Deactivation,coating and performance of nickel capillary columns for GLC

Electroformed nickel tubing was deactivated by chemical vapor deposition of silicon from silane gas and subsequent treatment with cyclooctamethyltetrasiloxane (D4). Standard activity tests performed on the uncoated tube and also on columns coated with crosslinked and uncrosslinked, nonpolar stationary phase, show that good quality flexible columns can be prepared from nickel tubing. The inner surface of the silicon coated tube was characterized by Auger depth profile analysis.     

A rapid enrichment method for the analysis of traces of metals in aqueous solutions

Summary For the determination of traces of heavy metals e. g. from distilled water, drinking water or waste water generally a suitable pretreatment of the samples is necessary. For this reason an enrichment method was developed which makes it possible to precipitate several metals together with carrier elements from aqueous solutions. To carry out the method, 10 to 500 ml of the sample are mixed with 1 ml of a diluted nitric acid to produce a weak acid starting state for the diverse samples. After addition of a reduction solution and the collector solution the metals are precipitated at a constant pH between 5.0 to 5.5 with diethylammonium-N,N-diethyldithio-carbamate. The precipitate can be collected by filtration on a membrane filter. It forms a thin layer on the membrane filter and adheres without any auxiliary products for a long time. The time required for the complete process is less than 15 minutes if the starting volume was about 100 ml. A special equipment is not necessary. In the determination of traces of metals from organic substances a special rapid decomposition method with the decomposition device BIOKLAV^® was developed. By this method it is possible to convert the organic matter into an aqueous solution without addition of any chemicals. The BIOKLAV is a cylindrical pressure vessel with a safety rapid lock. A 20 g sample of organic material, e. g. meat or similar foodstuff, with a water content of 70–80% is pre-dried in the closed vessel and thereafter burnt in oxygen with elevated pressure. After this procedure all traces of metals present in the starting sample are contained in an aqueous solution consisting on the condensed water from drying and the burning products of the organic matter. The time required for the complete process is less than 30 min. From the obtained solution traces of metals are to enrich by precipitation with carbamate. The determination of the traces of metals is possible by a suitable method of analysis like atomic absorption, ICP or X-ray fluorescence. In various water samples, like drinking water and waste water, traces of Cr, Ni, Fe, Cu, Zn, Cd, Pb, As, Hg and Se in amounts of 5–100g were determined. The recovery rate was 80–90%. In organic substances Hg, Cd, Pb and As in amounts ranging from 50–250 ng/g resp. in amounts of 1–5g were detected with recoveries of more than 80%.

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Ein schnelles Anreicherungsverfahren zur Bestimmung von Schwermetallspuren in wärigen Lösungen

Zusammenfassung Zur Bestimmung von Schwermetallspuren z. B. in destilliertem Wasser, Trinkwasser oder Abwasser ist im allgemeinen eine geeignete Probenvorbereitung erforderlich. Für diesen Zweck wurde ein Anreicherungsverfahren ausgearbeitet, um gleichzeitig mehrere Metalle zusammen mit Spurenfänger-elementen aus wäßrigen Lösungen ausfällen zu können. Danach werden 10–500 ml Probenlösung mit 1 ml verd. Salpetersäure versetzt, um bei den verschiedenen Proben jeweils einen schwach sauren pH-Wert einzustellen. Anschließend werden eine Reduktionslösung sowie die Spurenfängerlösung zugegeben und mit einer Pufferlösung ein pH von 5,0–5,5 eingestellt. Die gelösten Metallspuren werden mit Diäthylammonium-N,N-diäthyldithio-carbamat ausgefällt. Der Niedersclhlag wird auf einem Membranfilter gesammelt. Man erhält ohne Hilfsmittel einen dünnen elastischen Film, der lange Zeit auf dem Filter haftet. Bei einem Ausgangsvolumen von 100 ml dauert der gesamte Vorgang weniger als 15 min. Für die Bestimmung von Metallspuren in organischen Substanzen wurde ein Schnellaufschlußverfahren mit dem Aufschlußgerät BIOKLAV^® entwickelt. Damit ist es möglich, die organische Matrix ohne Zusatz von Chemikalien in eine wäßrige Lösung zu überführen. Der BIOKLAV ist ein zylindrisches Druckgefäß mit einem Sicherheitsschnellverschluß. 20 g Probenmaterial mit einem Wassergehalt von 70–80%, z. B. Fleisch oder ähnliche Lebensmittel, werden im geschlossenen Gefäß zuerst vorgetrocknet und anschließend in Sauerstoff bei erhöhtem Druck verbrannt. Nach dem Aufschluß befinden sich die zu erfassenden Metallspuren in einer wäßrigen Lösung, die aus dem kondensierten Wasser des Probenmaterials und den Verbrennungsprodukten der organischen Matrix herrührt. Der gesamte Aufschluß dauert weniger als 30 min. Aus der Lösung können die Metallspuren durch Fällung mit Carbamat angereichert werden. Die Bestimmung der Elementspuren erfolgt z. B. mit Atom-Absorptions-Spektrometrie (AAS), Optischer Emissions-spektrometrie mit Plasma-Anregung (ICP) oder Röntgen-Fluoreszenz-Analyse(RFA). In verschiedenen Wasserproben, wie z. B. Trinkwasser und Abwasser wurden Spuren von Cr, Ni, Fe, Cu, Zn, Cd, Pb, Hg und Se in Mengen von 5–100g bestimmt. Die Wiederfindungsrate war 80–90%. In organischen Substanzen wurden Hg, Cd, Pb und As in Massenanteilen von 50–250 ng/g bzw. in Mengen von 1–5g mit einer Wiederfindungsrate von mehr als 80% bestimmt.

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

Carbon Monoxide Triplet Rydberg Series in the f Complex Region

Using a multistep state-selective excitation scheme, fluorescence-dip spectra of carbon monoxide have been recorded in the energy region between 106 100 and 112 200 cm(-1). Prominent groups of bands were tentatively identified as transitions into the 6f em leader10f (v=0) and 9psigma em leader11psigma (v=0) triplet Rydberg series. For the f complex states, molecular constants have been calculated. The triplet f levels show an unusually large rotational constant and are located at higher energies than their singlet counterparts. Copyright 2001 Academic Press.     

First comparison of electric field induced second harmonic of near-infrared femtosecond laser pulses in reflection and transmission generated from Si/SiO<Subscript>2</Subscript> interfaces of a silicon membrane

For the first time electric field induced second harmonic (EFISH) generation of femtosecond (fs) laser pulses (λ=800 nm, τ=75±5 fs, rep. rate=80 MHz, E _pulse≤10 nJ) is observed in transmission through a thin free-standing silicon (Si) membrane of 10-μm thickness and compared to the well-known EFISH results in reflection by use of the z-scan technique. EFISH in reflection and transmission unequivocally originate from the front and rear Si/SiO₂ interfaces, respectively, with SiO₂ being the natural oxide on the Si surfaces. Frequency conversion is enhanced by photoinduced electric fields across the Si/SiO₂ interfaces caused by charge-carrier injection from Si into the oxide. The z-scan results and time-dependent measurements allow comparison of the EFISH signal amplitudes and time constants detected in transmission and reflection, demonstrating the need for further investigation.     

Two-dimensional slices of nonpseudoconvex domains with rough boundary

For a domain \(D\subset {\mathbb C}^n,\; n\ge 3\) , the set \(E\) is defined as the set of all points \(z\in {\mathbb C}^n\) for which the intersection of \(D\) with every complex \(2\) -plane through \(z\) is pseudoconvex. For \(D\) nonpseudoconvex, it is shown that \(E\) is contained in an affine subspace of codimension \(2\) . This results solves a problem raised by Nikolov and Pflug.     

Chemical characterization and screening of hydrocarbon pollution in industrial soils by headspace solid-phase microextraction.

A headspace solid-phase microextraction method, followed by a gas chromatographic-mass spectrometric analysis, has been developed for the screening of soil samples polluted by coal tar or refined petroleum products. Vapor pressures of target analytes were determined using a capillary GC method to identify environmentally important components with a sufficiently high vapor pressure to be analyzed in the headspace mode. The method was optimized under non-equilibrium conditions with simplicity and automation in mind and does not require any extraction procedure or sample preparation, other than grinding, drying and homogenizing. The analytical performance and the significance of the results for the purpose of chemical characterization, source discrimination, determination of individual isomer distributions and to calculate source or weathering ratios, is discussed.     

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