Comparison of Liquid–Liquid Extraction, Simultaneous Distillation Extraction, Ultrasound-Assisted Solvent Extraction, and Headspace Solid-Phase Microextraction for the Determination of Volatile Compounds in Jujube Extract by Gas Chromatography/Mass Spectrometry

Abstract

Jujube extract has a unique flavor that has been used as a common fragrance due to the volatile compounds. In this study, the volatiles of jujube extract were isolated by liquid–liquid extraction, simultaneous distillation extraction, ultrasound-assisted solvent extraction, and headspace solid-phase microextraction, and analyzed by gas chromatography–mass spectrometry. Altogether 92 compounds were identified by the four methods, of which 53 components were identified for the first time; however, only 21 compounds were identified by all these methods. The performance characteristics of the four pretreatment techniques were compared by principal component analysis which showed that the volatile compounds obtained by liquid–liquid extraction and ultrasound-assisted solvent extraction were similar both in categories and in content; whereas, the volatiles extracted by simultaneous distillation extraction, ultrasound-assisted solvent extraction, and headspace solid-phase microextraction greatly varied. The results indicated that a multi-pretreatment technique should be adopted in order to obtain the most complete information about the volatile compounds in jujube extract. The ultrasound-assisted solvent extraction method exhibited excellent repeatability and recoveries, and was very suitable for quantitative analysis. Although the recoveries and reproducibility of headspace solid-phase microextraction were inferior to the other methods, it was more sensitive than other methods.

Keywords:

• Jujube extract
• Liquid–liquid extraction
• Simultaneous distillation extraction
• Ultrasound-assisted solvent extraction
• Headspace solid-phase microextraction
• Gas chromatography–mass spectrometry

Notes

^{a, b, c, d} Different lower-case letters in the same row indicated the significant differences by one-way ANOVA (P < 0.05).

^e RT: Retention Time.

^f Each compound was identified based on the following criteria: MS, mass spectrum was identical with that in NIST mass spectral database; S, injection of the standard compounds on the same column under the same condition; RI, matching the retention indices that reported in the literatures.

Linear retention indices were calculated on DB-WAXetr.

^h Percentage amount of volatile compounds calculated on the basis of chromatographic peak areas.

ⁱ http://www.taytonn.com/index.php/products/viewer/all.

http://www.fao.org/food/food-safety-quality/scientific-advice/jecfa/jecfa-additives/en/.

http://www.flavornet.org/flavornet.html.

— concentrations of the compounds studied was so low that it exceeded the linear ranges.

^a The numbers of compounds are in accordance with Table 2.

Re-L: the spiked recoveries of low spiking level (50); RSD-L: the RSD of 50 spiked recoveries.

Re-M: the spiked recoveries of middle spiking level (100); RSD-M: the RSD of 100 spiked recoveries.

Re-H: the spiked recoveries of high spiking level (200); RSD-H: the RSD of 200 spiked recoveries.