Autocollimation spectroscopy for fast hydrogenic ions

We propose a new experimental method (Autocollimation Spectroscopy), which provides a strong suppression of systematic error contributions in the laser resonance spectroscopy of broad resonances. Using a bidirectional laser beam with a fixed wavelength in connection with high current pulsed ion beams an accuracy ofΔE _Exp/Γ≈5·10^?5 (Γ: resonance width) for the resonance energy seems to be achievable. Applying this technique to 2S-Lamb shift (LS) measurements on medium heavy ions would yield a precision ofΔE _Exp/E _LS≈1·10^?5, i.e. an improvement by a factor up to 100 as compared to present experiments.     

High speed determination of beta-receptor blocking agents in human urine by liquid chromatography/tandem mass spectrometry

Beta-receptor blocking agents are present on the international market in a huge variety. The International Olympic Committee prohibits the use of these drugs in several sport sections and doping control laboratories analyse urine samples of high-performance athletes with different techniques. Therefore, fast and reliable methods are required to enable a sensitive detection of many drugs and a high throughput of samples. In the present study a screening procedure is described using high speed liquid chromatography and multiple reaction monitoring to identify 32 beta-receptor blocking agents extracted from human urine. Urine specimens (blank urine samples, spiked urine samples and specimens of excretion studies) were hydrolysed, extracted and analysed within 7 min. Quasi-molecular ions (M(+) + H) of the beta-blockers are generated by means of an atmospheric pressure chemical ionization interface followed by collision-induced dissociation in a triple quadrupole mass spectrometer and subsequent detection of daughter ions. Proposals for the origin of common and individual secondary ions are presented.     

Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers

Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.     

Complexometric titration of Aluminium

A procedure is given for the complexometric titration of aluminium. A known volume of a standard solution of EDTA is added to the sample solution, and the excess is back-titrated with a zinc sulphate solution, dithizone being used as indicator. The titration is performed at pH = 4.0 — 4.5 and 40 — 50% alcohol is added as solvent for the indicator.The theoretical basis of the method is developed, and the theoretical titration error with various amounts of aluminium and zinc is calculated.The results of some titrations are given.     

First-principles calculations of K-edge X-ray absorption near edge spectra of some transition metal dimers

Theoretical X-ray absorption near-edge spectra have been evaluated for different bond lengths of Mn₂, Co₂ and Ni₂ using a modified Xα scattered-wave procedure.     

Direct high-performance liquid chromatographic method for enantioselective and diastereoselective determination of selected pyrethroic acids

This study reports on the direct HPLC stereoisomer separation of selected pyrethroic acids employing commercial cinchona alkaloid derived chiral stationary phases (CSPs). cis/trans-Chrysanthemic acid (cis/trans-CA), cis/trans-chrysanthemum dicarboxylic acid (cis/trans-CDCA), cis/trans-permethrinic acid (cis/trans-PA), and fenvaleric acid (FA) were resolved into the individual stereoisomers, i.e. enantiomers and diastereomers as well. To achieve satisfactory baseline separation an optimisation of the variables of the chromatographic method including chemical structure of the cinchona carbamate CSP, mobile phase composition, and flow rate was required. All four stereoisomers of PA were successfully separated in a single run (alphacis = 1.20, alphatrans = 1.26, critical Rs = 1.65) with an acetonitrile (ACN)-based polar-organic eluent. The complete baseline resolution of all CA stereoisomers succeeded in polar-organic (alphacis = 1.20, alphatrans = 1.35, critical Rs = 3.03) as well as in acetonitrile-based reversed-phase media (alphacis = 1.24, alphatrans = 1.22, critical Rs = 2.73). The latter elution mode was also found to be suitable for the enantio- as well as diastereoselective resolution of CDCA (alphacis = 1.09, alphatrans = 1.50, critical Rs = 1.43), which is to the best of our knowledge the first reported enantiomer separation of this analyte. The enantiomers of FA could be baseline separated employing also reversed-phase mode (alpha = 1.16, Rs = 2.91). These separation methods may be applied for quality control processes in the production of stereoisomerically pure insecticides as well as stereoselective toxicokinetic studies, as CDCA, PA, and FA are suitable biomarkers for monitoring human pyrethroid burden.