Determination of nanogram amounts of iodide by electrochemical isotope dilution analysis

An isotope dilution method involving electrodeposition to determine nanogram quantities of iodide has been developed. A known quantity of iodide in ethanol as solvent was labelled with¹³¹I⁻ and subsequently diluted with a predetermined amount of inactive iodide. Specific activities before and after the isotope dilution were established by anodically depositing small fractions of the halide in each sample on rotating silver micro electrodes and determining the activities of the electrodeposits. Amounts from 42 ng to 1 μg were determined, usually with an error of less than 2.5%.     

Determination of nanogram amounts of albumin by radioimmunoassay

A sensitive radioimmunoassay for the measurement of albumin was developed using the fact that an antibody will absorb to the walls of a polystyrene tube. Advantage was taken of the observation that when a mixture of labeled and unlabeled albumin reacts with a limited amount of antibody the radioactivity adsorbed is a function of the two albumin concentrations. The method was found to be sensitive enough to detect as little as 1 ng of rat albumin with a coefficient of variation of 12%.     

Determination of nanogram amounts of nickel by flameless atomic-absorption spectroscopy

A simple flameless atomizer, made from a heated graphite resistor, was investigated for the determination of nickel in various salts. The parameters characterizing its behaviour were optimized, to yield an absolute detection limit of 0.1 ng of nickel.     

Determination of nanogram amounts of cesium by a concentration-dependent distribution method

Paper impregnated with Prussian blue sorbs cesium in low concentration to a different extent if varying initial concentrations of cesium are present. This dependence can be employed for the determination of submicrogram amounts of cesium. The selectivity and precision of the method are discussed. The method is applied to the determination of specific activity in “carrier-free” ¹³⁷Cs samples.     

Determination of nanogram amounts of boron in some antimony compounds

Summary A method has been developed for determining boron in antimony compounds in the range 10^–7–10^–6%. The method comprises the isolation of the boron by distillation as methyl borate and its determination fluorimetrically with dibenzoylmethane. For the three materials analysed, SbCl₃, Sb₂O₃, and SbCl₅, individual procedures of dissolution as well as distillation were developed. The results obtained are reproducible, the mean deviation being about 12% at boron concentrations of 10^–7–10^–6%.

---

Zusammenfassung Ein Verfahren zur Bestimmung von 10^–7 bis 10^–6% Bor in Antimon-verbindungen wurde ausgearbeitet. Es umfaßt die Abtrennung des Bors durch Destillation als Methylborat und dessen fluorimetrische Messung mit Dibenzoylmethan. Für SbCl₃, Sb₂O₃ und SbCl₅ wurden jeweils eigene Arbeitsweisen der Auflösung und Destillation angegeben. Die Analysenergebnisse sind reproduzierbar; die mittlere Abweichung beträgt etwa 12% für Borkonzentrationen von 10^–7 bis 10^–6%.

     

Determination of nanogram amounts of bismuth in rocks by atomic absorption spectrometry with electrothermal atomization

Bismuth concentrations as low as 10 ng g^-1 in 100-mg samples of geological materials can be determined by atomic absorption spectrometry with electrothermal atomization. After HF—HClO₄ decomposition of the sample, bismuth is extracted as the iodide into methyl isobutyl ketone and is then stripped with ethylenediaminetetraacetic acid into the aqueous phase. Aliquots of this solution are pipetted into the graphite furnace and dried, charred, and atomized in an automated sequence. Atomic absorbance at the Bi 223.1-nm line provides a measure of the amount of bismuth present. Results are presented for 14 U.S. Geological Survey standard rocks.     

Determination of nanogram amounts of cadmium in water by electrothermal atomic absorption spectrometry after flotation separation

A method is described for the flotation an determination of ng-levels of cadmium in water. Cadmium in a 1-l sample of water is coprecipitated with hydrated zirconium oxide at pH 9.1 ± 0.1. The precipitate is floated with the aid of a surfactant solution and small air bubbles, separated and dissolved in dilute hydrochloric acid. The cadmium content is determined by electrothermal atomic absorption spectrophotometry. The method is applied to the determination of ng l^?1 levels of cadmium in fresh water. The time required for preconcentration of cadmium from a 1-l sample is 20 min per sample, after 20 min stirring.     

Candoluminescence-a new flame technique for trace analysis-II Determination of nanogram amounts of manganese

The yellow candoluminescence of manganese stimulated in a 8:1 w w calcium oxide-calcium sulphate matrix at the edge of a hydrogen-nitrogen-air flame is used to determine 0.1-3.0 ng of manganese in 1-mul samples. Large amounts of chloride ions enhance the emission, and many transition metals suppress it.     

Pneumatopotentiometric determination of nanogram amounts of cyanide

Hydrogen cyanide is liberated from aqueous samples by reaction with sulphuric acid and transferred by a stream of nitrogen to a silver porous membrane electrode. Some HCN passes through the membrane into an alkaline dicyanoargentate solution; the cyanide ion produced causes a decrease in the equilibrium Ag⁺ concentration and the change of potential is related to the amount of cyanide in the sample. The detection limit is 3.0 ng ml^?1 cyanide in the injected solution; the relative standard deviation is 0.82% for 17 ng of cyanide. Sulphide interferes (as H₂S) but can be removed on a lead acetate column.     

Adsorption of radioactive iodide by natural zeolites

The vacancy transfer probabilities of K to L₁, L₂ and L₃ shell were measured with a new method. The L X-ray yields of targets excited by 59.5 keV incident photons, i.e., above the K edge of elements, were detected with a high-resolution Si(Li) detector. For comparison with the experimental results, theoretical calculations were made using data available on radiative and radiationless transitions. The radiative transition values of these elements were taken from the relativistic Hartree-Slater model, those of the radiationless transitions from the Dirac-Hartree-Slater model. The measured values were found to be in good agreement with theoretical ones. The h_KLi (i = 1, 2, 3) values were calculated by measuring the L_1x, L_2x and L_3x X-ray production cross-sections.     

Kinetic spectrophotometric determination of nanogram amounts of cyanide

A sensitive kinetic method for determination of nanogram amounts of cyanide is reported. It is based on the measurement of the induction period imposed by cyanide on the copper(II)-catalysed oxidation of 3-hydroxybenzaldehyde azine (3-OHBAA) by potassium peroxydisulphate. Kinetic data are recorded spectrophotometrically at 465 nm, the maximum absorption wavelength of the oxidation product of 3-OHBAA. From the kinetic study and other experimental tests it may be concluded that the cyanide ion undergoes copper(II)-catalysed oxidation during the induction period. The calibration plot is linear in the range 150-600 ng/ml cyanide and the detection limit is 50 ng/ml. The precision of the method, expressed as the relative standard deviation, is 3.2% for 350 ng/ml cyanide. Good recoveries are obtained in applying the method to analysis for cyanide in water samples.     

Membrane detection of nanogram amounts of formate dehydrogenase

A method for the detection of nanogram amounts of formate dehydrogenase on membranes was developed. The optimization of the method was carried out for determination of the best mediator concentration and tetranitrotetrazolium blue. It was found that 5-methyl-phenazil methosulfate is a more effective mediator than phenazine methosulfate. Different types of membranes were tested and it was shown that nitrocellulose membrane provides a low background and the highest sensitivity. Under optimal conditions the detection limit was 15 ng of the enzyme in the probe.     

Determination of nanogram amounts of bromide and chloride by molecular emission cavity analysis based on gallium halide emission

By measuring the GaBr emission enhanced by iodide at 350 nm in a carbon cavity heated by a hydrogen/argon flame, 0–60 ng of bromide is determined with a detection limit of 0.5 ng μl^?1. In a similar way, gallium (0–20 ng) can be determined with a detection limit of 0.15 ng μl^?1. Interferences are reported. Chloride (0–1200 ng) is determined by means of GaCl emission; the detection limit is 50 ng μl^?1.     

Determination of nanogram amounts of primary aromatic amines and nitro compounds in blood and plasma.

A rapid and highly sensitive method, based on the direct fluorimetric scanning of thin-layer chromatograms, is described for the quantitative determination of flunitrazepam and its main metabolites in human blood or plasma. This method is generally applicable to aromatic nitro compounds that are reducible with tin(II) chloride. In particular, it is possible to determine primary amines in nanogram amounts. Fluorescamine is used as a regent to produce fluorescent derivatives. The method is suitable for pharmacokinetic studies of flunitrazepam and its main metabolites in human blood and plasma.     

Coulometric argentometry of microgram amounts of sulphide

Summary A coulometric argentometric method has been developed for determining microgram and submicrogram amounts of sulphide, based on the formation of silver sulphide at a silver electrode by constant applied voltage electrolysis. 0.1 N sodium hydroxide has been used as a supporting electrolyte. The electrolytic system consisted of a special cell and of a pair of electrodes (large area saturated calomel electrode and the silver working electrode). The optimum working potential of the silver electrode was found to be –360 mV vs. S.C.E. This method permits determinations of 0.01–20 g of sulphide in sample volumes up to 10 ml, the total volume in the electrolytic cell being 40 ml. In the range of 0.05–20 g of sulphide the accuracy was better than – 5% and the reproducibility was better than 1%; in case of 0.01 g of sulphide the accuracy was found to be about – 10% and the repoducibility amounted to 2.5%.

---

Zusammenfassung Eine coulometrisch-argentometrische Methode zur Bestimmung von Mikro- und Submikromengen Sulfid auf Grund der Bildung von Silbersulfid an einer Silberelektrode bei konstanter angelegter Spannung wurde ausgearbeitet. Als Grundelektrolyt wird 0,1 N Natronlauge benutzt. Die Bestimmung wird in einem speziellen Elektrolysiergefäß mit einer groß-flächigen Kalomel- und einer Silberelektrode ausgeführt. Das optimale Potential der Silberelektrode beträgt –360 mV gegen ges. Kalomelelektrode. Die Methode ermöglicht die Bestimmung von 0,01–20 g Sulfid in einer Probe von maximal 10 ml. Zwischen 0,05 und 20 g Sulfid ist der Fehler stets kleiner als – 5%; die Reproduzierbarkeit ist besser als 1%. Bei 0,01 g Sulfid wurde ein Fehler von – 10% und eine Reproduzierbarkeit von 2,5% gefunden.

---

---

Parts I and II: this journal 217, 252, 259 (1966).     

Coulometric argentometry of microgram amounts of sulphide

Summary The voltammetric behaviour of the silver sulphide-silver electrode in pure ammoniacal-alkaline electrolytes as well as in the presence of sulphide and the complex cation [Ag(NH₃)₂]⁺ have been investigated. It has been found that the silver sulphide-silver electrode behaves slightly irreversibly in ammoniacal-alkaline solutions of sulphide. On the basis of the results obtained the use of the silver sulphide-silver electrode for constant-current bipotentiometric and biamperometric end-point detection techniques appears to be convenient in the argentometric determination of sulphide.

---

Zusammenfassung Das voltammetrische Verhalten der Silbersulfid-Silber-Elektrode wurde in Ammoniak und Natronlauge enthaltenden Lösungen, auch in Anwesenheit von Sulfid und von komplexem Kation [Ag(NH_{3 2}]⁺, untersucht. Es wurde festgestellt, da\ sich die Silbersulfid-Silber-Elektrode in Sulfid enthaltenden Lösungen schwach irreversibel verhÄlt. Die gewonnenen Resultate zeigen die Möglichkeit, die genannte Elektrode zur bipotentiometrischen oder biamperometrischen Endpunktbestimmung bei der argentometrischen Sulfidbestimmung anzuwenden.

     

Coulometric argentometry of microgram amounts of sulphide

Summary A method has been developed for the direct determination of microgram amounts of sulphide by constant current coulometric argentometry in the supporting electrolyte 10^–3 M NaCN+0.1 M NaOH. Zero-current potentiometric, biamperometric, and constant current bipotentiometric end-point detection techniques with one or two silver sulphide-silver microelectrodes have been used. The influence of the composition of the supporting electrolyte on the net titration efficiency and the portion of primary electrode reaction at the generator anode in the presence of sulphide have also been investigated. This method permits the determination of 4–85 g of sulphide in a sample volume of 5 ml with an average error of ±1%, also in the presence of about 100 fold weight excess of chloride, bromide, iodide, thiocyanate, and thiosulphate.

---

Zusammenfassung Eine Methode zur direkten Bestimmung von Mikrogrammengen Sulfidschwefel wurde ausgearbeitet. Es handelt sich um eine coulometrische Argentometrie, die bei konstantem Strom im Grundelektrolyt 10^–3 M NaCN+0,1 M NaOH verläuft. Zur Indikation werden ein oder zwei Silbersulfid-Silber-Elektroden angewendet. Der Endpunkt wird biamperometrisch (angelegte Spannung 100 mV), bipotentiometrisch (erzwungener Strom 0,5 A) oder potentiometrisch ermittelt. Der Einfluß der Elektrolytenzusammensetzung auf die Titrationsausbeute wurde verfolgt und der Anteil der primären Elektrodenreaktion, die an der Generatorelektrode bei Anwesenheit von Sulfid verläuft, festgestellt und gemessen. In einem Probevolumen von 5 ml können 4–85 g Sulfid mit einem Fehler von ± 1% titriert werden, auch bei einem hundertfachen Überschuß von Chlorid, Bromid, Jodid, Thiosulfat und Thiocyanat.

---

---

Part III: 232, 103 (1967).