Response surface methodology (RSM) to evaluate both the extraction of triterpenes and sterols from jackfruit seed with supercritical CO and the biological activity of the extracts.

Jackfruit seeds are an underestimate residue having important biological activity such as anti-inflammatory, cytotoxicity and antimicrobial effects. However few researches have been done for this material using alternative extraction technologies, so this study aimed to evaluate the extraction of triterpenes and sterols from jackfruit seed by applying high- and low-pressure techniques. Response surface methodology (RSM) was used to determine the best conditions of pressure, temperature and CO flow rate for extraction with supercritical CO.

Dissolution of adhesive resins present in plastic waste to recover polyolefin by sink-float separation processes.

This study investigated the dissolution of adhesive resins present in polyolefin films that cause plastic materials to adhere to each other. The process of dissolution was made by the use of ethyl acetate and followed by separation through the sink-float process. The objective was to separate and characterize polyolefin films from plastic solid waste derived from recycled post-consumer paper.

Robust estimation of thermodynamic parameters (ΔH, ΔS and ΔCp) for prediction of retention time in gas chromatography - Part I (Theoretical).

An approach that is commonly used for calculating the retention time of a compound in GC departs from the thermodynamic properties ΔH, ΔS and ΔCp of phase change (from mobile to stationary). Such properties can be estimated by using experimental retention time data, which results in a non-linear regression problem for non-isothermal temperature programs. As shown in this work, the surface of the objective function (approximation error criterion) on the basis of thermodynamic parameters can be divided into three clearly defined regions, and solely in one of them there is a possibility for the global optimum to be found.

Robust estimation of thermodynamic parameters (ΔH, ΔS and ΔCp) for prediction of retention time in gas chromatography - Part II (Application).

For this work, an analysis of parameter estimation for the retention factor in GC model was performed, considering two different criteria: sum of square error, and maximum error in absolute value; relevant statistics are described for each case. The main contribution of this work is the implementation of an initialization scheme (specialized) for the estimated parameters, which features fast convergence (low computational time) and is based on knowledge of the surface of the error criterion. In an application to a series of alkanes, specialized initialization resulted in significant reduction to the number of evaluations of the objective function (reducing computational time) in the parameter estimation.

Fast and accurate numerical method for predicting gas chromatography retention time.

Predictive modeling for gas chromatography compound retention depends on the retention factor (ki) and on the flow of the mobile phase. Thus, different approaches for determining an analyte ki in column chromatography have been developed. The main one is based on the thermodynamic properties of the component and on the characteristics of the stationary phase.