Selective detection of fluoride based on a pyridinium n-phenolate-calix[4]pyrrole displacement assay: an undergraduate laboratory experiment

A two-step experiment is proposed for a third year class in experimental organic chemistry. Over a period of five weeks, the students synthesized calix[4]pyrrole, a receptor that is highly selective for fluoride, and a pyridinium N-phenolate dye. Subsequently, the students used the synthesized compounds to investigate a displacement assay on the basis of the competition in acetonitrile between fluoride and the dye for calix[4]pyrrole. The experiment increased the students' skills in organic synthesis and in the characterization of organic compounds, provided a very attractive and accessible illustration of important supramolecular phenomena, and allowed the study of a chromogenic chemosensor.

BIOFILMS BASED ON CANIHUA FLOUR (Chenopodium Pallidicaule): DESIGN AND CHARACTERIZATION

This work aims to (1) produce and characterize the flour obtained from two varieties of canihua, cupi and illpa-inia, and (2) evaluate the ability of these flours to form biofilms. The flours produced contain proteins, starches, lipids, organic substances containing phenol groups, and high percentages of unsaturated fatty acids. Films produced from the illpa variety presented lower water vapor permeability and larger Young’s modulus values than the films formed from the cupi variety. Both films were yellowish and displayed a high light blocking ability (as compared with polyethylene films), which can be attributed to the presence of phenolic compounds. Furthermore, they showed lesser solubility and water permeability than other polysaccharide films, which may be the result of the higher protein (12%–13.8%) and lipid (11%) contents in canihua flours, as well as the formation of a larger number of S–S bonds. On the other hand, these films presented a single vitreous transition temperature at low temperatures (< 0 °C), crystallization of the A and Vh types, and an additional diffraction peak at 2 = 7.5º, ascribed to the presence of essential fatty acids in canihua flour. Canihua flour can form films with adequate properties and shows promise for potential applications in food packaging, because it acts as a good barrier to incident ultraviolet light.

NOVEL SUPERABSORBENT HYDROGEL COMPOSITE BASED ON POLY(ACRYLAMIDE-CO-ACRYLATE)/NONTRONITE: CHARACTERIZATION AND SWELLING PERFORMANCE

A novel superabsorbent hydrogel (SH) composite based on a poly(acrylamide-co-acrylate) matrix filled with nontronite (NONT), a Fe(III)-rich member of the smectite group of clay minerals, is described in this manuscript. A variety of techniques, including FTIR, XRD, TGA, and SEM/EDX, were utilized to characterize this original composite. Experimental data confirmed the SH composite formation and suggested NONT was completely dispersed in the polymeric matrix. Additionally, NONT improved the water uptake capacity of the final material, which exhibited fast absorption, low sensitivity to the presence of salt, high water retention and a pH sensitive properties. These preliminary data showed that the original SH composite prepared here possesses highly attractive properties for applications in areas such as the agriculture field, particularly as a soil conditioner.

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1887 (A12).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1885 (A10).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1876/01 (A2,N1).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1880 (A6).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1877 (A3).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1888 (A13).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1886 (A11).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1889 (A14).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1879 (A5).

Gazette archéologique : recueil de monuments pour servir à la connaissance et à l'histoire de l'art antique / publié par les soins de J. de Witte,... et François Lenormant,... [et Robert de Lasteyrie,...]

1884 (A9).

PREDICTING THE BOILING POINT OF PCDD/Fs BY THE QSPR METHOD BASED ON THE MOLECULAR DISTANCE-EDGE VECTOR INDEX

The quantitative structure property relationship (QSPR) for the boiling point (Tb) of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was investigated. The molecular distance-edge vector (MDEV) index was used as the structural descriptor. The quantitative relationship between the MDEV index and Tb was modeled by using multivariate linear regression (MLR) and artificial neural network (ANN), respectively. Leave-one-out cross validation and external validation were carried out to assess the prediction performance of the models developed. For the MLR method, the prediction root mean square relative error (RMSRE) of leave-one-out cross validation and external validation was 1.77 and 1.23, respectively. For the ANN method, the prediction RMSRE of leave-one-out cross validation and external validation was 1.65 and 1.16, respectively. A quantitative relationship between the MDEV index and Tb of PCDD/Fs was demonstrated. Both MLR and ANN are practicable for modeling this relationship. The MLR model and ANN model developed can be used to predict the Tb of PCDD/Fs. Thus, the Tb of each PCDD/F was predicted by the developed models.