Application of liquid-phase microextraction to the analysis of plant and herbal samples

INTRODUCTION

The analysis of plant and herbal samples is a challenging task for analytical chemists due to the complexity of the matrix combined with the low concentration of analytes. In recent years different liquid-phase microextraction (LPME) techniques coupled with a variety of analytical equipment have been developed for the determination of both organic and inorganic analytes.

OBJECTIVE

Over the past few years, the number of research papers in this field has shown a markedly growing tendency. Therefore, the purpose of this review paper is to summarise and critically evaluate research articles focused on the application of LPME techniques for the analysis of plant and herbal samples.

RESULTS

Due to the complex nature of the samples, the direct application of LPME techniques to the analysis of plants has not often been done. LPME techniques as well as their modalities have been commonly applied in combination with other pretreatment techniques, including a solid-liquid extraction technique supported by mechanical agitation or auxiliary energies for plant analysis. Applications and the most important parameters are summarised in the tables.

CONCLUSION

This review summarises the application of the LPME procedure and shows the major benefits of LPME, such as the low volume of solvents used, high enrichment factor, simplicity of operation and wide selection of applicable detection techniques. We can expect further development of microextraction analytical methods that focus on direct sample analysis with the application of green extraction solvents while fully automating procedures for the analysis of plant materials.

Rapid Monitoring of Pharmacological Volatiles of Night-Flowering Evening-Primrose According to Flower Opening or Closing by Fast Gas Chromatography/Surface Acoustic Wave Sensor (Electronic zNose)

INTRODUCTION

Aroma is important in night-flowering species, as visually they can not be observed well. Thus, the analysis of the volatiles of evening-primrose is of great interest in biological fields and therapy. Furthermore, the analysis of volatiles demands rapid and simple procedure, because volatiles decompose.

OBJECTIVE

The aim of this study is to show the rapid monitoring of the volatiles of evening-primrose according to the flowering or closing by fast gas chromatography/surface acoustic wave GC/SAW. Moreover, calibration according to the sensor temperature of the GC/SAW was performed, achieving a high reproducibility and excellent sensitivity.

METHODOLOGY

GC/SAW is an effective analytical method that provides on-line measurements without pretreatment of sample. Headspace solid-phase micro-extraction coupled to gas chromatography mass spectrometry (HS-SPME-GC-MS) and dynamic headspace trapping and extraction with GC-MS were employed to confirm the identification of the volatiles of evening-primrose compared to GC/SAW.

RESULTS

Linalool was found to be the dominant component, comprising 96.4-25.2% of the total amount, according to the opening or closing. Interestingly, the amount of indole also varied according to the opening or closing (3.0-0.0%) such as linalool. Also, while the sensitivity increased with the reduction in the sensor temperature of the GC/SAW, the reproducibility showed a tendency to decrease.

CONCLUSION

The results showed that flower opening is related to the volatiles emission, which is pharmacological and plant defensive. GC/SAW can be a useful analytical method for the rapid monitoring of volatiles of evening-primrose according to the opening or closing as it provides second unit analysis, as well as simple, and aroma pattern recognition. Copyright © 2017 John Wiley & Sons, Ltd.

Headspace sampling of the volatile fraction of vegetable matrices

The evolution of vapour phase sampling of the volatile fraction of vegetable matrices, or of products directly related to them, over the period 1996-2007 is reviewed. High concentration capacity headspace (HCC-HS) and dynamic headspace (D-HS) techniques, that is headspace sampling approaches where the analytes in the vapour phase are concentrated into a sorbent, an adsorbent or a solvent, are considered. Advantages, disadvantages and applications to the vegetable field of several successful techniques based on these approaches are critically presented, including in-tube sorptive extraction (INCAT, HS-SPDE), headspace sorptive extraction (HSSE), solid-phase aroma concentrate extraction (SPACE), large surface area HCC-HS sampling (MESI, MME, HS-STE), headspace liquid-phase microextraction (HS-LPME) and dynamic headspace samplings (D-HS). The developments necessary to overcome some of the limits of the above approaches and techniques are also discussed in view of their application to new fields.