The possibility of regulating the retention and selectivity of monoalkyl- and polymethyl-substituted aromatic hydrocarbons in normal-phase high-performance liquid chromatography was investigated by modifying the non-polar (hexane) mobile phase with halide derivatives of hydrocarbons. Dichloromethane, chloroform, carbon tetrachloride and ethyl bromide were employed as modifiers. The decrease in ...

The gas-liquid chromatographic retention times on 0.5% SP-525 for 48 bile acids and related compounds as their methyl ester acetate derivatives are given. Ion tables for electron impact spectra have been compiled that permit direct access to ion structures for any given ion mass. Chemical ionization yields highly simplified mass spectra with two or three ions predominating for each compound. Wh...

A four-step strategy is described which is aimed at optimizing the separation parameters of the chromatographic fingerprint of herbal medicines. In the optimization procedure, a model is built to predict the retention time of components. The proposed model shows good retention prediction potency with an average relative deviation of 1.78%. The grid search method is used in optimizing gradient p...

Within the spectrum of current applications for cell culture technologies, efficient large-scale mammalian cell production processes are typically carried out in stirred fed-batch or perfusion bioreactors. The specific aspects of each individual process that can be considered when determining the method of choice are presented. A major challenge for perfusion reactor design and operation is the...

Six types of weight changes that occur when food is cooked by different methods are described. For five of these types, true retentions of nutrients (defined as calculations based on nutrient content of known weights of food before and after cooking) were compared with apparent retentions (defined as calculations based on nutrient content of moisture-free raw and cooked foods). Comparisons incl...

This study investigates the effects of attraction, retention, and incentive objectives on business unit pay strategy. Economic and psychological theories argue that differences in compensation objectives should lead to variations in organizations’ pay strategies, including decisions regarding the level of pay relative to its labor market and the emphasis on different compensation elements. Howe...

Reversed-phase ultrahigh-performance liquid chromatography (RP-UHPLC) method using two 15cm sub-2μm particles octadecylsilica gel columns is developed with the goal to separate and unambiguously identify a large number of lipid species in biological samples. The identification is performed by the coupling with high-resolution tandem mass spectrometry (MS/MS) using quadrupole - time-of-flight (Q...

The timing of augmented information, either prior to or following a memory retrieval attempt has profound, and opposing, influences on immediate performance and retention. This effect was investigated in 2 experiments in which participants learned typographical symbols used to enter information into a personal data assistant. The effects of the spacing of the second of 2 repetitions (Experiment...