Integrated system for temperature-controlled fast protein liquid chromatography comprising improved copolymer modified beaded agarose adsorbents and a travelling cooling zone reactor arrangement

An integrated approach to temperature-controlled chromatography, involving copolymer modified agarose adsorbents and a novel travelling cooling zone reactor (TCZR) arrangement, is described. Sepharose CL6B was transformed into a thermoresponsive cation exchange adsorbent (thermoCEX) in four synthetic steps: (i) epichlorohydrin activation; (ii) amine capping; (iii) 4,4′-azobis(4-cyanovaleric acid) immobilization; and ‘graft from’ polymerization of poly(N-isopropylacrylamide-co-N-tert-butylacrylamide-co-acrylic acid-co- N,N′-methylenebisacrylamide). FT-IR, 1H NMR, gravimetry and chemical assays allowed precise determination of the adsorbent’s copolymer composition and loading, and identified the initial epoxy activation step as a critical determinant of ‘on-support’ copolymer loading, and in turn, protein binding performance. In batch binding studies with lactoferrin, thermoCEX’s binding affinity and maximum adsorption capacity rose smoothly with temperature increase from 20 to 50 ºC. In temperature shifting chromatography experiments employing thermoCEX in thermally-jacketed columns, 44 – 51% of the lactoferrin adsorbed at 42 ºC could be desorbed under binding conditions by cooling the column to 22 ºC, but the elution peaks exhibited strong tailing. To more fully exploit the potential of thermoresponsive chromatography adsorbents, a new column arrangement, the TCZR, was developed. In TCZR chromatography, a narrow discrete cooling zone (special assembly of copper blocks and Peltier elements) is moved along a bespoke fixed-bed separation columnfilled with stationary phase. In tests with thermoCEX, it was possible to recover 65% of the lactoferrin bound at 35 ºC using 8 successive movements of the cooling zone at a velocity of 0.1 mm/s; over half of the recovered protein was eluted in the first peak in more concentrated form than in the feed. Intra-particle diffusion of desorbed protein out of the support pores, and the ratio between the velocities of the cooling zone and mobile phase were identified as the main parameters affecting TCZR performance. In contrast to conventional systems, which rely on cooling the 3 whole column to effect elution and permit only batch-wise operation, TCZR chromatography generates sharp concentrated elution peaks without tailing effects and appears ideally suited for continuous operation

Passivation of Hydrated Cement

Interface phenomena are the starting point for every corrosion reaction. In this work, the corrosion of calcium–silicate–hydrate (C–S–H) phases by water is investigated by implementing silicon wafers as substrates. The carbonation of these phases was avoided by synthesizing the samples in a controlled atmosphere. The passivation of these mineral surfaces is a significant step for materials sustainability. The coating of the surfaces with four different molecules is presented here: carbonation, sodium silicate layers, tetraethyl orthosilicates (TEOS), and octadecylphosphonic acid (ODPA) monolayers. The performance of every technique against corrosion by water is evaluated by infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, water contact angle, and pH measurements. Since the concentration of protons in water is the relevant parameter in this corrosion process, three different values were analyzed at the experiments. After comparing the passivation techniques, the results obtained by coating with ODPA are the most promising ones, and it is, therefore, applied to a more realistic model: hydrated cement. The passivation by ODPA is then analyzed to unravel the mechanism of hydrophobization, finding its dependence with the Ca/Si ratio of the surfaces, supported by first-principles calculations. The passivation by applying this kind of molecule is very promising because of its efficiency against water corrosion and due to the easiness of preparation of the surface before its application