High-p T αα andαp interactions

Properties of secondaries associated with a high-p _T charged trigger particle (3<p _T <5 GeV/c) were studied for αp and αα interactions at c.m. energies \(\sqrt s = 88\) GeV and 125 GeV, respectively. Thep _T distributions of secondaries in the away-jet and trigger-jet regions were compared with those for high-p _{T pp} interactions. No statistically significant differences were seen, except at lowp _T . Momentum and angular distributions of spectator and leading protons were studied as a function of charge and rapidity of the trigger hadron. The observed correlations between trigger charge and number of spectator protons provide evidence of valence quark contributions to the trigger jet.     

Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.     

Cycloaddition reaction of 2-azadienes derived from beta-amino acids with electron-rich and electron-deficient alkenes and carbonyl compounds. Synthesis of pyridine and 1,3-oxazine derivatives

Functionalized keto-enamines 6 were obtained by nucleophilic addition of enol ethers to the imine moiety of 2-azadienes derived from dehydroaspartic esters 4. Reactions of 2-azadiene 4c containing three electron-withdrawing substituents (CO(2)R) with enol ethers 5 in the presence of lithium perchlorate led to the formation of tetrahydropyridine derivatives 7 in a regio- and stereoselective fashion. 2H-[1,3]-oxazines 10 and pyridine derivatives 12 and 13 were obtained by heterocycloaddition reactions of electron-poor azadienes 4d-g containing two electron-withdrawing substituents (4-O(2)N-C(6)H(4), CO(2)R) in positions 1 and 4 with carbonyl derivatives (ethyl glyoxalate 9a and diethyl ketomalonate 9b) and the electron-deficient olefin tetracyanoethylene 11.     

Estimation of diuretic drugs in biological fluids by HPLC

Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.     

Selective determination of trimethylamine in air by liquid chromatography using solid phase extraction cartridges for sampling

The selective determination of trimethylamine (TMA) in air by liquid chromatography is reported. Sampling is effected by flushing air through C18-packed solid-phase extraction (SPE) cartridges at a flow rate of 15 mL/min for 15 min. Next, TMA is desorbed from the cartridges and injected into the chromatographic system. The analyte is then selectively retained on a precolumn (20 mm x 2.1 mm i.d., packed with 30 microm, Hypersil C18 phase), and derivatized on-line by injecting 9-fluorenylmethyl chloroformate (FMOC). Finally, the TMA-FMOC derivative is transferred to the analytical column (125 mm x 4 mm i.d., LiChrospher 100 RP18, 5 microm), and monitored at 262 nm. The method was applied to the measurement of TMA in air in the 0.25-2.5 microg interval (equivalent to concentrations of TMA of 1.1-11 mg/m3), providing good linearity, reproducibility and accuracy. The mean recovery of TMA was (96 +/- 7%) (n = 12), and the limit of detection was 0.05 microg. The proposed procedure allows the selective determination of TMA in the presence of other primary and secondary short-chain aliphatic amines.     

Derivatization of tertiary amphetamines with 9-fluorenylmethyl chloroformate for liquid chromatography: determination of N-methylephedrine

The fluorogenic reagent 9-fluorenylmethyl chloroformate (FMOC) was evaluated for the derivatization of tertiary amphetamines prior to liquid chromatographic analysis. Conditions for the derivatization were investigated, including the reaction time, the derivatization reagent concentration and the pH, using N-methylephedrine as a model compound. On the basis of these studies, a method for the quantification of N-methylephedrine is presented. The method involves derivatization with FMOC at ambient temperature and separation of the derivatives formed on a LiChrospher C18, 5 microns, 125 x 4 mm id column using acetonitrile-water gradient elution. The proposed procedure shows good linearity, accuracy and reproducibility in the 1.0-25.0 micrograms mL-1 concentration range. The limit of detection was 0.1 microgram mL-1 and the limit of quantification was 0.5 microgram mL-1. The utility of the assay was demonstrated by determining N-methylephedrine in water and urine samples.     

Liquid chromatographic determination of aliphatic amines in water using solid support assisted derivatization with 9-fluorenylmethyl chloroformate

Summary A simple and sensitive method has been developed for the liquid chromatographic determination of short-chain aliphatic amines in water. Analytes are retained in solid-phase extraction (SPE) cartridges, and then derivatized by drawing an aliquot of the fluorogeneic reagent 9-fluorenylmethyl chloroformate (FMOC) through the cartridges. After a certain reaction time the derivatives formed are desorbed with acetonitrile. The collected extracts are then chromatographed on a LiChrospher 100 RP₁₈ 125 mm×4 mm i.d., 5 μm, column using an acetonitrile-water gradient. The influence of experimental conditions (SPE material, volume of sample, concentration of FMOC, time of reaction and pH) has been investigated. Optimal results have been obtained with C₁₈ SPE cartridges using a sample volume of 5.0 mL. For derivatization, 0.25 mL aliquots of 25 mM FMOC have been used, the reaction time being only 2 min. The method has been applied to the quantification of several aliphatic amines: methylamine, ethylamine, dimethylamine,n-butylamine,n-pentylamine andn-hexylamine. Under the proposed conditions the percentages of analytes retained plus derivatized were of about 54–107% compared to those obtained with direct solution derivatization. The method provided good reproducibility, linearity and accuracy within the 0.050–1.0 mg L⁻¹ concentration range. The limits of detection were in the 0.25–5.0 μg L⁻¹ range. The utility of the described approach has been tested by analysing tap water, river water and industrial waste water.