Dispersive Solid Phase Extraction for In-Sorbent Surface Attenuated Total Reflection Infrared Detection

The combination of dispersive solid phase extraction (DSPE) and attenuated total reflection (ATR) infrared spectroscopy is presented using the joint determination of sorbic and benzoic acids in juice samples as a model analytical problem. The dispersive extraction process allows the selective extraction of the target analytes from the sample matrix allowing their preconcentration prior to their infrared detection. The extraction efficiency is improved compared to the conventional procedures since the interaction between sorbent and analytes is favored with the stirring process. Moreover, the extracted analytes are directly determined in the sorbent. As no elution step is required, analyte dilutions and consumption of organic solvents are avoided. The proposed approach has been qualitative and quantitative studied. The hierarchical cluster analysis permits the sample classification according to the relative concentration of the analytes. The precision of the quantitative analysis was better than 6% with analyte recoveries in the range 87-90%. The proposed method was applied to the analysis of different commercial fruit juice samples. Finally, the main advantages and limitations of the new proposal are presented and compared with existing alternatives.