A derivative UV spectrophotometric method for the determination of levothyroxine sodium in tablets

A derivative UV (D-UV) spectrophotometric method was developed for the determination of Levothyroxine Sodium (L-T₄) in tablets of different doses. Quantification was performed using the second derivative of the absorption spectrum at 253 nm (²D₂₅₃) in methanol: water (50: 50; v/v) (pH 11.2). The method was validated and compared with an HPLC procedure carried out using a RP-18 column (125 × 4 mm, 5 μm) and methanol: phosphoric acid (0.1%) (70: 30, v/v) (pH 3) as mobile phase. Flow rate was set at 1.5 mL/min, and detection was performed at 225 nm. The proposed D-UV method was linear in the range 3.0–40.0 μg/mL with an appropriate precision and accuracy, and it was selective for the drug under study. On the other hand, results obtained by ²D₂₅₃ analysis were similar to those obtained by HPLC, with no statistically significant differences between them. Therefore, it was concluded that the developed method is suitable for the determination of L-T₄ in tablets at the tested doses.     

SYNTHESIS,IDENTIFICATION AND SURFACE ACTIVITY OF 2-AMINE-2-DEOXY-3-O-n-OCTYL-D-GLUCOPYRANOSE HYDROCHLORIDE

The synthesis and identification of this product are described. Variations of surface tension of its aqueous solutions versus concentration (ranged between 3 and 95 mmol/L) and temperature (ranged between 20.0 and 47.5°C) are studied.

The isothermal plots of surface tension versus the logarithm of the concentration show a continous decrease, with a sharp change of slope at a concentration about 6.5 mmol/L, for all the studied temperatures. A second change of slope, less pronounced, appears for a higher concentration. This concentration value increases from 28 to 42 mmol/L when temperature is raised from 20.0 to 47.5°C.

The changes of slope can be attributed mainly to micellization of neutral amine molecules resulting from hydrolysis of surface active cations, which present a weak electrolytic character.     

A study of indoor radon in greenhouses in Mexico City, Mexico

Enclosed spaces in contact with soil, the main source of radon, like greenhouses have potentially high radon (²²²Rn) concentrations. Greenhouses are frequented by visitors and also are workplaces. The study of radon concentrations in greenhouses is, thus, a relevant concern for public health and environmental radiation authorities. For this study, the radon concentrations in 12 greenhouses in different locations within Mexico City were measured using nuclear track methodology. The detectors used for the study consisted of the well-known closed-end cup device, with CR-39 Lantrack^® as detector material. The measurements were carried out over a period of one year, divided into four three-month sub-periods. The lowest and highest annual mean radon concentrations found in individual greenhouses were 17.0 and 45.1 Bq/m³, respectively. The annual mean averaged over all 12 greenhouses was 27.3 Bq/m³. No significant seasonal variation was observed. Using the highest annual mean radon concentration found in an individual greenhouse, and an equilibrium factor of 0.4, the effective dose from ²²²Rn and its progenies was calculated to be 339.9 nSv/h. This corresponds to an annual dose rate of 679.8 μSv/y (0.057 WLM/y) for a worker spending 4 h a day, 5 days a week, 50 weeks a year, inside the greenhouse. For a visitor spending 12 h a year inside the greenhouse the annual dose is 2.469 μSv/y. The study of indoor radon concentrations in closed buildings such as greenhouses, which are both workplaces and open to visitors, is an important public health consideration.     

UCT-Kirchberg algebras have nuclear dimension one

We prove that every Kirchberg algebra in the UCT class has nuclear dimension 1. We first show that Kirchberg 2-graph algebras with trivial _K0$K_0$ and finite _K1$K_1$ have nuclear dimension 1 by adapting a technique developed by Winter and Zacharias for Cuntz algebras. We then prove that every Kirchberg algebra in the UCT class is a direct limit of 2-graph algebras to obtain our main theorem.     

Phosphatidylcholine‐Coated Iron Oxide Nanomicelles for In Vivo Prolonged Circulation Time with an Antibiofouling Protein Corona

We report the synthesis of micellar phosphatidylcholine‐coated superparamagnetic iron oxide nanoparticles as a new long circulation contrast agents for magnetic resonance imaging. Oleic acid‐coated Fe₃O₄ nanoparticles were first prepared through thermal degradation and then encapsulated into small clusters with a phosphatidylcholine coating to obtain hydrophilic nanomicelles. A thorough characterization confirmed the chemical nature of the coating and the excellent colloidal stability of these nanomicelles in aqueous media. Magnetization and relaxivity properties proved their suitability as magnetic resonance imaging (MRI) contrast agent and in vitro cell viability data showed low toxicity. Vascular lifetime and elimination kinetics in the liver were assessed by blood relaxometry and by in vivo MRI in rats and compared with “control” particles prepared with a polyethylene glycol derivative. These micellar particles had a lifetime in blood of more than 10 h, much longer than the control nanoparticles (≈2 h), which is remarkable considering that the coating molecule is a small biocompatible zwitterionic phospholipid. The protein corona was characterized after incubation with rat serum at different times by high‐throughput proteomics, showing a higher proportion of bound apolipoproteins and other dysopsonins for the phosphatidylcholine particles. The antibiofouling properties of this corona and its resistance to the adsorption of proteins corroborate the observed enhanced stability and prolonged systemic circulation.