C-Term Reduction in 3 μm Open-Tubular High-Aspect-Ratio Channels in AC-EOF Vortex Chromatography Operation.

The performance of liquid chromatography operation in open-tubular channels, the ideal chromatographic column format, is limited by slow mass transport between the mobile and stationary phase. We recently introduced a lateral mixing methodology ("vortex chromatography") to reduce Taylor-Aris dispersion by employing (small) AC-EOF (alternating current electroosmotic flow) fields oriented perpendicular to the conventionally applied, axially oriented pressure gradient, resulting in the reduction of the C-term by a factor of 3, studied in 40 × 20 μm (aspect ratio (AR) = 2) channels under unretained conditions. In the present contribution, a further increased performance gain for channel dimensions relevant for chromatographic applications is demonstrated.

Mind the B2: Life-Threatening Neonatal Complications of a Strict Vegan Diet during Pregnancy.

An increasing number of women of reproductive age follow vegan diets. Because vegan diets are deficient in a number of essential nutrients, guidelines address the necessity of supplementations such as iron, zinc, and vitamin B12. However, the risk of riboflavin (vitamin B2) deficiency is not properly addressed.

Application of generalized dispersion theory to vortex chromatography.

Acoustically induced secondary flows are applied to enhance lateral mass transfer beyond the relatively slow diffusion. This has the goal to reduce convective axial dispersion and the resulting band broadening which, in turn, limits the performance of column chromatography. Traditional approaches based on Taylor-Aris model are limited to one-dimensional rectilinear (unidirectional) tube- or channel-flows.

Autonomous capillary microfluidic devices with constant flow rate and temperature-controlled valving.

In this paper, we report on a capillary microfluidic device with constant flow rate and temperature-triggered stop valve function. It contains a PDMS channel that was grafted by a thermo-responsive polymer poly(N-isopropylacrylamide) (PNIPAm). The channel exhibits a constant capillary filling speed.

Inducing AC-electroosmotic flow using electric field manipulation with insulators.

Classically, the configuration of electrodes (conductors) is used as a means to determine AC-electroosmotic flow patterns. In this paper, we use the configuration of insulator materials to achieve AC-electroosmotic flow patterning in a novel approach. We apply AC electric fields between parallel electrodes situated on the top and bottom of a microfluidic channel and separated by an insulating material.