L. Sommer

Interaction of iron(II) and the simultaneous spectrophotometric determination of Fe, Cu, Zn, Co and Ni with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

SummaryThe reaction of Fe(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) is studied in detail and procedures for the sensitive determination of Fe(II) at pH 4.7 (acetate buffer), pH 9.0 (borate buffer) and in the presence of EDTA are optimized. A simultaneous determination of Fe, Cu, Zn, Co and Ni in aqueous medium and of Fe, Cu and Zn in blood serum with Br-PADAP at pH 9.0 using multivariate calibration with PLS evaluation of absorbance data also give satisfactory results.

Selective preconcentration of thallium on modified silica gel for its determination by flame emission and absorption spectrometry.

Thallium (0.02-20 mug) was successfully preconcentrated on silica gel C18 from 0.1M hydrochloric acid in the presence of various cationic surfactants as ion pairs with tetrachlorothallate(III), and subsequently eluted with 96% ethanol. Of various atomic spectrometric procedures considered, emission spectrometry in a nitrous oxide-acetylene flame is suitable for the final determination of thallium in plants, this is more sensitive for thallium than flame atomic absorption spectrometry.

Simultaneous determination of inorganic arsenic, antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of 75As, 82Se, 121Sb and 125Te by ICP-MS for amounts less than 10 µg L−1. Internal standards such as 72Ge and 209Bi were successfully used for the suppression of both influence of macro elements Na+, K+, Ca2+, Mg2+ or Al3+, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon™ SGX C18, C8, CN, NH2, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25–5 µg L−1) in the form of ion associates with cationic surfactants from 50–250 mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex®, 0.005 mol L−1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7 ± 0.2 and the mixture of acetone with ethanol in ratio 1 : 1 in the presence of 0.1 mol L−1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon™ SGX C18 and the above reagents were compared with the standard addition method.

Determination of copper by electrothermal AAS after electrodeposition on a graphite disk electrode

The electrodeposition of copper on a graphite electrode at a constant potential with subsequent atomization in the graphite atomizer HGA-400 has been studied. A special graphite disk electrode is suitable for electrochemical enrichment at E = -0.7 V vs. SCE and the determination of copper by electrothermal-atomic absorption spectrometry (ET-AAS) if atomized at 2300 degrees C. In this way copper was determined in potable water and free Cu(2+) could be distinguished from that bound in chelate speciations after using a suitable deposition potential of the working electrode. This approach seems to be an alternative to the commonly used anodic stripping voltammetry (ASV) for the preconcentration and determination of free metal ions.

Spektrophotometrische Titanbestimmung mit Chromotropsäure

ZusammenfassungDie Chromotropsäure ist ein analytisch wertvolles Reagens auf Eisen (III)23, Chrom (VI)9, Kupfer, Niob24 und besonders auf Titan (IV). Die Reaktion mit Chromotropsäure ist die empfindlichste (pD 5,9) und in Gegenwart von Ascorbinsäure weitgehend selektive Titanreaktion.In den Titan(IV)-lösungen bilden sich mit Chromotropsäure abhängig von der Zusammensetzung und dem pH-Wert der Lösung sowie von der Konzentration der Reaktionspartner stufenweise mehrere Chelate. In den Lösungen mit Reagensüberschuß liegen folgende Chelatgleichgewichte vor: TiO2+ + 2 H2R2 ⇄ TiO(RH)24− + 2 H+ (Absorptionsmaximum470 mμ), PH 0–2; TiO2+ + 2 H2R2− ⇄ TiOR26− + 4 H+ (470 mμ), pH1–3,5; TiOR26− + H2R2 ⇄ TiOR310− + 2 H+ (420 mμ), pH 3,2–7,0; TiOR26 + 2H2R2− ⇄ TiR412− + 2 H + H2O (470 mμ), pH 1,7–2,4.Die beiden stabilen Chelate TiOR26− und TiOR310− können bei begrenzten Reaktionsbedingungen zur spektrophotoinetrischen Titanbestimmung ausgenutzt werden. Die Bestimmung bei pH 2,9–3,2 und 467mμ in Gegenwart von Ascorbinsäure ermöglicht die Titanbestimmung neben einer Zahl von fremden Ionen. Sie ist die für die Praxis geeignetste Methode.

Spectrophotometric investigation of complexes with organic reagents for the optimization of spectrophotometric determinations (uv + vis) of inorganic analytes

ZusammenfassungDie Kenntnis von Komplexbildungsgleichgewichten der Elemente mit organischen Reagentien in Lösung, der thermodynamischen und optischen Parameter der Komplexe und deren Verteilung im System ist für die Auswahl optimaler Bedingungen für eine spektralphotometrische Elementbestimmung (uv + vis) wichtig. Alle notwendigen Parameter sind auf Grund einer eingehenden graphischen und mathematischen Interpretation spektralphotometrischer Daten zugänglich. Dieser Weg wird als Beispiel an drei ausgewählten spektralphotometrischen Reagentien, 4-(2-Pyridylazo)resorcin, 2-(2-Thiazolylazo)-4-methoxyphenol und 2-(2-Pyridylazo)-1-naphthol-4-sulfonsäure, gezeigt.SummaryThe knowledge of complex equilibria of elements with organic analytical reagents in solutions and that of thermodynamic and optical parameters of complexes and their distribution in the system is of considerable importance for the selection of optimal conditions for an exact spectrophotometric determination (uv + vis) of an element. All necessary parameters are available by means of a detailed graphical and numerical interpretation of spectrophotometric data. This approach is shown by example of some chromogenic reactions of 4-(2-pyridylazo)resorcin, 2-(2-thiazolylazo)-4-methoxyphenol and 2-(2-pyridylazo)-1-naphthol-4-sulphonic acid.

ber Reaktionen von Titan(IV) in wasserfreiem Medium

ZusammenfassungDie Reaktionen von TiIV mit einer Reihe organischer Reagentien in konz. Schwefelsäure, in Dimethylformamid und Methanol wurden analytisch bewertet. In wasserfreiem Medium kann das phenolische und enolische Hydroxyl, dessen Protonen bei der Reaktion abgespalten werden, als funktionsanalytische Gruppe für TiIV angesehen werden. Polyphenole mit o-Dihydroxylgruppierung gehören auch in wasserfreiem Medium zu den empfindlichsten Reagentien auf TiIV. Man kann die Titanreaktion in Dimethylformamid umgekehrt zum Nachweis des phenolischen und enolischen Hydroxyls benutzen. Die Reaktionen von NbV, TaV, MoVI, VV, SnIV und FeIII in konz. Schwefelsäure wurden mit denen von TiIV verglichen.

Der Nachweis des Titans mit Chromotropsure

ZusammenfassungUnter den Polyphenolen mit einer o- oder peri-Hydroxylgruppierung ist die Chromotropsäure das wertvollste Reagens auf TiIV. In schwach saurer Lösung ist die Empfindlichkeit groß (pD 5,9) und die Reaktion ist in Gegenwart von Ascorbinsäure weitgehend selektiv.

Simultaneous determination of metal traces by ICP-MS in environmental waters using SPE preconcentration on different polymeric sorbents

This paper deals with multielement profiling of microlements in the form of their isotopes 9Be, 51V, 59Co, 60Ni, 89Y, 111Cd, 208Pb, 232Th, and 238U. After their complexation by 4-(2-pyridylazo)resorcinol (PAR), 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt (ALS), 8-hydroxyquinoline-5-sulphonic acid (8-HQS), and ammonium pyrrolidinedithiocarbamate (APDC), the elements were preconcentrated and separated on Amberlite XAD-16 and Amberlite SDB-L prior to their analysis by inductively coupled plasma mass spectrometry. Various parameters such as pH, eluent type and volume, presence of surfactants and volume, and matrix effects on the retention of analytes were examined. Relative standard deviation and recovery values for four replicate determinations under optimal condition were in the range of 0.2–3.6 % and 59–98 %. The proposed method was applied to the determination of elements in lake water sample and industrial water. Recovery experiments with spiked water samples were performed.

Determination of aluminium, scandium and rare earth elements by emission flame spectrometry

SummaryEmission spectrometry in nitrous oxide-acetylene flames in combination with a highly resolving double monochromator and sensitive detecting system enables simple, sensitive and selective determinations of aluminium, scandium and all rare earth elements with exception of cerium in complicated matrices. Calibration plots are linear for a large concentration interval (≦ 100 μg·ml−1), detection limits are in ng · ml−1 level and RSD does not exceed 3% on the optimal concentration level of the particular element. The determination of Al, Sc, Eu and Yb showed particular advantages as to methods using ICP-spectrometry.