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Methane bubble dispersions in a water column can be observed in both vertical subsea piping as well as subsea gas seepages. Hydrate growth has been shown to occur at the gas–water interface under flowing conditions, yet the majority of the current literature is limited to quiescent systems. Gas hydrate risks in subsea piping have been shown to increase in late life production wells with increased water content and with gas-in-water bubble dispersions. The dissolution of subsea methane seepages into seawater, or methane release into the atmosphere, can be affected by hydrate film growth on rising bubbles. A high-pressure water tunnel (HPWT), was used to generate a turbulent, continuous water flow system representative of a vertical jumper line to study the relationship between bulk methane hydrate growth and bubble size during a production-well restart. The HPWT comprises a flow loop of 19.1 mm inner diameter and 4.9 m length, with a vertical section containing an optical window to enable visualization of the bubble and hydrate flow dynamics via a high-speed, high-resolution video camera. Additional online monitoring includes the differential pressure drop, viscosity, temperature, flow rates, and gas consumption. Experimental conditions were maintained at 275 K and 6.2 MPa during hydrate formation and 298 K and 1.4 MPa during hydrate dissociation. Hydrate growth using freshwater and saltwater (3.5 wt % NaCl) was measured at four flow velocities (0.8, 1.2, 1.6, and 1.9 m s–1). The addition of salt is shown in this work to alter the surface properties of bubbles, which introduces changes to bubble dynamics of dispersion and coalescence. Hydrate volume fractions and growth rates in the presence of salt were on average ∼32% lower compared to that in freshwater. This was observed and validated to be due to bubble size and dynamic factors and not due to the 1.5 K thermodynamic inhibition effect of salt. Throughout hydrate growth, methane bubbles in pure freshwater maintained larger diameters (2.4–4.2 mm), whereas the presence of salt promoted fine gas bubble dispersions (0.1–0.7 mm), increasing gas–water interfacial area. While gas bubble coalescence was observed in all freshwater experiments, the addition of salt limited coalescence between gas bubbles and reduced bubble size. Consequently, earlier formation of solid hydrate shells in saltwater produced early mass-transfer barriers reducing hydrate growth rates. While primarily directed toward flow assurance, the observed relationship between hydrates, bubble size, and saltwater also applies to broader research fields in subsea gas seepages and naturally occurring hydrates.

A sensitive and specific method for the determination of quinidine in plasma is described. Quinidine is extracted with chloroform, the extract is evaporated and reconstituted with methanol and the methanol extract is analyzed by high-performance liquid chromatography using a silica gel column. The recovery of quinidine from plasma varied between 93.0 to 100%. Quinidine levels as low as 12 ng/ml can be detected by this method.

The synthesis and characterization of a zwitterionic stationary phase bonded onto microparticulate silica is described. The bonded zwitterionic phase was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and quantitative analysis of the ligands by high performance liquid chromatography (HPLC) following chemical cleavage from the silica backbone. Chromatographic evaluation of this novel bonded phase indicates that it functions as a weak cation exchanger at pH values above 4.5, an anion exchanger at pH values below 7, and as a zwitterionic phase between these two values. The simultaneous separation of a mixture of cationic, anionic and zwitterionic solutes with this novel bonded phase is shown. Using nucleotides as model compounds, a correlation was developed between maximum solute retention and the pH values corresponding to maximum solute/stationary phase zwitterion overlap. The possibility for a quadrupolar retention mechanism of the bonded zwitterionic phase for zwitterionic solutes is explored.

A new class of chemically bonded zwitterion-exchange stationary phases are synthesized. These silica-based stationary phases incorporate anionic, cationic, as well as hydrophobic/hydrophilic sites in a single stationary phase. Characterization of these stationary phases are achieved by diffuse reflectance Fourier transform infrared and elemental analysis and gas and liquid chromatographic analysis of the ligands chemically cleaved from the silica backbone. The chromatographic behavior of these stationary phases are also evaluated with a series of test solutes. Besides being used for the separations of zwitterionic biolopolymers such as short peptides and tetracycline, the phases are also used as universal stationary phases, alternately as anion and cation exchangers, and in the reversed-phase mode for the separation of neutral species. The application of these novel stationary phases for the simultaneous separation of nucleosides/nucleotides and ionic/neutral catecholamines is shown. The quadrupolar interaction retention mechanism of the zwitterionic stationary phases is investigated by studying the retention of zwitterionic test solutes by these phases. Reported here is the separation of chiral amino acids with a bonded chiral zwitterionic microparticulate silica effected by using the two strong interactions provided by quadrupolar ion-pair formation between solute and ligand in combination with π,π-interaction.