The influence of surfactants on the behaviour of heavy metals in the system n-octanol-water

The partition of heavy metals between octanol and water in the presence of surfactants has been investigated. It is shown that metal ions can be extracted from water into the organic phase, n-octanol, as a model for biological materials in the presence of various anionic surfactants. Anions such as chromate can be extracted with the help of certain cationic surfactants. It was found that the extent of extraction depends on various parameters, such as the concentration of the surfactant, ionic strength and pH. With some anionic surfactants, the K_(ow) of lead or cadmium can reach values of 200 from waters of low ionic strength, decreasing as the ionic strength increases.     

Chemistry as a branch of analytical chemistry

Summary An approach to the teaching of chemistry and of analytical chemistry is presented, suitable for use at the 2nd or 3rd year level. The present tendency to subdivide chemistry into many small units is countered by this suggestion to use a comprehensive course on analytical chemistry as a means of reuniting the subdivisions of modern chemistry.

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Chemie als Zweig der analytischen Chemie

Zusammenfassung Der Unterricht in Chemie und analytischer Chemie des 2. oder 3. Studienjahres wird von einem neuen Gesichtspunkt aus gesehen: der heutigen Tendenz, Chemie in diverse Teilgebiete zu zergliedern, wird der Vorschlag eines allgemeinen Lehrganges in analytischer Chemie entgegengestellt, mit dessen Hilfe eine Wiedervereinigung der Teilgebiete der modernen Chemie erzielt werden kann.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

A coherent mechanical submillimeter frequency shifter

Highly correlated transmit and local oscillator signals for use in a narrowband heterodyne system are derived from a single submillimeter source. One component is Doppler shifted in frequency by a mechanically rotating device before transmission. The frequency translation does not lead to significant spectral deterioration. Under the condition of only a small differential delay between transmit and local oscillator paths, most phase and frequency instabilities of the submillimeter source are eliminated at the intermediate frequency. The paper describes the frequency shifter's mode of operation and a practical 637GHz design. Based on this design we simulate the effect of various imperfections in the frequency translation process on the output spectrum. Preliminary measurements at 140GHz are included.     

Systems theory in analysis-I: definitions and interpretations in the basic terms of systems theory

The twelve basic terms of systems theory-system, element, relation, function, structure, organization, feedback, Black Box, model, input-output analysis, trial-and-error method, simulation-are given general definitions and are also interpreted in terms of chemical analysis. The distinction between a generally acceptable brief and precise definition and an interpretation peculiar to one particular specialized field avoids, in the case of universally used terms, a biased view and conception. Simple systems are deliberately chosen and the terms used are clarified by means of diagrams. A system-oriented approach is outlined, with feedback-coupled stages (defining the problems, setting the limits, designing the model, simulation) which has proved useful in practical systems analysis and in systems design. The working group will report, in subsequent publications, on specific analytical systems which are of considerable importance in automation. Those with special interests in these fields are warmly invited to communicate their critical opinions, suggestions, and examples of interpretations based on these definitions.     

The determination of the COOH substiuent effect for branched carboxylic acids from carbon-13 chemical shifts

The carboxyl substituent effects for branched carboxylic acids have been determined by carbon-13 Fourier ransform nuclear magnetic resonance of eighteen measured and reported branched acids. For α-branched systems the substituent effects are α = 15.3 ppm, β = 2.6 ppm, γ = ?1.9 ppm, δ = 0.9 ppm and ? = 0.5 ppm. For other branched acids, the determined carboxyl substituent effects are α = 19.2 ppm, β = 2.1 ppm, γ = ?1.4 ppm, δ = 0.6 ppm, and ? = 0.6 ppm.     

Studies in qualitative inorganic analysis. Part XLIII

Summary A sensitive and convenient test is proposed for benzoate, in which the anion gives a colour reaction with lanthanum nitrate in the presence of iodine and ammonia. Benzoate has been identified in the presence of salicylate by thin-layer chromatography.

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Zusammenfassung Ein empfindlicher und brauchbarer Nachweis von Benzoat wurde vorgeschlagen, dem eine Farbreaktion mit Lanthannitrat in Gegenwart von Jod und Ammoniak zugrundeliegt. In Gegenwart von Salicylat wird Benzoat dünnschichtchromatographisch identifiziert.

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Part XLII: Mikrochim. Acta [Wien]1972, 188.     

Three-dimensional chemical concentration maps in a microfluidic device using two-photon absorption fluorescence imaging

Two-photon absorption fluorescence is employed within a microfluidic device to create a three-dimensional chemical concentration map for mixing uniformity characterization. This multiphoton technique images fluorescence intensity directly and provides a simple, rapid, and readily employed route to composition characterization within microfluidic systems.     

The Role of Lateral Tension in Calcium-Induced DPPS Vesicle Rupture

We assess the role of lateral tension in rupturing anionic dipalmitoylphosphatidyserine (DPPS), neutral dipalmitoylphosphatidylcholine (DPPC), and mixed DPPS-DPPC vesicles. Binding of Ca(2+) is known to have a significant impact on the effective size of DPPS lipids and little effect on the size of DPPC lipids in bilayer structures. In the present work we utilized laser transmission spectroscopy (LTS) to assess the effect of Ca(2+)-induced stress on the stability of the DPPS and DPPC vesicles. The high sensitivity and resolution of LTS has permitted the determination of the size and shape of liposomes in solution. The results indicate a critical size after which DPPS single shell vesicles are no longer stable. Our measurements indicate Ca(2+) promotes bilayer fusion up to a maximum diameter of ca. 320 nm. These observations are consistent with a straightforward free-energy-based model of vesicle rupture involving lateral tension between lipids regulated by the binding of Ca(2+). Our results support a critical role of lateral interactions within lipid bilayers for controlling such processes as the formation of supported bilayer membranes and pore formation in vesicle fusion. Using this free energy model we are able to infer a lower bound for the area dilation modulus for DPPS (252 pN/nm) and demonstrate a substantial free energy increase associated with vesicle rupture.     

Narrowband heterodyne reception using unstabilized sources

Source power for laboratory-type experiments is often limited at millimeter and submillimeter wavelengths. This requires the use of sensitive receiving equipment. Cooled square-law detectors and narrowband heterodyne detectors are examples. We have developed a coherent mechanical frequency shifter, which makes possible narrowband heterodyne detection without the need for highly frequency stable sources. Identical frequency and phase fluctuations of the transmit and local oscillator signals derived from one source are eliminated at the intermediate frequency. The widely tunable frequency shifter, designed for a 637GHz scale-model radar, was tested in a 140GHz non-radar configuration. We investigated the receiver's minimum coherently resolvable bandwidth and its sensitivity. Several types of sources were compared for the effect of local oscillator amplitude noise on receiver sensitivity at low intermediate frequency.     

Thermal analysis of tetracycline hydrates: I. Preparation and identification

The known hydrates of tetracycline base have been studied, and their intermediates true hydrates themselves, have been identified. Differences in physical and chemical properties of these hydrates have been studied and will be reported in a later paper.