Ashequl Alam Rana

Chemical Characteristics of Hydroxyapatite fromOyster Shell by Thermo-Chemical Process

Oyster shell is basically made of calcium carbonate. An attempt is made to convert calcium carbonate of oyster shell to hydroxyapatite (HA), a substitute material for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. In the present work, hydroxyapatite (HA) was successfully synthesized by wet precipitation method using Ca (NO3)2, and (NH4)2HPO4, and NH4OH as starting materials. The oyster shell was found to decompose within 10000C to all the carbonate phases. The calcined oyster shells were then treated with acids followed by different chemicals in ammoniacal media maintaining proper stoichiometry to produce fine hydroxyapatite (HA) as filter cake with a Ca/P molar ratio of 1.67. The dried HA powder was extremely pure. Different characterization techniques were adopted both for calcined oyster shell and HA by scanning electron microscopy (SEM), X-ray diffractometer (XRD), fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analyzer (TGA). The absorption bands corresponding to phosphate and hydroxyl functional group which are characteristics of hydroxyapatite were confirmed by FTIR. Besides its effectiveness in bone substitution, the prepared HA holds great potential in the field of dental application.

Effect of High Density Poly (Vinyl Octadecanoate) Grafted Silica Stationary Phase on Physiochemical Properties and Shape Selectivity Enhancement of Polycyclic Aromatic Hydrocarbons (PAHs) in RP-HPLC

High dense Poly (vinyl octadecanoate) grafted silica stationary phase (Sil-from-VOD) have been prepared by radical chain-transfer “grafting from” approach. Another Poly (vinyl octadecanoate) grafted silica stationary phase (Sil-to-VOD) was prepared by conventional one-step telomerization (“grafting to”) method. Both phases were characterized qualitatively and quantitatively. Thermogravimetric analysis and elemental analysis data showed that Sil-from-VOD have higher grafting density as compared with Sil-to-VOD. A combination of DRIFT-IR, 13C CP/MAS NMR and 29Si CP/MAS NMR revealed that Sil-from-VOD have more transconformation than Sil-to-VOD while suspended-state1H NMR proved that Sil-from-VOD was less mobile than Sil-to-VOD. Both phases along with a commercial ODS column (ODS-p) were applied to RP-HPLC and evaluated by PAHs as solutes. Sil-from-VOD, prepared by “grafting from” approach and having high density provided better retentivity and selectivity for PAHs compared to other reference columns.