Primary alcohol-induced coacervation in alkyl polyglucoside micellar solution for supramolecular solvent-based microextraction and chromatographic determination of phthalates in baby food

This study reports for the first time the phenomenon of supramolecular solvent formation based on alkyl polyglucoside as an amphiphile and primary alcohol as a coacervation agent. The physical properties (density, kinematic viscosity, phase diagram for ternary system) of the supramolecular solvent were investigated, and a mechanism for its formation was proposed. A green and simple microextraction procedure for preconcentration and determination of phthalates in baby foods packaged in plastic packaging was developed as proof-of-concept example. The microextraction procedure assumed separation of analytes from solid phase sample in micellar solution of decyl glucoside and in situ formation of supramolecular solvent for analytes preconcentration after addition of n-heptanol. The determination of phthalates in obtained extracts was implemented by high-performance liquid chromatography with UV-Vis detection. The limits of detection, calculated from a blank test based on 3σ, were determined to be 10 μg kg-1 for dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, and di-n-octyl phthalate. The developed procedure did not require filtration of sample suspension, and assumed the use of green and biodegradable substances for the supramolecular solvent formation across a wide pH range.

Development and validation of an ultra high performance liquid chromatography-tandem mass spectrometry method for the determination of phthalate esters in Greek grape marc spirits

An Ultra High Performance Liquid Chromatography - Tandem Mass Spectrometry method has been developed for the analysis of 12 phthalate esters in Greek grape marc spirits. The phthalates were separated on a U-VDSpher PUR 100 C18-E (100 mm x 2.0 mm, 1.8 μm) column by gradient elution. The analytes were ionized by positive electrospray ionization using the multiple reaction monitoring mode. The standard addition method was used for quantification and the Student's t-test was carried out to evaluate the matrix effect. The accuracy of the method was assessed by recovery experiments resulting in values from 81.6 to 109.6%. The detection limits ranged from 0.3 to 33.3 μg L^-1.The proposed method was validated and successfully applied to the analysis of 45 samples collected from Greece and Cyprus. All phthalate esters proved to be present at least once in the analysed grape marc spirits samples, except only in cases of diphenyl phthalate and diisodecyl phthalate, while for the regulated phthalates only bis (2-ethylhexyl) phthalate was quantified above the legislative concentration limits.

Unusual stacking with electrokinetic injection of cationic analytes from micellar solutions in capillary zone electrophoresis

Electrokinetic injection (EKI) in capillary zone electrophoresis (CZE) of charged analytes is by the electroosmotic flow (EOF) and electrophoretic mobility of analytes. In most forms of stacking with EKI, the sample ions were introduced via electrophoretic mobility and concentrated in a stacking boundary inside the capillary. In this work, we describe the unusual stacking of cationic analytes via EKI of sodium dodecyl sulfate (SDS) micelles into a fused silica capillary filled with acidic background solution (BGS) with 40-50 % acetonitrile. The analytes prepared with SDS micelles were injected because of their interaction with micelles or effective electrophoretic mobility. We observed two peaks from an analyte, and this suggested the concentration of analytes into two stacking zones. These two adjacent stacking zones were surprisingly maintained inside the capillary during EKI although the EOF was moving towards the inlet. The zones were identified as the SDS micelles (micelles zone) and organic solvent-rich stacking zone (solvent-rich zone) where the micelles zone was closer to the inlet end of capillary. The analytes concentrated in the solvent-rich zone through the mechanism of micelle to solvent stacking (MSS). The concentrated analytes in the micelles zone were from the concentrated analytes that electrophoretically migrated into the micelles zone from the solvent-rich zone during EKI. The analytes in the micelles zone were then re-stacked by MSS and formed the second sharp peak in CZE. This was prevented by reduction of acetonitrile concentration in the inlet BGS. A sensitivity enhancement factor of more than 100 was obtained for model cationic drugs (diphenhydramine and imipramine).