Application of displacement reactions in flame photometry-II Emission flame photometric determination of alkaline earth metals in the presence of interfering anions

For the emission flame photometric determination of strontium and barium in the presence of interfering ions such as phosphate, sulphate, arsenate and oxalate, calibration or simple standard addition methods cannot be used. Greatly reduced errors can be achieved by dividing the sample solution into four equal parts and adding to each certain known amounts of two metal ions. One of these is identical to the determinand (e.g., strontium or barium) the other has similar characteristics to it (e.g., calcium). The amounts of these metals are chosen so that the total (molar) concentration of these should be identical in all solutions, but the ratio of the concentrations of the two metals should be different. The emission of the determinand metal must be measured, and a standard addition plot produced. The amount of determinand present in the sample can be obtained from the intersection of the emission vs. concentration line with the concentration axis.     

Determination of calcium in the presence of interfering anions by flame photometry using an oxygen-enriched air-acetylene flame and a displacement method

Summary The interferences due to phosphate, oxalate, sulphate, arsenate, borate, nitrate and perchlorate in the flame photometric determination of calcium can be eliminated by the use of an oxygen-enriched airacetylene flame and the addition of excess sulphate to the sample. A method for the determination of calcium in the presence of these interferences is described and some results (1.0 and 0.5 mmole of Ca/l) are given.

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Flammenphotometrische Calciumbestimmung in Gegenwart störender Anionen mit Hilfe einer Sauerstoff-angereicherten Luft-Acetylen-Flamme und eines Verdrängungsverfahrens

Zusammenfassung Die Störungen durch Phosphat, Oxalat, Sulfat, Arsenat, Borat, Nitrat und Perchlorat konnten durch Verwendung einer Sauerstoff-angereicherten Luft-Acetylen-Flamme und durch Zusatz von überschüssigem Sulfat zur Probe verhindert werden. Eine entsprechende Methode wird beschrieben und einige Ergebnisse (1,0 und 0,5 mMol Ca/l) mitgeteilt.

     

Divalent activation in temporary phosphate tethers: highly selective cuprate displacement reactions

Desymmetrization of a readily derived pseudo-C(2)-symmetric monocyclic phosphate via highly diastereoselective anti-S(N)2' allylic displacement reactions is reported. This method utilizes of a wide variety of zinc-derived organocuprates to afford E-1,2-syn-configured phosphate acid building blocks. Extension of this protocol to unsymmetric monocyclic phosphates exclusively yields 1,2-anti-configured products. Within this study, stereoelectronic factors, coupled with allylic strain, ultimately govern regio- and diastereoselective cuprate reactions, further substantiating the Corey mechanism for organocuprate additions into allylic esters. [reaction: see text]     

An indirect flame emission spectrometry method for the determination of traces of sulphur. I

Summary An accurate and simple indirect method of flame emission spectrometric determination of small quantities of elemental sulphur is described. The method is based on the reduction of elemental sulphur by means of sodium borohydride and oxidation of the resulting boron-sulphur compounds to sulphate by means of hydrogen peroxide. The determinations can be carried out in the presence of methanol, acetone, dimethylformamide, toluene and benzene. The detection limit of the reported method is 1 ppm of sulphur.

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Indirekte etnissionsspektroskopische Bestimmungsmethode für Spuren elementaren Schwefels. I.

Zusammenfassung Eine genaue und einfache, indirekte, emissionsspektroskopische Methode zur Bestimmung geringer Mengen elementaren Schwefels wurde ausgearbeitet. Sie besteht in der Reduktion des elementaren Schwefels mit Hilfe von Natriumborhydrid und in der Oxydation der entstehenden Bor-Schwefel-Verbindung zu Sulfat mit Hilfe von Wasserstoffperoxid. Die Analyse wurde in Methanol, Aceton, Dimethylformamid, Toluol und Benzol durchgeführt. Die Erfassungsgrenze beträgt 1 ppm Schwefel.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

An indirect flame emission spectrometry method for the determination of sulphur and sulphur compounds. II

Microchimica Acta - An accurate and simple indirect method of flame-emission spectrometric determination of small quantities of elemental sulphur and many sulphur compounds, without their prior...     

Spectrophotometric determination of inorganic phosphate in soil extracts by a single-solution non-reductive method

A previous method involving crystal violet—12-molybdophosphate formation is modified by including all reagents into a single solution. The apparent molar absorptivity is 0.84 × 10⁵ l mol^-1 cm^-1. The results obtained for a series of soil extracts correlate well with those obtained by a reductive method.     

The determination of rubidium and caesium in geological materials by atomic emission spectrophotometry with a nitrous oxide-acetylene flame

An atomic emission spectrophotometric procedure is presented for the determination of rubidium and caesium at the per cent and p.p.m. levels. A nitrous oxide-acetylene flame and a potassium ionization buffer are used. There is no need for prior separation, pre-concentration or general matrix matching of standards.     

Elimination of phosphate interference in flame photometric determination of strontium and barium

The interference of phosphate in the flame emission of calcium, strontium and barium was studied. The emission intensity decreases proportionally to the amount of interfering anion up to a maximum depression for equimolar amounts of phosphate to metal. A thermostable phosphate is formed before the cation enters the flame. Appropriate addition of lanthanum restores the three alkaline earth lines to their intensities in absence of phosphate, the lanthanum displacing, the alkaline earths from their phosphates before the hot region of the flame is reached.     

On the matrix effect in the determination of main components of dolomite by atomic flame emission and absorption spectrometry

Summary The matrix effects in the determination of the main components of dolomite by flame emission (Na, K) and atomic absorption spectrometry (Ca, Mg, Fe, Mn) have been examined according to the methodology based on the theory of design of experiments. The influence of some auxiliary compounds added to a sample solution has been investigated. The determination of Fe and Mn proved to be specific. The matrix effect has been eliminated in the determination of K by adding a mixture of NaCl and H₃PO₄, in the determination of Na by KCl spectral buffer, in the determination of Mg by NaCl buffer and in the case of Ca by SrCl₂ as a spectral buffer.

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Untersuchung über den Matrixeffekt bei der Bestimmung der Hauptbestandteile von Dolomit durch Atomemissions- und -absorptionsspektrometrie

Zusammenfassung Mit Hilfe methodisch geplanter Versuche wurde der Einfluß der Matrix auf die Bestimmung von Na und K (Emission) sowie Ca, Mg, Fe und Mn (Absorption) untersucht. Ebenso wurde der Einfluß verschiedener Zusätze geprüft. Die Bestimmung von Fe und Mn erwies sich als spezifisch. In den anderen Fällen konnte die Matrixstörung durch folgende Zusätze behoben werden: Gemisch von NaCl und H₃PO₄ für K, KCl für Na, NaCl für Mg, SrCl₂ für Ca.

     

Influence of ultrasonic waves on phosphate determination by the molybdenum blue method

Polymeric bonds between molybdate monomeric ions in acidic medium were broken by 40 kHz ultrasonic wave irradiation, improving the reaction kinetics with o-phosphate in the presence of ascorbic acid. It could be assumed that the ultrasonic wave irradiation of molybdate solution in acidic medium during 1.0 min was sufficient to increase the rate of the molybdenum blue formation. The approach was applied to the o-phosphate determination in natural waters. Precise results were obtained in the range from 0.05 to 0.50 μg ml⁻¹ (r=0.9994; N=6), and the detection limit was estimated as 0.027 μg ml⁻¹ PPO₄. Advantages over the classical analogous procedure are emphasised.     

Detection of sulphate by flame emission spectrometry

A reasonably simple method for the determination of sulphate is presented. The method is based on disulphur molecular emission, produced in a hydrogen-nitrogen diffusion flame, utilizing a conventional atomic absorption spectrometer, with simple accessories to handle in-line ion-exchange pretreatment. A simplex program was written and used to obtain optimum experimental conditions. Disulphur emission was found to occur at temperatures from below 150°C; the optimum temperature is ca. 200°C. The method can be used for the determination of sulphate down to ca. 10 mg S l^?1.     

Indirect method for the determination of aluminium by atomic-absorption spectrometry using an air-acetylene flame

The enhancement of the atomic-absorption signals of iron, cobalt, nickel and chromium in a fuel-rich air-acetylene flame by small amounts of aluminium makes possible the indirect determination of aluminium in the concentration range 0.01-10 ppm. The optimization of working conditions and the occurrence of interferences are reported.     

Determination of rubidium in blood by flame emission spectrometry

Rubidium in plasma and whole blood was determined by flame atomic emission spectrometry after dilution 10× and 100× respectively with a 2.5 g Cs l^?1 solution used as an ionization suppressor. The method is more sensitive than inductively coupled plasma, and much simpler than, e.g., neutron activation analysis.     

Effects of analyte reduction by flame gases through heterogenous reactions in flame spectrometry

A simplified model describing vaporisation with simultaneous reduction to an involatile species and assuming that the rate of reduction is limited by the diffusion of reducing species from the flame gases to the particle surface is presented. Under these conditions the fraction vaporised may be independent of the particle size and linear calibration curves may be found even with incompletely vaporised aerosol particles.     

Matrix modification--the use of protein-free solutions in the determination of metals in blood by flame atomic fluorescence and emission spectrometry

A procedure is described for matrix modification in the determination of metals in blood by flame spectrometric methods. The protein is removed by precipitation with dilute nitric acid and centrifugation and the supernatant liquid is used for direct analysis. Nitric acid is compared with other acids as the precipitant. The technique is simple, contamination-free and provides a solution which may be directly compared with aqueous calibration standards. Its application for determination of clinically important metals by flame atomic fluorescence and emission spectrometry is demonstrated.     

The flame photometric determination of calcium in phosphate,carbonate, and silicate rocks

A flame photometric method of determining calcium in phosphate, carbonate, and silicate locks has been developed Aluminum and phosphate interference was overcome by the addition of a large excess of magnesium. The method is rapid and suitable for routine analysis Results obtained are within ± 2% of the calcium oxide content.     

Elimination of anionic interference in flame photometric determination of calcium in the presence of phosphate and sulphate

Studies on the interference of phosphate and sulphate in the flame emission of calcium as calcium chloride have shown that there is a fall of intensity corresponding initially to the quantity of the interfering anion, the emission intensity reaching a constant value at a certain ratio of PO₄^-3 or SO₄^-2 to Ca⁺².On addition of appropriate quantities of lanthanum (or iron) to the sample, the intensity of the calcium emission lines is restored to the value it had when the interfering anions were absent.It is postulated that lanthanum replaces calcium in a phosphate- or sulphate-containing compound, that without lanthanum does not form calcium ions even at high temperature.     

Kinetic analysis of nonisothermal solid-state reactions: determination of the kinetic parameters by means of a nonlinear regression method

A nonlinear regression method has been proposed for a simultaneous calculation of the activation energy, frequency factor, and reaction order from a single TG curve. This method was based on the new temperature integral approximation proposed in this paper and the Levenberg–Marquardt method. The newly proposed nonlinear regression method was applied for determining the kinetic parameters from two simulated TG curves. The results of the calculations were compared with values obtained by the traditional method. It can be concluded from this comparison that the new nonlinear regression method is more accurate than the traditional method for the determination of the kinetic parameters of solid-state heterogeneous reactions.