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Showing papers in "Analyst in 1992"


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The water-soluble titanium(IV)-porphyrin complex, oxo[5, 10, 15, 20, 20-tetra(4-pyridyl)porphrinato]titanium(IV)[TiO(tpyH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide as mentioned in this paper.
Abstract: The water-soluble titanium(IV)–porphyrin complex, oxo[5, 10, 15, 20-tetra(4-pyridyl)porphyrinato]titanium(IV)[TiO(tpyH4)4+], was found to enhance the spectrophotometric determination of trace amounts of hydrogen peroxide. A 0.05 mol dm–3 hydrochloric acid solution containing TiO(tpypH4)4+ was used (the Ti—TPyP reagent), the absorbance of which decreased at 432 nm as hydrogen peroxide was added. This was due to the consumption of the TiO(tpypH4)4+ complex following the formation of peroxo[5, 10, 15, 20-tetra(4-pyridyl)porphyrinato]titanium(IV). The decrease in absorbance at 432 nm (ΔA432) was proportional to the concentration of hydrogen peroxide, from 1.0 × 10–8 to 2.8 × 10–6 mol dm–3, in the sample solution (25 pmol–7.0 nmol per assay). The reaction was accelerated by hydrogen ions; the presence of 1.6 mol dm–3 perchloric acid was found to promote complexation to the greatest extent. A ΔA432 of 1.9 × 105 was found for 1 mol dm–3 hydrogen peroxide. A measurement precision of 1.2% for 1.0 × 10–6 mol dm–3 hydrogen peroxide (n= 8) was obtained. The reagent can be used for the determination of hydrogen peroxide in water samples such as tap water and rainwater over the range from 1.05 × 10–7 to 3.34 × 10–5 mol dm–3.

382 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: By co-immobilizing a hydrogen peroxide-producing oxidase with the peroxidase, amperometric biosensors can be made that respond to the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions.
Abstract: An apparent direct electron transfer between various electrode materials and peroxidases immobilized on the surface of the electrode has been reported in the last few years. An electrocatalytic reduction of hydrogen peroxide stars at about +600 mV versus a saturated calomel (reference) electrode (SCE) at neutral pH. The efficiency of the electrocatalytic current increases as the applied potential is made more negative and starts to level off at about –200 mV versus SCE. Amperometric biosensors for hydrogen peroxide can be constructed with these types of peroxidase modified electrodes. By co-immobilizing a hydrogen peroxide-producing oxidase with the peroxidase, amperometric biosensors can be made that respond to the substrate of the oxidase within a potential range essentially free of interfering electrochemical reactions. Examples of glucose, alcohol and amino acid sensors are shown.

351 citations



Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The improved procedure described here for the removal of starch and hydrolysis of NSP applies to all three techniques, but only the method for measurement of sugars by gas-liquid chromatography is described here in full.
Abstract: An improved method is described for the measurement of total, soluble and insoluble dietary fibre as non-starch polysaccharides (NSP). An established procedure is modified to allow more rapid removal of starch and hydrolysis of NSP. In its present form the procedure is simpler and more robust than those previously published. In the modified method starch is removed enzymically within 50 min and NSP is precipitated with ethanol and then hydrolysed by treatment with sulfuric acid for 2 h. The constituent sugars can in turn be measured by gas–liquid chromatography, high-performance liquid chromatography or more rapidly by colorimetry. The improved procedure described here for the removal of starch and hydrolysis of NSP applies to all three techniques, but only the method for measurement of sugars by gas–liquid chromatography is described here in full.

165 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100-200 ng l-1.
Abstract: A rapid, sensitive and selective method for the differential determination of CrIII and CrVI in natural waters is described. Chromium(VI) can be determined directly by flow injection on-line sorbent extraction preconcentration coupled with electrothermal atomic absorption spectrometry using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of CrIII to CrVI by potassium peroxydisulfate. Chromium(III) can be calculated by difference. The optimum conditions for sorbent extraction of CrVI and oxidation of CrIII to CrVI are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 µl samples was achieved after preconcentration for 60 s, giving detection limits of 16 ng l–1 for CrVI and 18 ng l–1 for total Cr (based on 3σ). Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100–200 ng l–1. The selectivity of the determination of CrVI was evaluated by analysing spiked reference materials in the presence of CrIII, resulting in quantitative recovery of CrVI.

160 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: Four As compounds were successfully separated and detected by single-column ion chromatography with inductively coupled plasma (ICP) mass spectrometric detection by reducing the mass spectral interferent ArCl+ by chromatographically resolving chloride from the negatively charged arsenic species.
Abstract: Four As compounds were successfully separated and detected by single-column ion chromatography with inductively coupled plasma (ICP) mass spectrometric detection. The mass spectral interferent ArCl+ was reduced by chromatographically resolving chloride from the negatively charged arsenic species. Determination of four As species was investigated in urine, club soda and wine. Detection limits of 0.16 ng of As(III), 0.26 ng of As(v), 0.073 ng of dimethylarsinic acid (DMA) and 0.18 ng of methylarsonic acid (MMA) in wine were obtained. Sensitivity was further improved by using an He-Ar mixed gas ICP as the ionization source. However, the intensity of the ArCl+ interference was also increased using this plasma. Detection limits of 0.063 ng of As(III), 0.037 ng of As(v), 0.032 ng of DMA and 0.080 ng of MMA in club soda were achieved using the He-Ar plasma source. Similar limits of detection were found in urine and wine.

140 citations


Journal ArticleDOI
01 Jan 1992-Analyst

135 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The adsorption of glucose oxidase at a platinum electrode followed by immobilization in an electrochemically polymerized phenol film was found to be a reproducible method for the fabrication of enzyme microelectrodes responsive to glucose.
Abstract: The adsorption of glucose oxidase at a platinum electrode followed by immobilization in an electrochemically polymerized phenol film was found to be a reproducible method for the fabrication of enzyme microelectrodes responsive to glucose. The observed responses were comparable to those predicted on the basis of monolayer coverage of the enzyme. The electrodes were found to be stable for more than 40 d on storage at 4 °C.

113 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: In this paper, lead-II ion-selective polyvinyl chloride membrane electrodes based on monobenzo-15-crown-5 (MB15C5), MB 15C5-phosphotungstic acid (PW) and MB 15 C5−phosphomolybdic acid (PMo) as neutral carriers were prepared.
Abstract: Lead(II) ion-selective poly(vinyl chloride) membrane electrodes based on monobenzo-15-crown-5 (MB15C5), MB15C5–phosphotungstic acid (PW) and MB15C5–phosphomolybdic acid (PMo) as neutral carriers were prepared. All these crown ether electrodes gave linear responses with near-Nernstian slopes of 30 mV per decade within the concentration range 1 × 10–1–1 × 10–5 mol dm–3 Pb2+. The Pb2+ electrodes based on MB15C5–PW and MB15C5–PMo showed better sensitivities, with detection limits of 1 × 10–6 mol dm–3, than the electrode based on MB15C5 with a detection limit of 1 × 10–5 mol dm–3. Selectivity coefficients of various interfering ions for these electrodes were determined and were sufficiently small for most of them. Among these electrodes, the electrode based on pure MB15C5 exhibited the best selectivity. Effects of the pH of test solutions, the concentrations of internal solutions in the electrodes and the composition of the membranes were investigated.

109 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: In this article, the design, fabrication and evaluation of chemically modified screen-printed carbon electrodes are described with particular emphasis being placed on the practical details for sensor construction, and some preliminary results for the selective determination of reduced glutathione in human whole blood are also presented.
Abstract: The design, fabrication and evaluation of chemically modified screen-printed carbon electrodes is described with particular emphasis being placed on the practical details for sensor construction. This work employed cyclic and differential-pulse voltammetry, together with amperometry in stirred solutions to investigate systematically electrodes containing phthalocyanine and ferrocene-based mediators for the determination of several important biomolecules. An overview of the development of an amperometric assay using the enzyme glutathione peroxidase, and some preliminary results, for the selective determination of reduced glutathione in human whole blood is also presented.

104 citations


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The response mechanism of poly(pyrrole) to a selection of gases and vapours was investigated using two techniques: measurement of resistance change and mass changes using a piezoelectric quartz crystal microbalance with the objective of characterizing responses for incorporation in sensor arrays as discussed by the authors.
Abstract: The response mechanism of the conducting polymer poly(pyrrole) to a selection of gases and vapours was investigated using two techniques: measurement of resistance change and mass changes using a piezoelectric quartz crystal microbalance with the objective of characterizing responses for incorporation in sensor arrays. Bromide-doped films were exposed to methanol, hexane, 2-2-dimethylbutane, ammonia and hydrogen sulfide. Polymers of different thicknesses were also exposed to methanol vapour and the response profiles were studied. The responses were all of a Fickian type except the piezoelectric signal, which exhibited an anomalous non-Fickian response to methanol. This suggests that the poly(pyrrole) resistance changes frequently observed are partly due to one stage in the two-stage sorption perhaps involving the swelling of the polymer. It was concluded that the response mechanism of poly(pyrrole) sensing of different gases and vapours is due to a mixed response involving electronic effects and physical effects.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The location-specific differences in the distribution of 90Sr and, to a lesser extent, 137Cs arise because of fallout speciation rather than because of local environmental factors.
Abstract: A sequential extraction procedure has been applied to study the speciation of Chernobyl-derived radionuclides (137Cs and 90Sr) in soils from Norway, and from Byelorussia and the Chernobyl region in the USSR. Most 137Cs (>80%) was strongly associated with soil components, whereas 90Sr was more mobile, up to 70% being found in the easily extractable fractions. The 90Sr : 137Cs ratio decreased with the distance from the reactor, reflecting the higher proportion of hot particles deposited in the regions close to the reactor, and the easily extractable fraction of 90Sr was significantly lower in the soils collected from the Chernobyl area. The distribution of stable Cs and stable Sr in the extraction fractions was similar for the various sites. Therefore, the location-specific differences in the distribution of 90Sr and, to a lesser extent, 137Cs arise because of fallout speciation rather than because of local environmental factors.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic separations with element-selective detection using inductively coupled plasma mass spectrometry (ICP-MS).
Abstract: A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element-selective detection using inductively coupled plasma mass spectrometry (ICP-MS). The DIN injects all of the sample into the ICP and has a dead volume of less than 1 µl. Charged species of arsenic and tin are separated as ion pairs on a micro-scale (1 mm i.d.), packed, reversed-phase column. Detection limits are 0.2–0.6 pg for arsenic and 8–10 pg for tin. For methanol + water eluents, the signal is highest at 25% methanol and stays within 25% of this maximum as the methanol fraction is varied from 20 to 80%. Compared with LC–ICP-MS with conventional nebulizers, the absolute detection limits and chromatographic resolution are substantially superior, and the dependence of analyte signal on solvent composition is somewhat less severe with the DIN.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The accuracy and precision of the proposed method were established by the analysis of Seronorm lyophilized human whole blood standards for methyl- and inorganic mercury, and no statistical difference between the sum of these two species determined by the GC-MPD based method and the recommended total mercury concentrations in the Seron Worm samples was observed.
Abstract: Methyl- and inorganic mercury were extracted from human whole blood samples, as their diethyldithiocarbamate complexes, into toluene and butylated by using a Grignard reagent. The mercury species were then separated by gas chromatography (on a 12 m non-polar DB-1 capillary column) and detected by a microwave-induced plasma atomic emission spectrometric (GC-MPD) system. The accuracy and precision of the proposed method were established by the analysis of Seronorm lyophilized human whole blood standards for methyl- and inorganic mercury. No statistical difference (t-test) between the sum of these two species determined by the GC-MPD based method and the recommended total mercury concentrations in the Seronorm samples was observed. Results for the determination of methyl- and inorganic mercury in 60 controls and 90 previously occupationally exposed (to inorganic mercury) workers are presented to illustrate the practical utility of the proposed method. No significantly elevated inorganic mercury concentrations between the two groups were evident.


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A flow injection system for on-line microwave digestion of slurried samples with direct elemental determinations by flame atomic absorption spectrometry is described in this article, which is optimized for slurry mass, acid strength and tube and microwave cavity geometry.
Abstract: A flow injection (FI) system for on-line microwave digestion of slurried samples with direct elemental determinations by flame atomic absorption spectrometry is described. Organically based elemental reference samples were prepared as slurries in 5% v/v HNO3 and the system was optimized for slurry mass, acid strength and tube and microwave cavity geometry. Bubble formation during digestion was controlled by post-digestion cooling and pressure regulation. Comparison of direct and FI calibrations indicated no apparent loss in sensitivity. Various samples were examined and elemental recoveries for Ca, Fe, Mg and Zn were typically found to be in the range 94–107% with precisions of less than 4.5% relative standard deviation. The major source of error was found to be in the dispersion of solids (<180 µm) as slurries in dilute HNO3. The through put of samples in the system developed was found to be 1–2 min per sample.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: Speciation of 90Sr and 137Cs in soils and bottom sediment was determined and migration of each chemical form was described by a convective-dispersive equation taking into account transformation processes of radionuclide species in soils or bottom sediments.
Abstract: Field and laboratory experiments have been used to study the behaviour of long-lived radionuclides in the zone affected by the Chernobyl accident. Speciation of 90Sr and 137Cs in soils and bottom sediments was determined. The principal distinction of the Chernobyl fallout was that it contained a relatively small proportion of exchangeable forms because a considerable fraction of the radionuclides was incorporated as part of the insoluble fuel particles. Disintegration of fuel particles in soils and bottom sediments results in transition of non-exchangeable forms into exchangeable forms. Radionuclide species have different pathways and rates of migration in soils and bottom sediments. Migration of each chemical form was described by a convective–dispersive equation taking into account transformation processes of radionuclide species in soils or bottom sediments. Adsorption of 90Sr and 137Cs in the environment is controlled by the cation-exchange capacity and the selectivity of the solid phase (i.e., soil, bottom sediments and suspended matter) and the cationic composition of the liquid phase (i.e., soil solution, surface run-off and river or lake water). The corresponding parameters for the processes were obtained.


Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: Reversed-phase high-performance liquid chromatography with ultraviolet detection was optimized for the simultaneous separation and quantification of nine organic mercury compounds: methyl-, ethyl-, phenyl-, methoxyethyl, ethoxyethyl-, benzoic and tolylmercury, mersalylic acid and nitromersol.
Abstract: Reversed-phase high-performance liquid chromatography with ultraviolet detection was optimized for the simultaneous separation and quantification of nine organic mercury compounds: methyl-, ethyl-, phenyl-, methoxyethyl-, ethoxyethyl-, benzoic and tolylmercury, mersalylic acid and nitromersol. The nine compounds were successfully separated on octadecylsilane columns (200 × 3 mm i.d.) by gradient elution with a methanol–water mixture ranging from 30 to 50% v/v. The detection limits for the various compounds are in the range 7.0–95.1 µg dm–3. For the extraction of five organomercurials from spiked soils, eight different extraction solutions were tested to differentiate between the total content and the available/soluble fraction of the analytes. Ammonium acetate solutions (1 mol dm–3) and water proved to be suitable agents for the estimation of the available and soluble fractions of methyl-, ethyl-, benzoic, methoxyethyl- and ethoxyethylmercury. For the determination of the total content of methyl- and benzoic mercury in soils, solutions of potassium iodide (1 mol dm–3)–ascorbic acid (0.1 mol dm–3) and oxalic acid (1 mol dm–3) provided recoveries in the range 53–81%. None of the solutions tested is suitable for the extraction of ethyl-, methoxyethyl- and ethoxyethylmercury.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radions were evaluated with a compartment model and the highest rate was found for Chernobyl-derived radiocaesium.
Abstract: The vertical activity distributions of fallout 238Pu, 239+240Pu, 241Am, 134Cs and 137Cs in a forest soil (Hapludult) were determined at several locations in a spruce stand separately according to their origin (global fallout or Chernobyl fallout). To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radionuclides were evaluated with a compartment model. In the top organic horizons (LOf1 and Of2), the migration rates for all radionuclides from both sources were above 0.5 cm per year. In the Oh horizon the migration rates observed for global fallout Pu, Am and Cs were similar (0.2–0.4 cm per year). Compared with Pu, however, the mobility of Am is slightly, but statistically significantly, enhanced. The highest rate in this layer was found for Chernobyl-derived radiocaesium (2cm per year). In the layers of the mineral horizon (depth 0–2, 2–5 and 5–10 cm) the observed migration rates were very similar for global fallout Pu (0.08–0.7 cm per year) and Am (0.1–2 cm per year). In comparison, the migration rate of global fallout radiocaesium was about half in each layer. The highest rate was observed again for Chernobyl-derived radiocaesium (0.5–3 cm per year).

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A number of analytical enzymes including galactose oxidase, malate dehydrogenase and alcohol oxidase have been stabilized in a dry form by use of a novel, patented polymer–carbohydrate system, having a shelf life of over 2 years when stored at 4 °C.
Abstract: A number of analytical enzymes including galactose oxidase, malate dehydrogenase and alcohol oxidase (from the methylotrophic yeast, Hansenula polymorpha) have been stabilized in a dry form by use of a novel, patented polymer–carbohydrate system. The enzymes were dried under vaccum at ambient temperature in the presence of a positively charged (cationic), soluble polymer such as diethylaminoethyl (DEAE)-dextran, and a carbohydrate sugar alcohol, lactitol. The dried enzymes retained high activity under conditions of thermal stress at 37 °C. Long term stability testing of alcohol oxidase indicated that 100% of the enzyme activity was retained for up to 2 months incubation at 37 °C in the presence of the stabilizers. In comparison, unstabilized enzyme, which was dried in phosphate buffer alone, retained only 26% activity after 7 d of incubation at 37 °C. Stabilized alcohol oxidase preparations have been used to produce an alcohol assay reagent kit, having a shelf life of over 2 years when stored at 4 °C. Activity loss during the drying step was also reduced in the presence of the stabilizers. This type of stabilization system has application in the long term storage of active enzymes, enzyme products and in the area of enzyme-based analytical reagents and biosensors.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: In this article, the mutual separation and preconcentration of VV and VIV using chelating functional group immobilized silica gels (CISs) was studied, based on inductively coupled plasma atomic emission spectrometric detection.
Abstract: The mutual separation and preconcentration of VV and VIV using chelating functional group immobilized silica gels (CISs) has been studied, based on inductively coupled plasma atomic emission spectrometric detection. Ethylenediamine-bonded (ED–CIS) and ethylenediaminetriacetate-bonded (ED3A-CIS) silica gels were used. A two-column system consisting of a first column of ED–CIS and a second column of ED3A-CIS was developed for on-line separation and preconcentration of VV and VIV. In the pH range 2.5–3.0, ED–CIS retains VV and separates it completely from VIV, whereas ED3A-CIS collects both VV and VIV. The second column can be used to preconcentrate VIV in the breakthrough solution from the first column. Separation is achieved with recoveries of 91–105%. The recovery of both ions is 98% or better. An enrichment factor of 40 is obtained, with which the detection limit of V with inductively coupled plasma atomic emission spectrometry is improved down to 60 pg ml–1. The method was applied successfully to V speciation in natural waters.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A chemical optical sensing system (optode) for ZnII based on a lipophilized metal ion indicator dye [1-octadecyloxy-4-(2-pyridylazo)resorcinol; ETH 2464] dissolved in a plasticized poly(vinyl chloride) membrane has been developed as discussed by the authors.
Abstract: A chemical optical sensing system (optode) for ZnII based on a lipophilized metal ion indicator dye [1-octadecyloxy-4-(2-pyridylazo)resorcinol; ETH 2464] dissolved in a plasticized poly(vinyl chloride) membrane has been developed. In the measuring range from 1 × 10–6 to 3 × 10–3 mol dm–3 Zn2+(pH 4.8), the absorbance response shows a good correlation with the theoretically derived formulae. The optode membranes were found to reach 95% of the final signal within 5 min (t95). When exposed to a continuous sample flow (1 ml min–1), the optode membrane did not lose a perceptible amount of the indicator over a period of 10 h. The selectivity of the optode membrane for the response towards Zn2+ ions in pH-buffered solutions is described.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: In this paper, an ultrasensitive adsorptive-catalytic stripping (voltammetric and potentiometric) procedure for determining trace levels of chromium in the presence of cupferron is described.
Abstract: An ultrasensitive adsorptive–catalytic stripping (voltammetric and potentiometric) procedure for determining trace levels of chromium in the presence of cupferron is described. The method offers higher sensitivity than previous adsorptive stripping schemes for chromium. Optimum experimental conditions were found to be a 1 × 10–3 mol l–1 piperazine-N,N′-bis(ethanesulfonic acid)(PIPES) solution (pH 7.0) containing 1 × 10–4mol l–1 cupferron and a preconcentration potential of –0.82 V. A preconcentration time of 1 min results in a detection limit of 1.0 ng l–1. The relative standard deviation at 100 ng l–1 is 2.4%(n= 20, for 20 s preconcentration). The stripping potentiometric scheme allows convenient measurements of chromium in the presence of dissolved oxygen. The identical stripping response for chromium(III) and chromium(VI) solutions makes the method applicable to the measurement of the total chromium content. The simultaneous determination of chromium and uranium is illustrated. The merits of the proposed procedure are demonstrated by the analysis of soil and groundwater samples.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A selection of the major developments in the field of analytical methodology for elemental speciation over the period from January 1986 to December 1990, as well as a number of methods for elements most frequently studied will be discussed.
Abstract: This paper describes a selection of the major developments in the field of analytical methodology for elemental speciation over the period from January 1986 to December 1990. Methods for a number of elements will be highlighted. Judging by the number and diversity of published reports, there has been increasing interest and activity in the development of new and modified analytical methods. Further, it is very encouraging to observe the number of papers concerned with the accuracy and precision of such analytical methods, and with comparisons between two or more methods. Among electrochemical methods of analysis, anodic stripping voltammetry has provided an important basis for measurements of concentrations of labile metals in aqueous media. The fastest growing area of method development is the coupling of separation methods, usually chromatography, with a single- or multi-element detector. Most importantly, inductively coupled plasma mass spectrometry has recently been described as a very sensitive, multi-element detector. The success of a ‘coupled’ method is greatly dependent on a suitable interface. Several papers have been published recently describing useful interfaces. Chemical extraction procedures continue to occupy an important place. Applications of analytical elemental speciation methods have included environmental, biological, clinical and geological samples. A number of methods for elements most frequently studied will be discussed.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: The analytical results obtained by the proposed method agreed with those of the Fe(3+)-thiocyanate spectrophotometric method, and concentrations in the saliva and urine of smokers were found to be significantly higher than those of non-smokers.
Abstract: A simple ion-chromatographic method has been developed for the determination of trace amounts of thiocyanate in human saliva and urine. Thiocyanate separation and detection were carried out on an ODS column coated with cetyldimethylamine and by an ultraviolet detector, respectively. Citrate solution (1 mmoll–1) was used as the mobile phase. Thiocyanate was clearly separated from many organic and inorganic anions found in saliva and urine samples. The analytical results obtained by the proposed method agreed with those of the Fe3+–thiocyanate spectrophotometric method. Thiocyanate concentrations in the saliva and urine of smokers were found to be significantly higher than those of non-smokers.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: It is demonstrated that both arsenobetaine and arsenocholine are unstable when incubated in daylight in the presence of hydrogen peroxide, i.e., an oxidizing environment, and it is tempting to speculate that arsenOBetaine could be converted into hydride-generating arsenic compounds during storage or cooking of seafood.
Abstract: Arsenobetaine and arsenocholine are considered to be non-toxic and are present as a relatively large proportion of total arsenic in seafoods, and they do not respond to hydride generation. The present study describes the effect of seafood consumption on the urinary concentration of hydride-generating arsenic compounds measured by a newly developed flow injection atomic absorption spectrometric (FI-AAS) method. Consumption of plaice, pighvar and tunny resulted in a 2-fold increase, and consumption of mussels produced a 6-fold increase in the urinary level of hydride-generating arsenic compounds. Hence, a person who has consumed mussels may be suspected of being occupationally or environmentally exposed, if the level of consumption of this seafood is unknown. As the FI-AAS method cannot be used to detect arsenobetaine and arsenocholine, the observed increase in urinary concentration of hydride-generating arsenic compounds after consumption of seafood must originate either from hydride-generating arsenic compounds in the seafood or from degraded arsenobetaine or arsenocholine. The present study has demonstrated that both arsenobetaine and arsenocholine are unstable when incubated in daylight in the presence of hydrogen peroxide, i.e., an oxidizing environment. Hence, it is tempting to speculate that arsenobetaine could be converted into hydride-generating arsenic compounds during storage or cooking of seafood. The feasibility of speciation methods based on high-performance liquid chromatographic (HPLC) separation and on-line analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) and FI-AAS was also investigated. The FI-AAS system is approximately 35 times more sensitive to the hydride-generating arsenic species than the ICP-AES system. Consequently, an HPLC–FI-AAS speciation method could be useful in analyses for arsenic species in urine from highly exposed persons, or persons suspected of being unable to, or having a reduced ability to, methylate inorganic arsenic compounds.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: A system for on-line treatment of liquid samples in a microwave oven digestor was evaluated for use with cold vapour (CV) and hydride generation (HG) atomic absorption spectrometry (AAS).
Abstract: A system for on-line treatment of liquid samples in a microwave oven digestor was evaluated for use with cold vapour (CV) and hydride generation (HG) atomic absorption spectrometry (AAS). Various oxidation mixtures were tested and those based on bromination (bromate–bromide–acid) and peroxodisulfate (persulfate–acid–complexing agent) were found to be compatible with and most appropriate for CVAAS and HGAAS. The composition of reagents and the analytical conditions were optimized for the determination of mercury, arsenic, bismuth, lead and tin in urine and environmental waters. The limits of detection were 0.01 and 0.2 µg l–1 for mercury, with and without amalgamation, respectively, 0.5 µg l–1 for arsenic, 0.07 µg l–1 for bismuth and 0.1 µg l–1 for tin and the sample throughput was between 13 and 30 h–1.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: In this paper, a continuous hydride generator is described which incorporates a combined generator/separator, and the system has been further modified to allow on-line pre-reduction of arsenic(V) to arsenic(III) by L-cysteine.
Abstract: A continuous hydride generator is described which incorporates a combined generator/separator. The low acid concentrations necessary in the tetrahydroborate(III)—L-cystein mediated determination of most hydride-forming elements require that the gas is purged from solution. As the hydride transfer reaction is so rapid, this allows both the hydride-forming reaction and the stripping reaction to take place in the same vessel. The system has been further modified to allow on-line pre-reduction of arsenic(V) to arsenic(III) by L-cysteine. Detection limits for arsenic, germanium and selenium are 4, 0.3 and 8 ng ml–1, respectively, at a sample flow rate of 15 ml min–1. Application of the system to the determination of arsenic in water is described. Concentrations of arsenic in several Ontario waters were found to be in the range 7–600 ng ml–1, Interferences from nickel and palladium, two of the most strongly interfering elements in the continuous hydride generation process, are diminished to a greater extent with the system described here than with the conventional high acid continuous system.

Journal ArticleDOI
01 Jan 1992-Analyst
TL;DR: An analytical system for automated on-line pre-treatment of liquid samples in a microwave oven for flow injection cold vapour and hydride generation atomic absorption spectrometry has been designed and evaluated as discussed by the authors.
Abstract: An analytical system for automated on-line pre-treatment of liquid samples in a microwave oven for flow injection cold vapour and hydride generation atomic absorption spectrometry has been designed and evaluated. The system is based on a focused microwave oven and a new manifold with two coils. A reaction coil and a ballast-load coil are placed and oriented within the digestor in a manner providing a reliable long-term operation and increased reaction time. Samples are mixed with an appropriate oxidation reagent and loaded on an autosampler; all further operations of sample uptake, digestion, measurement, calibration and data processing are performed automatically with a sample throughput rate of 20–40 h–1. For the determination of mercury at ng l–1 levels using amalgamation the sample throughput decreased to 7–20 h–1. Introducing hot sample digests into the mercury/hydride system resulted in an increased sensitivity, particularly for peak height absorbance.