Showing papers in "Analyst in 1981"
TL;DR: In this article, a laser-inductively coupled plasma microprobe was used for volatilisation of solid samples into the plasma, which produced linear calibrations for a range of elements.
Abstract: A laser-inductively coupled plasma microprobe has been assembled from commercially available instruments, viz., a laser microprobe and an inductively coupled plasma source optical-emission spectrometer (ICP), together with a simply constructed sample chamber and a light-activated switch. The purpose of the combination was the volatilisation of solid samples into the plasma. The system was tested with a series of standard steel samples, which produced linear calibrations for a range of elements. The absolute detection limits obtained were comparable to those obtained with solution nebulisation on the same ICP and the precision was good for elements homogeneously distributed in the sample. Initial work on calibration for silicate rocks was undertaken.
139 citations
TL;DR: In this article, the performance of an instrument using an inductively coupled plasma as an ion source with a high resolution mass filter to analyse the extracted ions is described, and the spectral characteristics of the technique are discussed.
Abstract: The performance of an instrument using an inductively coupled plasma as an ion source with a high resolution mass filter to analyse the extracted ions is described. A description of the experimental system is given and the spectral characteristics of the technique are discussed. The current performance of the technique for simple solution analysis is described, and the future potential for trace element analysis and isotope ratio measurement is assessed.
133 citations
123 citations
113 citations
TL;DR: In this article, a technique for the determination of "inorganic" arsenic(III), "methylarsenic" and "dimethylarsenic", species is described which is based on the trapping of arsines and selective volatilisation into a heated quartz atomiser tube situated in the optical path of an atomic-absorption spectrometer.
Abstract: A technique for the determination of “inorganic” arsenic(III) and arsenic(V), “methylarsenic” and “dimethylarsenic” species is described which is based on the trapping of arsines and selective volatilisation into a heated quartz atomiser tube situated in the optical path of an atomic-absorption spectrometer. Improved reproducibility is obtained by the use of a continuous flow reduction stage and detection limits are approximately 0.25 ng (based on twice the standard deviation of 10 blank measurements). For a typical sample volume of 10 ml this corresponds to a detection limit of 0.025 ng ml–1 of arsenic. Interferences were investigated and depression of results was observed in the presence of silver(I), gold(III), chromium(VI), iron(II), iron(III), germanium(IV), molybdenum(VI), antimony(III), antimony(V), tin(II), manganese(VII) and nitrite. Various approaches to overcoming such interferences were investigated, and for general use masking with EDTA is advocated. The choice of extraction procedures for speciation analysis is discussed.
112 citations
TL;DR: In this paper, a comparison between the use of flame, electrothermal and inductively coupled plasma atomisation techniques for the analysis of slurries is made and the results show that atomisation efficiency in nebuliser-based systems is dependent on sample transport efficiency, particle size, atomisation temperature and sample matrix.
Abstract: A comparison is made between the use of flame, electrothermal and inductively coupled plasma atomisation techniques for the analysis of slurries. For flame atomisation, pulsed nebulisation must be used and for inductively coupled plasma atomisation a high-solids cross-flow nebuliser is essential. The results show that atomisation efficiency in nebuliser-based systems is dependent on sample transport efficiency, particle size, atomisation temperature and sample matrix. For analytical determinations it is necessary to grind the sample to a particle size of less than 10 µm and to use standards that are closely matched to the samples. For electrothermal atomisation, particle-size effects become significant only above 25 µm when sampling becomes the major source of error.
74 citations
TL;DR: In this article, a method based on dithiocarbamate pre-concentration and inductively coupled plasma emission spectrometry is described for the simultaneous determination of cadmium, copper, iron, molybdenum, nickel, vanadium and zinc in sea water.
Abstract: A method based on dithiocarbamate pre-concentration and inductively coupled plasma emission spectrometry is described for the simultaneous determination of cadmium, copper, iron, molybdenum, nickel, vanadium and zinc in sea water. The metals are extracted from 500 g of sea water with ammonium tetramethylenedithiocarbamate-diethylammonium diethyldithiocarbamate in chloroform and back-extracted into nitric acid; the sea water concentration factor is 250 or 500. Advantages of the method include high precision, simplicity of calibration and a detection capability in the nanograms per litre range. The method has been applied to Japan Sea, Pacific Ocean and Atlantic Ocean samples.
60 citations
TL;DR: A variety of sample presentation and atomisation methods have been examined to obtain sufficient sensitivity for the trace determination of tin tetraalkyls and alkyltin chlorides (RnSnCl4n; R = methyl or ethyl; n= 1-4) after their separation by gas-liquid or by high-performance liquid-liquid chromatography.
Abstract: A variety of sample presentation and atomisation methods have been examined to obtain sufficient sensitivity for the trace determination of tin tetraalkyls and alkyltin chlorides (RnSnCl4–n; R = methyl or ethyl; n= 1–4) after their separation by gas-liquid or by high-performance liquid-liquid chromatography. Detection limits range from 10–20 µg (flame atomisation) to 1 µg (direct pyrolysis) and 2–20 pg (hydride reduction followed by direct pyrolysis). The construction of systems including an automated hydride generator is described.
58 citations
TL;DR: In this paper, a method based on high-performance liquid chromatography (HPLC) with electrochemical detection is described for the determination of aromatic and aliphatic isocyanates in air.
Abstract: A method based on high-performance liquid chromatography (HPLC) with electrochemical detection is described for the determination of aromatic and aliphatic isocyanates in air. 1-(2-Methoxyphenyl)piperazine is used as the electrogenic reagent. It forms electrochemically active derivatives with all of the isocyanates of occupational hygiene interest that are readily oxidised at carbon electrodes. In addition, these derivatives are strongly absorbing in the ultraviolet region, enabling a combination of electrochemical and ultraviolet detectors to be employed to provide additional qualitative information if required.Comparison is made between the electrochemical detection method and HPLC-ultraviolet detection methods for isocyanate analysis. The electro-chemical detection method was found to be significantly more sensitive than the ultraviolet detection methods for the determination of phenyl isocyanate, toluene diisocyanate, hexamethylene diisocyanate and (4,4′-diisocyanatodiphenyl)methane in air.
54 citations
TL;DR: Two methods are described for the determination of total inorganic arsenic in fish and fish products: the distillation method and the chelation and extraction of in organic arsenic after sample dissolution in sodium hydroxide solution.
Abstract: Two methods are described for the determination of total inorganic arsenic in fish and fish products. The first method involves separation of the inorganic arsenic by distilling it from 6.6 N hydrochloric acid. The second method involves chelation and extraction of inorganic arsenic after sample dissolution in sodium hydroxide solution, with subsequent back-extraction and oxidation. In both methods the arsenic concentration is measured, after hydride generation by atomic-absorption spectrophotometry with atomisation in a flame-heated silica tube: with the first method the solution contains arsenic(III), and in the second the solution contains arsenic(V). Results obtained by both methods are in agreement over a range of samples. The distillation method is favoured for reasons of efficiency and economy in time. The derived limit of detection and confidence intervals are given.
49 citations
TL;DR: In this paper, the authors compared the performance of different electrodes for detecting tetraphenylborate salts of barium complexes in detergent powders, and found that the electrode based on Antarox CO-430 is superior in its response to non-ionic surfactants.
Abstract: Electrodes having PVC matrix membranes consisting of 2-nitrophenyl phenyl ether and sensors of the tetraphenylborate salts of barium complexes with Antarox CO-730, Antarox CO-430, Lutensol AO7 and Monflor 51 are compared with the corresponding electrodes of barium complexes with Antarox CO-880. Generally, they are inferior to the Antarox CO-880 electrodes for sensing barium ions. However, all of the electrodes respond to non-ionic surfactants in the manner described previously for the Antarox CO-880 system.The electrode based on Antarox CO-430 is considered to be superior in its response to non-ionic surfactants and shows some selectivity towards these materials compared with its response towards cationic and anionic surfactants. The electrode has been evaluated for determining Dobanol 25-7, Synperonic 7 and Lutensol AO7 in detergent powders with good recoveries of the non-ionic surfactants and relative standard deviations ranging between 0.8 and 4.0%. The recommended procedure is based on known (standard) addition which, although taking up to 2 h to complete, is faster than analate addition.
TL;DR: In this article, the redox behavior of molybdovanadophosphate at a glassy carbon electrode is described and a procedure is given for the voltammetric determination of phosphate as molybdenamide at a carbon electrode in a static system.
Abstract: The redox behaviour of molybdovanadophosphate at a glassy carbon electrode is described and a procedure is given for the voltammetric determination of phosphate as molybdovanadophosphate at a glassy carbon electrode in a static system. Procedures are also given for the voltammetric flow injection determination of phosphate, silicate, arsenate and germanate by the injection of heteropolyacids pre-formed in various aqueous, aqueous acetone and aqueous ethanolic reagents into eluents consisting of the reagent blank. This procedure effectively eliminates the background signal of the blank and allows precise determinations to be made. Plots of electrode potential against the current obtained are given.Silicate and phosphate can be determined at 10–7 and 10–6M levels, respectively. Arsenate has only been determined at the 10–5M level, and the precise determination of germanate is difficult owing to adsorption at the glassy carbon electrode.
TL;DR: Using high performance liquid chromatography it has been possible to separate 14 lanthanide elements in less than 40 min by elution with an α-hydroxyisobutyric acid concentration gradient LiChrosorb KAT cation exchanger (10 µm) as discussed by the authors.
Abstract: Using high-performance liquid chromatography it has been possible to separate 14 lanthanide elements in less than 40 min by elution with an α-hydroxyisobutyric acid concentration gradient LiChrosorb KAT cation exchanger (10 µm) is used as the packing material and the eluted lanthanides are detected with an ultraviolet detector after complexation with Arsenazo III The detection limit is about 01 µgDeterminations of the rare-earth composition in monazite sand and rare-earth impurities in high-purity lanthanum(III), cerium(IV), samarium(III) and yttrium(III) oxides were carried out The proposed method is more convenient than others, and the separation of major components is not necessary in analyses of high-purity rare earths; the elution time is only about 1 h
TL;DR: An enzymatic method for the determination of alcohol using flow injection analysis is described, and in both instances the result is available less than 30 s after injection.
Abstract: An enzymatic method for the determination of alcohol using flow injection analysis is described. Samples are suitably diluted and introduced directly into the system. Blood alcohol is analysed by the stop-flow technique at a rate of 70–80 samples per hour and the results are compared with those from headspace gas chromatography. Alcohol in several beverages is analysed by the continuous-flow technique at a rate of up to 120 samples per hour. In both instances the result is available less than 30 s after injection.
Journal Article•
TL;DR: A method for the separation of 17 different polynuclear aromatic hydrocarbons (PAHs) has been developed and work on stubble smoke has been confined to benzo[a]pyrene only.
Abstract: A method for the separation of 17 different polynuclear aromatic hydrocarbons (PAHs) has been developed. After separation by thin-layer chromatography, the PAHs are examined by high-performance liquid chromatography using ODS and PPS stationary phases. The elution times of all 17 compounds relative to benzo[a]pyrene have been computed. Six representative compounds have been added to bierwurst and to water to check recovery values. Work on stubble smoke has been confined to benzo[a]pyrene only. The method of extraction and clean-up varies with the substrate but the method of determination of the PAH compounds in the final extract is the same in all three cases. Confirmation of identity is obtained by measuring the peak-height ratios for each PAH at two different excitation and emission wavelength combinations. The limit of detection of benzo[a]pyrene is 0.02 µg kg–1 in food, 0.3 ng l–1 in water and 150 pg per filter in smoke. Recoveries of the six representative compounds are generally in the range 75–100% at levels approaching the limit of detection.
TL;DR: In this article, a spectrophotometric titration method is described for the determination of some alkaloids and their dosage forms using 0.005 M chloranilic acid solution in 1,4-dioxan as the titrant.
Abstract: A spectrophotometric titration method is described for the determination of some alkaloids and their dosage forms using 0.005 M chloranilic acid solution in 1,4-dioxan as the titrant. The end-point is determined by measuring the change in absorbance of the sample at 535 nm. Quantitative recoveries with good reproducibility are reported for atropine, emetine, reserpine, strychnine, yohimbine and four dosage forms. The least-squares method for the end-point location in the spectrophotometric titration is also proposed.
TL;DR: In this article, the response characteristics of barium ion-selective electrodes to various alkoxylates have been investigated in aqueous and annealing test solutions in the presence and absence of the barium ions and the presence of sodium and potassium salts.
Abstract: The response characteristics of barium ion-selective electrodes to various alkoxylates have been investigated in aqueous and aqueous-ethanol test solutions in the presence and absence of barium ions and in the presence of sodium and potassium salts.The observed potentiometric response is an increase in the e.m.f. of the barium ion-selective electrode of up to about 100 mV, according to the amount of added alkoxylate in the 2 × 10–5–10–3M range. The response is linear with log[alkoxylate], but is characterised by a break in the linearity, which is attributed to the critical micelle concentration (CMC) of this class of non-ionic surfactants.The alkoxylates studied include nonylphenoxypoly (ethyleneoxy) ethanols (NPs) of the Antarox CO series, namely, CO-430, -630, -730, -850, -880 and -890; octylphenoxypoly (ethyleneoxy)ethanols (OPs), namely, Antarox CA-620 and Triton X-100; a sorbitan-9-octadecanoate poly (ethyleneoxy)ethanol, namely, Tween 80; alkylpoly (ethyleneoxy)ethanols, namely, Dobanol 25–7, Lutensol AO7 and Synperonic 7; a fluoroalkyl poly(ethyleneoxy)ethanol, namely, Monflor 51; poly(ethylene glycol)(PEG) 1540; and poly(propylene glycol)(PPG) 1025. CMCs were characterised in all instances except for PEG 1540, where the increases in the e.m.f. values were smaller than for the other materials studied.Anionic surfactants gave small decreases in e.m.f., but the cationic surfactant, benzyldimethylhexadecylammonium chloride, gave a large increase in e.m.f. characteristic of a cationic response.Exposure to alkoxylates reduced the lifetime of the barium ion-selective electrodes.
TL;DR: Four of the biogenic amines thought to occur in chocolate were analysed and quantified at varying levels in extracts of several kinds of chocolate and chocolate liquors.
Abstract: Some biogenic amines occur in a wide variety of foods including cheese, fish, bakery products, milk products and chocolate. This study was undertaken to analyse and quantify four of the biogenic amines thought to occur in chocolate. Tyramine, tryptamine, 2-phenylethylamine and serotonin (5-hydroxytryptamine) were chosen as the amines of interest. Two high-performance liquid chromatographic (HPLC) systems were used for the final analysis of amine extracts. Both systems employed dual detection, with the first using ultraviolet absorbance at 254 nm and the formation of a post-column o-phthaldehyde derivative. The second method used ultraviolet absorbance at 254 nm and the natural fluorescence of the four amines. Thin-layer chromatography (TLC) was performed on all of the extracts to provide further confirmation. All four amines were detected and quantified at varying levels in extracts of several kinds of chocolate and chocolate liquors.
TL;DR: In this paper, a flow injection analysis (FIA) method is described for the continuous, rapid determination of chemical oxygen demand (COD), which uses acidic potassium permanganate solution as both an oxidant and a spectrophotometric reagent, and glucose as a standard.
Abstract: A method is described for the continuous, rapid determination of chemical oxygen demand (COD). The method is based on flow injection analysis (FIA) and uses acidic potassium permanganate solution as both an oxidant and a spectrophotometric reagent, and glucose as a standard. COD values for aqueous environmental samples, such as industrial wastewaters, are compared with those obtained using the Japanese Industrial Standard (JIS) method and are found to be within an error range of ±30%. The method is comparable to other manual and automatic methods and has several advantages. A sampling rate of 20 samples per hour can be achieved, and the detection limit and precision are 5 mg l–1 as COD and 0.6%, respectively. Chloride ion up to levels of 6000 mg l–1 does not interfere, even in the absence of silver salts.
TL;DR: In this article, the blue hexanol extract exhibits a maximum absorption at 605-615 nm, and the molar absorptivity and Sandell's sensitivity were found to be 5.24 × 104 l mol−1 cm−1 and 0.00088 µg cm−2, respectively.
Abstract: Nitrite ion reacts with 4-nitroaniline in hydrochloric acid medium to form 4-nitrophenyldiazonium chloride, which couples with naphth-1-ol in alkaline medium to give a purple azo dye (λmax.= 580 nm, Iµ= 3.7 × 104 l mol–1 cm–1). The dye can be extracted into higher alcohols. This extraction process is used for the determination of sub-microgram amounts of nitrite spectrophotometrically. Of the alcohols studied (butanol, pentanol, isopentanol, hexanol and octanol), hexanol was found to be the most suitable extractant. The blue hexanol extract exhibits a maximum absorption at 605–615 nm. Beer's law is obeyed over the nitrite concentration range 0.02–0.14 p.p.m. The molar absorptivity and Sandell's sensitivity were found to be 5.24 × 104 l mol–1 cm–1 and 0.00088 µg cm–2, respectively. The optimum reaction conditions for diazotisation, full colour development and the effect of variables have been studied. Several common ions do not interfere with the method if appropriate masking agents are used. The method has been applied successfully to the determination of nitrite in samples of river water.
TL;DR: In this article, a sensitive and precise method for the determination of microgram amounts of palladium, based on the ion associate of the anionic palladium(II)-thiocyanate complex with Methylene Blue (MB), has been developed.
Abstract: A sensitive and precise method for the determination of microgram amounts of palladium, based on the ion associate of the anionic palladium(II)-thiocyanate complex with Methylene Blue (MB), has been developed. The ion associate is floated with benzene and dissolved in acetone, and its molar absorptivity is found to be 1.7 × 105 l mol–1 cm–1 at 660 nm. The formation of the ion associate takes place over a wide pH range (1–6). The method is selective; interfering metals include silver, platinum, ruthenium, molybdenum and tungsten. The composition of the ion associate has been established as [MB+]2[Pd(SCN)42–]. The proposed method has been applied to the determination of trace amounts of palladium in high-purity silver after its preliminary separation from the matrix as palladium dimethylglyoximate.
TL;DR: A high-performance liquid chromatographic procedure for the determination of tryptophan has been developed using the native fluorescence of the molecule as a means of detection and results showed the two methods to be statistically equivalent.
Abstract: A high-performance liquid chromatographic procedure for the determination of tryptophan has been developed using the native fluorescence of the molecule as a means of detection. Proteins were hydrolysed with 6 M sodium hydroxide solution in the presence of maltodextrin, which has been demonstrated to prevent tryptophan degradation. Comparison of results from the proposed method with those from an existing procedure developed by Slump and Schreuder showed the two methods to be statistically equivalent. A wide range of feeds and feed ingredients were analysed, and the measured tryptophan levels were within the range expected from published data. The proposed method is rapid, sensitive and specific, and is recommended for routine laboratory use.
TL;DR: In this article, a range of Chromosorbs and Tenax-GC have been compared with regard to their efficiency as adsorbents for volatile odorous compounds using a very simple model system.
Abstract: A range of Chromosorbs and Tenax-GC have been compared with regard to their efficiency as adsorbents for volatile odorous compounds using a very simple model system. When desorption was accomplished by solvent elution using acetone, Chromosorb 103 provided the best recoveries of those investigated (between 90 and 95%). In situations where thermal lability of trapped compounds is not a problem, use of Tenax-GC and thermal desorption at about 250 °C would be recommended on the basis of this survey, during which this approach consistently provided recoveries greater than 96% from small sample volumes. The latter procedure was applied to the analysis of an industrial malodour from an animal rendering factory, and using gas chromatography-mass spectrometry over 35 compounds (92% of the total odour sample) were positively identified. In particular, a range of alkylthiophenes may be characteristic of this particular odour.
TL;DR: A high-performance liquid chromatographic method has been developed for the determination of riboflavin and flavin mononucleotide using a C22 reversed-phase column packing material, which agrees well with those obtained by microbiological assay.
Abstract: A high-performance liquid chromatographic method has been developed for the determination of riboflavin and flavin mononucleotide (FMN) using a C22 reversed-phase column packing material. Mean recoveries of 100%(±5%) for riboflavin and 102%(±2%) for FMN were obtained. Multiple determinations of the vitamin in two samples indicated a precision of ±5%. The results agree well with those obtained by microbiological assay. Riboflavin and FMN are eluted within 9 min, and the total time for the analysis of most samples is 3.5 h. The lifetime of the reversed-phase column is far greater than that of silica columns. After 500 sample loadings no deterioration of column efficiency occurred. The method is suitable for the determination of riboflavin down to the 0.01 mg per 100 g level. For samples with a lower vitamin content trace enrichment can be used, which involves only a few minutes' extra analysis time.
TL;DR: In this article, the experimental conditions leading to maximum charge-transfer bands were also studied and the proposed procedures have been applied successfully to pure samples and drug formulations with good accuracy The average recovery was 10026-10084% with piperazine-iodine and 9933-10033% with Piperazine-chloranil charge transfer complexes, with an average standard deviation for each method of 08-39%
Abstract: Iodine-piperazine or chloranil-piperazine charge-transfer complexes have been used for the sensitive assay of piperazine or its salts; these complexes exhibit intense absorption bands in the electronic spectrum The molecular ratios of the reactants in the complexes have been established and the experimental conditions leading to maximum charge-transfer bands were also studied The proposed procedures have been applied successfully to pure samples and drug formulations with good accuracy The average recovery was 10026–10084% with piperazine-iodine and 9933–10033% with piperazine-chloranil charge-transfer complexes, with an average standard deviation for each method of 08–39%
TL;DR: In this article, a procedure for the quantitative determination of seven known major constituents in sun-dried roots, rhizomes and commercially powdered samples of Piper methysticum was described.
Abstract: A procedure is described for the quantitative determination of seven known major constituents in sun-dried roots, rhizomes and commercially powdered samples of Piper methysticum. A 3.0–8.0-g amount of powdered sample is extracted with chloroform in a Soxhlet apparatus for 6 h. After evaporation of solvent the extract (about 0.35 g) is dried at 100 °C for 2 h and then dissolved in chloroform to about 0.7%m/V concentration. The resulting solution is analysed by gas-liquid chromatography using dual 1.5 m × 4 mm i.d. glass columns, containing 3%m/m of OV-1 on Chromosorb W HP, and dual differential flame-ionisation detectors with nitrogen as carrier gas, the column temperature being 210 °C. There is no interference from the eight other trace constituents, non-polar low-boiling compounds or polar “tarry” material.