Modeling the effects of type and concentration of organic modifiers, column type and chemical structure of analytes on the retention in reversed phase liquid chromatography using a single model

A previously proposed model for representing the retention factor (k) of an analyte in mixed solvent mobile phases was extended to calculate the k of different analytes with respect to the nature of analyte, organic modifier, its concentration and type of the stationary phase. The accuracy of the proposed method was evaluated by calculating mean percentage deviation (MPD) as accuracy criterion. The predicted vs. observed plots were also provided as goodness of fit criteria. The developed model prediction capability compared with a number of previous models (i.e. LSER, general LSER and Oscik equation) through MPD and fitting plots. The proposed method provided acceptable predictions with the advantage of modeling the effects of organic modifiers, mobile phase compositions, columns and analytes using a single equation. The accuracy of developed model was checked using the one column and one analyte out cross validation analyses and the results showed that the developed model was able to predict the unknown analyte retention and the analytes retentions on unknown column accurately.     

Mathematical Representation of Fluorescence Intensity of Probes in Aqueous Binary Solvent Mixtures

Fluorescence intensities of propranolol and atenolol in binary solvent mixtures at various temperatures are measured and mathematical models are proposed to represent the fluorescence intensity data. The results showed that the proposed models are able to correlate/predict the data with reasonable error. The fluorescence intensity of pyridoxal HCl in binary solvents at 25 °C is also determined and represented by the proposed model as an additional test probe.     

Aldehyde Oxidase Activity and Stability in Water-Miscible Organic Solvents

In this study, the catalytic activity of aldehyde oxidase was investigated in various water-miscible organic solvents for the first time. The enzyme was partially purified from rabbit liver, and its activity was determined in the absence/presence of nine hydro-organic mixtures. The effects of pH and temperature on the enzyme activity were also investigated. The activity was reduced in the presence of all nine organic solvents. However, in some cases, the residual activity remained almost unchanged throughout the incubation of enzyme at 35 °C for 24 h. Considering potential advantages of doing reactions in the presence of organic solvents, these results could be of value. The enzyme showed different behavior in the reaction solutions making it difficult to formulate results in a single comprehensive model. The results indicated that binding and cleavage of the substrate are influenced in the presence of organic solvents.     

Discrimination of Saffron Based on Thin-Layer Chromatography and Image Analysis

JPC – Journal of Planar Chromatography – Modern TLC - This paper presents a new method based on thin-layer chromato-graphic separation, and image analysis (TLC-IA) of saffron colorant...     

Solubility of Ketoconazole in Polyethylene Glycol 200 + Water Mixtures at 298.2–318.2 K

The solubility of ketoconazole in binary mixtures of polyethylene glycol 200 (PEG 200) + water is reported at temperatures ranging from 298.2 to 318.2 K. The Jouyban–Acree model and its combined version including the van’t Hoff equation were used for correlating the reported data; the obtained mean relative deviations are 9.5 and 9.9 %, respectively. Also, two previously trained versions of the Jouyban–Acree model were used for predicting the reported data points in which the prediction errors were 34.6 and 31.0 %.     

Nickel-aluminum layered double hydroxide as a nano-sorbent for the solid phase extraction of selenium, and its determination by continuous flow HG-AAS

We have used a nano-structured nickel-aluminum layered double hydroxide (Ni-Al LDH) for the extraction of trace levels of selenium prior to its determination by continuous-flow hydride generation atomic absorption spectrometry. Extraction is based on the adsorption of Se(IV) anions on the Ni-Al-nitrate LDH, and/or their exchange with the nitrate anions in the LDH interlayer. The effects of pH value, amount of nanosorbent, eluent type and concentration, sample volume and flow rate were optimized. No appreciable matrix effects were observed. Under optimum conditions, the limit of detection (defined as three times the standard deviation of the blank signal divided by the slope of the calibration plot) is 10 pg?mL^?1, and the relative standard deviation is 2.8 %. The sorption capacity and preconcentration factor are 10 mg?g^?1 and 33, respectively. The method was successfully applied to the determination of Se(IV) in tap water, river water, well water, wastewater and oyster tissue (certified reference material, CRM 1566b).

Comments concerning “Study of solute–solvent and solvent–solvent interactions in pure and mixed binary solvents”

A number of mathematical equations representing the solute solubility in monosolvent and binary solvent mixtures are discussed. This work is a commentary to the article of Maitra and Baghchi that appeared in this journal.     

Solution thermodynamics and preferential solvation of triclocarban in {1,4-dioxane (1) + water (2)} mixtures at 298.15 K

The equilibrium solubility and preferential solvation of triclocarban in {1,4-dioxane (1) + water (2)} mixtures at 298.15 K was reported. Mole fraction solubility varies continuously from 2.85 × 10^–9 in neat water to 2.39 × 10^–3 in neat 1,4-dioxane. Solubility behaviour was adequately correlated by means of the Jouyban-Acree model. Based on the inverse Kirkwood-Buff integrals, preferential solvation parameters were calculated. Triclocarban is preferentially solvated by water in water-rich mixtures (0.00 < x₁ < 0.18) and also in 1,4-dioxane-rich mixtures (0.78 < x₁ < 1.00) but preferentially solvated by 1,4-dioxane in mixtures with similar solvent compositions.     

Equilibrium solubility,preferential solvation and apparent specific volume of sucrose in some {cosolvent (1) + water (2)} mixtures at 298.2 K

Sucrose is the most widely used sweetener in food and pharmaceuticals. Solubility data of this excipient in aqueous cosolvent mixtures is not abundant. Thus, the main objective of this research was to determine and correlate the equilibrium solubility of sucrose in some {cosolvent (1) + water (2)} mixtures at 298.2 K. Cosolvents were ethanol, propylene glycol and glycerol. Shaken flask method was used to determine isothermal solubility. Concentration measurements were performed by means of density determinations. Solubility of sucrose decreases non-linearly with the addition of cosolvent to water. By means of the inverse Kirkwood–Buff method it is shown that sucrose is preferentially solvated by cosolvent in water-rich mixtures but preferentially solvated by water in cosolvent-rich mixtures. Jouyban–Acree model correlates solubility values with the mixtures composition for all cosolvent systems. Moreover, apparent specific volume of sucrose was also calculated from density and compositions.