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Diluted Samples (diluted + sample)
Selected AbstractsDetermination of ethyl glucuronide in human serum by hyphenation of capillary isotachophoresis and zone electrophoresisELECTROPHORESIS, Issue 8 2008Michaela Nováková Abstract The determination of ethyl glucuronide (EtG), a marker of recent alcohol consumption, in human serum by hyphenation of capillary ITP (CITP) and CZE is reported. For CITP step, 1×10,2,M hydrochloric acid adjusted with ,-aminocaproic acid (EACA) to pH,4.4 was used as the leading electrolyte, and 1×10,2,M nicotinic acid with EACA, pH,4.4, was used as the terminating electrolyte (TE). All electrolytes contained 0.2% hydroxypropylcellulose to suppress electroosmosis. In CITP, EtG was separated from fast serum macrocomponents chloride, phosphate, lactate, and acetate. Zones of microcomponents including EtG that migrated between acetate and nicotinate were forwarded to the second capillary filled with a BGE identical with the TE. Conductivity detection was used in the CITP step. Sensitive detection in the CZE step was performed using indirect spectrophotometric detection at 254,nm. The assay is based on a 1:5 dilution of serum with deionized water and has a concentration LOD for EtG in diluted sample of 9.8×10,9,M. The method was used for the determination of EtG in sera of volunteers consuming alcohol. [source] Evaluation of Bitterness in Enzymatic Hydrolysates of Soy Protein Isolate by Taste Dilution AnalysisJOURNAL OF FOOD SCIENCE, Issue 1 2008W.H. Seo ABSTRACT:, Although enzymatic hydrolysates of soy protein isolate (SPI) have physiological functionality, partially hydrolyzed SPI exhibits bitter taste depending on proteases and degree of hydrolysis (DH). To determine proteolysis conditions for SPI, it is important to evaluate bitterness during enzymatic hydrolysis. Taste dilution analysis (TDA) has been developed for the screening technique of taste-active compounds in foods. The objectives of the present study were to evaluate bitterness of enzyme-hydrolyzed SPI by TDA and to compare bitterness of SPI hydrolysates with respect to kinds of proteases and DH. SPI was hydrolyzed at 50 °C and pH 6.8 to 7.1 to obtain various DH with commercial proteases (flavourzyme, alcalase, neutrase, protamex, papain, and bromelain) at E/S ratios of 0.5%, 1%, and 2%. The DH of enzymatic hydrolysates was measured by trinitrobenzenesulfonic acid method. The bitterness of enzymatic hydrolysates was evaluated by TDA, which is based on threshold detection in serially diluted samples. Taste dilution (TD) factor was defined as the dilution at which a taste difference between the diluted sample and 2 blanks could be detected. As DH increased, the bitterness increased for all proteases evaluated. Alcalase showed the highest TD factor at the same DH, followed by neutrase. Flavourzyme showed the lowest TD factor at the entire DH ranges. At the DH of 10%, TD factor of hydrolysate by flavourzyme was 0 whereas those by protamex and alcalase were 4 and 16, respectively. These results suggest that TDA could be applied for the alternative of bitterness evaluation to the hedonic scale sensory evaluation. [source] Comparison of analytical approaches for liquid chromatography/mass spectrometry determination of the alcohol biomarker ethyl glucuronide in urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2010Anders Helander Official guidelines originating from a European Union directive regulate requirements for analytical methods used to identify chemical compounds in biological matrices. This study compared different liquid chromatography/electropray ionization mass spectrometry (LC/ESI-MS) and tandem mass spectrometry (LC/ESI-MS/MS) procedures for accurate determination of the conjugated ethanol metabolite and alcohol biomarker ethyl glucuronide (EtG) in urine, and the value of combined EtG and ethyl sulfate (EtS) measurement. Analysis was carried out on 482 urines following solid-phase extraction (SPE) sample cleanup or using direct injection of a diluted sample. SPE combined with LC/MS/MS was demonstrated to be the most selective and sensitive method and was chosen as reference method. The EtG results by different methods showed good correlation (r,=,0.96,0.98). When comparing five reporting limits for EtG in the range 0.10,1.00,mg/L, the overall agreement with the reference method (frequency of true positives plus true negatives) was 82,97% for direct-injection LC/MS/MS, 90,97% for SPE-LC/MS, 86,98% for direct-injection LC/MS, and 86,98% for direct-injection LC/MS analysis of EtG and EtS. Most deviations were attributable to uncertainty in quantitation, when the value was close to a cutoff but the respective results were slightly above and below, or vice versa, the critical limit. However, for direct-injection LC/MS/MS, despite earning 4 identification points, equally many negative results were due to a product ion ratio outside the ±20% deviation accepted by the guidelines. These results indicate that the likelihood of different analytical methods to provide reliable analytical results depends on the reporting limit applied. Copyright © 2010 John Wiley & Sons, Ltd. [source] Quantitation of talinolol and other ,-blockers by capillary electrophoresis for in vitro drug absorption studiesELECTROPHORESIS, Issue 15 2003Bilal Awadallah Abstract A capillary zone electrophoresis method is described for the enantioseparation of talinolol using heptakis(2,3-diacetyl-6-sulfo)-,-cyclodextrin (HDAS-,-CD) as a chiral selector. After liquid-liquid extraction of talinolol from physiological solution, electrokinetic injection was employed to improve the sensitivity. The use of a coated capillary was necessary to achieve stable and reproducible enantioseparations. A baseline separation of the talinolol enantiomers was achieved in less than 10 min using 100 mM phosphate solution as background electrolyte and pH 3.5, at the presence of 3.0 mM HDAS-,-CD and at 20°C. In addition, this analytical condition proved to be useful for the enantioseparation of a number of other ,-blocking agents such as alprenolol, atenolol, bisoprolol, celiprolol, metipranolol, oxprenolol, and sotalol. For determing talinolol, the method could be validated in terms of precision, accuracy and linearity, and was found to be suitable in determination of talinolol enantiomers in highly diluted samples obtained from in vitro experiments. [source] Evaluation of Bitterness in Enzymatic Hydrolysates of Soy Protein Isolate by Taste Dilution AnalysisJOURNAL OF FOOD SCIENCE, Issue 1 2008W.H. Seo ABSTRACT:, Although enzymatic hydrolysates of soy protein isolate (SPI) have physiological functionality, partially hydrolyzed SPI exhibits bitter taste depending on proteases and degree of hydrolysis (DH). To determine proteolysis conditions for SPI, it is important to evaluate bitterness during enzymatic hydrolysis. Taste dilution analysis (TDA) has been developed for the screening technique of taste-active compounds in foods. The objectives of the present study were to evaluate bitterness of enzyme-hydrolyzed SPI by TDA and to compare bitterness of SPI hydrolysates with respect to kinds of proteases and DH. SPI was hydrolyzed at 50 °C and pH 6.8 to 7.1 to obtain various DH with commercial proteases (flavourzyme, alcalase, neutrase, protamex, papain, and bromelain) at E/S ratios of 0.5%, 1%, and 2%. The DH of enzymatic hydrolysates was measured by trinitrobenzenesulfonic acid method. The bitterness of enzymatic hydrolysates was evaluated by TDA, which is based on threshold detection in serially diluted samples. Taste dilution (TD) factor was defined as the dilution at which a taste difference between the diluted sample and 2 blanks could be detected. As DH increased, the bitterness increased for all proteases evaluated. Alcalase showed the highest TD factor at the same DH, followed by neutrase. Flavourzyme showed the lowest TD factor at the entire DH ranges. At the DH of 10%, TD factor of hydrolysate by flavourzyme was 0 whereas those by protamex and alcalase were 4 and 16, respectively. These results suggest that TDA could be applied for the alternative of bitterness evaluation to the hedonic scale sensory evaluation. [source] Magneto-optical spectroscopy of (Zn,Co)O epilayersPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2006W. Pacuski Abstract We present a magneto-optical study of (Zn,Co)O layers grown by molecular beam epitaxy. We observed sharp lines related to 4A2,2E intra-ionic Co2+ transitions, and to the A , B and C excitons. Intra-ionic transitions observed by absorption and photoluminescence were used to determine the values of the parameters describing the isolated Co ions, such as the easy-plane magnetic anisotropy and the g -factor of the S = 3/2 Cobalt spin. Excitonic transitions observed in reflectivity were used to determine the giant Zeeman splitting and to estimate the effective coupling ,N0(, , , ),A ,B = 0.4 eV between excitons and Cobalt spins. Due to the electron,hole exchange within the exciton, this effective spin,exciton coupling is much weaker than the exchange integrals for free carriers, estimated to be N0|, , , | , 0.8 eV, with a positive value of (, , , ) if the normal ordering of the valence band of ZnO is assumed. The Zeeman splitting of diluted samples and the magnetic circular dichroism (for a higher Co content) are proportional to the magnetization of the paramagnetic, isolated Cobalt ions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development of the second-order derivative UV spectrophotometric method for direct determination of paracetamol in urine intended for biopharmaceutical characterisation of drug productsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 7 2003Jelena Paroj Abstract Paracetamol is a widely used nonsalicylate analgesic and antipyretic drug. The existing methods for the determination of paracetamol in biological fluids are mainly HPLC techniques, although there are some reported methods based on spectrophotometric determinations. However, all these methods involve some extraction or derivatisation procedures. In the present study the UV spectra of investigated samples were recorded over the wavelength range 220,400 nm (, step 0.21 nm; scan speed 60 nm/min) and second-order derivative spectra were calculated. Second-order derivative spectra of different blank urine samples displayed the presence of a zero-crossing point at 245,247 nm defined as ,zc. The zero-order absorption spectra of paracetamol in water displays maximum absorbance at 243 nm, while in second derivative spectra, a minimum peak at 246 nm was observed. Therefore, the application of zero-crossing technique to the second-derivative UV absorption spectrum should be useful for the determination of paracetamol using 2D,zc. The proposed method enables determination of total paracetamol in urine directly and simply by reading the 2D,zc of the diluted samples. The obtained results were in good accordance with published data on cumulative urinary excretion after per oral administration of paracetamol obtained applying different spectrophotometric methods of determination. It could be useful for biopharmaceutical characterisation of drug products (monitoring of the levels of paracetamol in urine in bioavailability testing, for the evaluation of in vitro,in vivo correlation and screening of different formulations during drug product development). Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||