On-Chip Coupling of Isoelectric Focusing and Free Solution Electrophoresis for Multidimensional Separations

Herr, Amy E.; Molho, Joshua I.; Drouvalakis, Katerina A.; Mikkelsen, J. C.; Utz, Paul J.; Santiago, Juan G.; Kenny, Thomas W.

doi:10.1021/ac026239a

Cited by 191 publications

(191 citation statements)

References 37 publications

(64 reference statements)

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“…We perform the experiments in an electrokinetic focusing flow configuration which is similar to the primary step of a pinched flow electrokinetic injection (or a three-inlet-channel mixing scheme), where the centre sample stream and sheath flows have mismatched ionic conductivities. As mentioned above, these conditions are relevant to on-chip electrokinetic practices with conductivity gradients such as sample injection for field-amplified sample stacking (see Ren & Li 2004;Bharadwaj & Santiago 2005), flow control and separations of streams with indeterminate sample chemistry, low-Reynolds-number micromixing (see Oddy et al 2001), and flow at the intersection of multidimensional assays using heterogeneous buffer streams (see Herr et al 2003). We explore variations of applied electric field and centre-to-sheath conductivity ratios that impose variations of the electric Rayleigh number across four orders of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Convective instability of electrokinetic flows in a cross-shaped microchannel

Posner¹,

Santiago²

2006

J. Fluid Mech.

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126

132

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We present a parametric experimental study of convective electrokinetic instability (EKI) in an isotropically etched, cross-shaped microchannel using quantitative epifluorescence imaging. The base state is a three-inlet, one-outlet electrokinetic focusing flow configuration where the centre sample stream and sheath flows have mismatched ionic conductivities. Electrokinetic flows with conductivity gradients become unstable when the electroviscous stretching and folding of conductivity interfaces grows faster than the dissipative effect of molecular diffusion. Scalar images, critical applied fields required for instability, and temporal and spatial scalar energy are presented for flows with a wide range of applied d.c. electric field and centre-tosheath conductivity ratios. These parameters impose variations of the electric Rayleigh number across four orders of magnitude. We introduce a scaling for charge density in the bulk fluid as a function of local maximum conductivity gradients in the flow. This scaling shows that the flow becomes unstable at a critical electric Rayleigh number (Ra e, = 205) and applies to a wide range of applied field and centre-tosheath conductivity ratios. This work is relevant to on-chip electrokinetic flows with conductivity gradients such as field amplified sample stacking, flow at the intersections of multi-dimensional assays, electrokinetic control and separation of sample streams with poorly specified chemistry, and low-Reynolds number micromixing.

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Section: Introductionmentioning

confidence: 99%

Convective instability of electrokinetic flows in a cross-shaped microchannel

Posner¹,

Santiago²

2006

J. Fluid Mech.

Self Cite

126

132

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“…Cui et al [8] discussed their use of methylcellulose to reduce electroosmosis and peak drift for IEF in a polydimethylsiloxane (PDMS) device, and Manz's research group demonstrated sub-second separation of two proteins in a free-flow IEF bed [9]. In addition, coupling IEF with a different separation mechanism (e.g., free-solution electrophoresis) in an orthogonal channel has been carried out for 2-D separations [10][11][12]. Efforts have also been reported that integrate IEF with multiple 2-D channels; these devices have a potential to perform better separation than conventional 2-D slab gel electrophoresis [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Effects of separation length and voltage on isoelectric focusing in a plastic microfluidic device

Das

Fan

2006

Electrophoresis

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This paper describes the investigation on the effects of separation length and voltage on IEF in a plastic microfluidic device. A LIF, whole-channel imaging detection (WCID) system was developed to monitor proteins while they were moving under an electric field. IEF was carried out in a separation medium consisting of carrier ampholytes and a mixture of linear polymers (hydroxyethylcellulose and hydroxypropylcellulose). We found that the IEF separation resolution is essentially independent of separation length when the same voltage is applied, which agrees with the theory. This result supports the notion that IEF in a microfabricated device leads to more rapid analysis without sacrificing the resolving power. A higher separation voltage also brought about more rapid analysis and superior separation resolution. IEF of two proteins (green fluorescence protein and R-phycoerythrin) was achieved in 1.5 min when 500 V was applied across a 1.9-cm channel. We found that a linear relationship exists between the focusing time and the inverse of the electrical field strength. In addition, we confirmed the phenomenon in which the pH gradient was compressed to the middle of a channel, and we found that the relative amount of the gradient compression decreased with the channel length.

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“…Thus, the application of a high voltage is effective to obtain high-speed separation with high efficiencies in MCIEF. 35,36 To make sure, we checked the effect of Joule heating on the efficiency. In Eq.…”

Section: Mcief On Short Channel Chipmentioning

confidence: 99%

High-speed Analysis of Proteins by Microchip Isoelectric Focusing with Linear-imaging UV Detection

2009

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High-speed analyses of proteins by microchip isoelectric focusing (MCIEF) were investigated on straight channel chips. By employing a commercially available microchip electrophoresis instrument equipped with a linear-imaging UV detector, sample proteins focused in a separation channel could be detected without a mobilization step. Typically, standard proteins were focused within 210 s at different positions in a separation channel with its total length of 38.8 mm on the basis of their pI values. The linear relationship between the focused position of each protein and its pI value was observed in the pH range from 6 to 10. The formation process of a pH gradient in the microchannel and the effects of the applied voltage and the channel length on the MCIEF separation were also investigated.

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On-Chip Coupling of Isoelectric Focusing and Free Solution Electrophoresis for Multidimensional Separations

Cited by 191 publications

References 37 publications

Convective instability of electrokinetic flows in a cross-shaped microchannel

Convective instability of electrokinetic flows in a cross-shaped microchannel

Effects of separation length and voltage on isoelectric focusing in a plastic microfluidic device

High-speed Analysis of Proteins by Microchip Isoelectric Focusing with Linear-imaging UV Detection

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