Showing papers in "Analyst in 1969"
TL;DR: The standard method described by Barker and Summerson for measuring lactic acid concentration has been modified to give a simpler and more rapid procedure, which is applicable to plasma or other biological fluids, and is more convenient for routine laboratory analyses.
Abstract: The standard method described by Barker and Summerson for measuring lactic acid concentration has been modified to give a simpler and more rapid procedure, which is applicable to plasma or other biological fluids, and is more convenient for routine laboratory analyses.
256 citations
TL;DR: Lung tissue hydrolysis with varying concentrations of hydrochloric acid, sulphuric acid and sodium hydroxide, under various conditions, has been studied and no reduction in hydroxyproline yield was observed when the acid hydrolyses were prolonged for several days.
Abstract: Two procedures developed earlier by the authors for the spectrophotometric determination of hydroxyproline have been tested on hydrolysates of dried formalin-fixed and ethanol-fixed lung tissues. The effects of dilution of the hydrolysates and of the presence of various amounts of sodium chloride have been studied, as well as several methods commonly used to remove competing amino-acids or other interfering materials from hydrolysates before the spectrophotometric determination of amino-acids. Several amino-acids reported to cause interference in other spectrophotometric methods for hydroxyproline determination have a negligible effect in the procedures used in the present study.Lung tissue hydrolysis with varying concentrations of hydrochloric acid, sulphuric acid and sodium hydroxide, under various conditions, has been studied. No reduction in hydroxyproline yield was observed when the acid hydrolyses were prolonged for several days. A simple procedure is described, in which hydrolysis takes place overnight at 105° C in a polypropylene tube enclosed by a glass tube fitted with a spring-loaded stopper; this procedure has given good results over a long period.
84 citations
TL;DR: In this article, the Technicon Auto Analyzer was used for the determination of boron in plant tissue with azomethine H, and the preparation of the reagent as the condensation product of H-acid and salicylaldehyde was given.
Abstract: A routine procedure in which the Technicon Auto Analyzer is used for the determination of boron in plant tissue with azomethine H is described. The preparation of the reagent as the condensation product of H-acid and salicylaldehyde is given. The reagent is highly sensitive to boron, and only copper, iron and aluminium interfere. These interference effects are eliminated with an EDTA solution. The procedure is performed in aqueous medium thus simplifying its adaptation to an automated system and its use for routine determination.
74 citations
TL;DR: In this paper, the hydrogen-ion functions measured in this way can be empirically converted into concentrations for use in calculating equilibrium constants, when thermodynamic equilibrium constants cannot be calculated from such measurements it is preferable to report concentration quotients.
Abstract: Results obtained with three commercial pH meters, by measuring the e.m.f. of cells consisting of glass electrodes coupled with either calomel or silver chloride reference electrodes, are compared with the hydrogen-ion concentrations in solutions with three different background electrolytes at five or six different levels of salt concentration. The hydrogen-ion functions measured in this way can be empirically converted into concentrations for use in calculating equilibrium constants. When thermodynamic equilibrium constants cannot be calculated from such measurements it is preferable to report concentration quotients. Concordance is demonstrated among values of the second-stage ionisation constant for sulphosalicylic acid, measured in different ionic media and with different reference electrodes, when all values are converted into concentration quotients.
65 citations
TL;DR: A distillation step has been incorporated into the automated determination of ammonia by the indophenol method as discussed by the authors, and interference from metal ions and the need for dialysis of turbid solutions have been eliminated.
Abstract: A distillation step has been incorporated into the automated determination of ammonia by the indophenol method.By this means the application of the method has been extended, and interference from metal ions and the need for dialysis of turbid solutions have been eliminated. The reliability of the method has been improved without loss of speed.
58 citations
TL;DR: In this paper, a nitrate-specific ion electrode was used to determine the nitrate content in soil extracts. But the results were not compared with analyses carried out by two colorimetric methods.
Abstract: This paper deals with investigations on nitrate determination with a nitrate-specific ion electrode. Analytical results for the nitrate content in soil extracts are compared with analyses carried out by two colorimetric methods. The extracting agents used are 0·02 N copper sulphate, 2 N potassium chloride and distilled water. Results for nitrate determinations in soil suspensions and corresponding filtrates are also compared.The stability of soil extracts, the influence of variation in the ratio of grams of soil to millilitres of extracting agent and in the shaking time, interferences caused by ionic strength and anions, accuracy and reproducibility are also discussed.The investigation shows that nitrate determination with the electrode is reliable both for soil extracts and for soil suspensions. The determination is rapid, and the interferences are not serious.
53 citations
TL;DR: In this paper, a procedure and results are given for the determination of Si, Al, Ti, Fe, Ca, Mg, K, Na and Mn in twelve standard silicate rocks of widely varying compositions.
Abstract: A procedure and results are given for the determination of Si, Al, Ti, Fe, Ca, Mg, K, Na and Mn in twelve standard silicate rocks of widely varying compositions. A comprehensive study has been made of potential interferences in order that the method should be applicable over a wide range of sample compositions. The lithium metaborate-nitric acid dissolution system is used to enable previously developed colorimetric and spectrographic procedures with similar parting solutions to be used for determining important silicate constituents that cannot be determined directly by atomic absorption.
53 citations
TL;DR: A method is proposed for the determination of selenium in plant materials at levels as low as 0·005 p.p.m. in dried material.
Abstract: The determination of very small amounts of selenium in plant samples with 2,3-diaminonaphthalene has been investigated. Losses of selenium are prevented by a controlled wet-oxidation procedure in a silicone bath. A method is proposed for the determination of selenium in plant materials at levels as low as 0·005 p.p.m. in dried material.
50 citations
TL;DR: A general, comprehensive scheme for the extraction of organophosphorus pesticides from river waters and sewage effluents is described and includes details of an improvement that enables all of the pesticides to be detected on thin-layer chromatoplates with a phosphorus-specific ammonium molybdate spray.
Abstract: A general, comprehensive scheme for the extraction of organophosphorus pesticides from river waters and sewage effluents is described. The pesticides, after extraction with chloroform, are determined by gas and thin-layer chromatography. The procedure includes details of an improvement that enables all of the pesticides to be detected on thin-layer chromatoplates with a phosphorus-specific ammonium molybdate spray. The use of gel chromatography on columns of Sephadex LH 20 as an adjunct to identification is also described.
38 citations
TL;DR: Thermal losses of polonium-210 and lead-210 from caribou bone and from reindeer muscle have been measured and caesium-137 andPolonium is partly volatilised at all temperatures above 100° C.
Abstract: Thermal losses of polonium-210 and lead-210 from caribou bone and of caesium-137 and polonium-210 from reindeer muscle have been measured in the temperature range 100° to 1000° C. Polonium is partly volatilised at all temperatures above 100° C, although from bone, the loss was small below 200° C. Negligible amounts of lead-210 are lost from bone samples heated below 600° C, but losses from muscle were observed to occur above 150° C. To avoid losses of caesium-137, muscle samples should not be heated above 300° C.
33 citations
TL;DR: In this article, a sensitive and selective molecular-emission method for the determination of chloride, bromide and iodide is described, involving measurement of the intense InCl, InBr and InI band-emissions signals.
Abstract: A sensitive and selective molecular-emission method for the determination of chloride, bromide and iodide is described, involving measurement of the intense InCl, InBr and InI band-emission signals. A cool nitrogen-hydrogen diffusion flame is used and measurements are made at 360, 376 and 410 nm, respectively. Chloride can be determined in the presence of a large excess of bromide and iodide, bromide in the presence of a large excess of chloride and iodide, and iodide in the presence of a large excess of chloride. The use of other flame types and the gallium halide system are also described.
TL;DR: The method is considered to be satisfactory for the purposes of a field survey when the determination of the approximate level of mycotoxin contamination of cereals and groundnuts in the shortest possible time is of prime importance.
Abstract: A method is proposed for the analysis of samples for three mycotoxins, aflatoxin, ochratoxin and sterigmatocystin, by suitable treatment of a single sample extract. Based on the subjective evaluation of thin-layer chromatograms of the extract, results can be reproduced with an accuracy of ±20 per cent. The method is considered to be satisfactory for the purposes of a field survey when the determination of the approximate level of mycotoxin contamination of cereals and groundnuts in the shortest possible time is of prime importance. Problems encountered with samples that have high oil contents or that are darkly pigmented are dealt with by appropriate modifications of the method.
TL;DR: In this article, a study of factors affecting the operation of high temperature hollow-cathode lamp discharges for the emission-spectrographic determination of trace elements in steels, high temperature alloys and related materials is presented.
Abstract: A study has been made of factors affecting the operation of high temperature hollow-cathode lamp discharges for the emission-spectrographic determination of trace elements in steels, high temperature alloys and related materials. The factors studied include electrode geometry, carrier-gas pressure and exposure times. The effect of these parameters on element sensitivity and the precision of analysis is discussed.The analysis of dissimilar alloy types has been shown to present problems associated with inter-element effects, and the magnitude of these effects is illustrated. A simple method for overcoming inter-element effects is described, involving the addition of silicon as a buffer to both samples and standards. Results by this method for the analysis of a wide variety of materials from calibration graphs based on a single set of synthetic powder standards are presented. It is possible by this technique to obtain quantitative trace-analysis results without the necessity of providing chemically analysed standards.
TL;DR: A simple and rapid method of micro sampling by using a tantalum boat enables nanogram amounts of thallium in 50 to 100 µl of blood and urine to be determined with an accuracy and precision of 3 to 5 per cent, representing an increase in sensitivity of at least twenty-five times over conventional atomic-absorption spectrophotometry.
Abstract: Flame-spectrophotometric and atomic-absorption methods of assaying trace amounts of thallium in biological material have been investigated. With the Perkin-Elmer, Model 303, spectrophotometer atomic absorption is the more sensitive and yields detection limits comparable with those reported in the literature for the most sensitive types of flame-emission equipment. A simple and rapid method of micro sampling by using a tantalum boat is described. It enables nanogram amounts of thallium (down to 3 ng) in 50 to 100 µl of blood and urine to be determined with an accuracy and precision of 3 to 5 per cent. This represents an increase in sensitivity of at least twenty-five times over conventional atomic-absorption spectrophotometry. The results obtained with the tantalum boat are susceptible to inter-element interferences, and calibration by using the additions method is essential for accurate quantitative results.
TL;DR: In this paper, a chromatographic procedure involving anion exchange in a mixed solvent system has been developed to obtain selective separation of the required radioisotopes from other activities induced during the irradiation.
Abstract: Lutetium, ytterbium and terbium have been determined in some standard rocks from U.S. Geological Survey by neutron-activation analysis. A chromatographic procedure involving anion exchange in a mixed solvent system has been developed to obtain selective separation of the required radioisotopes from other activities induced during the irradiation. Lutetium and ytterbium are eluted in the same fraction, while terbium is obtained in a separate fraction. Chemical yield determination is performed by re-activation. The precision of the method is found to be about ±5 to 15 per cent. for the samples analysed.
TL;DR: In this paper, the electrogenerated chemiluminescence of twenty-four aromatic compounds in dimethylformamide solution has been investigated as a potential analytical technique for their determination.
Abstract: Measurement of the electrogenerated chemiluminescence of twenty-four aromatic compounds in dimethylformamide solution has been investigated as a potential analytical technique for their determination. The emission spectra, calibration results and limits of determination are presented. Experimental requirements and optimum conditions for the electrogeneration of the light-emitting species are described.
TL;DR: In this article, a modified method with a gain in sensitivity and reproducibility was proposed, which can be applied to 0·05 to 20 µg of nitrogen and is also suitable for the solvent extraction with isobutyl alcohol.
Abstract: A critical study has been made of the well known spectrophotometric determination of nitrogen as ammonia, originally based on the reaction of ammonia with hypochlorite and phenol producing a blue coloured indophenol.This has resulted in a modified method with a gain in sensitivity and reproducibility.The absorptivity of indophenol found with this method is 0·60 per p.p.m. of nitrogen per cm at a wavelength of 625 nm, which is an improvement on the methods previously reported.The standard deviation is 0·0013 p.p.m. at the 0·2 p.p.m. level in 50 ml of colour developed solution. The solution obtained after colour development is also suitable for the solvent extraction with isobutyl alcohol. The method described in this paper can be applied to 0·05 to 20 µg of nitrogen.
TL;DR: A method has been developed for the analysis of samples containing capsaicin in amounts above and below 10 mg per 100 g, using a thin-layer procedure and a chloroform-ethanol mixture.
Abstract: A method has been developed for the analysis of samples containing capsaicin in amounts above and below 10 mg per 100 g. The same thin-layer procedure is used for all samples, but preliminary extraction varies according to the level of capsaicin in the sample.For levels above 10 mg per 100 g, the sample is extracted with diethyl ether; for lower levels, the ether is removed by distillation, the residue dissolved in ethanol and the solution shaken with light petroleum to remove colouring matter. The ethanolic solution containing the capsaicin is evaporated to dryness and the residue extracted with ether.The extract is transferred on to a Kieselgel G layer and developed with a chloroform-ethanol mixture. The capsaicin is made visible with iron(III) chloride-potassium ferricyanide reagent.
TL;DR: In this article, a detailed investigation has been made of the accuracy of sodium-responsive glass electrodes for determining sodium (1 to 50 µg per litre) in high purity waters (e.g., condensed steam and boiler feed-water) from power stations.
Abstract: A detailed investigation has been made of the accuracy of sodium-responsive glass electrodes for determining sodium (1 to 50 µg per litre) in high purity waters (e.g., condensed steam and boiler feed-water) from power stations. The electrode potential can be made to follow the Nernst equation down to a sodium concentration of about 1 µg per litre by controlling the pH of the sample and by using a continuous flow of the sample past the electrode. Octadecylamine seriously affected the response of the electrodes, but other impurities likely to be present in power-station waters caused no significant effects. The standard deviation of analytical results varied from 0·4 to 1·2 µg per litre at concentrations of 2 and 26 µg of sodium per litre. Details of a recommended analytical procedure for discrete samples are given.
TL;DR: In this paper, a chromatographic method is described for the extraction and clean-up of organochlorine pesticide residues in animal fats and oils, fatty animal tissues, vegetable oils, dairy products and eggs.
Abstract: A chromatographic method is described for the extraction and clean-up of organochlorine pesticide residues in animal fats and oils, fatty animal tissues, vegetable oils, dairy products and eggs. The sample mixed with Celite is packed into a small column and the pesticide residues eluted with a little dimethyl sulphoxide. The eluate is then adsorbed on Florisil and the residues recovered from the dimethyl sulphoxide by elution with hexane. The amount of material passing through the clean-up is usually less than 0·01 per cent. of the sample.
TL;DR: In this paper, the authors reviewed the use of Landolt reactions among quantitative catalytic methods and presented the theoretical background of the method on a kinetic basis, showing that there is no need for instrumentation and temperature control.
Abstract: The place of Landolt reactions among quantitative catalytic methods is reviewed. By measuring the time lapse of the incubation period of a Landolt reaction (the reaction time) and plotting its reciprocal values versus catalyst concentration, a calibration graph can be obtained. The advantages of the use of Landolt reactions are as follows: there is no need for instrumentation and temperature control is simple. Theoretical backgrounds of the method are presented on a kinetic basis. During the analyses the uncatalysed and the catalysed reactions proceed simultaneously. The uncatalysed reaction can be examined separately if reaction time measurements are taken in the absence of the catalyst. Having obtained the velocity constant of the former, results of measurements of the reaction times of the simultaneous reactions can be evaluated to obtain the velocity constant of the catalysed reaction alone. The experimentally obtained calibration graph shows a linear correlation between reciprocal reaction time versus catalyst concentration; the rigorous kinetic examination, however, yields to a partly exponential correlation. By expanding the exponential member into a Taylor series and examining the error that arises by neglecting the non-linear members the simple linear correlation can be explained. Sensitivity, selectivity and precision of the methods are briefly discussed.
TL;DR: A spectrophotometric method for the determination of small amounts of mercury, thallium and gold is presented and Beer's law is followed up to absorbance of unity.
Abstract: A spectrophotometric method for the determination of small amounts of mercury, thallium and gold is presented. The sample is wet ashed with a nitric acid-hydrochloric acid mixture, and interferences are eliminated by adding ethylene glycol monomethyl ether and EDTA. Thallium interference is eliminated by adding sodium metabisulphite for mercury and gold, whereas excess oxidant interference is eliminated by adding hydroxylamine for thallium and gold. Because gold interferes in the determination of thallium and mercury, it is determined separately after heating the sample to volatilise the mercury. Iodide forms complexes with mercury and gold, whereas bromide forms complexes with thallium and gold. Crystal violet produces a tolueneextractable compound with these complexes in an acidic medium. A single extraction step suffices to determine 0·1 µg of each element in a 1-cm cell with a standard spectrophotometer at 605 nm; Beer's law is followed up to absorbance of unity. The method has been tested with urine, air, vegetation, water, soil, rocks and sediments.
TL;DR: In this paper, the emission spectra produced by nebulisation of organic liquids into a nitrogen-hydrogen diffusion flame burning in air, and into a laminar-flow pre-mixed airhydrogen flame were analyzed.
Abstract: A study is presented of the emission spectra produced by nebulisation of organic liquids into a nitrogen-hydrogen diffusion flame burning in air, and into a laminar-flow pre-mixed air-hydrogen flame. Both flames exhibit low background emissions and that of the diffusion flame is particularly low even over the OH-band region. Carbon, hydrogen and oxygen-containing compounds exhibit intense bands for CH, CHO, C2 and OH species. Nitrogen-containing organic compounds additionally display NH, NO and CN bands; chlorine-containing compounds give CCl bands in the diffusion flame; sulphur compounds give CS and S2 bands; and phosphorus compounds give HPO and PO bands.The spectral distribution of these bands and their intensities indicate that many types of organic compound can be characterised and identified by direct observation of their emission spectra during combustion in these cool flames.
TL;DR: There are numerous variations of the standard procedure, thus extending the range of application, and this is demonstrated with examples from the fields of drug research, phytochemistry, analysis of food additives and residues, and from organic and inorganic chemistry.
Abstract: A simple thermo micro procedure is described for the separation of many substances from solid materials and the direct transfer of these substances to the starting point of a thin-layer chromatographic plate. The sample is introduced into a glass cartridge with a conical tip, and heated rapidly for a short time at a pre-set temperature. The emerging vapours are deposited as a spot on the thin-layer chromatographic plate, which is then chromatographed in the usual way. There are numerous variations of the standard procedure, thus extending the range of application, and this is demonstrated with examples from the fields of drug research, phytochemistry, analysis of food additives and residues, and from organic and inorganic chemistry.
TL;DR: Bromophenol blue and bromothymol blue have been used in the past for the spectrophotometric determination of cationic surfactants, by extraction into 1,2-dichloroethane of the blue complex formed between the dye and the surfactant.
Abstract: Bromophenol blue and bromothymol blue have been used in the past for the spectrophotometric determination of cationic surfactants, by extraction into 1,2-dichloroethane of the blue complex formed between the dye and the surfactant. The method is shown to be unsatisfactory because the dyes can exist in both blue and yellow forms, and often an uncontrollable change of colour occurs in the organic phase. Picric acid, which produces a stable, intensely coloured complex with surfactants, is suggested as a substitute. The pH of the aqueous solutions is restricted to the range 4 to 12; high ionic strengths are not deleterious.
TL;DR: The cationic species ferroin is proposed for the determination of microgram amounts of anionic detergents by absorptiometry, and the development of the method is described in this article.
Abstract: The cationic species ferroin is proposed for the determination of microgram amounts of anionic detergents by absorptiometry, and the development of the method is described. For application to samples in aqueous solutions, the ferroin reagent has an iron(II) concentration of 50 p.p.m. and a molar excess of 1,10-phenanthroline of from 5 to 6. For sewage analysis, the reagent contains 500 p.p.m. of iron(II) and has a 1,10-phenanthroline-to-iron(II) ratio of 2·5. A typical precision for aqueous solution samples is ±1·4 per cent. and for sewage samples ±3·7 per cent. The results for sewage samples have been compared with those by the routine methylene-blue method. Interferences of common ions have been studied and the method has been used to assess the relative purity of three anionics used as reference standards. Some advantages of ferroin over methylene blue are suggested.Ferroin reagents should be replaced by iron(II)-bipyridyl reagents when samples contain more than a few p.p.m. of thiocyanate.
TL;DR: In this paper, a dilute solution of detergent is slightly acidified and mixed with 20 ml of the cobaltothiocyanate reagent and 20ml of dichloromethane, the mixture is shaken and allowed to separate.
Abstract: A dilute solution of the detergent is slightly acidified and mixed with 20 ml of the cobaltothiocyanate reagent and 20 ml of dichloromethane, the mixture is shaken and allowed to separate.The intensity of the colour of the dichloromethane is measured and the percentage of non-ionic detergent is calculated from straight-line calibration graphs.Graphs are given for varying amounts of ethylene oxide units per molecule and also for varying hydrophobic molecules. In addition, poly(ethylene glycols) of varying molecular weights were checked by this method, together with synthesised fatty acid-poly(ethylene glycol) esters in an attempt to find a relationship between molecular weight and the slope of the graph. It was found that both the hydrophobic and hydrophilic portions of the molecule affect the slope.Anionic detergents interfere in this determination, but a simple method to overcome this interference is given.
TL;DR: In this article, a method for determining the total sulphur content of soils is described that is sufficiently rapid (less than 4 minutes per sample) and sensitive (lower limit of detection less than 10 p.m.p.
Abstract: A method for determining the total sulphur content of soils is described that is sufficiently rapid (less than 4 minutes per sample) and sensitive (lower limit of detection less than 10 p.p.m. of sulphur) for survey and fertility investigations. A simple correction for matrix effects, caused by large variations (10 to 90 per cent.) of organic matter content has been found, based on the loss of weight at 450° C.
TL;DR: In this article, a kinetic and analytical study of the reaction of vanadium(IV) with potassium bromate is reported, and a possible mechanism is proposed for the reaction, which is found to obey the rate equation.
Abstract: A kinetic and analytical study of the reaction of vanadium(IV) with potassium bromate is reported. The kinetics were studied in perchloric acid media and the reaction was found to obey the rate equation [graphic omitted]. A value for k0 of 7·50 minute–1 was obtained at 20° C and an ionic strength of 0·10 M. Values for K1 of 88·8 lmole–1 and for the activation energy of 19 kcal. mole–1 were obtained, and a possible mechanism is proposed for the reaction.The determination of vanadium(IV) by photometric titration with potassium bromate is feasible at concentrations of vanadium(IV) down to 2 × 10–3M and at sulphuric acid concentrations above 0·06 M. An accuracy of ±0·5 per cent. is obtained for concentrations of vanadium(IV) between 5 and 10 × 10–3M. Under these acid conditions bromate acts as a five electron oxidant and bromine is a primary product of the reaction.
TL;DR: In this article, a submerged oscillator-capillary technique is described, which produces a frequency and phase-stable intermittent fluid supply at 50 Hz to the flame of a flame spectrophotometer.
Abstract: A submerged oscillator-capillary technique is described, which produces a frequency and phase-stable intermittent fluid supply at 50 Hz to the flame of a flame spectrophotometer. With this technique the background radiation from the flame can be suppressed.The cooling effect of the nebulised water on the flame is overcome by the choice of a suitable organic solvent. The usefulness of the technique is demonstrated with typical spectral curves.