环保型酸式自动滴定管的研制与应用

介绍了一种环保型酸式自动滴定管的结构、特点及使用方法。这种滴定管节省试剂,废液排放量极小,操作简单、省时,克服了常规微量滴定管精密度差、装液难、零点和滴定终点不易控制的缺点。通过数理统计方法,将环保型酸式自动滴定管与标称容量为50mL的常规酸式滴定管平行测定结果进行了比较,试验证明,该滴定分析的精密度、准确度不仅与50mL常规酸式滴定管相当,而且操作性还优于50mL常规酸式滴定管。     

Residual aqueous ozone determination by gas diffusion reverse flow injection analysis

A novel system based on reverse flow injection analysis with a gaseous diffusion step (GD-r-FIA) has been developed for the analysis of ozone. It includes an automatic microburet injection system. The ozone diffuses through a microporous membrane of polyvinylidene difluoride (PVDF) from the donor stream to the acceptor stream containing nitrite ions. The nitrite concentration in the acceptor solution decreases due to the ozone reduction reaction. In this way, a simple indirect measurement of the ozone concentration can be performed using the Griess–Ilosvay reaction for the nitrite ion. This correlates with the decrease in absorbance of the azoic dye formed with the ozone concentration in the donor stream. The system has been optimised by investigating the effect of the nitrite concentration in the acceptor stream on the diffusion flow. The optimum nitrite concentration was set at 0.250 ppm with a flow rate of 1.5 ml/min. The efficiency of the ozone diffusion through the membrane was only 4.4%. This affects the average sensitivity, which is low (0.0092±0.0012 AU/ppm), although the detection limit is similar to that obtained with other reported methods (0.03 ppm). The main advantage of the system reported here is that it has a linear range that is an order of magnitude broader than those observed for other GD-FIA systems. This is especially useful for continuous monitoring systems, since the residual ozone concentration is normally between 0.05 and 5.0 ppm. Additionally, using the reverse flow injection analysis (FIA) technique minimises chemical consumption and residue generation. Finally, the stability of the ozone solution and the repeatability and reproducibility of the method have been studied.     

Temporal ratiometry to assess dynamic concentration distributions of fluorescent molecules in single live cells during continuous diffusional dosing

The introduction of specific molecules into live cells is a widely used approach to probe cellular mechanisms. Recently, we have reported on the sustained dosing of molecules into single cells via a microscopic diffusion port. Here we describe temporal ratiometry, a method to reconstruct intracellular concentration distribution of the delivered molecules as it varies in time during dosing. To characterize this method, we analyzed fluorescence intensity maps obtained during delivery of Lucifer Yellow CH, LY, a polar fluorophore into A7r5 vascular smooth muscle cells, normal rat kidney epithelial cells (NRKE), and MCF-7 human breast cancer cells. Temporal ratiometry indicates a linear increase in concentration of LY in these cells with a nearly uniform distribution during 20 min of delivery. The method cancels the effects of varying cell height and variable accessible volume on the measured intensities at different locations within the cell. Temporal ratiometry will be useful to estimate dynamic changes in intracellular concentration distributions and thus, facilitate the understanding of transport, binding, sequestration, and efflux of molecules introduced into cells.     

Insights into the Self-Filling Effects of Branched Isopropyl Groups on the Conformational and Supramolecular Properties of Isopropoxyprism[6]arene

In this work, the direct macrocyclization of a prism[6]arene macrocycle bearing branched alkyl chains on the rims is reported. Isopropoxyprism[6]arene adopts in solution and in the solid state a cuboid D₂-conformation in which four isopropyl groups are folded inside the cavity, to give C−H⋅⋅⋅π interactions and filling the internal void. The conformational features of isopropoxyprism[6]arene have been studied by dynamic ¹H NMR experiments. The presence of branched isopropyl chains on the prism[6]arene rims, stabilizes the cuboid D₂-conformation to a greater extent than ethyl or propyl groups in PrS[6]^Et and PrS[6]^nPr. The higher resistance of PrS[6]^iPr to open its cuboid D₂ conformation, with respect to PrS[6]^Et and PrS[6]^nPr, also affected its binding abilities. In fact, alkylammonium-based endo-cavity complexes of PrS[6]^iPr show lower binding constant values than the analogous propoxy/ethoxy-prism[6]arene complexes.