Simultaneous Ultrasound-Assisted Emulsification−Extraction of Polar and Nonpolar Compounds from Solid Plant Samples

Abstract

A new approach to solid sample preparation for the simultaneous isolation of polar and nonpolar compounds using a microemulsion as leaching medium is proposed. Methanol/water (dispersed-phase)-hexane (continuous-phase) emulsions formed in the presence of ultrasound and a solid sample allow polar and nonpolar compounds to be transferred to the dispersed and continuous phase, respectively. The efficiency of this dual sample preparation approach was assessed in the characterization of natural products of variable hardness including acorns, grape seeds, and alperujo (a residue of olive oil production). The time needed for quantitative extraction of the target fractions (phenol compounds and fatty acids) is 9 min for acorns and alperujo and 20 min for grape seeds; the longer time needed for grape seeds can be attributed to higher matrix hardness. Such good performance can be ascribed to the ultrasound-enhanced formation of methanol/water microdroplets 1-15 microm in size, which act as solid-liquid microextractors spanning a large surface area. The presence of the sample was found to greatly improve emulsion stability, which can be ascribed to the amphiphilic nature of the fatty acids in the samples. Following leaching and separation of the two phases by centrifugation, the polar and nonpolar fractions were analyzed by HPLC-diode array detection and GC/MS, respectively. The proposed approach provides extraction efficiency similar to the Folch method (reference method for fat extraction, 4.5 h) in a shorter time and extraction efficiency equal to or higher than the stirring-based method (reference method for phenol compounds extraction, 24 h).

LC Determination of Trace Biogenic Amines in Foods Samples with Fluorescence Detection and MS Identification

“…However, their presence in excessive amounts may induce several health disorders such as nausea, respiratory discomfort, hot flushes, cold sweat, palpitations, headaches, red rash, hyper/hypo tension, etc. [5]. The determination of biogenic amines in foods is of great interest not only due to their toxicity, but also because they can be a good indication of the freshness of food.…”

Simultaneous determination of serotonin and creatinine in urine by combining two ultrasound‐assisted emulsification microextractions with on‐column stacking in capillary electrophoresis

“…To achieve high enrichment factors, reduce the consumption of organic solvents, and provide efficient coupling with the small injection volume used in CE, liquid-phase microextraction (LPME) in the three-phase mode has been employed for sample pretreatment [24,25]. Either in single drop or in hollow fiber mode, three-phase microextraction requires a prolonged extraction time, typically 30 min to 1 h. Recently, dispersive microextraction such as ultrasound-assisted emulsification microextraction (USAEME) has been applied to recover target analytes from complex matrices [26][27][28]. During analyte extraction process, the small droplets formed by emulsification act as micro-extractors with greatly enhanced surface area to accelerate mass transfer and improve enrichment.…”

Ultrasound-assisted emulsification microextraction of trace amounts of Co and Mn ions prior to flame atomic absorption spectrometry

“…26,27 They also successfully applied ultrasound-assisted emulsification (USAE) for the first time to determine some polar and non-polar compounds in solid plant samples. 28 High extraction efficiency in a short period of time is the main advantage of USALLE. Regueiro et al, 29 applied a miniaturized approach to USALLE by using a micro volume of organic phase to provide the advantage of both DLLME and USALLE.…”