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Separation Time (separation + time)
Selected AbstractsOptimal separation times for electrical field flow fractionation with Couette flowsELECTROPHORESIS, Issue 20 2008Jennifer Pascal Abstract The prediction of optimal times of separation as a function of the applied electrical field and cation valence have been studied for the case of field flow fractionation [Martin M., Giddings J. C., J. Phys. Chem. 1981, 85, 727] with charged solutes. These predictions can be very useful to a priori design or identify optimal operating conditions for a Couette-based device for field flow fractionation when the orthogonal field is an electrical field. Mathematically friendly relationships are obtained by applying the method of spatial averaging to the solute species continuity equation; this is accomplished after the role of the capillary geometrical dimensions on the applied electrical field equations has been assessed [Oyanader M. A., Arce P., Electrophoresis 2005; 26, 2857]. Moreover, explicit analytical expressions are derived for the effective parameters, i.e. diffusivity and convective velocity as functions of the applied (orthogonal) electrical field. These effective transport parameters are used to study the effect of the cation valence of the solutes and of the magnitude of the applied orthogonal electrical field on the values of the optimal time of separation. These parameters play a significant role in controlling the optimal separation time, leading to a family of minimum values, for particular magnitudes of the applied orthogonal electrical field. [source] Determination of glyoxal and methylglyoxal in the serum of diabetic patients by MEKC using stilbenediamine as derivatizing reagentELECTROPHORESIS, Issue 21 2007Muhammad A. Mirza Abstract An analytical method has been developed for the separation of glyoxal (Go), methylglyoxal (MGo), and dimethylglyoxal (DMGo) by MEKC using stilbenediamine (SD) as derivatizing reagent, separation time 6.5,min, SDS as micellar medium at pH,8, and sodium tetraborate (0.1,M) as buffer. Uncoated fused-silica capillary, effective length 50,cm×75,,m id; applied voltage 20,kV and photodiode array detection, were used. Calibration was linear within 0.02,150,,g/mL with detection limits 3.5,5.8,ng/mL. Go and MGo, observed for diabetic and healthy volunteers, were within 0.098,0.193,,g/mL Go and 0.106,0.245,,g/mL MGo with RSD 1.6,3.5 and 1.7,3.4%, respectively, in diabetics against 0.016,0.046,,g/mL Go and 0.021,0.066,,g/mL MGo with RSDs 1.5,3.5 and 1.4,3.6%, respectively, in healthy volunteers. Go and MGo in diabetics were also measured by standard addition and DMGo as an internal standard. Additives do not contribute significantly to Go and MGo matrix. [source] Role of geometrical dimensions in electrophoresis applications with orthogonal fieldsELECTROPHORESIS, Issue 15 2005Mario A. Oyanader Abstract The role of geometrical dimensions in electrophoresis applications with axial and orthogonal (secondary) electric fields is investigated using a rectangular capillary channel. In particular, the role of the applied orthogonal electrical field in controlling key parameters involved in the effective diffusivity and effective (axial) velocity of the solute is identified. Such mathematically friendly relationships are obtained by applying the method of spatial averaging to the solute species continuity equation; this is accomplished after the role of the capillary geometrical dimensions on the applied electrical field equations has been studied. Moreover, explicit analytical expressions are derived for the effective parameters, i.e., diffusivity and convective velocity as functions of the applied (orthogonal) electric field. Previous attempts (see Sauer et al., 1995) have only led to equations for these parameters that require numerical solution and, therefore, limited the use of such results to practical applications. These may include, for example, the design of separation processes as well as environmental applications such as soil reclamation and wastewater treatment. An illustration of how a secondary electrical field can aid in reducing the optimal separation time is included. [source] A microfabricated hybrid device for DNA sequencingELECTROPHORESIS, Issue 21 2003Shaorong LiuArticle first published online: 6 NOV 200 Abstract We have created a hybrid device of a microfabricated round-channel twin-T injector incorporated with a separation capillary in order to extend the straight separation distance for high speed and long readlength DNA sequencing. Semicircular grooves on glass wafers are obtained using a photomask with a narrow line-width and a standard isotropic photolithographic etching process. Round channels are made when two etched wafers are face-to-face aligned and bonded. A two-mask fabrication process has been developed to make channels of two different diameters. The twin-T injector is formed by the smaller channels whose diameter matches the bore of the separation capillary, and the "usual" separation channel, now called the connection channel, is formed by the larger ones whose diameter matches the outer diameter of the separation capillary. The separation capillary is inserted through the connection channel all the way to the twin-T injector to allow the capillary bore flush with the twin-T injector channels. The total dead-volume of the connection is estimated to be , 5 pL. To demonstrate the efficiency of this hybrid device, we have performed four-color DNA sequencing on it. Using a 200 ,m twin-T injector coupled with a separation capillary of 20 cm effective separation distance, we have obtained readlengths of 800 plus bases at an accuracy of 98.5% in 56 min, compared to about 650 bases in 100 min on a conventional 40 cm long capillary sequencing machine under similar conditions. At an increased separation field strength and using a diluted sieving matrix, the separation time has been reduced to 20 min with a readlength of 700 bases at 98.5% base-calling accuracy. [source] Sequencing of real-world samples using a microfabricated hybrid device having unconstrained straight separation channelsELECTROPHORESIS, Issue 21 2003Shaorong Liu Abstract We describe a microfabricated hybrid device that consists of a microfabricated chip containing multiple twin-T injectors attached to an array of capillaries that serve as the separation channels. A new fabrication process was employed to create two differently sized round channels in a chip. Twin-T injectors were formed by the smaller round channels that match the bore of the separation capillaries and separation capillaries were incorporated to the injectors through the larger round channels that match the outer diameter of the capillaries. This allows for a minimum dead volume and provides a robust chip/capillary interface. This hybrid design takes full advantage, such as sample stacking and purification and uniform signal intensity profile, of the unique chip injection scheme for DNA sequencing while employing long straight capillaries for the separations. In essence, the separation channel length is optimized for both speed and resolution since it is unconstrained by chip size. To demonstrate the reliability and practicality of this hybrid device, we sequenced over 1000 real-world samples from Human Chromosome 5 and Ciona intestinalis, prepared at Joint Genome Institute. We achieved average Phred20 read of 675 bases in about 70 min with a success rate of 91%. For the similar type of samples on MegaBACE 1000, the average Phred20 read is about 550,600 bases in 120 min separation time with a success rate of about 80,90%. [source] Collection of peripheral progenitor cells in paediatric patients with a new programme for the collection of mononuclear cellsJOURNAL OF CLINICAL APHERESIS, Issue 3 2003R. Moog Abstract When harvesting peripheral progenitor cells (PPC) in children, the special situation of their circulatory system has to be taken into account. Therefore, extracorporeal blood volume and product volume should be small to avoid side effects. Nine children (age 2,14 years, weight 12.8,58.5 kg) with malignancies underwent 10 PPC collections with the MNC programme of the Amicus blood cell separator. The disposable kit was primed with red blood cells (RBCs) or human albumin to avoid circulatory side effects. The children were monitored for blood pressure and heart rate during the whole apheresis procedure. A median blood volume of 4,577 ml (range 3,536,8,596 ml) was processed in a separation time of 270 min (range 176,331 min). The median product weight was 81 g (range 53,107 g) and the yield of CD 34 antigen expressing cells was 12.5 × 106/kg body weight (range 1.8,26 × 106/kg body weight). Only one child had to undergo a second apheresis to collect the desired transplantation dose. The median platelet contamination of the product was 0.32 × 1011 (0.13,0.85 × 1011). No circulatory side effects were observed. Blood flow alarms occurred in seven of ten aphereses and one collection had to be terminated due to insufficient flow. PPC can be efficiently collected in children with the MNC programme without circulatory side effects. The platelet contamination of the product was low due to the elutriation principle of the collection process, thereby avoiding thrombocytopenic bleeding episodes in the patients. J. Clin. Apheresis, 18:111,114, 2003. © 2003 Wiley-Liss, Inc. [source] Performance of hollow-fiber flow field-flow fractionation in protein separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2005Ilyong Park Abstract Since hollow-fiber flow field-flow fractionation (HF FlFFF) utilizes a cylindrical channel made of a hollow-fiber membrane, which is inexpensive and simple in channel assembly and thus disposable, interests are increasing as a potential separation device in cells, proteins, and macromolecules. In this study, performance of HF FlFFF of proteins is described by examining the influence of flow rate conditions and length of fiber (polyacrylonitrile or PAN in this work) on sample recovery as well as experimental plate heights. The interfiber reproducibility in terms of separation time and recovery was also studied. Experiments showed that sample recovery was consistent regardless of the length of fiber when the effective field strength (equivalent to the mean flow velocity at the fiber wall) and the channel void time were adjusted to be equivalent for channels of various fiber lengths. This supported that the majority of sample loss in HF FlFFF separation of apoferritin and their aggregates may occur before the migration process. It is finally demonstrated that HF FlFFF can be applied for characterizing the reduction in Stokes' size of low density lipoproteins from blood plasma samples obtained from patients having coronary artery disease and from healthy donors. [source] MOLECULAR SYSTEMATICS OF RIVER DOLPHINS INFERRED FROM COMPLETE MITOCHONDRIAL CYTOCHROME- B GENE SEQUENCESMARINE MAMMAL SCIENCE, Issue 1 2002Guang Yang Abstract 1,140 bp of the complete mitochondrial cytochrome- b gene sequences of baiji (Lipotes vexillifer), franciscana (Pontoporia blainvillei), and Ganges river dolphin (Platanista gangetica gangetica) were determined to address the systematic position and phylogeny of extant river dolphins with combination of homologous sequences of other cetaceans. The neighbor-joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) phylogenetic analyses all identified the river dolphins into three lineages, i. e., Platanista, Lipotes, and Inia+Pontoporia. The Lipotes did not have sister relationship with either Platanista or Inia+Pontoporia, which strongly supported the referral of Lipotes to a separate family, i. e., Lipotidae. There were very high sequence divergences between all river dolphin genera, suggesting a relatively longer period of separation time than those among other odontocete families. [source] Comparison of 1- and 2-day protocols for myocardial SPECT: a Monte Carlo studyCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2005H. H. El-Ali Summary Background:, Myocardial perfusion single-photon emission computed tomography (SPECT) is carried out by combining a rest and a stress study that are performed either on one day or two separate days. A problem when performing the two studies on 1 day is that the residual activity from the first study contributes to the activity measured in the second study. Aim:, Our aim was to identify and evaluate trends in the quantification parameters of myocardial perfusion images as a function of separation time between rest and stress. Methods:, A digital phantom was used for the generation of heart images and a Monte Carlo-based scintillation camera program was used to simulate SPECT projection images. In our simulations, the rest images were normal and the stress images included lesions of different types and localization. Two programs for quantification of myocardial perfusion images were used to assess the different images in an automated and objective way. Results:, The summed difference scores observed with the 2-day protocol were 3 ± 1 (mean ± SD) higher for AutoQUANT and 2 ± 1 higher for 4D-MSPECT compared with those observed with the 1-day protocol. The extent values were 2% points higher for the 2-day protocol compared with the 1-day protocol for both programs. Conclusions:, There are differences in the quantitative assessment of perfusion defects depending on the type of protocol used. The contribution of residual activity is larger when a 1-day protocol is used compared with the 2-day protocol. The differences, although small, are of a magnitude that results in a clear shift in quantification parameters. [source] Optimal separation times for electrical field flow fractionation with Couette flowsELECTROPHORESIS, Issue 20 2008Jennifer Pascal Abstract The prediction of optimal times of separation as a function of the applied electrical field and cation valence have been studied for the case of field flow fractionation [Martin M., Giddings J. C., J. Phys. Chem. 1981, 85, 727] with charged solutes. These predictions can be very useful to a priori design or identify optimal operating conditions for a Couette-based device for field flow fractionation when the orthogonal field is an electrical field. Mathematically friendly relationships are obtained by applying the method of spatial averaging to the solute species continuity equation; this is accomplished after the role of the capillary geometrical dimensions on the applied electrical field equations has been assessed [Oyanader M. A., Arce P., Electrophoresis 2005; 26, 2857]. Moreover, explicit analytical expressions are derived for the effective parameters, i.e. diffusivity and convective velocity as functions of the applied (orthogonal) electrical field. These effective transport parameters are used to study the effect of the cation valence of the solutes and of the magnitude of the applied orthogonal electrical field on the values of the optimal time of separation. These parameters play a significant role in controlling the optimal separation time, leading to a family of minimum values, for particular magnitudes of the applied orthogonal electrical field. [source] High-sensitivity detection of biological amines using fast Hadamard transform CE coupled with photolytic optical gatingELECTROPHORESIS, Issue 17 2007Kevin L. Braun Abstract Here, we report the first utilization of Hadamard transform CE (HTCE), a high-sensitivity, multiplexed CE technique, with photolytic optical gating sample injection of caged fluorescent labels for the detection of biologically important amines. Previous implementations of HTCE have relied upon photobleaching optical gating sample injection of fluorescent dyes. Photolysis of caged fluorescent labels reduces the fluorescence background, providing marked enhancements in sensitivity compared to photobleaching. Application of fast Hadamard transform CE (fHTCE) for fluorescein-based dyes yields a ten-fold higher sensitivity for photolytic injections compared to photobleaching injections, due primarily to the reduced fluorescent background provided by caged fluorescent dyes. Detection limits as low as 5,pM (ca. 18,molecules per injection event) were obtained with on-column LIF detection using fHTCE in less than 25,s, with the capacity for continuous, online separations. Detection limits for glutamate and aspartate below 150,pM (1,2,amol/injection event) were obtained using photolytic sample injection, with separation efficiencies exceeding 1×106,plates/m and total multiplexed separation times as low as 8,s. These results strongly support the feasibility of this approach for high-sensitivity dynamic chemical monitoring applications. [source] | |||||||||||||