorimetric procedure for the determination of paracetamol via its hydrolysis product, p-aminophenol. The hydrolysis product of phenacetin, p-phenetidine, does not undergo this reaction. Several other active ingredients with which paracetamol is often formulated have been shown not to interfere. Total paracetamol and phenacetin can be determined by an indophenol reaction after hydrolysis and oxidation with acidified hypochlorite.
TL;DR: In this paper, the degree of esterification of the methyl ester of galacturonic acid is determined in the same way after hydrolysing the ester with sodium hydroxide in the presence of Cat-Floc.
Abstract: The determination of residues of carboxylic acids (mainly galacturonic acid) in industrial pectins is carried out by colloid titration using a new titrant, Cat-Floc (Poly-NN-dimethyldiallylammonium chloride). The degree of esterification of the methyl ester of galacturonic acid is determined in the same way after hydrolysing the ester with sodium hydroxide in the presence of Cat-Floc. The same samples were analysed by the method of acid-base titration and by colloid titration, and the results obtained are compared and discussed.
TL;DR: Comparative titrimetric determinations of ascorbic acid in some fruits, vegetables and beverages gave higher results than the voltammetric method.
Abstract: It has been shown that the oxidation of ascorbic acid at a carbon paste electrode is similar to that at a platinum electrode. The half-peak potential is somewhat higher than the half-wave potential at a dropping-mercury electrode. The peak current is proportional to the concentration of ascorbic acid in the range 10–6–10–3M and the reproducibility is better than ±1 per cent. Chloride and sulphur compounds, such as sulphides and thiols, do not interfere, and sulphite can be determined at the same time as the ascorbic acid. Some substituted phenols interfere but can often be detected by reversing the direction of polarisation. Reductones interfere but tin(II) and manganese(II) do not. A method has also been developed to determine ascorbic acid in the presence of an excess of iron. Different extraction media are discussed in terms of their influence on the redox potential of iron.Comparative titrimetric determinations of ascorbic acid in some fruits, vegetables and beverages gave higher results than the voltammetric method.
TL;DR: A rapid method is described for the determination, in aqueous systems, of two widely used herbicides known commercially as paraquat and diquat, and there is some loss of linearity of response, possibly as a result of adsorption of the herbicides on the glass surfaces of the vessels used.
Abstract: A rapid method is described for the determination, in aqueous systems, of two widely used herbicides known commercially as paraquat and diquat. Pyrolysis of these herbicides under carefully controlled conditions, followed by gas-chromatographic analysis of the pyrolysate, allows detection of the herbicides down to 0·01 p.p.m. At the lowest concentration levels (0·01–0·1 p.p.m.), there is some loss of linearity of response, possibly as a result of adsorption of the herbicides on the glass surfaces of the vessels used. This effect may have resulted in substantial errors in previously reported low levels of paraquat and diquat and may also occur in the determination of other ionic herbicides.
TL;DR: In this paper, gas-sensing membrane electrodes have been assessed for use in the determination of carbon dioxide in power station waters, and the Radiometer, Type E5036, electrode has the most satisfactory performance.
Abstract: Gas-sensing membrane electrodes have been assessed for use in the determination of carbon dioxide in power station waters. The Radiometer, Type E5036, electrode has the most satisfactory performance, and the system is convenient and simple for the investigation of abnormal levels of carbon dioxide that arise at start-up or during the commissioning stages; the limit of detection (about 0·1 µg ml–1) is not low enough for the routine monitoring of normal operation levels. The electrode has been used for both discrete analysis and on-line continuous monitoring. Standard deviations of 2·0, 0·3 and 0·13 µg ml–1 were obtained at concentration levels of 23·2, 5·00 and 2·32 µg ml–1, respectively. The response times at concentrations greater than 1 µg ml–1 were found to be within the range 3–7 min for a 10-fold increase in concentration. Of the species expected in power stations only sulphite ion, at high concentration, caused interference.
TL;DR: In this paper, a simple radiochemical neutron activation method for the determination of arsenic and selenium in soils is described, after fusion of the soil with alkali and removal of the insoluble hydroxides.
Abstract: A simple radiochemical neutron-activation method for the determination of arsenic and selenium in soils is described. After fusion of the soil with alkali and removal of the insoluble hydroxides, arsenic and selenium are determined in the solution, after acidifying it with hydrochloric acid, by a simple precipitation with thioacetamide. Chemical yields are determined by re-irradiation of the sulphide precipitate. The method is suitable for studies of the normal concentrations of arsenic and selenium in soils.
TL;DR: All vitamin A derivatives are found to give clean oxidation waves with a 0·05 M solution of lithium perchlorate in methanol-benzene as the supporting electrolyte, and a glassy carbon electrode as the working electrode.
Abstract: All vitamin A derivatives are found to give clean oxidation waves with a 0·05 M solution of lithium perchlorate in methanol-benzene as the supporting electrolyte, and a glassy carbon electrode as the working electrode. The determination of the vitamin in pharmaceutical preparations is carried out via direct extraction without prior saponification.The dependence on pH of the half-peak potentials of vitamins A and D, and of provitamins D, is examined with both carbon paste and glassy carbon electrodes.It is shown that the voltammetric technique does not distinguish between vitamins A1 and A2, nor between vitamins D2 and D3. A method for the determination of vitamin A in margarine is given. Some attempts have also been made to determine vitamin D in mixtures with vitamin A. Partition chromatography with Celite-polyethylene glycol gives a clean separation of vitamin D from vitamin A, which makes voltammetric determination of vitamin D possible without further purification.
TL;DR: A modified thiochrome procedure for the assay of thiamine is described, which eliminates the use of ion-exchange columns and elutions with hot, saturated potassium chloride solution that are employed in most other methods.
Abstract: A modified thiochrome procedure for the assay of thiamine is described. It eliminates the use of ion-exchange columns and elutions with hot, saturated potassium chloride solution that are employed in most other methods. The times required for extraction and dephosphorylation have been examined critically and shortened.
TL;DR: In this paper, the authors used synchronously excited fluorescence emission spectroscopy to identify fluorescent contact traces from many rubber articles, and may be characterised, after extraction, by synchronous excited fluorescence.
Abstract: Fluorescent contact traces are transferred from many rubber articles, and may be characterised, after extraction, by synchronously excited fluorescence emission spectroscopy. The fluorescence is due mainly to extender and process oils, to antioxidants, and to polynuclear aromatic hydrocarbons. Variation in these components in tyre treads, caused by variation in manufacture and wear, enables tread rubbers, and their prints, to be efficiently distinguished from one another. Fluorescent tyre print formation is controlled by the nature of the surface, and by contact time and pressure. Some of the fluorescent material solvent-extracted from such prints is present initially as non-fluorescent particles of rubber. Tyre sidewall rubbers are distinguished from tread rubbers by differences in the extraneous polynuclear aromatic hydrocarbon emissions and, in the case of radial tyres, principally by differences in extender oil emissions. The techniques described are also applied to traces left by footwear and by erasers, to the detection of mineral oil in failed brake seals, and can be generally applied in the comparative examination of rubbers.