Chemical gradients drive a diverse set of biological processes ranging from nerve transduction to ovulation. At present, the most common method for quantifying chemical gradients is microscopy. Here, a new concept for probing spatial and temporal chemical gradients is reported that uses a multi-layer microfluidic device to measure analyte concentration as a function of lateral position in a mic...

An electrochemical flow cell with a boron-doped diamond dual-plate microtrench electrode has been developed and demonstrated for hydroquinone flow injection electroanalysis in phosphate buffer pH 7. Using the electrochemical generator-collector feedback detector improves the sensitivity by one order of magnitude (when compared to a single working electrode detector). The diffusion process is sw...

We describe an Electronic Nose (ENose) system which is able to identify the type of analyte and to estimate its concentration. The system consists of seven sensors, five of them being gas sensors (supplied with different heater voltage values), the remainder being a temperature and a humidity sensor, respectively. To identify a new analyte sample and then to estimate its concentration, we use b...

Conventional analysis of molecular interactions by surface plasmon resonance is achieved by the observation of optical density changes due to analyte binding to the ligand on the surface. Low molecular weight interaction partners are normally not detected. However, if a macromolecule such as DNA can extend beyond the evanescent field and analyte interaction results in a large-scale contraction,...

The United States Environmental Protection Agency (EPA) requires the determination of important trace elements in a variety of environmental samples. Graphite furnace atomic absorption methods are recommended for some elements including As, Se, Cd, Pb, Tl, Sb, Ag, Be and Cr. Graphite furnace analyses can be difficult due to chemical and spectral interferences. Quantification in atomic absorptio...

A refractive index sensor based on dual-core photonic crystal fiber (PCF) with hexagonal lattice is proposed. The effects of geometrical parameters of the PCF on performances of the sensor are investigated by using the finite element method (FEM). Two fiber cores are separated by two air holes filled with the analyte whose refractive index is in the range of 1.33-1.41. Numerical simulation resu...

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder with incidence expected to increase four-fold over the next decade. Extensive research efforts are focused upon identifying new treatments, and early diagnosis is considered key to successful intervention. Although imaging and cerebrospinal fluid biomarkers have shown promise in identifying patients in very early stages of th...

We describe a simple, stable, and high-resolution surface plasmon resonance ~SPR! sensor using a quadrant cell photodetector. The sensor focuses a diode laser through a prism onto a gold film that is divided into two areas, one for reference and the other for sensing analyte. The angular shifts of the SPR generated in the two areas are detected with a quadrant cell photodetector. Because signal...

The selective desorption/ionization of analytes using nanomaterials is investigated using metallic nanoparticles. By replacing the sodium citrate capping of gold nanoparticles with self-assembled monolayers, we are able to both enhance analyte ionization and selectively capture analytes. Capping gold nanoparticles with a monolayer of 4-mercaptobenzoic acid enhances analyte ionization while grea...

Surface Plasmon Resonance Imaging (SPRI) is an optical technique emerged as a powerful tool for the simultaneous monitoring of interactions of biomolecules arrayed onto gold substrates. To take fully advantage of the SPRI approach a precise control of the fluidic of the analyte solution is imposed. The diffusion between the flowing buffer and the analyte solution which is established within the...