Showing papers in "Analyst in 1989"
170 citations
TL;DR: The results suggest that the Artemia cyst is a unique material in which ascorbic sulphate is present in large amounts whereas fish tissues do not contain this form of vitamin C.
Abstract: A modified spectrophotometric assay for ascorbic acid and its derivatives based on their reaction with 2,4-dinitrophenylhydrazine (DNPH) is described Using standard ascorbic acid or ascorbic sulphate solutions, together with animal tissue or compound diet extracts, the conditions for ascorbic acid degradation were determined For the differential measurement of reduced ascorbic acid (AA), dehydroascorbic acid (dAA) and ascorbic sulphate (AS), five series of simultaneous determinations were performed These included the use of (1) KBrO3 for the hydrolysis of AS, (2) 2,6-dichlorophenolindophenol as an oxidant, (3) DNPH to form a hydrazone derivative with dAA and (4 and 5) two blanks (where ascorbate was degraded) to correct for interfering substances A variety of vertebrate and invertebrate tissues were examined for their ascorbate content, and the advantages of the modified procedure over currently available assays are discussed The results suggest that the Artemia cyst is a unique material in which ascorbic sulphate is present in large amounts whereas fish tissues do not contain this form of vitamin C
153 citations
TL;DR: In this article, the authors used 2-nitrophenyl octyl ether as the solvent mediator and potassium tetrakis(p-chlorophenyl)borate as the ion exchanger in a poly(vinyl chloride) matrix.
Abstract: Sodium-selective electrodes were prepared with polymeric membranes containing ester and ketone derivatives of p-tert-butyl calix[4]arene. The electrodes were prepared with 2-nitrophenyl octyl ether as the solvent mediator and potassium tetrakis(p-chlorophenyl)borate as the ion exchanger in a poly(vinyl chloride) matrix. Several of the ligands examined produced electrodes with near-Nernstian slopes, detection limits of ca. 10–5M for sodium and excellent selectivity against a range of common cations.
126 citations
TL;DR: In this paper, o-xylylene bis(diisobutyldithiocarbamate) was synthesized and used as neutral carriers in membrane electrodes to improve the selectivity for Cu2+.
Abstract: o-Xylylene bis(diisobutyl- and methyloctadecyl-dithiocarbamate) were synthesised and used as neutral carriers in membrane electrodes to improve the selectivity for Cu2+. The electrodes based on these ionophores, with o-nitrophenyl octyl ether as a plasticising solvent mediator and potassium tetrakis-(p-chlorophenyl)borate as an anion excluder, exhibit a linearity range of 10–1–10–6Mand have a Nernstian slope of 28–29 mV per decade at 25 °C. The highly selective electrode based on o-xylylene bis(diisobutyldithiocarbamate) rejected the interference of alkali, alkaline earth and transition metal cations by a factor in the range 102–104 and showed a high selectivity for Cu2+ even in chloride and bromide media. The properties of the electrodes are discussed and also compared with those of o-xylylene bis(diethyldithiocarbamate) under similar measurement conditions.
114 citations
TL;DR: In this article, a simple manipulation of the use of commercially available equipment is described that allows the simultaneous determination of nitrogen and 15N at levels as low as 10 nmol of total nitrogen.
Abstract: Recent developments in continuous-flow isotope ratio mass spectrometry have considerably enhanced the ability to make rapid and precise measurements of the stable isotope 15N. Although the amounts of nitrogen required for precise analyses have been reduced considerably, the levels required remain a limitation for many applications. A simple manipulation of the use of commercially available equipment is described that allows the simultaneous determination of nitrogen and 15N at levels as low as 10 nmol of total nitrogen.
110 citations
TL;DR: A simple, rapid and accurate method for the simultaneous determination of ascorbic acid, caffeine and paracetamol in drug formulations has been developed and results are reported for several commercially available drugs.
Abstract: A simple, rapid and accurate method for the simultaneous determination of ascorbic acid, caffeine and paracetamol in drug formulations has been developed. Peak currents were measured with a glassy carbon electrode at +0.350, +0.618 and +1.425 V versus a saturated calomel electrode for ascorbic acid, paracetamol and caffeine, respectively. Perchloric acid (0.1 M) - methanol (1 + 1) was used both as a solvent and supporting electrolyte. The optimum modulation amplitude, pulse repeat time and scan rate of the polarographic analyser were found to be 50 mV, 0.5 s and 5 mV s-1, respectively and the linear calibration ranges for ascorbic acid, caffeine and paracetamol were 0-35, 0-50, and 0-55 micrograms ml-1, respectively. The relative standard deviations for 9.30 micrograms ml-1 of ascorbic acid, 8.50 micrograms ml-1 of caffeine and 7.30 micrograms ml-1 of paracetamol were 1.3, 2.5 and 0.7%, respectively. Results are reported for several commercially available drugs.
100 citations
TL;DR: The results suggest that the majority of soluble cadmium in retail pig kidney is associated with a metallothionein-like protein that survives both cooking and simulated in vitro gastro-intestinal digestion.
Abstract: The speciation of cadmium in retail pig kidney has been examined by size-exclusion chromatography (SEC) coupled directly to inductively coupled plasma mass spectrometry (ICP-MS). Approximately 35% of the cadmium from uncooked kidney was soluble after aqueous extraction at pH 8 and SEC - ICP-MS revealed three discrete peaks whose retention times corresponded to estimated relative molecular masses of 1.2 x 10(6), 7.0 x 10(4) and 6 x 10(3)-9 x 10(3). In the cooked kidney, 35% of the Cd was soluble and was all associated with a peak of a relative molecular mass (Mr) of 6 x 10(3)-9 x 10(3). After simulated gastric digestion of cooked pig kidney at pH 2.5, 60% of the cadmium was solubilised and associated with a species of Mr less than 1 x 10(3). When the digest was also subjected to simulated intestinal digestion at pH 6.8, a single peak, which corresponded to 20% of the original cadmium, was eluted. This peak co-eluted with the single peak extracted at pH 8.0 from the cooked kidney. It was also of similar estimated Mr to the single broad peak observed after simulated gastro-intestinal digestion of equine renal metallothionein (Mr = 1.1 x 10(4]. The results suggest that the majority of soluble cadmium in retail pig kidney is associated with a metallothionein-like protein that survives both cooking and simulated in vitro gastro-intestinal digestion.
94 citations
94 citations
84 citations
TL;DR: In this article, cyclic voltammetry, differential-pulse voltammetric (DPV), amperometry and flow injection with electrochemical detection were used to investigate the electrochemical behavior of reduced glutathione (GSH) at a carbon paste electrode and also at an electrode doped with cobalt phthalocyanine (CPC).
Abstract: Cyclic voltammetry, differential-pulse voltammetry (DPV), amperometry and flow injection with electrochemical detection were used to investigate the electrochemical behaviour of reduced glutathione (GSH) at a carbon paste electrode and also at a carbon paste electrode doped with cobalt phthalocyanine (CPC). The modified electrode was found to reduce greatly the overpotential necessary for the oxidation of GSH at the electrode surface; the process was dependent on the ionic strength and pH of the supporting electrolyte. The oxidation of GSH in the presence of CPC was found to occur at two potentials, 0.27 and 0.75 V versus a saturated calomel electrode. Using DPV the first wave was found to give optimum sensitivity for the measurement of GSH concentations in the range 2.5 × 10–6–6.25 × 10–5M; whereas the second was preferential for GSH concentrations of 1.25 × 10–4–2.5 × 10–3M. Electrode deterioration rendered the other techniques unsuitable for routine quantitative analyses. Similar investigations were also carried out on a carbon-epoxy resin composite electrode containing CPC; the various techniques were used to optimise the electrode response for the determination of GSH in biological fluids. This electrode was found to be superior to the graphite paste electrode as GSH could be determined in flowing or stirred solutions. The modified composite electrode was stable and could be used over a period of at least 10 h. The limits of detection were 10 ng ml–1 and 450 pg injected on column for amperometry and high-performance liquid chromatography with electrochemical detection (LCEC), respectively. Preliminary studies using LCEC have shown that the method is suitable for the determination of circulating levels of GSH in human plasma.
84 citations
TL;DR: The DBD-F reacted quantitatively with thiols after 10 min at 50 degrees C and pH 8.0 and the reaction rates were several times higher than those with ABD-F; it is suggested that the electron withdrawing effect of the dimethylsulphonamide group (SO2NMe2) is larger than that of the sulphonamidegroup (so2NH2).
Abstract: 4-(N,N-Dimethylaminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) was synthesised for use as a more reactive, thiol-specific fluorogenic reagent than 4-(aminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (ABD-F). The former had negligible fluorescence whereas its thiol derivatives fluoresced intensely at about 510 nm (excitation occurred at about 380 nm). The DBD-F reacted quantitatively with thiols after 10 min at 50 °C and pH 8.0 and the reaction rates were several times higher than those with ABD-F; it is suggested that the electron withdrawing effect of the dimethylsulphonamide group (SO2NMe2) is larger than that of the sulphonamide group (SO2NH2). No reaction occurred with alanine, proline, cystine or cysteic acid under the same conditions. The fluorescence intensities of the derivatives were found to be higher in neutral and acidic media than in alkaline solutions. The thiol derivatives of DBD-F were separated by high-performance liquid chromatography and detected fluorimetrically, the detection limits being 0.92, 0.16, 0.13, 0.16 and 0.32 pmol for cysteine, glutathione, homocysteine, N-acetylcysteine and α-mercaptopropionylglycine, respectively. The method was applied to the determination of thiols in rat tissues.
TL;DR: In this paper, the authors used the IEEE Copyright © 2005 IEEE This material is posted here with permission of the IEEE Such permission does not imply IEEE endorsement of any of Teesside University's products or services Internal or personal use of this material is permitted However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieeeorg
Abstract: Copyright © 2005 IEEE This material is posted here with permission of the IEEE Such permission of the IEEE does not in any way imply IEEE endorsement of any of Teesside University's products or services Internal or personal use of this material is permitted However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to pubs-permissions@ieeeorg
TL;DR: In this paper, a review of the ligands used to measure trace elements in aqueous solution, and of the elements which can be determined using cathodic stripping voltammetry (CSV) is given.
Abstract: Large advances have been made in the application of cathodic stripping voltammetry (CSV) to the determination of trace elements in the environment. A monomolecular layer of complexes on a mercury electrode is allowed to adsorb directly from aqueous solution during the pre-concentration step, which is followed by measurement of the reduction current by means of a potential scan to more negative potentials. The entire adsorbed layer is reduced during the potential scan, causing the voltammetric measurement to be very sensitive to low dissolved analyte concentrations. A review is given of the ligands used to measure trace elements in aqueous solution, and of the elements which can be determined. The adsorption step of what are in fact fairly soluble (in water) complexes is controlled by a mixture of effects related to π-orbital electrons and electrostatic interactions. The high sensitivity to the analyte is a result of the efficient (complete) electrochemical reduction of the monomolecular layer of adsorbed material. Although not a multi-element technique, CSV is superior to other analytical techniques in the automated monitoring of trace elements in natural waters including sea water, and in the study of speciation. An added advantage is related to the comparatively low cost and simplicity of the instrumentation.
TL;DR: The direct coupling of ion-exchange chromatography to flame atomic absorption spectrometry (AAS) has been achieved by employing a Babington type nebuliser and the system was applied to the determination of the ratio of iron(II) to iron(III) in wines.
Abstract: The direct coupling of ion-exchange chromatography to flame atomic absorption spectrometry (AAS) has been achieved by employing a Babington type nebuliser. The system enables all the processes on the column to be followed directly at flow-rates of between 1 and 5 ml min–1. The potential of the system was investigated for the determination of various iron species in synthetic samples containing iron(II) and iron(III) in ionic or chelated form by employing various ion-exchange (Dowex 50-X8, Dowex 1-X8) and sorptive (Amberlite XAD-2) resins, respectively. In some instances where direct coupling was impossible, owing to the physical properties of the effluent or eluent, conventional analyses of chromatographically separated iron species were performed by flame AAS. The optimum concentration range, limit of detection and reproducibility of measurement were also determined for a particular column capacity. When direct coupling was employed, the detection limit for the separated iron species was 15 µg with a relative standard deviation (RSD) of ±3% and, using the conventional method of analysis, 2–5 µg with an RSD of ±1%. On the basis of these results the system was applied to the determination of the ratio of iron(II) to iron(III) in wines.
TL;DR: In this paper, the average valencies of copper and bismuth in the superconducting Bi-Sr-Ca-Cu-O system have been determined using a coulometric titration technique.
Abstract: The average valencies of copper and bismuth in the superconducting Bi-Sr-Ca-Cu-O system have been determined using a coulometric titration technique. Both copper(III) and bismuth(V) were allowed to react with an excess of copper(I) and the excess of copper(I) was then back-titrated by an anodic oxidation. Bismuth(V) was determined alone by taking advantage of the reaction with manganese(II). In the Bi-Sr-Ca-Cu-O sample having a high transition temperature (Tc) of 90 K, the average valencies of copper and bismuth were found to be 2.144 and 3.119, respectively, using these techniques.
TL;DR: A fairly sensitive spectrophotometric method is described, based on the formation of a chloroform-soluble, coloured ion-association complex between the drug and Methylene Violet at pH 7.6.
Abstract: A fairly sensitive spectrophotometric method for the determination of ibuprofen, ketoprofen, piroxicam, diclofenac sodium, mefenamic acid or enfenamic acid in bulk samples and pharmaceutical preparations is described, based on the formation of a chloroform-soluble, coloured ion-association complex between the drug and Methylene Violet at pH 7.6.
TL;DR: In this paper, a flow injection system based on potentiometric detection and designed for on-line monitoring of ammonia in freshwater streams is described, where a specially constructed all-solid state tubular flow-through ammonium electrode was used in conjunction with a gas-diffusion chamber to enhance its selectivity.
Abstract: A flow injection system based on potentiometric detection and designed for on-line monitoring of ammonia in freshwater streams is described. A specially constructed all-solid state tubular flow-through ammonium electrode was used in conjunction with a gas-diffusion chamber to enhance its selectivity. Construction of the electrode involved the in situ formation and direct casting of the sensing nonactin-poly(vinyl chloride) membrane on to a mouldable conducting filled polymer (epoxy resin loaded with graphite), which acted as an internal solid contact, without an inner solution. The electrode response under dynamic conditions both with and without the gas-diffusion chamber was evaluated. After optimisation of the flow system parameters, over 30 samples with a wide range of ammonia concentrations (2 × 10–5–10–2M) could be processed per hour with a detection limit of ca. 10–6M. The performance of the monitoring system under on-line conditions in a water treatment plant is also described.
TL;DR: A method is described for the determination of formaldehyde and acetaldehyde in mainstream cigarette smoke by the collection and reaction of the aldehydes with 2,4-dinitrophenylhydrazine in aqueous acetonitrile.
Abstract: A method is described for the determination of formaldehyde and acetaldehyde in mainstream cigarette smoke. This involved the collection and reaction of the aldehydes with 2,4-dinitrophenylhydrazine in aqueous acetonitrile. The high-performance liquid chromatographic separation and measurement of the various components directly in this reaction solution eliminated the need for a clean-up stage. Cigarette yields of greater than 5 micrograms of formaldehyde and 50 micrograms of acetaldehyde could be determined to estimated relative standard deviations of 0.07 and 0.05, respectively.
TL;DR: In this paper, a rapid in-line photochemical digestion for use with flow injection (Fl) to determine the dissolved organic phosphorus (DOP) in natural waters is described, which includes a simple ultraviolet (UV) photoreactor and uses the tin(II) chloride reduction of phosphomolybdate for the spectrophotometric determination of the dissolved reactive phosphorus (DRP) produced by photo-oxidation.
Abstract: A rapid in-line photochemical digestion for use with flow injection (Fl) to determine the dissolved organic phosphorus (DOP) in natural waters is described. The Fl system includes a simple ultraviolet (UV) photoreactor and uses the tin(II) chloride reduction of phosphomolybdate for the spectrophotometric determination of the dissolved reactive phosphorus (DRP) produced by the photo-oxidation. Samples in the range 0.1–4 and < 0.1 mg l–1 of P can be analysed at rates of 72 and 50 samples h–1, respectively. The effective detection limit of the technique was 0.01 mg l–1. Comparison of the results for DOP obtained using the proposed method were in good agreement with those obtained using standard methods. The DRP could also be determined using the same Fl manifold but without UV irradiation.
TL;DR: A combination of three automated methods has been developed to determine total cyanide, free cyanide [i.e., HCN(aq)+ CN–], iron-cyanide complexes and thiocyanate, and Shielding the samples from diffuse daylight appeared to be necessary to prevent rapid photolysis of the iron-cyclic complexes.
Abstract: A combination of three automated methods has been developed to determine total cyanide, free cyanide [i.e., HCN(aq)+ CN–], iron-cyanide complexes and thiocyanate. The methods are based on a continuous-flow technique, combined with spectrophotometric detection, and have a detection limit of 0.6 µg l–1. The distinction between iron-cyanide complexes and free cyanide plus thiocyanate was made by UV irradiation and distillation with citric acid. The distinction between free cyanide and thiocyanate was made by masking free cyanide with formaldehyde. Rapid and complete recovery of iron-cyanide complexes was obtained; the interference from nitrate was minimised. Shielding the samples from diffuse daylight appeared to be necessary to prevent rapid photolysis of the iron-cyanide complexes.
TL;DR: In this paper, a reliable procedure for the simultaneous determination of ultra-trace levels of cobalt and nickel in sea water is proposed, in which the complexes of the two metals with dimethylglyoxime are analyzed by cathodic stripping square-wave voltammetry based on adsorptive collection at a hanging mercury drop electrode.
Abstract: A reliable procedure for the simultaneous determination of ultra-trace levels of cobalt and nickel in sea water is proposed, in which the complexes of cobalt and nickel with dimethylglyoxime are analysed by cathodic stripping square-wave voltammetry based on adsorptive collection at a hanging mercury drop electrode. After comparing differential-pulse cathodic stripping voltammetry with cathodic stripping square-wave voltammetry for the determination of cobalt and nickel, the latter technique was adopted because of its inherently greater sensitivity and faster scan rate. The variation of the resolution between the cobalt and nickel peaks and of the peak currents with ligand concentration, buffer concentration, pH, adsorption time and potential, and of the instrumental parameters such as scan rate, pulse height and frequency was studied. The effect of surfactants and foreign metal ions was also examined. The advantages of the proposed method are rapid determination, high sensitivity and good precision. The detection limits for cobalt and nickel are approximately 8 pM and 0.05 nM, respectively. The applicability of this method to the analysis of sea water was assessed by the determination of cobalt and nickel in Mediterranean sea water samples.
TL;DR: The determination of iron isotope ratios in blood, without prior sample preparation, using inductively coupled plasma mass spectrometry with sample introduction by electrothermal vaporisation (ETV) is described to assess changes in the fractional absorption of iron during human pregnancy.
Abstract: The determination of iron isotope ratios in blood, without prior sample preparation, using inductively coupled plasma mass spectrometry (ICP-MS) with sample introduction by electrothermal vaporisation (ETV) is described. Following oral administration of 5 mg of enriched 54FeSO4 and intravenous administration of 200 micrograms of 57FeSO4 to non-pregnant women, the 54Fe: 56Fe and 57Fe: 56Fe isotope ratios in serum were measured reliably within 20 min per sample in quintuplicate. Changes in the fractional absorption of iron during human pregnancy could therefore be assessed.
TL;DR: Oxytetracycline and doxycycline were determined in pharmaceutical samples, urine and honey without any pre-treatment of the samples and first-derivative spectra were used.
Abstract: Derivative spectrophotometric methods have been developed for determining oxytetracycline and doxycycline and for resolving their binary mixtures. Oxytetracycline and doxycycline were determined in pharmaceutical samples, urine and honey without any pre-treatment of the samples. In all instances, first-derivative spectra were used.
TL;DR: Of the three reagents, DBD-F seemed to be applicable to the determination of amino acids and the proline derivatives synthesised were higher in neutral and acidic solutions than in alkaline solution.
Abstract: The reactivities of three reagents, 4-(N,N-dimethylaminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), 4-(aminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (ABD-F) and 4-(fluorosulphonyl)-7-phenoxy-2,1,3-benzoxadiazole (PBD-SO2F), towards thiols and amines were compared All three reacted with thiol compounds to give derivatives which fluoresced at ca 515 nm (excitation at ca 388 nm) However, the PBD-SO2 derivatives were not very stable The rate of reaction of DBD-F with proline was faster than that of PBD-SO2F or ABD-F The three reagents and their hydrolysates exhibited extremely low fluorescence The fluorescence intensities of the proline derivatives synthesised were higher in neutral and acidic solutions than in alkaline solution The strength of the fluorescence intensities was in the order PBD-SO2-proline > DBD-proline > ABD-proline at all pH values tested The mean values of the maximum wavelengths of DBD-proline, ABD-proline and PBD-SO2-proline were 596 nm (λex = 466 nm), 602 nm (λex = 466 nm) and 566 nm (λex 453 nm), respectively Of the three reagents, DBD-F seemed to be applicable to the determination of amino acids Nine amino acid derivatives of DBD-F were separated by reversed-phase high-performance liquid chromatography and detected with fluorescence at 590 nm (λex = 450 nm) The detection limits were in the sub-picomole range
TL;DR: In this paper, the mass of the collectors used without affecting element recovery was reduced by reducing the amount of nickel in the collectors by a factor of 20, compared with the 10 g proposed by other workers.
Abstract: Fire assay is a classical method used for the separation of platinum group elements and gold (PGE + Au) by pre-concentration with a collector. In the nickel sulphide fire assay, nickel and sulphur are used for the collection of PGE + Au. We have successfully reduced the mass of the collectors used without affecting element recovery. The PGE + Au are recovered from 25 g of SARM-7 reference material with only 0.5 g of nickel, compared with the 10 g proposed by other workers. The inherent blank problem due to impurities in the reagents is eliminated when the mass of nickel is reduced by the factor of 20 proposed.
TL;DR: In this article, a rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00 −10.0 µg ml−1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution.
Abstract: A rapid and precise continuous-flow method is described for the determination of acetaminophen (1.00–10.0 µg ml–1) based on the chemiluminescence produced by its reaction with cerium(IV) in acidic solution. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing drugs. The results obtained for the assay of commercial pharmaceutical preparations compared well with those obtained by a reference method and demonstrated good accuracy and precision.
TL;DR: A variety of applications of the technique of Fourier transform (FT) Raman spectroscopy using a near-infrared laser excitation source have now begun to emerge.
Abstract: A variety of applications of the technique of Fourier transform (FT) Raman spectroscopy using a near-infrared laser excitation source have now begun to emerge The design and construction of a bench-top, analytical-grade FT Raman spectrometer are described Its specifications are explained and its performance and convenience of use are reported A variety of analytical applications of the FT Raman technique have been surveyed to demonstrate the versatility of the spectrometer
TL;DR: In this article, various decomposition methods were examined for the determination of 21 elements in atmospheric particulates, and the performance of the recommended procedure was confirmed by analysing the National Bureau of Standards, Standard Reference Material 1648 Urban Particulate Matter.
Abstract: Various decomposition methods were examined for the determination of 21 elements in atmospheric particulates. Alkali fusion with sodium carbonate and boric acid was selected for the determination of Si, Ti, Al, Fe, Mn, Mg, Ca, Ba and Cr, decomposition with HF-HNO3-HCl for Na, K, Pb, Zn, Cd, Co, Cu, Li, Ni and V and decomposition with HF-HNO3-H2SO4-KMnO4 for As and Sb. The determinations were carried out using hydride generation atomic absorption spectrometry for As and Sb, air-acetylene flame atomic absorption spectrometry for Cr, Ca, Co, Fe, Mg, Mn, Ni, K, Li, Na, Cd, Cu, Pb and Zn and dinitrogen oxide-acetylene flame atomic absorption spectrometry for the other elements. The performance of the recommended procedure was confirmed by analysing the National Bureau of Standards, Standard Reference Material 1648 Urban Particulate Matter. The recommended procedure was applied to the analysis of total atmospheric particulates and of particulates smaller than 10 µm.
TL;DR: In this article, a set of more than 200 thin-target cross-sections for the production of radionuclides and stable He, Ne and Xe isotopes has so far been measured.
Abstract: In the course of a systematic investigation of proton-induced reactions up to p-energies of 3000 MeV, the target elements O, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Rh, Ba, Lu and Au were irradiated with 600-MeV protons at the CERN synchrocyclotron. A consistent set of more than 200 thin-target cross-sections for the production of radionuclides and stable He, Ne and Xe isotopes has so far been measured. Here, 199 cross-sections for the production of radionuclides are presented. On the basis of the new data the quality of existing semi-empirical equations for the calculation of spallation cross-sections is discussed. In a more physical approach, the production of residual nuclides in the course of the intranuclear cascade was calculated using Monte Carlo techniques and compared with experimental cross-sections.
TL;DR: The physical and chromatographic volumes associated with a liquid chromatography column have been considered theoretically and their interrelationship is discussed in this article, where the two chromatographically important dead volumes, the kinetic dead volume and the thermodynamic dead volume, have been identified and it is shown that, whereas the volume of the moving phase was common to all solutes, the thermodynamics dead volume was unique to each solute.
Abstract: The physical and chromatographic volumes associated with a liquid chromatography column have been considered theoretically and their inter-relationship is discussed. The two chromatographically important dead volumes, the kinetic dead volume and the thermodynamic dead volume, have been identified and it is shown that, whereas the kinetic dead volume (the volume of the moving phase) was common to all solutes, the thermodynamic dead volume was unique to each solute. The solute dependence of the thermodynamic dead volume resulted from any exclusion characteristics that the stationary phase possessed. Stationary phases based on silica exhibited strong exclusion properties and hence the thermodynamic dead volume for silica-based phases was strongly dependent on solute size. It followed that the pertinent thermodynamic dead volume had to be determined strictly for each solute. It also followed that correlation of retention with solvent composition could not be carried out employing k′(solute capacity factor) values, as these were dependent on accurate dead volume measurements. It is recommended that for such a correlation, corrected retention volumes are employed and then only where the solute is eluted at sufficiently high k′ values. Under such circumstances any errors that would result from incorrect dead volume measurements are minimised. Experimental methods are given for the evaluation of all chromatographically pertinent volumes and, as an example, the procedures were applied to a Zorbax C8 reversed-phase column. The data obtained are discussed in the light of the theory presented.