I. Havezov

Arsenic speciation in waste waters by extraction chromatography followed by atomic absorption spectrometry

SummaryA method is described for the determination of arsenic(III) and arsenic(V) in water samples. The sample (adjusted to pH 2.5 to 3.5 with HCl or NaOH) is passed through a chromatographic column filled with inert support modified with the organotin reagent (C8H17)2SnCl2. Under these conditions arsenate is quantitatively retained, while arsenite is not. Arsenate is eluted from the column with 2 mol/l HCl (1–2 ml). Both effluate [As(III)] and eluate [As(V)] are analyzed by flame or graphite furnace AAS. The method was applied to the analysis of waste waters from a metallurgical plant and potable water from the same region. Recoveries are in the range of 85–115%.

Graphite-furnace atomization of phosphorus

Abstract The slopes of the ln (absorbance) vs. T −1 dependences for platform/graphite furnace atomization of phosphorus in the presence of Ni 2+ or La 3+ modifiers are measured, and found to be similar to the theoretical slope calculated for isothermal atomization. It is concluded that in both cases the atomization mechanism is the same and is expressed by P 2(gas) ⇄ 2P (gas) ; P (gas) ⇄ P * (gas) . The atomic absorption signal for phosphorus appears and reaches its maximum later when the atomization is carried out from the platform in the presence of modifiers. Hence atomization takes place under nearly isothermal conditions and is much more efficient, thus providing the best conditions for the determination of phosphorus. Treatment of a deteriorated graphite surface with ZrOCl 2 solution repairs any defects and improves the sensitivity of phosphorus determination.

Determination of ortho- and pyrophosphates in waters by extraction chromatography and flow-injection analysis

Extraction-chromatographic separation of ortho- and pyrophosphate anions on an inert support modified with an organotin extractant was studied and used for their subsequent determination in a flow-injection system. The proposed FIA manifold includes an extraction-chromatographic mini-column, on which the phosphate anions are separated and preconcentrated, and a post-column spectrophotometric detector. For the determination of orthophosphate, the absorbance of the reduced 12-molybdophosphoric acid is monitored at 660 nm. The sum of ortho- and pyrophosphate can be determined after preliminary hydrolysis of pyrophosphate to orthophosphate in neutral solution at 50 degrees by use of inorganic pyrophosphatase. For a sample volume of 6 ml, the calibration graph is linear within a range of 5.0-100.0 ng/ml P. The limit of detection is 0.3 ng/ml P. The recovery of the ions to be determined is not less than 96%, the relative error is not worse than 4%. The proposed method was used for the analysis of river water samples.

Flameless atomic-absorption determination of phosphorus using ZrC coated graphite atomizer tubes

ZusammenfassungDurch Verwendung einer ZrC-beschichteten Graphitrohrküvette wurde eine wesentliche Erhöhung der Empfindlichkeit erzielt, ohne daß eine Zugabe von La(NO3)3 nötig wäre. Bei Küvettenwechsel ändert sich die Empfindlichkeit nicht. Das maximale Signal wird während der ersten 2–3 Bestimmungen erreicht. Das Atomisierungssignal bleibt im Bereich zwischen 2600 und 2800 °C praktisch unverändert. Das Signal/Rausch-Verhältnis ist bei 2600 °C am größten. Die Nachweisgrenze beträgt 0,05 ppm bei 50 μl. Die Methode wurde zur Analyse von Stahlstandardproben angewendet.SummaryA flameless atomic-absorption method for determination of phosphorus is developed, employing zirconium treated graphite tubes. The great improvement of the sensitivity with these tubes eliminates the necessity of adding La(NO3)3. The sensitivity does not vary from tube to tube and its maximal value is attained within the first 2–3 firings. The atomization signal is practically the same within the range of 2,600–2,800° C when the rise of the temperature is high (> 1,500° C/s). The best signal to noise ratio is obtained at 2,600° C. The detection limit is 0.05 ppm with injection of 50 μl. The method is applied to the analysis of a standard steel sample.

Atomic-absorption spectrophotometric determination of beryllium in β-Al2O3 ceramics

ZusammenfassungDie Probe wird schnell bei 300 ± 50° C in „starker Phosphorsäure“ aufgeschlossen. Nach entsprechendem Verdünnen wird Beryllium mittels AAS unter Verwendung einer N2O/C2H2-Flamme bestimmt. Die Methode ist für die Bestimmung von 0,01–20% Be im β-Al2O3 geeignet. Der Variationskoeffizient beträgt 0,6% (bei 0,7% Be in der Probe). Bei verschiedenen Brennerhöhen wurde die Wirkung von Al(III) und von Phosphorsäure auf die Atomisation von Beryllium untersucht. Phosphorsäure verringert die chemischen Störungen (Aluminat- und Carbidbildung) und begünstigt die Atomisierung.SummaryAn atomic-absorption determination of beryllium inβ-Al2O3 ceramics is described. The sample is dissolved rapidly and completely at 300 ± 50°C in “strong phosphoric acid”. The determination is carried out by means of a N2O/C2H2 flame after dilution. The effects of phosphoric acid and aluminium(III) on the signal for beryllium at optimal flame stoichiometry and various burner heights are investigated. Phosphoric acid enhances the atomization and minimizes the interference effects. The proposed method allows the determination of beryllium in the range of 0.01–20% with a variation coefficient of 0.6% (at 0.7% Be in β-Al2O3 ceramics).