01817nas a2200289   4500008004100000022001400041245012900055210006900184260001600253300001000269490000800279520093300287653001501220653004101235653001401276653001101290653002401301653003501325100001401360700001601374700001501390700001301405700001701418700001501435700001701450856006001467       2002                        eng d  a0021-967300aInitial study of using a laminar fluid diffusion interface for sample preparation in high-performance liquid chromatography.0 aInitial study of using a laminar fluid diffusion interface for s  c2002 Apr 19  a33-400 v9543 a<p>This report describes a new microfluidic device called the H Filter for sample preparation prior to HPLC. The H Filters make possible a diffusional transfer of an analyte from a sample stream into a stream of a "receiver" fluid. Existing mathematical models can be used for optimizing experimental conditions. The authors have selected the extraction of the antibiotic cephradine from blood to demonstrate the utility of the new device. The extracts of blood samples spiked with cephradine levels between 0.2 and 100 microg/ml were analyzed using a C8 reversed-phase column and UV detection at 260 nm. The HPLC results were in good agreement with theory. The recovery of 32.2+/-2.8% was uniform over the entire range of cephradine concentrations. The new method completely avoids the use of centrifuges, that is otherwise typical for most current methodologies for the preparation of blood samples prior to HPLC analysis.</p>10aCephradine10aChromatography, High Pressure Liquid10aDiffusion10aHumans10aReference Standards10aSpectrophotometry, Ultraviolet1 aJandik, P1 aWeigl, B, H1 aKessler, N1 aCheng, J1 aMorris, C, J1 aSchulte, T1 aAvdalovic, N  uhttps://www.microfluidicsciences.com/drupal/?q=node/22402929nas a2200301   4500008004100000022001400041245016000055210006900215260001300284300001100297490000800308520199700316653003702313653001302350653001402363653002102377653001602398653001902414653002102433653002102454653001302475653001402488100001602502700001802518700001402536700001702550856006002567       2001                        eng d  a0937-063300aLab-on-a-chip sample preparation using laminar fluid diffusion interfaces--computational fluid dynamics model results and fluidic verification experiments.0 aLabonachip sample preparation using laminar fluid diffusion inte  c2001 Sep  a97-1050 v3713 a<p>Microfluidic structures for the generation of laminar fluid diffusion interfaces (LFDIs) for sample preparation and analysis are discussed. Experimental data and the results of fluid modeling are shown. LFDIs are generated when two or more streams flow in parallel in a single microfluidic structure without any mixing of the fluids other than by diffusion of particles across the diffusion interface. It has been shown that such structures can be used for diffusion-based separation and detection applications. The method has been applied to DNA desalting, the extraction of small proteins from whole blood samples, and the detection of various constituents in whole blood, among other examples. In this paper the design and manufacture of self-contained microfluidic cartridges for the extraction of small molecules from a mixture of small and large molecules by diffusion is demonstrated. The cards are operated without any external instrumentation, and use hydrostatic pressure as the driving force. The performance of the cartridges is illustrated by separating fluorescein from a mixture of fluorescein and dextran of molecular weight 2 x 10(6). In a single pass, 98.6% of dextran was retained in the product whereas 43.1% of fluorescein was removed. The method is adjustable for different separation requirements, and computational fluid dynamics (CFD) models are shown that demonstrate the tuning of various microfluidic parameters to optimize separation performance. Other applications of LFDIs for establishment of stable concentration gradients, and the exposure of chemical constituents or biological particles to these concentration gradients are shown qualitatively. Microfluidic chips have been designed for high-throughput screening applications that enable the uniform and controlled exposure of cells to lysing agents, thus enabling the differentiation of cells by their sensitivity to specific agents in an on-chip cytometer coupled directly to the lysing structure.</p>10aChemistry Techniques, Analytical10aDextrans10aDiffusion10aEquipment Design10aFluorescein10aMicrochemistry10aModels, Chemical10aMolecular Weight10aRheology10aViscosity1 aWeigl, B, H1 aBardell, R, L1 aKesler, N1 aMorris, C, J  uhttps://www.microfluidicsciences.com/drupal/?q=node/227