A method for semi-continuous measurement of dissolved elemental mercury in industrial and natural waters

Mercury in aqueous systems can be present in different chemical forms. Of these, dissolved elemental Hg(0) (DEM) is of great importance because it can readily be partitioned between air and water. Analytical methods used for determining DEM are conventionally based on removal of Hg(0) by purging, pre-concentration on gold and detection by either cold vapour atomic absorption (CV-AAS) or atomic fluorescence spectrophotometry (CV-AFS). At present, there is no agreed protocol for the measurement of DEM in aqueous samples. A new method is described here, which is based on continuous stripping of DEM by mercury-free nitrogen in a flow injection mode and detection by CV-AAS. The partitioning of DEM between aqueous and gas phases is largely dependent on the composition of the former. Moreover, calibration using the standard addition method is not possible due to the reactivity of DEM introduced from calibration solutions. Calibration is therefore done by reference measurements using a manual method for DEM involving quantitative removal and CV-AFS detection. DEM is then determined in the water sample by applying the partitioning factor. The optimised method is precise, sensitive and linear over a wide concentration range. It has provided comparable results with the manual method when applied on board a research vessel in the Mediterranean Sea (0.02–0.05 ng L^?1) and during a pilot laboratory-scale experiment on industrial aqueous media from wet flue gas desulphurisation (WFGD) equipment (2–300 ng L^?1).     

Triggered release of aqueous content from liposome-derived sol-gel nanocapsules

Liposomes prepared from a mixture of L-alpha-dipalmitoylphosphatidylcholine and the PEGilated phospholipid N-(carbonylmethoxypoly(ethylene glycol 2000))-1,2-distearoyl-sn-glycero-3-phosphoethanolamine were used as templates for the production of silica and alkylated silica approximately 100 nm capsules, "liposils", entrapping aqueous solutions of anionic dyes. Triggered release of this content was successfully affected by either low-frequency ultrasound or by microwave treatments. Cryo-TEM was used to follow the formation process of these particles, which are aggregated in a chain-like manner. A mechanism explaining this phenomenon is suggested.     

Sol–gel one-pot synthesis in soft conditions of mesoporous silica materials ready for drug delivery system

The present work reveals a new and simple strategy, a one-step sol–gel procedure, to encapsulate a low water-soluble drug in silica mesostructured microparticles and to improve its release in physiological media. The synthesis of these new materials is based on the efficient solubilisation of a poorly water-soluble drug in surfactant micelles (Tween 80, a pharmaceutical excipient) which act as template for the silica network. A strict control of the sol–gel process and the parameters procedure in soft conditions (concentration, pH, temperature) was applied to reach the solubilisation limit of the drug in the micellar solution so as to optimise its encapsulation. Even if this one-pot procedure could appear limited by the low drug loading, it could provide an interesting alternative for the formulation of many recent highly active but very poorly soluble drugs.