1,720,992 research outputs found
Determination of lead, cadmium, chromium, and arsenic in 13 herbs of tocolysis formulation using atomic absorption spectrometry
No full text[[abstract]]The contents of Pb, Cd, Cr, and As in 13 herbs of tocolysis formulations were studied using three kinds of sample pretreatment and atomic absorption spectrometry. Thirteen herbs were pretreated with either incineration, wet digestion, or microwave digestion, and the results of recoveries and precision about these elements were compared. The average recoveries of 13 herbs via incineration, wet digestion, and microwave digestion pretreatments were 80 +/- 12%, 85.7 +/- 3.3%, and 94.5 +/- 2.1%, respectively. Among them, microwave digestion pretreatment had the highest recovery and precision. The average relative standard deviations for the four measured elements (Pb, Cd, Cr, and As) from incineration, wet digestion, and microwave digestion pretreatments were 8.8 +/- 1.7%, 7.1 +/- 3.3%, and 3.4 +/- 0.8%, respectively. The detection limits for Pb, Cd, Cr, and As using microwave digestion pretreatment were 0.45 ppb, 0.03 ppb, 0.20 ppb, and 0.64 ppb, respectively. Concentrations of Pb, Cd, Cr, and As measured from the tocolysis formulation using microwave digestion pretreatment were 28.0 +/- 0.7 ppb, 1.11 +/- 0.03 ppb, 8.5 +/- 0.3 ppb, and 1.52 +/- 0.04 ppb, respectively. Lead was found to have the highest concentration among the four determined elements in 13 herbs. Schizonepetae Herba contained the highest Ph (60.5 +/- 2.1 ppb), Cr (23.3 +/- 0.5 ppb), and As (8.8 +/- 0.1 ppb) among the 13 herbs. Ligustici Rhizoma contained the highest Cd (3.76 +/- 0.04 ppb) among the 13 herbs.[[note]]SC
Determination of magnetic susceptibility of various ion-labeled red blood cells by means of analytical magnetapheresis
No full text[[abstract]]Analytical magnetapheresis is a newly developed technique for separating magnetically susceptible particles. The magnetically susceptible particles are deposited on a bottom plate after flowing through a thin (<0.05 cm) separation channel under a magnetic field applied perpendicular to the flow. Particles with various magnetic susceptibilities can be selectively deposited and separated by adjusting the applying magnetic force and flow rates. Magnetic susceptibility is an important parameter for magnetic separation. Magnetic susceptibility determination of various ion-labeled red blood cells (RBCs) using analytical magnetapheresis with a simple theoretical treatment is reported in this study. Susceptibility determination is based on the balance between maximal channel flow rate and magnetically induced flow rate for deposition. We tried a new approach to determine particle magnetic susceptibilities using a balance of magnetic and drag forces to control magnetically induced particle velocities. The Er3+, Fe3+, Cu2+, Mn2+, Co2+, and Ni2+ ions were used to label RBC at various labeling concentrations for susceptibility determination. The susceptibilities determined for various ion-labeled RBC under two magnetic field intensities fell within a 10% range. The average viabilities of various ion-labeled RBCs were 96.1 +/- 0.8%. The susceptibility determination generally took less than 10 min. Determined susceptibilities from analytical magnetapheresis differed by 10% from reference measurements using a superconducting quantum interference device (SQUID) magnetometer. The cost and time for analysis is much less using analytical magnetapheresis. This technique can provide a simple, fast, and economical way for particle susceptibility determinations. (C) 2003 Elsevier B.V. All rights reserved.[[note]]SC
Impurity analysis of 1,4-dioxane in nonionic surfactants and cosmetics using headspace solid-phase microextraction coupled with gas chromatography and gas chromatography-mass spectrometry
No full text[[abstract]]1,4-Dioxane impurity in nonionic surfactants and cosmetics were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Experimental results show that there is no significant difference using SPME-GC and SPME-GC-MS for analysis of 1,4-dioxane in three types of nonionic surfactants at the 95% confidence level. The relative standard deviation (R.S.D.) values of each analytical method were smaller than 3%. The amount of 1,4-dioxane was found to vary from 11.6 +/- 0.3 ppm to 73.5 +/- 0.5 ppm in 30% of nonionic surfactants from manufacturers in Taiwan. These methods were linear over the studied range of 3-150ppm with correlation coefficients higher than 0.995. The recoveries of 1,4-dioxane for these nonionic surfactants following SPME were all higher than 96 +/- 1% (n = 3). The detection limits of 1,4-dioxane for these nonionic surfactants following SPME were from 0.06 ppm to 0.51 ppm. The experimentally determined level of 1,4-dioxane in cosmetics from manufacturers in Taiwan varied from 4.2 +/- 0.1 ppm to 41.1 +/- 0.6 ppm in 22% of daily used cosmetics following SPME coupled with GC and GC-MS. Conventional solvent extraction takes around 1 h for extraction and reconcentration but SPME takes only around 10 min. SPME provides better analyses of 1,4-dioxane in nonionic surfactants and cosmetics than conventional solvent extraction and head space pretreatments in term of simplicity, speed, precision, detection limit, and solvent consumption. (c) 2004 Elsevier B.V. All rights reserved.[[note]]SC
New method of blood typing using analytical magnetapheresis
No full text[[abstract]]We report a new method of blood typing based on the agglutination of red blood cell (RBC) with serum-treated magnetic particles in analytical magnetapheresis. Blood typing of ABO was demonstrated. The agglutination patterns of RBCs are different for different blood types and can be used to determine the ABO blood typing in analytical magnetapheresis. Six samples can be tested in each run. The running time was less than 10 min. Magnetic particles were prepared in the laboratory. The amount of RBCs needed for the agglutination test was about 1.0 mu l of adult blood. The blood typing of ABO was used to illustrate the capable applications of analytical magnetapheresis to nonmagnetic samples like cells without magnetic labels. Analytical magnetapheresis has a great potential for cell related analysis. (c) 2005 Elsevier B.V. All rights reserved.[[note]]SC
Solid-phase microextraction coupled with gas chromatography and gas chromatography - Mass spectrometry for public health pesticides analysis
No full text[[abstract]]Public health pesticides in two-component mixed solutions were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography mass spectrometry (GC-MS). The two-component mixed solutions used were allethrin mixed with cyfluthrin, cypermethrin mixed with tetramethrin, and transfluthrin mixed with cyfluthrin. Quantitative SPME-GC and SPME-GC-MS analyses using calibration and standard addition methods were evaluated. Using SPME pretreatment saved several tens to hundreds of mL of organic solvent. Quantitative analyses of the SPME-GC and SPME-GC-MS using the calibration and standard addition methods showed promise for simple, fast, and solventless public health pesticide analysis.[[note]]SC
Assessment of Cell Viability Using the Chronoamperometric Method Based on Screen-Printed Electrodes
No full text[[abstract]]This study investigates suitable electrochemical mediators and optimal mediator concentration for breast cancer cells, MDA-MB-231. The optimized mediators were 1mM ferricyanide and 10 mu M menadione. The specifications for the chronoamperometric detection of ferrocyanide were a linear range of 0.020.36mM. The detection limit was 5.0 mu M and the spiked recovery was 95%99%. The oxidation currents increased linearly with cultured cell density. Cell viabilities determined using electrochemical methods confirmed those determined by MTT assay. The running time can be reduced to less than 30min. The chronoamperometric method can be used as an alternative method for rapidly assessing the viability of breast cancer cells.[[note]]SC
Integrating the QCM detection with magnetic separation for on-line analysis
No full text[[abstract]]We investigate the feasibility of coupling the quartz crystal microbalance (QCM) with magnetic separation for on-line analysis. A flow cell was integrated with QCM and magnetic force for the analysis of magnetic and nonmagnetic samples. The resonant frequency change (Delta f) of QCM was related to the amount of deposited magnetic nanoparticles. This experiment demonstrates that QCM can be used as an on-line detector for magnetic separation. The QCM also gives a characteristic response of the binding between the streptavidin and biotin labeled On the magnetic nanoparticles. Biotin-labeled magnetic nanoparticles were flowed through a gold electrode of QCM to deposit as a matrix for selective capturing streptavidin. The resonant frequency change of QCM was proportional to the amounts of streptavidin captured by biotin. This technique can provide a simple, economic, and automatic method for on-line detection of biomarkers. (C) 2008 Elsevier B.V. All rights reserved.[[note]]SC
Detection of c-reactive protein based on immunoassay using antibody-conjugated magnetic nanoparticles
No full text[[abstract]]We report a detection method for C-reactive protein (CRP) based on competitive immunoassay using magnetic nanoparticles under magnetic fields: Functional magnetic nanoparticles were prepared and conjugated with anti-CRP for immunoassay. Magnetic nanoparticles labeled with anti-CRP were flowed through a separation channel to form depositions for selective capture of CRP under magnetic fields. Free CRP and a fixed number of CRP-labeled particles were used to compete for a limited number of anti-CRP binding sites on the magnetic nanoparticles. The deposited percentages of CRP-labeled particles at various concentrations of free CRP were determined and used as a reference plot. The determination of CRP in the unknown sample was deduced from the reference plot using the deposited percentages. The running time was less than 10 min. The CRP concentration of serum sample was linearly over the range of 1.2-310 mu g/mL for deposited percentages of CRP-labeled particles. The detection limit of this method was 0.12 mu g/ mL which was similar to 8-fold lower than the typical clinical cutoff concentration (1 mu g/mL). This method can provide a fast, simple, and sensitive way for protein detection based on competitive immunoassay using magnetic nanoparticles under magnetic fields.[[note]]SC
Separation method based on affinity reaction between magnetic and nonmagnetic particles for the analysis of particles and biomolecules
No full text[[abstract]]A separation method is reported for particle and biochemical analysis based on affinity interactions between particle surfaces under magnetic field. In this method, magnetic particles with immunoglobulin G (IgG) or streptavidin on the surface are flowed through a separation channel to form a deposition matrix for selectively capturing nonmagnetic analytes with protein A or biotin on the surface due to specific antigen (Ag)-antibody (Ab) interactions. This separation method was demonstrated using model reactions of IgG-protein A and streptavidin-biotin on particle surface. The features of this new separation method are (1) the deposited Ag-Ab complex can be examined and further analyzed under the microscope, (2) a kinetic study of complex binding is possible, and (3) the predeposited matrix can be formed selectively and changed easily. The detection limits were about 10(-11) g. The running time was less than 10 min. The selectivities of studied particles were 94% higher than those of label-controlled particles. This method extends the applications of analytical magnetapheresis to nonmagnetic particles. Preliminary study shows that this separation method has a great potential to provide a simple, fast, and selective analysis for particles, blood cells, and immunoassay related applications. (c) 2006 Elsevier B.V. All rights reserved.[[note]]SC
Solid-phase microextraction coupled with liquid chromatography for determination of beta-carotene in food
No full text[[abstract]]Public health pesticides in two-component mixed solutions were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography mass spectrometry (GC-MS). The two-component mixed solutions used were allethrin mixed with cyfluthrin, cypermethrin mixed with tetramethrin, and transfluthrin mixed with cyfluthrin. Quantitative SPME-GC and SPME-GC-MS analyses using calibration and standard addition methods were evaluated. Using SPME pretreatment saved several tens to hundreds of mL of organic solvent. Quantitative analyses of the SPME-GC and SPME-GC-MS using the calibration and standard addition methods showed promise for simple, fast, and solventless public health pesticide analysis.[[note]]SC
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