Imrich Sebestian

Preparation and properties of reversed phases

Abstract The preparation of monomeric reversed phases (RPs) with C1-C18 alkyl groups are described. Methods for checking the quality of RPs are discussed. The retentions of polar and non-polar samples were found to be influenced by the eluent, the length of the organic “bristle”, the carbon content of the RP, the pore size distribution of the silica support and the total porosity of the stationary phase. The efficiency is a function of (among other factors) the composition of the eluent, the capacity ratio, the length of the bristle, the sieve fraction and the packing density. The maximum sample size is 10 times greater than that with silica and increases with increasing carbon content of the RP. The speed of analysis increases with decreasing length of the bristle. The mechanism of sorption procedures should be discussed with extreme caution after the quality of the RP has been defined.

Optimization of reversed-phase separations☆

Abstract The influence of the eluent composition on the retentions of samples achieved with reversed phases (RP), including tailing, is discussed. An “eluotropic series” for RP is proposed. Analogies between the retention orders in liquid chromatography with RP and in gas chromatography with graphitized carbon black are pointed out. The separations of ten mixtures important in routine work are described.

Stationäre phasen mit SiN bindung für die flügkeitschromatographie

Abstract SiN bonded stationary phases for liquid chromatography The preparation of SiN bonded stationary phases for high-pressure liquid chromatography on the surface of silica with a specific surface area of 370 m2/g is described. The organic part of the stationary phase has a monomeric structure. In order to “modify” the selectivity to a required value, one or more functional groups, such as −COOH, −SO3H, −NH2, −CN or −NO2, are introduced into the aliphatic chain. The spatial requirement of the organic “bristles” varies between 55 and 400 A2. Peak broadening, capacity ratios and mass transfer terms were determined in the linear velocity range 0.5–10 cm/sec with n-heptane, methanol and water as eluents. The change in the relative retention as a function of the eluent and of the functional groups is discussed.

Neuartige kationenaustauscher auf kieselgelbasis : I. Darstellung und eigenschaften

Abstract New types of cation exchanger based on silica gel. I. Preparation and properties The preparation and the properties of cation exchangers based on silica gel chemically modified with alkyl groups (“brushes” with  SiC  bond) are described. A maximum exchange capacity with a minimum cleavage of the  SiC  bond was achieved after sulfochloration by a gas—solid reaction. The exchange capacity depends on the specific surface of the silica gel carrier (250 μequiv./g with 300 m2/g). The cation exchangers are stable against high pressure, and neither swell nor shrink. The bed volume is independent of the pH value and the ionic strength is independent of the eluent. The exchangers are stable in the pH range 0–8; their temperature stability is excellent.