Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytical and Bioanalytical Chemistry (v.356, #2)
Supercritical fluid chromatography in drug analysis: a literature survey by Amparo Salvador; M. Angeles Jaime; Gladys Becerra; M. De La Guardia (pp. 109-122).
The applications of supercritical fluid chromatography to the analysis of drugs have been carefully revised from the literature compiled in the Analytical Abstracts until March 1994. Easy-to-read tables provide useful information about the state-of-the-art and possibilities offered by SFC in pharmaceutical analysis. The tables comprise extensive data about samples analyzed, pharmaceutical principles determined, solvents used and sample quantity injected, supercritical fluids and modifiers employed, injection system, instrumentation, experimental conditions for chromatographic separations (density, pressure, flow, temperature), characteristics of columns employed (type, support, length, diameter, particle film thickness, stationary phase), detectors, type of restrictors, and also some analytical features of the methods developed (such as retention time, resolution, sensitivity, limit of detection and relative standard deviation).
An alternating pulse current technique for potentiometric stripping analysis (APC-PSA) by H. P. Beck; T. Schiestel (pp. 123-126).
The response signal in PSA measurements – the transition time τ – can be considerably amplified by using a special pulse technique which we call “alternating pulse current (APC)”. The sensitivity of the method is thereby considerably increased. This is achieved by modulating the current with a high frequency in a square wave mode during the stripping phase in such a way, that cathodic and anodic pulses alternate, so that the species to be determined is stripped and – at least partially – redeposited during the procedure. The transition time τ is not affected by the absolute values of the currents and of the times they flow. The amplification is determined by their respective ratios only. The equations holding are derived and proven experimentally by measurements on very dilute Pb solutions. The APC-PSA technique has also been applied for systems termed ‘irreversible’ such as U and Tc, where also a considerable amplification could be achieved. The probable reasons are discussed and future developments and investigations are depicted.
Performance and application potential of ion-molecule reaction mass spectrometry (IMR-MS) in the analysis of complex gas mixtures by H. Schubert; U. Guntow; K. Hofmann; R. Schlögl (pp. 127-137).
The mild ionisation technique of IMR mass spectrometry in combination with a tuneable cell for the charge transfer reaction allows to study mixtures of small molecules with low fragmentation and chemical selectivity. Temporal resolution down to 100 ms and quasisimultaneous multicomponent trend analyses can be combined in a flexible way responding to changing analytical requirements. The research instrument of ATOMIKA provides digital control over a range of parameters and ionisation sources. Its performance is characterised in several applications ranging from purity tests over the detection of small oxygenate organic molecules to more complex reaction systems of heterogeneous catalytic performance testing.
Determination of antimony, arsenic, bismuth and copper by inductively coupled plasma atomic emission spectrometry in the electrorefining of copper by Tero Piippanen; Jouni Tummavuori (pp. 138-142).
Inductively coupled plasma atomic emissionspectrometry (ICP-AES) has been applied as a rapid and routine method for the analysis of process electrolytes in the electrorefining of copper. Antimony, arsenic, bismuth and copper have been selected as major electrolyte constituents. For these elements profound statistical studies of spectral and interelement effects have been carried out. For As, Bi and Sb two analyte wavelengths have been selected, and for Cu one relatively insensitive analyte line has been chosen due to the high Cu concentration in samples. Best analytical lines were: As at 193.759 nm, Bi at 306.772 nm, Sb at 206.833 nm and Cu at 216.953 nm. Multiple linear regression proved to be very capable in the search of the best analytical wavelength and identifying interfering elements. Using simple acid based standards all elements investigated can be determined separately in complicated matrices with satisfactory results. Differences between true values and measured values can be partly eliminated by appropriate calculational methods.
Use of cupferron as a precipitant for the determination of impurities in high-purity iron by ICP-AES by Yûetsu Danzaki (pp. 143-145).
Impurities in high-purity Fe were determined by ICP-AES using zinc as an internal standard after a precipitation-separation with cupferron. The detection limits (in μg/g) of the impurity elements were as follows: V 0.03, Hf 0.1, Mo 0.1, Nb 0.1, Ga 0.3, Zr 0.6 and Ti 0.9.
Study of the absorption spectra of the 4f electron transition of the Nd and Er complexes with 2-isobutylformyl-1,3-dione-indane in the presence of TX-100 and its analytical application by Qi Ping; Wang Naixing; Si Zhikun; Yang Jinghe; Li Zhendong (pp. 146-149).
The absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 2-isobutylformyl-1,3-dione-indane and TX-100 have been studied by normal and derivative spectrophotometry. Their molar absorptivities at the maximum absorption bands are about 7.2 (at 571 nm) times greater for neodymium and 13.1 (at 519 nm) times greater for erbium than those in the absence of the complexing agents. Use of second derivative spectra both eliminates the interference from other rare earths and increases the sensitivity from neodymium and erbium. Beer’s law is obeyed from 0∼20 μg/ml for neodymium and 0∼25 μg/ml for erbium. The relative standard deviations are 1.2% and 1.6% for 5.0 μg/ml of neodymium and 8.0 μg/ml of erbium, respectively. The detection limits (signal-to-noise ratio=2) are 0.14 μg/ml and 0.20 μg/ml. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.
Determination of magnesium and calcium ions in seawater by capillary zone electrophoresis by Keiichi Fukushi; Kazuo Hiiro (pp. 150-154).
Capillary zone electrophoresis is proposed for the determination of magnesium and calcium ions in seawater. A carrier solution containing EDTA was adopted for the complexation of these ions and the effect of sodium chloride concentration in the sample solutions on the results was examined. It was found that magnesium and calcium ions could be determined without any pretreatment by injecting 100-fold diluted seawater samples. Linear calibration graphs were obtained for standard solutions containing up to 10.0 mg/l of calcium ion when both peak area and peak height were used. On the other hand, a linear calibration graph was obtained for standard solutions containing up to 20.0 mg/l of magnesium ion when the peak area was used, while a curved one was obtained when the peak height was used. Relative standard deviations were 0.8 and 1.2% when a standard solution containing 5.0 mg/l of magnesium and 8.0 mg/l of calcium ions was analysed 8 times using the peak area. Limits of detection for magnesium and calcium ions were 0.13 and 0.26 mg/l, respectively. The proposed method was applied to the determination of magnesium and calcium ions in surface and bottom seawater samples.
Water-in-oil emulsion containing oxine for the collection of traces of copper(II) in water by Masataka Hiraide; Kennichi Ishikawa; Hiroshi Kawaguchi (pp. 155-158).
An oil type emulsion containing tiny encapsulated droplets of hydrochloric acid has been used for the concentration of traces of copper(II) ions in water. Milligram quantities of oxine and a non-ionic surfactant (Span-80) were dissolved in 5–10 ml of chloroform and mixed vigorously with 3 ml of 1 mol/l hydrochloric acid by ultrasonic irradiation. The resulting water-in-oil type emulsion was gradually added to 50–500 ml of water sample and dispersed by stirring as numerous small globules (0.1 to 0.5 mm in diameter). The copper diffused through the chloroform layer into the small droplets of hydrochloric acid, which occurred quantitatively in the sample of pH 3–10. After separating the emulsion by sedimentation, it was demulsified by heating to segregate the aqueous and organic phases. The copper in the aqueous phase was successfully determined by GFAAS. The emulsion method allows to perform both extraction and back-extraction more easily and rapidly than the conventional liquid-liquid extraction method.