Determination of chlorine containing species in explosive residues using chip-based isotachophoresis

A new method has been developed to allow the determination of the chlorate, chloride and perchlorate anions in inorganic explosive residues to be made using isotachophoresis (ITP). To enable a good separation of these species to be achieved the method involves the use of two complexing agents. Indium(III) is used to allow the determination of chloride whilst using nitrate as the leading ion and alpha-cyclodextrin is used to allow the separation of chlorate and perchlorate. Separations were carried out using a miniaturised poly(methyl methacrylate) (PMMA) separation device. The method was applied to analysing both model samples and actual inorganic explosive containing residue samples. Successful determinations of these samples were achieved with no interference from other anions typically found in inorganic explosive residues. Limits of detection (LOD) for the species of interest were calculated to be 0.80 mg l(-1) for chloride, 1.75 mg l(-1) for chlorate and 1.40 mg l(-1) for perchlorate.     

A colorimetric determination of thorium

A colorimetric method for the determination of thorium is proposed. It is based upon the precipitation of thorium with a standard solution of oxalic acid and the subsequent reaction of the excess oxalic acid with a standard solution of potassium permanganate. The absorbancy of the remaining permanganate solution is directly proportional to the thorium present. The variables affecting this method have been critically studied. Reliable determinations can be made in the range of 3 to 30 mg of thorium in 1 cm cells when the colored solution is diluted to 250 ml. Most interfering substances can be removed by electrolysis in a mercury cathode cell or by the precipitation of thorium with potassium iodate.     

A total dissolution method for determination of the α-emitting isotopes of uranium and thorium in deep-sea sediments

A method is described for the determination of specific activities of the natural α-emitting isotopes of uranium and thorium in deep-sea marine sediments. Such information is needed primarily for estimation of sediment accumulation rates. The method is based on total dissolution of sample after fusion with potassium fluoride (to dissolve silicates) and with sodium/potassium pyrosulphate (to dissolve other refractory minerals and convert to the sulphate system). Uranium and thorium fractions are purified for electroplating by anion exchange, with elements naturally present used as carriers. Final determinations are made by α-spectrometry by means of isotopic tracers added at the outset of processing. Experience gained with different types of deep-sea sediment is discussed.     

Periodatometric determination of organotrithiocarbonates and mercaptans (via trithiocarbonate formation)

A method has been described for the direct visual and potentiometric determination of organotrithiocarbonates in bicarbonate medium in the presence of potassium iodide, using potassium periodate as an oxidimetric reagent. The method was extended to the determination of mercaptans after their quantitative transformation to the corresponding organotrithiocarbonates through reaction with carbon disulfide in the presence of alkali. The resulting trithiocarbonates are titrated with periodate in the manner described herein. The excess of carbon disulfide does not interfere in these determinations. Organotrithiocarbonates are smoothly, rapidly, and quantitatively oxidized to the corresponding bis(alkyl/aryl mercapto thiocarbonyl) disulfides with the oxidant under the specified conditions.     

Determination of ceftriaxone sodium in pharmaceutical formulations by flow injection analysis with acid potassium permanganate chemiluminescence detection.

Based on the chemiluminescence (CL) emission generated from the oxidation of ceftriaxone sodium alkali hydrolysate by potassium permanganate in polyphosphoric acid (PPA), a novel determination method for ceftriaxone sodium was developed by using a flow-injection technique. The calibration curve appears to be linear in the range between 0.05 and 100 microg mL(-1) with a detection limit (3sigma) of 25 ng mL(-1), and a relative standard deviation (RSD) of 0.6% for eleven replicate determinations of 5.0 microg mL(-1) ceftriaxone sodium. The proposed method has been successfully utilized for the determination of ceftriaxone sodium in pharmaceutical formulations, while the chemiluminescence reaction mechanisms were investigated.     

Processing of signals from an ion-elective electrode array by a neural network

Neural network software is described for processing the signals of arrays of ion-selective electrodes. The performance of the software was tested in the simultaneous determination of calcium and copper(II) ions in binary mixtures of copper(II) nitrate and calcium chloride and the simultaneous determination of potassium, calcium, nitrate and chloride in mixtures of potassium and calcium chlorides and ammonium nitrate. The measurements for the Ca²⁺/Cu²⁺ determinations were done with a pH-glass electrode and calcium and copper ion-selective electrodes; results were accurate to ±8%. For the K⁺/Ca²⁺NO^?₃/Cl^? determinations, the measurements were made with the relevant ion-selective electrodes and a glass electrode; the mean relative error was ±6%, and for the worst cases the error did not exceed 20%.     

Determination of small quantities of potassium and sodium in stony meteoritic material,rocks and minerals

A flame photometric method for the determination of potassium (0.005 0.1%) and sodium (0.01 1.0%) in stony meteorites and other silicate materials is described using a Beckman Model DU flame photometer. A simple scanning procedure eliminated background radiation and a small correction for the effect of magesium on potassium radiation was calculated. Results obtained by this procedure agree well with an evaporative technique and isotope dilution determinations.     

Estimation of postmortem interval by hypoxanthine and potassium evaluation in vitreous humor with a sequential injection system

The estimation of the time since death known as postmortem interval (PMI) is a main issue in the field of forensic science and legal medicine. In this work it is proposed a sequential injection system for the determination of hypoxanthine and potassium in the same sample of vitreous humor since the concentrations of both parameters change with PMI and the vitreous humor has been regarded as the ideal extracellular fluid for these kinds of determinations. By measuring both parameters the accuracy of estimation of PMI can be increased, and the effects of factors which influence the values in postmortem chemistry minimized.Hypoxanthine determination is based on its oxidation to uric acid (290 nm), catalyzed by immobilized xanthine oxidase, and the quantification of potassium levels in vitreous humor was performed using a tubular potassium ion-selective electrode. With a unique analytical cycle both analytes were evaluated being potassium levels determined during the degradation of hypoxanthine in the enzymatic reactor.Working concentration ranges between 6.04-40.00 μmol L⁻¹ and 7.00 × 10⁻⁵ to 1.00 × 10⁻¹ mmol L⁻¹ were obtained, for hypoxanthine and potassium, respectively.The method proved to be reproducible with R.S.D. <5% for hypoxanthine and <3% for potassium. Sampling rate was approximately 30 per hour for the sequential determination of both parameters being 15 and 60 determinations per hour if hypoxanthine or potassium, where evaluated independently. Statistical evaluation at the 95% confidence level showed good agreement between the results obtained, for the vitreous humor samples, with both the SIA system and the comparison batch procedures. Moreover the methodology has low environmental impact in agreement with the demands of green analytical chemistry as only 2.7 mL of chemical waste is produced during both determinations.     

Coulometrische bestimmung von thiosulfat

A method is developed for the coulometric determination of thiosulphate with iodine electrically generated from potassium iodide. Depending on the fineness of the regulation of the current and of the measurement of the time, the method is applicablc to determinations in the macro, micro and submicro range. Moreover, with this method, the previous preparation and utilisation of iodine solutions can be avoided entirely.Owing to these possibilities it is proposed to standardize thiosulphate solutions henceforward electrolytically by the measurement of the coulombs needed. Furthermore it is proposed to introduce the coulomb into the volumetric analysis as a standard.     

Analysis of mixtures of citric and oxalic acids based on their oxidation with potassium permanganate and manganese(III) sulfate

A determination of mixtures of citric and oxalic acids has been developed based on quantitative oxidation of the two substances with excess potassium permanganate to carbon dioxide and water and on quantitative oxidation of oxalic acid to carbon dioxide and water and of citric acid to carbon dioxide and formic acid with excess manganese(III) sulfate. The content of the two substances in mixtures can be calculated from the different consumption in these two oxidimetric determinations; a single standard solution of potassium permanganate can also be used for the preparation of manganese(III) sulfate.     

Determination of organic carbon in natural water with inductively coupled plasma/atomic emission spectrometry after evaporation of inorganic carbon

The performance of a continuous flow system interfaced with a sequential inductively coupled plasma/atomic emission spectrometer (ICP/AES) was evaluated for the determination of organic carbon in water. Optimal conditions for evaporation of carbonates before determination or organic carbon was established and working ranges were determined. The method applied for the determination of organic carbon in natural water was compared to determinations made by an elemental analyzer.     

A comparative study of different extraction systems for the spectrophotometric determination of potassium with 18-crown-6

A comparative study on the extractive-spectrophotometric determination of potassium with 18-crown-6 employing different colored counterions and organic extraction solvents is described.Extraction systems using methyl orange/chloroform, bromcresol purple/chloroform and bromcresol green/benzene demonstrated good preliminar features for such purpose and are studied in detail. Analytical performance characteristics including: sensitivity, selectivity, precision, linearity, etc. are given for each method. The main disadvantage of this type of determinations is the lack of reproducibility. Some explanations to this fact are discussed.A new method for the determination of trace amounts of potassium based on its extraction into chloroform with 18-crown-6 and methyl orange is proposed. The linear working range goes from 0.5 to 7 ppm of potassium, the apparent molar absorptivity being 8.8 × 10³ liters mol^?1 · cm^?1, and the precision, expressed in terms of relative standard deviation, of ±4.6%.     

Trace metal and metalloid species determination: evolution and trends

Metal species determination has seen considerable evolution during the last decade. The issues addressed by total metal determinations using standard spectrochemical analyses deliver only a minimal amount of information required to appropriately inform decision making. In molecular analyses, coupled instrumentation systems allow us to obtain molecular information for assisting in identifying the compounds of interest. Metal species determinations will provide additional information beyond that available from total metal determinations. Many total metal determinations will be replaced with elemental speciation determinations when species-selective risk/benefit assessment is a priority. This paper discusses the differences between traditional inorganic metals analysis and metal species determinations and outlines new trends.     

溴酸钾-二甲酚橙体系-顺序注射-催化光度法测定痕量钒

在酸性介质条件下,钒(Ⅳ)能显著催化溴酸钾对二甲酚橙的氧化褪色反应。据此建立了测定痕量钒(Ⅳ)的顺序注射催化光度法。方法的线性范围为0.5~50ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%~108%。     

坚果及其制品中匹克司残留量气相色谱测定法

确立了坚果及其制品中匹克司残留量的气相色谱测定方法试样采用甲醇提取，经ＰＴ－硅镁柱净化，ＧＣ－ＥＣＤ测定，方法简便，快速灵敏，检出限０．０２＊１０＾－３ｇ／ｋｇ，添加回收率８７．４％－９３．２％，相对标准偏差４．４％－６．８８％．。     

Sequential determination of salicylic and acetylsalicylic acids by amperometric multisite detection flow injection analysis

An amperometric multisite detection flow injection analysis (FIA) system was developed for sequential determination of 2 analytes with a single sample injection and single detector. Tubular composite carbon electrodes with an inner diameter similar to that of the FIA manifold tubing were constructed so that measurements could be made without impairing the sample plug hydrodynamic characteristics. The electrochemical behavior of the tubular voltammetric cell in a low-dispersion FIA manifold and the behavior of the FIA system incorporating this type of voltammetric cell intended for multisite detection were evaluated by performing measurements with potassium hexacyanoferrate(II). Feasibility of the approach was demonstrated in the sequential determination of salicylic and acetylsalicylic acids in pharmaceutical products at a fixed potential of 0.98 V. The system allows sequential determination of salicylic acid concentrations ranging from 1.0 x 10(-5) to 5.0 x 10(-5) M and acetylsalicylic acid concentrations between 1.0 x 10(-3) and 5.0 x 10(-3) M with good precision on both detection sites and with relative standard deviations (RSDs) > or = 1.5% (n = 10) and 2.1% (n = 10), respectively. A comparison of these results with those of the U.S. Pharmacopeia procedure showed RSDs <5.0 and 1.0% for salicylic acid and acetylsalicylic acid, respectively. The proposed method enables 15 determinations per hour, which corresponds to the analysis of approximately 8 samples per hour. The detection limits of the methodology were approximately 3.5 x 10(-6) and 1.1 x 10(-5) M, respectively, for the first and second monitoring sites.     

溴酸钾二甲酚橙体系-顺序注射-催化光度法测定痕量钒

在酸性介质条件下,钒(Ⅳ)能显著催化溴酸钾对二甲酚橙的氧化褪色反应。据此建立了测定痕量钒(Ⅳ)的顺序注射催化光度法。方法的线性范围为0.5⁵0ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%50ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%¹08%。     

Thermometrische Schnellanalyse von Martin- und Hochofenschlacken sowie anderen Silicaten

Summary A novel method has been developed for the rapid analysis of silicates. Each component is determined from the temperature variation of the solution resulting from the addition to the test solution of a selectively reacting reagent. By suitable construction of the instrument the concentration of the component to be determined can be read directly in per cent. The determination of a component takes usually 4 to 8 minutes.In the test solution a temperature change proportional to the concentration of the component to be determined has been produced by the following reagents: sulphuric acid for barium, ammonium peroxodisulphate for iron, hydrogen peroxide for titanium, hydrofluoric acid for silicic acid, potassium permanganate for sulphur, ammonium molybdate and hydrogen peroxide for phosphate, potassium permanganate for manganese, potassium oxalate for calcium, diammonium hydrogenphosphate for magnesium, ascorbic acid for chromium. The above components can be determined without any separations. Only in the case of aluminium a separation of silicic acid from aluminium by dehydrating with perchloric acid in necessary. Thereafter the aluminium can be determined with hydrofluoric acid.The precision of the determinations is practically identical with the precision of the usual plant methods.     

Determination of selectivity coefficients of ion-selective electrodes by a matched-potential method

A new method is proposed for the determination of selectivity coefficients of ion-selective electrodes. A reference solution of the primary ion is used and potential changes are measured after adding either the primary ion or secondary ion. Increasing concentrations of the secondary ion are added to provide the same potential change as obtained for a fixed added concentration of the primary ion. The ratio of the primary-to-secondary ion concentrations for this potential change represents the selectivity coefficient. This method is illustrated by the use of a sodium glass electrode and a potassium valinomycin electrode. Results obtained are compared with those from conventional determinations of selectivity coefficients. The advantages of this method are discussed.     

Post-source decay mass spectrometry: optimized calibration procedure and structural characterization of permethylated oligosaccharides

Permethylated oligosaccharides were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) using a reflectron time-of-flight instrument in the post-source decay (PSD) mode. Under these ionization conditions, such derivatives yield intense signals corresponding to sodium or potassium cationized molecular species. Fragments observed in the PSD spectra result exclusively from cleavage of glycosidic bonds, preferentially at N-acetylhexosamine residues. A systematic study was carried out on a series of permethylated oligosaccharides to allow rationalization of the fragmentation processes. Fragments originating from both the reducing and the non-reducing ends of the oligosaccharide yield information on sequence and branching. Moreover, glycosyl residues linked in position 3 of HexNAc units give rise to a highly specific elimination process, which allows unambiguous assignment of (1-3) interglycosidic linkages. Special attention was paid to the structural analysis of oligosaccharides carrying the commonly encountered fucosyl and sialyl end-caps. In the case of sialylated residues, a targeted methodology involving desialylation and specific CD3-labeling of the nascent free hydroxyl groups was developed to mark the initial location of sialic acid residues along the oligosaccharide backbone. As accurate mass determination of fragment ions is essential for their assignment, a simplified protocol for the calibration in the PSD mode is described. This procedure allows the determination of the correction function parameters required to process the data for an instrument that employs post-acceleration detection. MALDI/PSD-MS of permethylated oligosaccharides, by providing structural information at the low picomole level, appears to be a valuable complement, or an alternative, to the techniques currently in use for carbohydrate structural analysis.