PubMed · 15710921
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Malvinder S Parmar. 2005-02-15. Treating C. difficile.. https://doi.org/10.1503/cmaj.1041195
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Graft polymerization using potassium diperiodatocuprate as initiator was found to be an effective and convenient method for grafting functional polymer of N,N-dimethylaminoethyl methacrylate (DMAEMA) onto superporous polyacrylamide gels, so-called cryogels (pAAm cryogels). It was possible to achieve grafting degrees up to 110% (w/w). The two-step graft polymerization i.e. first activation of the matrix followed by displacement of initiator solution with the monomer solution, decreased pronouncedly the soluble homopolymer formation. The efficiency of graft polymerization using a two-step technique increased up to 50% (w/w) at a monomer conversion of 10%, compared to 10% graft efficiency with 60-70% monomer conversion for one-step direct graft polymerization. The pAAm cryogels grafted in one-step and two-step procedures, respectively, behaved similarly when binding low-molecular weight ligand but showed very different behavior for sorption of a high-molecular-weight ligand, bovine serum albumin (BSA). The differences in behavior were rationalized assuming different structure of the graft polymer layers and tentacle-type BSA binding to the grafted polymer.
Tobramycin is one of a class of aminoglycoside antibiotics that lack a good chromophore, and is therefore difficult to determine using reversed-phase HPLC with absorbance detection. This is especially true for determining the quantity of each impurity. We show that tobramycin and its major impurities, including kanamycin B and neamine (neomycin A), can be separated on a strong anion-exchange column using a weak potassium hydroxide eluent (2.00 mM) at a column temperature of 30 degrees C, and directly detected by integrated pulsed amperometric detection (IPAD). The resolution (United States Pharmacopeia (USP) definition) between tobramycin and kanamycin B ranged from 5.71 and 6.06 over 7 days of consecutive analysis (5.92+/-0.07, n = 590 injections). Due to the difficulty of producing weak hydroxide eluents of the required purity (i.e. carbonate-free), this method depends on automatic eluent generation to ensure method ruggedness. This method exhibited good long-term (50 days, 2368 injections) retention time stability with R.S.D.s of 0.4% and 0.3% for tobramycin and kanamycin B, respectively. Peak area R.S.D.s for tobramycin and kanamycin B (10 microM each, 20 microL injection) over 7 days (572 injections) were 2.3% and 1.9%, respectively. Method robustness was evaluated by intentionally varying the flow rate, eluent concentration, column temperature, and column. Based on the results of these evaluations, this method can be used for tobramycin identity, assay, and purity.
The focus of this work has been the study of Cr(VI) removal from ground waters and the simultaneous concentration for its reuse using three different technological alternatives: anion-exchange resins, liquid-liquid extraction assisted by hollow fibre membranes and emulsion pertraction. The viability of the considered objectives, i.e., Cr(VI) separation (<0.5 g/m3) and concentration for reuse (>20,000 g/m3) has been checked and a comparative analysis of the three technologies has been performed. Although the flexibility and ease of operation of non-dispersive solvent extraction, anion-exchange resins and emulsion pertraction lead to higher velocities of chromium removal, yet still maintaining similar concentration efficiencies.