Tomoo Miwa

Anodic stripping voltammetry of lead with microliter volumes of electrolytes and silver-plated glassy carbon electrodes

Abstract Nanogram quantities of lead are determined by anodic stripping voltammetry with sufficient precision and rapidity, by using a 100-μl electrolyte and a silver-plated glassy carbon microelectrode. This method is applied to the determination of lead at the low ppm level in 0.5—1 mg of high-purity zinc.

Speciation of copper in fresh waters

Abstract The cations and readily dissociable complexes of copper are separated from copper adsorbed on inorganic and organic particulate species in river and pond waters by selective sorption on a strong-acid cation-exchange resin, AG 50W-X12, and a chelating resin, Chelex-100, for atomic absorption spectrometry. The sorption behaviour after the pH change and removal of carbon dioxide suggests that the dominant low-molecular-weight copper species in river waters are neutral CuCO03 and Cu2+ ions.

Differential-pulse anodic stripping voltammetry of copper with a chemically-modified glassy carbon electrode

Abstract Copper at the low or fractional ng g−1 level in 0.1 M oxalic acid solutions at pH 1.6 is electrodeposited on a chemically-modified glassy carbon electrode with surface-bound groups at −0.6 V vs. Ag/AgCl (3.3 M KCl). The deposit is then anodically stripped in the same solution, a current-potential curve being recorded by the differential-pulse technique. The advantages of this electrode over an unmodified glassy carbon electrode include higher sensitivity, precision and selectivity; the modified electrode can be used 50–100 times without further treatment.

Speciation of silica in high-purity water

Abstract A 1-l water sample was concentrated to 20ml by freezing and analyzed for soluble, colloidal and insoluble silica by the spectrophotometric heteropoly blue method and by inductively coupled plasma/atomic emission spectrometry. High-purity water obtained from a vitreous-silica sub-boiling distillation still contained a few micrograms of insoluble silica per liter.

Determination of traces of heavy metals in positively charged inorganic colloids in fresh waters

SummaryDetermination of Traces of Heavy Metals in Positively Charged Inorganic Colloids in Fresh Waters After removal of suspended particulate matter by centrifugation followed by filtration through 0.4-μm membrane filters, humic substances and other negatively charged species are sorbed on a small column of macroreticular weak-base anion exchanger DEAE-Sephadex A-25 at fast flow rates. Positively charged inorganic colloids pass through the column and are collected on a 0.015-μm membrane filter, which is then ultrasonically treated with 1M nitric acid for the determination of copper, lead and cadmium by differential pulse anodic stripping voltammetry with a static mercury drop electrode. Up to O.2μg 1−1 of the heavy metals are found in positively charged inorganic colloids in river, pond and tap waters.

Determination of traces of chlorine in tantalum metal by cathodic stripping voltammetry

SummaryFractional to a fewμg of chloride ion is electrodeposited on a silver microanode from a hydrofluoric-nitric acid solution containing 0.1 g of tantalum. The deposit is then cathodically removed in a potassium nitrate solution, a current-voltage curve being recorded. The advantages of this method are high sensitivity, excellent precision, and simplicity.ZusammenfassungBruchteile weniger Mikrogramm Chloridionen werden aus einer Flußsäure-Salpetersäurelösung, die 0,1 g Tantal enthält, elektrolytisch an einer Silbermikroanode abgeschieden. Die abgeschiedene Menge wird dann kathodisch in eine Kaliumnitratlösung übergeführt, wobei eine Stromspannungskurve aufgezeichnet wird. Der Vorteil dieser Vorgangsweise ist ihre hohe Empfindlichkeit, ihre hervorragende Genauigkeit und Einfachheit.

Anodic stripping square-wave voltammetric determination of lead in high-purity bismuth

Abstract Anodic stripping voltammetry of lead with a mercury-plated platinum electrode and the square-wave technique is described. In combination with anionexchange separation in nitric and hydrochloric acid media, this method is applicable to the determination of down to 0.01 p.p.m. of lead in high-purity bismuth. The error is about ±5% at the 0.6 p.p.m. level

Determination of trace heavy metals associated with suspended particulate matter in pond water by microscale anodic stripping voltammetry

SummaryLess than 1 milligram of suspended particulate matter in a 50-ml water sample was separated by centrifugation, decomposed with 22μl of 2∶10∶10 perchloric-nitric-hydrofluoric acid mixture, and analyzed for copper, lead, cadmium and zinc by microscale differential pulse anodic stripping voltammetry with a hanging mercury drop electrode in 300μl of 0.06M perchloric acid. The procedure was simple and rapid, because a single Teflon microvessel was used throughout the whole procedure.ZusammenfassungWeniger als 1 mg suspendierter Teilchenmaterie wurde durch Zentrifugieren abgetrennt, mit 22μl eines Gemisches HClO4∶HNO3∶HF (2∶10∶10) zersetzt und darin Cu, Pb, Cd und Zn durch„Differential-Pulse-Anodic-Stripping-Voltammetry“mit hängender Hg-Tropfelektrode in 300μ l 0.06M Perchlorsäure bestimmt. Das Verfahren ist einfach und schnell, es bedarf dazu nur eines Mikrokölbchens aus Teflon.

Anodic stripping voltammetry of copper and bismuth

SummaryMicrogram and nanogram quantities of copper and bismuth are electrodeposited on a glassy carbon electrode from 10M hydro-fluoric-1M nitric acid solutions. The deposit is then anodically removed in 0.1M perchloric acid or 0.1–12M hydrochloric acid, a current-voltage curve being recorded. Copper and bismuth at p. p. b. levels in sponge zirconium are determined by this technique with 5 M hydrochloric acid as stripping electrolyte within 3 hours.ZusammenfassungMikrogramm- und Nanogrammengen Kupfer und Wismut wurden aus 10-m flußsauren, 1-m salpetersauren Lösungen elektrolytisch an einer Glas- kohleelektrode abgeschieden und nachher in 0,1-m Perchlorsäure oder 0,1-bis 12-m Salzsäure anodisch gelöst, wobei eine Stromspannungskurve aufgezeichnet wurde. Auf diese Art wurden ppb-Mengen Kupfer und Wismut innerhalb 3 Stunden in Zirkoniumschwamm unter Verwendung von 5-m Salzsäure als Elektrolyt bei der anodischen Auflösung bestimmt.

Determination of traces of lead in titanium dioxide powder by microscale anodic stripping voltammetry

SummaryA 1- to 10-mg sample of titanium dioxide powder is decomposed with 35μl of 28M hydrofluoric acid in a closed Teflon microvessel. In the same vessel, more than 95% of lead is electrodeposited on a glassy carbon microelectrode from 250μl of electrolyte at pH 4.3 for differential pulse anodic stripping voltammetry. Low ppm of lead is determined by the proposed method with an error of less than 5% within 1 h.ZusammenfassungEine Einwaage von 1–10 mg Titandioxid wird mit 35μl 28M Flußsäure in einem geschlossenen Teflongefäß aufgeschlossen. Im selben Gefäß werden mehr als 95% der anwesenden Bleimenge aus 250μl Elektrolyt bei pH 4,3 an einer glasförmigen Kohle-Mikroelektrode abgeschieden und der Differential-Puls-Anodic-Stripping-Voltammetrie zugeführt. Geringe Bleimengen lassen sich mit Hilfe dieses Verfahrens mit einem Fehler von weniger als 5% innerhalb einer Stunde bestimmen.