Spectrophotometric determination of tellurium in trace quantities by use of an ion-association complex.
The formation of an ion-association complex by the interaction of iodotellurate(IV) with cetyltrimethylammonium bromide is used as the basis of an extractive procedure to determine tellurium in the range 2.5-12.5 mug in a final aqueous phase volume of 20 ml. The method is simple, reliable and sensitive. Selectivity is achieved by separation of tellurium on aluminium hydroxide as collector.
Selective and sensitive liquid-liquid extraction and spectrophotometric determination of tellurium(IV) using sulfur containing reagent
Abstract A simple strategy is developed for the extractive spectrophotometric determination of tellurium(IV) by using sulfur containing reagent, 4-(4'-chlorobenzylideneimino)-3-methyl-5-mercapto-1, 2, 4-triazole (CBIMMT). The [tellurium(IV)-CBIMMT] complex quantitatively extracted in dichloromethane from 3 mol L−1 of hydrobromic acid medium. The 1:2 [tellurium (IV)-CBIMMT] orange coloured complex has λmax 423 and 494 nm and stable for more than 48 h. The extracted complex have molar absorptivity 0.6686 × 104 L mol−1 cm−1 and 0.4274 × 104 L mol−1cm−1 while Sandell's sensitivity is 0.01908 µg cm−2 and 0.03115 µg cm−2 at 423 nm and 494 nm is respectively. The system adheres to Beer's law upto 20 µg mL−1 at both wavelengths; however Ringbom's plot suggests optimum concentration range is 7.0–12.5 µg mL−1 and 8.0–14.5 µg mL−1 at 423 and 494 nm respectively. The limit of detection of the method is 0.15 µg mL−1. The method has been applied for analysis of environmental and real samples.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.