Search results for "Microwave"

Validated fast procedure for trace element determination in basil powder

2011

Abstract An inductively coupled plasma optical emission spectroscopic (ICP-OES) method has been developed and fully validated for trace element determination in basil samples. The method involves the previous sample digestion, under pressure, with a mixture of HNO 3 , HCl and H 2 O 2 inside a microwave oven, 42 elements were studied and 33 elements (Al, As, Ba, Ca, Cr, Co, Cu, Fe, Pb, Li, Mg, Mn, Mo, Ni, K, Se, Na, Sr, Tl, Ti, V, Zn, Sc, Y, La, Ce, Nd, Tb, Ho, Er, Tm, Yb, Lu) were determined quantitatively in basil leaves obtained from Morocco and Spain. The method provided recovery percentages from 89% to 113% for spiked concentrations at mg kg −1 and μg kg −1 . Accurate results were found…

Studies of electron heating on a 6.4 GHz ECR ion source through measurement of diamagnetic current and plasma bremsstrahlung

2011

Diamagnetic current and low energy (2–70 keV) x-ray bremsstrahlung measurements taken on a 6.4 GHz electron cyclotron resonance ion source (ECRIS) are presented as a function of microwave power, neutral gas pressure and magnetic field configuration. X-ray flux from confined electrons and plasma energy density depend logarithmically on microwave power. This result differs from previous studies performed on ECRISs that operate at higher microwave frequencies, in which the x-ray power increases in an essentially linear fashion with the microwave power. X-ray power and plasma energy density both saturate as the neutral pressure is increased beyond a certain value. The gradient of the magnetic f…

Key Ingredients for Mastery of Chemical Microwave Processes

2012

Radiation-induced defects and their recombination processes in the x-ray storage phosphor BaBr2:Eu2 

2003

The recombination processes in the x-ray storage phosphor BaBr2:Eu2+ were investigated by optical and magneto-optical methods. A structure-sensitive investigation of the defects involved in the recombination processes was performed by detecting the microwave-induced changes in the recombination luminescence in a high magnetic field. F centres as well as VK hole centres are created after x-irradiation at low temperatures. The low-energy recombination band peaking at about 460 nm is due to F–VK centre recombinations, whereas the two high energy bands at 282 and 315 nm are probably due to recombinations of self-trapped excitons.

Determination of mineral and trace element concentrations in pine needles by ICP-OES: evaluation of different sample pre-treatment methods

2008

In the present study, the determination of mineral and trace elements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) from pine needles using three sample pre-treatment methods followed by inductively coupled plasma optical emission spectrometry, was examined. Sample pre-treatment methods tested were microwave digestion, ultrasound-assisted digestion and dry ashing. The new ultrasound-assisted digestion method was optimised by the analysis of the standard reference material (SRM) 1575a (pine needles) sample. The speed of dry ashing method was significantly increased by ultrasound dissolution after ashing. All the ICP-OES measurements were performed in robust plasma conditions which were tested…

ChemInform Abstract: Microwave-Assisted Organocatalytic Enantioselective Intramolecular Aza-Michael Reaction with α,β-Unsaturated Ketones.

2012

The combination of an epi-hydroquinine catalyst and pentafluoropropionic acid accelerates the process.

Rapid hydrolysis of benzodiazepines to benzophenones in a microwave oven

1989

Abstract A microwave oven is used to carry out the complete hydrolysis of diazepam to the corresponding benzophenone in only 10 min, at 650 W, with good recovery. The reaction yield is evaluated by first-derivative UV spectrophotometry.

A preliminary approach to mineral intake in the Spanish diet established from analysis of the composition of university canteen menus

2012

Abstract The concentration of mineral elements in complete menus has in Spain been determined in order to establish the levels of essential and toxic elements and their contribution to the maximum recommended intake. Thirteen university canteen menus obtained from the Burjassot campus, in Valencia, were analysed to establish a first approach on mineral composition in the Spanish diet. The menus were composed of a mixture of cereals, meat, fish, vegetables, fruits and dairy products. Samples were crushed, homogenized and lyophilized, and 25 elements were determinated by inductively coupled plasma optical emission spectroscopy (ICP-OES) after digestion of samples in a microwave oven. Menu sam…

Negative pressure cavitation-microwave assisted preparation of extract of Pyrola incarnata Fisch. rich in hyperin, 2'-O-galloylhyperin and chimaphili…

2013

Abstract A novel and effective extraction method, namely negative pressure cavitation-microwave assisted extraction technique (NMAE), was developed for the preparation of extracts of Pyrola incarnata Fisch., which are rich in the main constituents hyperin, 2′-O-galloylhyperin and chimaphilin. Single factor experiments and Box–Behnken design (BBD) were combined with a response surface methodology to examine factors affecting extraction. Maximum extraction yields of hyperin, 2′-O-galloylhyperin and chimaphilin (1.339 ± 0.029, 4.831 ± 0.117 and 0.329 ± 0.011 mg/g, respectively) were achieved under the following optimised conditions: 700 W microwave power, 50 °C extraction temperature, 30:1 mL/…

Focused microwave-assisted Soxhlet extraction: An expeditive approach for the isolation of lipids from sausage products

2003

A prototype of extractor based on the conventional Soxhlet principles but assisted in the cartridge zone by focused microwaves is proposed for accelerating the extraction of lipids from sausage products. The extraction process has been optimised using a multivariate design involving the main variables influencing the performance of the prototype (namely, irradiation power P, irradiation time T and number of cycles C). Under the optimum working conditions (P=160 W, T=10 s and C=14), the extraction of lipids from different Spanish sausage products is complete in 45 min. The extracts thus obtained have been compared with those provided by conventional Soxhlet extraction for 8 h by development …