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A novel mass spectrometric method is applied to rapid, accurate, quantitative analysis of chiral phenylglycine. Transition-metal-bound complex ions containing the chiral phenylglycine are generated by electrospray ionization mass spectrometry and subjected to collision-induced dissociation. The ratio of the two competitive dissociation rates is related to the enantiomeric composition of the mixture, allowing the determination of enantiomeric contamination in the intermediates.
Asunto(s)
Glicina/análogos & derivados , Espectrometría de Masa por Ionización de Electrospray/métodos , Glicina/análisis , Glicina/química , Cinética , EstereoisomerismoRESUMEN
This paper presents a method whereby trace elements in NH(4)Cl-NH(3) medium are adsorbed on activated carbon in a micro-flow-injection (FI) semi-online sorbent extraction preconcentration system and then determined by graphite furnace atomic absorption spectrometry (GFAAS). The analytical performance of the proposed method for determining Cd, Mn and Pb was studied. A microcolumn packed with activated carbon was used as a preconcentration column (PCC). The metals to be determined were preconcentrated onto the column for 60 s and then rinsed with 0.02% (v/v) HNO(3) and eluted with 30 microl of 2 mol l(-1) HNO(3). Compared with the direct injection of 30 microl of aqueous sample solution, enrichment factor of 32, 26, and 21 and detection limits (3sigma) of 0.4, 4.7, and 7.5 ng l(-1) for Cd, Mn and Pb, respectively, were obtained with 60 s sample loading at 3.0 ml min(-1) for sorbent extraction, 30 microl of eluate injection, and peak area measurement. The precisions (RSD, n=6) were 2.8% at the 0.05 microg l(-1) level for Cd, 3.0% at the 0.3 microg l(-1) level for Mn, and 3.1% at the 0.5 microg l(-1) level for Pb. The experimental results indicate that the procedure can eliminate the fundamental interferences caused by alkali and alkaline earth metals and the application of it to the determination of Cd, Mn and Pb in some water samples is successful.
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The development of liquid core waveguide in recent years was reviewed and evaluated concisely. It was shown that the combination of liquid core waveguide and the ΔI measurement was an ideal strategy to improve the sensitivity of spectrophotometry
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Object To study the microwave assisted procedure for the extraction of baicalin from root of Scutellariae baicalensis Georgi Methods An MSP 100D domestically made microwave sample preparation system with a maximum power of 850 watts was used. The effects of solvents, pressure/temperature of solvents and microwave radiation time on the yield of baicalin were studied by orthogonal experimental design. Results The optimal experimental conditions were extraction at 70% of microwave power with 30 times of 35% ethanol at a constant heating pressure/temperature of 0.15 MPa for 30 s. Conclusion The microwave assisted extraction not only takes a shorter time with better parallel results, but also gave an increased yield of about 10% as compared with ultrasonic extraction.
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A new method has been developed in this paper for determining sulphide and sulphur dioxide simultaneously. Two emission lines, 202.6 nm and 214.3 nm which are emitted from hollow cathode lamps (HCL) of magnesium and tellurium, respectively, were used as radiation sources for measurement of absorbances of H(2)S at 202.6 nm and SO(2) at 214.3 nm or 202.6 nm. The detection limit for S(2-) was shown to be 0.01 mug/ml and the detection limits for SO(2) with 202.6 nm and 214.3 nm lines were 0.05 and 0.2 mug/ml, respectively. The method has been employed to satisfactorily analyse practical samples.