Lower Retention (lower + retention)

Distribution by Scientific Domains


Selected Abstracts


STABILITY OF ANTHOCYANINS, PHENOLS AND FREE RADICAL SCAVENGING ACTIVITY THROUGH SUGAR ADDITION DURING FROZEN STORAGE OF BLACKBERRIES

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2009
MIRELA KOPJAR
ABSTRACT Influence of sugar and mixtures of sugar on color retention of two varieties of blackberries, Thornfree and Cacanska bestrna, were investigated during storage at ,18C for 12 months. After harvest, blackberries were coated with sugars (sucrose, fructose and glucose) and different sugar (sucrose + fructose + glucose, fructose + glucose, fructose + sucrose) mixtures. Anthocynin content, total phenol content and free radical scavenging activity of prepared samples were evaluated. Ratio of fruit : sugar was 1:1. The highest anthocyanin retention was in blackberry samples with glucose addition and the lowest in samples with sucrose addition, in both cultivars. Blackberry samples with sucrose addition had even lower retention than samples without sugar addition. Samples with an addition of other sugars had higher retention of anthocyanin than samples stored without sugars. PRACTICAL APPLICATION Possibility of phenols retention of blackberries due to sugar addition, during cold storage was investigated. Results showed that glucose had the most positive effect on anthocyanins retention as well as total phenolic compounds content. For that reason, certain amount of sucrose in fruit preserves can be replaced by addition of glucose, and for that reason retention of phenolic compounds can be higher and, as could be expected, more effective against oxidative stress in human body due to intake of product formulation with glucose. [source]


Preparation and characterization of polymethacrylate monolithic capillary columns with dual hydrophilic interaction reversed-phase retention mechanism for polar compounds

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009
Urban
Abstract Monolithic columns for capillary hydrophilic interaction liquid chromatography (HILIC) were prepared in fused-silica capillaries by radical co-polymerization of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide and ethylene dimethacrylate in various binary and ternary porogen solvent mixtures with azobisisobutyronitrile as the initiator of the polymerization reaction. Columns showed mixed separation modes: reversed-phase (RP) in water-rich mobile phases and HILIC at high concentrations of acetonitrile (>60,80%) in aqueous,organic mobile phases. A continuous change in retention was observed at increasing concentration of water in acetonitrile, giving rise to characteristic U-turn plots of retention factors versus the concentration of water in the mobile phase, with minima corresponding to the transition between the mechanisms controlling the retention. The selectivity of organic polymer monolithic columns for HILIC separations can be varied by adjusting the concentration of sulfobetaine monomer and the composition of the porogen solvent in the polymerization mixture. Under HILIC conditions, the monolithic capillary sulfobetaine columns show separation selectivities for polar phenolic acids similar to those of a commercial silica-based sulfobetaine ZIC-HILIC column, which, however, has limited selectivity in the RP mode due to lower retention. [source]


The effects of curing cycles on properties of the epoxy system 3221/RH glass fabric composites

POLYMER COMPOSITES, Issue 4 2008
Hong Xuhui
In this work, the epoxy system 3221 and its glass fabric laminates were thermally cured under different curing temperatures. The curing degree of the resin was increased with elevated reaction temperature. Dynamic mechanical analysis was performed on the laminate coupons and glass transition temperature (Tg) and relative stiffness (E,) of composites were measured before and after soaked in distilled water at 70C. A shift in glass transition temperature to higher values and the splitting of the tan , curve were observed with extent of cure under dry conditions. Tg values shifted to lower temperatures after immersion. Under wet condition, the change in Tg1 was very small when the curing degree was up to 96%. The relative stiffness experienced a reduction both in initial modulus and the initial sharp drop temperature after immersion. It also suggested that the excessively high curing temperature (>130C) had a negative effect on the retention of relative stiffness under wet condition. Both the interlaminar shear strength and dielectric properties of laminates were determined before and after immersion. The compared results demonstrated that the elevated curing temperature played a good influence on both of the properties before aged. However, for samples cured above 130C, lower retention of interlaminar shear strength and poor dielectric properties were observed during immersion due to their higher moisture contents. POLYM. COMPOS., 2008. 2008 Society of Plastics Engineers [source]


Influence of the pore structure on the properties of silica based reversed phase packings for LC

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2005
Zoltan Szab
Abstract This paper describes the preparation and investigation of new, highly loaded, monomeric, silica based, reversed phase C18 and C30 packings. The influence of pore structure and endcapping on the properties of C18 and C30 packings is described. Using hydrothermal procedures, silicas with predictable pore size (9.3,25.5 nm) and surface area have been prepared. Silylation with long chain silanes substantially alters the pore structure of the silica: pore size and pore volume decrease. A new parameter, the volumetric surface coverage [mm3m,2] has been introduced. This parameter , calculated from on-column measured porosity data , indicates the pore volume portion occupied by the hydrocarbon chains. Endcapping does not significantly change the pore structure of the bonded phases. The reduced retentions (reduced with respect to unit area: [k/m2]) , a good measure for comparing the retention behaviour of packings with different surface areas , are similar for most of the phases, demonstrating good accessibility of the pores for the solutes. Slightly lower retentions were found on the endcapped than on the non-endcapped phases for probes with dense ,-electron system (e. g. polyaromatic hydrocarbons) demonstrating the contribution of silanophilic interactions to the retention. The phases had been successfully used for various demanding separations, e. g. for the separation of flavonoids, carotenoids, resveratrol, and tocopherol isomers, fullerenes, and anions. [source]