Search results for "Libration"
showing 10 items of 901 documents
Use of micellar mobile phases for the chromatographic determination of clorazepate, diazepam, and diltiazem in pharmaceuticals
2001
An ODS-2 column, a micellar mobile phase of high elution strength containing 0.1M sodium dodecyl sulfate and 3% (v/v) butanol, and ultraviolet detection at 230 nm are used for the determination of either of two benzodiazepines (clorazepate and diazepam) and a benzothiazepine (diltiazem) in pharmaceuticals. The procedure is shown to be competitive against conventional chromatography with methanol-water mobile phases, especially for diltiazem. The composition of the micellar mobile phase is selected using a predictive strategy based on an accurate retention model and assisted by computer simulation. Calibration graphs are linear at least in the 2.5 to 20 microg/mL, 4 to 20 microg/mL, and 5 to…
Identification of Leguminosae gums and evaluation of carob-guar mixtures by capillary zone electrophoresis of protein extracts.
2002
A procedure for the extraction and capillary zone electrophoresis (CZE) separation of proteins from carob, guar and tara gums in a background electrolyte (BGE) of pH 9 containing 0.1% polyvinyl alcohol is described. The CZE protein profiles exhibit characteristic peaks for each one of the Leguminosae gums, which can be used to construct models capable of identifying samples of carob, guar and tara gums, and predicting the guar content in binary carob-guar mixtures of different geographical origin and harvested in different years. The classification and prediction models are constructed by using linear discriminant analysis (LDA) and multiple linear regression (MLR), respectively. An excelle…
Identification of unknown pesticides in fruits using ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry
2007
Abstract Ultra-high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC-QqTOF-MS) is an emerging technique offering more rapid and efficient separation, as well as the possibility to obtain accurate mass measurement and tandem mass spectrometry (MS/MS). This paper deals with the use of UPLC-QqTOF-MS to identify the pesticide residues present in complex pear extracts. Carbendazim, imazalil, and ethoxyquin were successfully identified because of the accurate mass determination of their protonated molecule and their major fragments in the product ion mass spectra. A few plastic and latex additives were also found, most of them probably coming from the packaging …
Determination of titanium by adsorption-voltammetry with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP)
1990
The 1:1 complex between titanium (IV) and 5-Br-PADAP can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The detection limit is 3×10−10 mol/l Ti (0.015 ppb). Calibration curves are linear for solutions containing 4×10−10 to 5×10−8 mol/l Ti(IV) and an enrichment time of 3 min. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 5000-fold excess of iron.
Cavity ring down spectrometry for disease diagnostics using exhaled air
2017
In this paper we report the current stage of the development of a cavity ring-down spectrometer (CRDS) system using exhaled human breath analysis for the diagnostics of different diseases like diabetes and later lung cancer. The portable CRDS system is made in ultraviolet spectral region using Nd:Yag laser 266 nm pulsed light. Calibration of the CRDS system was performed using generated samples by KinTek automated permeation tube system and self-prepared mixtures with known concentration of benzene and acetone in air. First experiments showed that the limits of detection for benzene and acetone are several tens of ppb.
The 4th international comparison on EPR dosimetry with tooth enamel
2011
This paper presents the results of the 4th International Comparison of in vitro electron paramagnetic resonance dosimetry with tooth enamel, where the performance parameters of tooth enamel dosimetry methods were compared among sixteen laboratories from all over the world. The participating laboratories were asked to determine a calibration curve with a set of tooth enamel powder samples provided by the organizers. Nine molar teeth extracted following medical indication from German donors and collected between 1997 and 2007 were prepared and irradiated at the Helmholtz Zentrum Munchen. Five out of six samples were irradiated at 0.1, 0.2, 0.5, 1.0 and 1.5 Gy air kerma; and one unirradiated s…
Determination of total mercury in nuts at ultratrace level
2014
Abstract Total mercury, at μg kg−1 level, was determined in different types of nuts (cashew nut, Brazil nuts, almond, pistachio, peanut, walnut) using a direct mercury analyser after previous sample defatting and by cold vapour atomic fluorescence spectrometry. There is not enough sensitivity in the second approach to determine Hg in previously digested samples due to the strong matrix effect. Mercury levels in 25 edible nut samples from Brazil and Spain were found in the range from 0.6 to 2.7 μg kg−1 by using the pyrolysis of sample after the extraction of the nut fat. The accuracy of the proposed method was confirmed by analysing certified reference materials of Coal Fly Ash-NIST SRM 1633…
Photo-induced chemiluminescence-based determination of diphenamid by using a multicommuted flow system
2007
This manuscript deals with the application of molecular connectivity calculations to predict the photo-induced chemiluminescent behaviour of the family of herbicides grouped as amides. Several compounds of this group were theoretically studied by means of a general discriminant equation formerly obtained, being 18 of them (plus eight from the chloroacetanilide sub-group) predicted with a high probability as photo-induced chemiluminescent. Empirical confirmation of the chemiluminometric behaviour was performed with some few commercially available amide herbicides. On the basis of these results, a new multicommutation-photo-chemiluminescent method is proposed for the determination of the diph…
Optimization of transmission near infrared spectrometry procedures for quality control of pesticide formulations
2006
The use of different response functions to be optimized in the frame of the use of near infrared spectrometry for quality control of active principles in agrochemical formulations has been evaluated. Both, simple functions, based on parameters like sensitivity, repeatability, accuracy, signal to noise ratio, limit of detection or sample throughput, and a complex function, considering all the aforementioned aspects, were employed in the development of a new method for Iprodione determination in agrochemicals. Optimization strategies were based on the previous screening of the most important instrumental factors like number of cumulated scans, nominal resolution, mirror velocity and zero fill…
PLS-NIR determination of total sugar, glucose, fructose and sucrose in aqueous solutions of fruit juices
1997
Abstract An analytical procedure has been developed for the direct determination of sugars in fruit juice samples. The method is based on the partial least-squares (PLS) treatment of first derivative near infrared (NIR) spectroscopic data obtained between 1200 and 2450 nm, using 1 mm pathlength cell and a multicomponent calibration set, including seven binary mixtures and 10 ternary mixtures of glucose, fructose and sucrose. The limit of detection values found are of the order of 0.2 g/100 ml for total sugar and 0.2, 0.4 and 0.5 g/100 ml for glucose, fructose and sucrose, respectively. Relative standard deviation values obtained vary from 0.4% to 2.3% for six independent measurements of ind…