Microdetermination of magnesium in biological fluids

A modified procedure for the spectrophotometric determination of serum magnesium is described in which a direct addition of serum is made to a two-piece color reagent system. One solution contains an optimized concentration of the color reagent Magon, 1-azo-2-hydroxy-3-2-(2,4-dimethylcarboxanilido)-naphthalene-1′-(2-hydroxybenzene-5-sulfonate) sodium salt, in a dimethyl sulfoxide medium for binding magnesium and also EGTA, ethylene-bis(oxyethylenenitrilo)-tetraacetic acid, for binding calcium. The other is an alkaline solution of dilute cyanide to bind copper and iron and provide the optimum reaction pH. By means of these ingredients the simple procedure involves a reaction with serum magnesium while masking the interference of calcium and trace metals and allowing the reaction to take place without either separation or deproteinization steps. Optimized characteristics are shown for a linear reaction involving a variable reaction blank in the procedure where calcium is measured against a blank that is constant in its makeup. The linearity of the procedural reagent blank, with respect to its own concentration, helps attain the required linear results for the overall system and this is described by spectral studies.     

Verteilung der Molybdatoarsensäure und Molybdänsäure zwischen wäßriger Lösung und einigen organischen Lösungsmitteln

Solvent extraction behaviour of molybdoarsenic acid is very similar to that of molybdophosphoric acid. It is best extracted by i-butanol, methylisobutylketone or ether/butanol-mixture. Separation of molybdophosphoric from molybdoarsenic acid is best effected by a n-butanol/chloroform-mixture and sufficiently good by butyl acetate. Selective extraction of molybdoarsenic acid from molybdophosphoric acid cannot be attained. The lowest blank distribution and absorbance of the molybdate reagent are obtained from sulphuric acid solutions. HCl and HClO₄ are less suitable, from this point of view, but decompose heteropolyacids to a lesser extent.     

Spectrophotometric study of a direct determination of serum calcium

A modification of a direct manual procedure for serum calcium has been developed in which a one-piece color reagent is used. When a micro amount of serum is added to the reagent, rapid and stable color formation occurs enabling the procedure to serve either as a manual stat system of in robotized automatic instrumentation. Total color measurement is not attained in such a procedure owing to the described regressive nature of the reagent blank. However, accurate and linear reaction characteristics are effectively achieved. The use of a low dielectric solvent, EG, served well for repressing the ionization of the blank while allowing linear and reproducible calibration characteristics.     

Determination of the fungicide ferbam in wheat grains after adsorption onto microcrystalline naphthalene

A procedure was developed for the determination of iron(III) dimethyldithiocarbamate by converting it into iron(II)-bathophenanthroline-tetraphenylborate complex, which was then adsorbed onto microcrystalline naphthalene. The absorbance was measured at 534 nm against a reagent blank. Beer's Law was obeyed over the concentration range of 0.4-20 microg mL in final solution. Ten replicate determinations on 70 microg ferbam solutions gave a mean absorbance of 0.36, with a relative standard deviation of 0.91%. The method is sensitive and highly selective. It was applied for the determination of ferbam in a commercial sample and in mixtures with various dithiocarbamates (ziram, zineb, maneb) and wheat grains.     

Purification and characterizing properties of analytical reagent quinizarin-2-sulphonic acid and its sodium salt

Quinizarin-2-sulphonic acid and its sodium salt have been purified for analytical use. The thermal analysis behaviour and the infrared and NMR spectra of the reagent have been recorded. Absorptiometry at 465 nm is recommended for the assay of solutions. Spectrophotometric measurements, corrected for fading, are treated by a PITMAP-type procedure to obtain acid dissociation constants for the reagent. Finally, some reactions with metal ions are surveyed briefly.     

Studies on the extraction of Copper(II) with 4-alkyldithiocarboxylate derivatives of 1-phenyl-3,5-dioxopyrazolidine

The extraction behaviour of copper(II) from acid solutions (pH 0-6) was studied with the new reagent 4-alkyldithiocarboxylate-3,5-dihydroxy-l-phenylpyrazol (HL; alkyl = n-butyl, n-dodecyl). The species extracted was found to be ML(2). The reagent was used to separate copper(II) from iron(III) in an acidic lixiviation solution of a mineral sample composed of enarguite (Cu(3)AsS(4)) and pyrite (FeS(2)). Additionally, the extraction efficiency of this new reagent was compared with the commercially available LIX 984 N extradant of copper (II).     

The polarographic behaviour of ketoprofen and assay of its capsules using spectrophotometric and voltammetric methods

The quantitative determination of ketoprofen using spectrophotometric and voltammetric methods are described. The spectrophotometric procedure depends upon the reaction of ketoprofen with N-bromosuccinimide (NBS). The residual reagent is then determined by formation of violet colour with 2,2-diphenyl-l-picryl hydrazine (DPPH(2)). The consumed NBS would correspond to ketoprofen. Beer's law is valid over the concentration range 5-80 mug/ml of the drug. Direct current (DC) polarography allows to study the reduction behaviour of ketoprofen at the dropping mercury electrode (DME) using different supporting electrolytes at different pH values. Direct current stripping voltammetry (DCSV) was used for the quantitative measurements of the drug. The calibration graph of peak current vs concentration was linear from 0.254 x 10(-2) to 0.254 mug/ml. In model solutions as little as 5.08 x 10(-4) ng/ml ketoprofen can be detected by DCSV. Both methods were applied successfully for the determination of ketoprofen either in pure or dosage forms.     

Study of the electrochemical behaviour of amphetamine and its derivatives in aqueous solution

The polarographic behaviour of amphetamine-type drugs in acid and alkaline solutions was investigated. Differential pulse polarography (DPP) with a dropping mercury electrode (DME) was used to monitor these drugs in aqueous solution. DPP and cyclic voltammetry (CV) were also utilised to study the electrode process of some 2-phenylethylamines derivatised with 4-N,N-dimethylaminobenzaldehyde (Ehrlich’s reagent) and 2,4-dinitrofluorobenzene, known as Sanger’s reagent, respectively.     

Constant-current stripping analysis for iron(III) by adsorptive accumulation of its Solochrome Violet RS complex on a carbon-fibre electrode

The optimum experimental conditions with respect to pH, adsorption potential and Solochrome Violet RS concentration for the constant-current stripping determination of iron(III) have been investigated. The suggested procedure has been used for the determination of iron(III) in tap water and the accuracy investigated both by analysing standard solutions and by comparison with results obtained by atomic-absorption spectrometry. The relative precision was 6-13% and the detection limit for iron(III), set by the reagent blank, was approximately 1 mug/l. The results obtained with a mercury-film coated carbon-fibre flow electrode have been compared with those obtained with a hanging mercury drop electrode. The advantages of measuring electrode potential vs. time instead of vs. current have been evaluated.     

HPLC studies of isomeric chromium-N-benzoylphenylhydroxylaminates

Summary N-Benzoylphenylhydroxylarnine complexes of some metals have been investigated by HPLC. The green chromium complex formed by this reagent shows conclusive evidence of the presence of geometrical isomers. It is photosensitive and changes to a brown modification when irradiated with ultra violet or visible light. Elution behaviour of the complexes has been studied with different solvent mixtures. Attempts have been made to characterize the complexes from different measurements.

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Untersuchung von isomeren Chrom-N-benzoylphenylhydroxylaminaten durch HPLC

     

低空白镍锍试金预富集中子活化分析测定地球化学标准物质中的铂族元素

研究了镍锍试金预富集中子活化分析测定岩石样品中的铂族元素。纯化捕集剂氧化镍,大大降低了化学分离全流程铂族元素的空白。取样量为50g时,所需溶剂各元素的空白值为(ng/g):Pt<0.05、Pd<0.05、Os<0.01、Ru<0.05、Rh<0.05、Ir=0.002。用平面锗探测器测定Rh使测定下限降低了两个数量级,对几种国标地球化学标准物质的测定结果与推荐值基本符合。     

Determination of calcium, iron and manganese in moss by automated discrete sampling flame atomic absorption spectrometry as an alternative to the ICP-MS analysis

An automated, fast and reliable procedure has been developed for flame atomic absorption analysis of Ca, Fe and Mn in moss. The method is suitable for routine analysis of a large number of moss samples and allows sequential determination of all three elements in the same solution. In order to inhibit the matrix interference on Ca and to level the diverse analytical behaviour of the moss matrix, approximately 1% La was added to both samples and standard solutions as well. An integrated system of ‘sandwich-type’ air segmented discrete sample introduction and flame atomic absorption detection (ASDI-FAAS) was successfully applied. It works at ‘solvent-air-sample-air-solvent’ mode, which tolerates the introduction of high salt content solutions, reduces reagent and sample consumption and allows the application of data treatment models to pseudo-steady state signals for bettering the repeatability. For moss samples containing high Ca and Fe concentrations, equivalent procedure was used by turned on 45° burner head without worsening the analytical characteristics. Concerning these three elements, the method is suggested as a cheaper, easier and more trustworthy alternative with a better precision to the inductively coupled plasma-mass spectrometry (ICP-MS) one. The ASDI-FAAS results were used for selection of appropriate isotopes and correction procedures for ICP-MS determination. Both methods show good agreement of the Ca, Fe and Mn results that correspond to the moss reference materials tested.     

Solvent extraction and separation of gallium(III), indium(III), and thallium(III) with tributylphosphate

A systematic study has been made of the solvent extraction behaviour of milligram amounts of gallium(III), indium(III), and thallium(III) with TBP from hydrochloric acid, and of thallium(III) from nitric acid, sulphuric acid and buffer solutions of different pH. The effect of the metal ion concentration, acid concentration, reagent concentration, salting-out agent, and diverse ions have been critically examined. A scheme for separation of gallium(III), indium(III), and thallium(III) from each other and for their determination is proposed.     

Heats of preferential adsorption of chelates

A method employing a flow calorimeter for determining heats of preferential adsorption of certain organic chelates of metals from organic solutions is described. Experimental heats of adsorption are correlated with the chromatographic behaviour of the chelates and it is shown that irreversible retention on a column occurs when the heat is greater than 6 kcal mole^-1 for the first stage of the two-stage adsorption pro cess. The special case of the 2-methyl-8-quinoline chelate of copper(II) and its elution with solutions of the reagent is examined in more detail: heats of preferential adsorption decrease with increasing concentrations of reagent and the optimum experimental concentration can be predicted from the heat results.     

Photometric determination of trace selenium in aqueous media

A new procedure is developed for the photometric determination of trace selenium in aqueous solutions. The selection of 2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride as a reagent for selenium is justified. The proposed sample preparation procedure involves gas extraction of selenium as hydrogen selenide followed by its liquid-adsorption extraction from the gas phase to an aqueous reagent solution with the formation of a water-insoluble formazan. Formazan formed upon the absorption of hydrogen selenide is extracted with isoamyl alcohol. The concentration of selenium is determined from the absorbance of the formazan extract in the isoamyl alcohol. The procedure allows the determination of 10–120 μg/L selenium.     

The determination of small amounts of long-chain tertiary alkylamines and quarternary ammonium salts

Bromocresol green has been investigated as an alternative to ammonium erdmannate for the absorptiometric determination of small amounts of long-chain alkylamines and quaternary ammonium salts in aqueous solution in a solvent extraction procedure. The molecular absorption coefficient of the reagent at 615 nm is about 3 times that of the erdmannate ion at 353 nm; visual methods of comparison are simplified by the blue colour of the bromocresol green anion The sensitivity of both the bromocresol green and the erdmannate method may be increased by stripping the coloured reagents into a small volume of aqueous solution. Both methods are free of interference from iron, but the present procedure has the disadvantage of a blank which depends both on the pH and on the concentration of excess reagent.     

Synthesis and preliminary analytical evaluation of the chemiluminescence from (4-[4-(dichloromethylsilanyl)-butyl]-4'-methyl-2,2'-bipyridyl)bis(2,2'-bipyridyl)ruthenium(II) covalently bonded to silica particles

This paper describes, for the first time, a simple and effective synthetic route for covalently bonding the chemiluminescence reagent, (4-[4-(dichloromethylsilanyl)-butyl]-4'-methyl-2,2'-bipyridyl)bis(2,2'-bipyridyl)ruthenium(II) onto silica particles. The subsequent preparation of chemically regeneratable detection cells and their preliminary analytical evaluation with both sequential injection analysis and flow injection analysis are also reported. Unoptimised analytical figures of merit were established for standard solutions of codeine and sodium oxalate with detection limits calculated from three times the standard deviation of the blank signal, of 1 x 10(-8) M and 3 x 10(-7) M respectively. The chemically immobilised reagent exhibited some intriguing solvent and kinetic effects, which are also briefly discussed.     

Study of the electrochemical behaviour of amphetamine and its derivatives in aqueous solution

The polarographic behaviour of amphetamine-type drugs in acid and alkaline solutions was investigated. Differential pulse polarography (DPP) with a dropping mercury electrode (DME) was used to monitor these drugs in aqueous solution. DPP and cyclic voltammetry (CV) were also utilised to study the electrode process of some 2-phenylethylamines derivatised with 4-N,N-dimethylaminobenzaldehyde (Ehrlich’s reagent) and 2,4-dinitrofluorobenzene, known as Sanger’s reagent, respectively. Received: 19 March 1998 / Revised: 17 September 1998 / Accepted: 21 September 1998     

A robust multi-syringe system for process flow analysis. Part 3. Time based injection applied to the spectrophotometric determination of nickel(II) and iron speciation.

A new software-controlled time-based system for sample or reagent introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one multi-port selection valve, the time-based injection of precise known volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Two multi-syringe time-based injection (MS-TBI) systems were implemented: first, the injection of a sample in a multiple-channel manifold where the sample would sequentially merge and react with different reagents, and second, the sequential injection of several solutions (sample and reagents) into a particular flowing stream. The first system was applied to the spectrophotometric determination of nickel(II) in diluted samples from the acidic nickel ore leaching process, by using ammonium citrate as carrier, a saturated solution of iodine as oxidizing agent and alkaline dimethylglyoxime as chromogenic reagent. The sampling frequency attained was 57 h-1. Determinations on process samples compared well at the 95% confidence level with the reference values obtained by ICP-OES. The second time-based injection system was applied to the speciation of iron. Total iron and iron(II) concentrations were separately and sequentially determined using 1,10-phenanthroline in acetic buffer medium as reagent. The developed manifold allowed the optional use of two different carrier solutions, containing or not containing ascorbic acid, for performing the separate determinations. Also, in the sequential procedure, plugs of reducing carrier were alternatively intercalated before the sample injections used for total iron determinations. Sampling frequencies of 68 injections per hour were routinely used. Accuracy was assessed by analyzing synthetic known mixtures of Fe(III) and Fe(II) standard solutions. Recoveries of 98-100.5% with a maximum relative standard deviation of 3.6% were found. Results obtained for various samples of fertilizers agreed well with those attained by the standard batch procedure.     

Systematic error arising from ‘sequential’ standard addition calibrations. 2. Determination of analyte mass fraction in blank solutions

The use of a sequential standard addition calibration (S-SAC) can introduce systematic errors into measurements results. Whilst this error for the determination of blank-corrected solutions has previously been described, no similar treatment has been available for the quantification of analyte mass fraction in blank solutions - a crucial first step in any analytical procedure. This paper presents the theory describing the measurement of blank solutions using S-SAC, derives the correction that needs to be applied following analysis, and demonstrates the systematic error that occurs if this correction is not applied. The relative magnitudes of this bias and the precision of extrapolated measurements values are also considered.