فقہی قاعدہ

The experts from various fields have maintained some rules and regulations in understanding and acquiring skills in this field of knowledge. This is due to their efforts which make very simple to understand it similarly the experts of ʽilm-ul-Fiqah i.e. Mujtahedyn and respected Fuqahāʼ have formulated some rules and regulations in the light of Qurʼan, Sunnah and decision act of companions of Muhammad (SAW) which also made it not only simple but it furnish skills and strategies in solving problems in field of Fiqah.

Applications of Succinate Linked Polysaccharides in Macromolecular Prodrug Design and Metal Sorpton

Polysaccharides especially cellulose and pullulan are currently receiving much attention for industrial applications. Present study reports the synthesis, characterization and application of three succinate bonded polysaccharides, i.e., succinylated hydroxypropylcellulose (HPC), hydroxyethylcellulose (HEC) and pullulan. For macromolecular prodrug design, hydroxypropylcellulose-succinic anhydride (HPC-SAn) conjugate was synthesized by applying homogeneous conditions and HPC–SAn conjugate so formed was further attached to salicylic acid (SA) drug through covalent linkage by using ZrOCl2.8H2O as a catalyst for esterification. The resulting HPC-SAn-SA conjugate was subjected to multiple crosslinking using oxalyl chloride as cross-linking agent. The resultant cross-linked prodrug (CL-HPC-SAn-SA conjugate) was characterized using different spectroscopic techniques. UV/Vis analysis of the HPC-SAn-SA conjugate has indicated that it contains 26 mg of SA per 100 mg of CL-HPC-SAn-SA. CL-HPC-SAn-SA showed reasonably good swelling properties in water and at different physiological pH values (6.8 and 7.4). Kinetic studies revealed that CL-HPC-SAnSA followed second order swelling kinetics. Additionally, the CL-HPC-SAn-SA conjugate showed stimuli responsive (pH 7.4/1.2) swelling-deswelling properties. It was found by thermal analysis that CL-HPC-SAn-SA was thermally more stable compared to pure SA. These crosslinked prodrugs obtained after multiple crosslinking of drugs with polysaccharides may find their applications in the field of medicines and pharmaceutics. The second part of the study deals with the use of succinylated polysaccharides for metal sorption. For this purpose, Pull-Suc and HEC-Suc were synthesized applying homogeneous reaction by the esterification of pullulan and HEC with succinic anhydride in the presence of dimethyl amino pyridine (DMAP) as a catalyst. These conjugates were then converted into their sodic forms, i.e., Pull-Suc-Na and HEC-Suc-Na by alkaline treatment using saturated NaHCO3 solution. These novel sorbents were characterized using different spectroscopic techniques such as FT-IR, solidstate CP/MAS 13C NMR and thermal analysis. The Pull-Suc-Na and HEC-Suc-Na were then used for heavy metal removal from aqueous solution. The pHs corresponding to zero point charge of both sorbents were determined. A model study for the removal of Cd(II) from distilled water (DW) and spiked high-hardness groundwater (GW) by these chemically modified pullulan and HEC was conducted. Effect of contact time (5-120 min) and pH (2-8) on Cd-uptake by sorbents (Pull-Suc-Na and HEC-Suc-Na) was investigated. Sorption data was subjected to different kinetic and isotherm models but pseudo second order kinetic and Langmuir isotherm model provided the best fit to the experimental data. Maximum sorption capacities calculated by Langmuir model were found to be 476.2 mg g-1 from DW and 454.5 mg g-1 from GW by Pull-Suc-Na and 669.0 mg g-1 from DW and 630.0 mg g-1 from GW by HEC-Suc-Na. Such high values for removal of Cd(II) from GW suggest selectivity of these sorbents for removal of Cd in the presence of alkaline earth metal cation naturally presence in GW. Both the sorbents showed negligible decrease in Cd-uptake over five regeneration cycles suggesting their repeated use. Afterwards, both sorbents Pull-Suc-Na and HEC-Suc-Na were used to sorb Pb(II), Cr(VI), Co(III), Cu(II) and Ni(II) ions from aqueous solution by batch wise methodologies. The effects of initial metal concentration, sorbent dosage, contact time, pH and temperature were investigated. The data at optimized conditions was subjected to isotherm analyses. Langmuir isotherm and pseudo second order kinetic model provided the best fit to the experimental data of sorption of metal ions. Maximum sorption capacities of Pb(II), Cr(VI), Co(III), Cu(II) and Ni(II) from aqueous solution as calculated by Langmuir isotherm model were found to be 1000, 909.1, 625.0, 588.0 and 500.0 mg g-1, respectively by HEC-Suc-Na and 714.3, 588.2, 416.6, 357.1 and 250.0 mg g-1, respectively by Pull-Suc-Na. The negative values of ∆G° and ∆H° indicated spontaneity and exothermic nature of sorption. In order to simulate the real conditions, i.e., to prepare mediums containing heavy metal ions altogether, competitive sorption of these metal ions by the both sorbents was carried out. Results of competitive sorption reveal that the sorption capacities of Pb(II), Cr(VI), Cd(II), Ni(II) Co(VI) and Cu(VI) are in the order Pb(II) ˃ Cr(VI) ˃ Cd(II) ˃ Ni(II) ˃ Co(II) ˃ Cu(VI) for both HEC-Suc-Na and Pull-Suc-Na.