Question: After mixing my mobile phase and using it over the course of several weeks, the retention times of my compounds gradually increase, ending up approximately 20–30% longer. Upon preparing a new mobile phase, the retention times almost immediately return to where they originally were. Then, the situation occurs again over the lifetime of the new mobile phase. This cannot be a pump proble...

This work aims to evaluate the efficiency of ultrasonic degassing when applied to the AlSi9Cu3 alloy when compared with other degassing techniques. The mechanism of aluminium degassing is discussed. A suitable ultrasonic degassing apparatus including a novel MMM (Multi-frequency Multimode Modulated) technology, able to supply up to 1.2 kW power under a frequency up to 25 kHz, was developed spec...

I review the methodology of "high-performance" liquid chromatography as applied to therapeutic drug monitoring. Aside from direct injection of sample, sample cleanup involves miscible and immiscible organic solvent extractions, solid-phase extraction, and size separations. Column considerations are bonded phases, column dimensions, particle size, guard columns, stability, pH range, and reproduc...

Adsorption isotherms of p-nitrophenol from its aqueous solutions on two samples of activated carbon fibres and two samples of granulated activated carbons have been determined in the concentration range 40~800 mg/L (ppm). The surface of these carbons was modified by oxidation with nitric acid and oxygen gas, and by degassing the carbon surface under vacuum at temperatures of 400, 650 and 950C. ...

We present a chemical model of magma degassing based on nine volatile species part of S-O-H-C-Fe-bearing rhyolitic melts. It is based on equilibrium, closed-system degassing, and does not take in account the crystallization of mineral phases. For given initial conditions at depth, the model calculates the gas composition as pressure decreases, as well as physical variables controlling conduit f...

The present study aimed to evaluate the effect of degassing on an extrusion process, with respect to extrudate quality and drug release properties. Processed formulations were extruded with and without a degassing vent port at various locations along the barrel. All the experiments were performed under constant processing temperature, feeding rate, and screw speed. During the extrusion process,...

In up-flow anammox reactors, one of the contributing factors to biomass wash-out is the adherence of nitrogen gas produced by the anammox reaction to biomass. In this study, we operated an up-flow anammox reactor equipped with a degassing membrane to minimize the biomass wash-out from the reactor by separating the produced gas from the biomass. In addition, both the effect of degassing on the a...

Furnas volcano, in São Miguel island (Azores), being the surface expression of rising hydrothermal steam, is the site of intense carbon dioxide (CO2) release by diffuse degassing and fumaroles. While the diffusive CO2 output has long (since the early 1990s) been characterized by soil CO2 surveys, no information is presently available on the fumarolic CO2 output. Here, we performed (in August 20...

The behavior of C, H, and S in the solid Earth depends on their oxidation states, which are related to oxygen fugacity (fO2). Volcanic degassing is a source of these elements to Earth's surface; therefore, variations in mantle fO2 may influence the fO2 at Earth's surface. However, degassing can impact magmatic fO2 before or during eruption, potentially obscuring relationships between the fO2 of...

Terrestrial-like exoplanets may obtain atmospheres from three primary sources: capture of nebular gases, degassing during accretion, and degassing from subsequent tectonic activity. Here we model degassing during accretion to estimate the range of atmospheric mass and composition on exoplanets ranging from 1 to 30 Earth masses. We use bulk compositions drawn from primitive and differentiated me...