Elsevier

Talanta

Volume 206, 1 January 2020, 120181
Talanta

Novel nanofibrous sorbents for the extraction and determination of resveratrol in wine

https://doi.org/10.1016/j.talanta.2019.120181 Get rights and content

Highlights

  • Nanofibrous and microfibrous polymers were tested for on-line extraction.

  • Resveratrol was selectively extracted from red wine samples.

  • Composite nPVDF/μPCL showed better clean-up efficiency than C-18 sorbent.

  • Dopamine coated fibers featured an enhanced retention of polar impurities.

Abstract

On-line SPE HPLC method using nanofibrous sorbents for the extraction and determination of resveratrol in wine was developed and validated. Different types of nanofibrous and microfibrous polymers were tested and compared with commercial monolithic C18 sorbent. Polyamide and polyacrylonitrile nanofibers and composite materials composed of respective polycaprolactone and poly(vinylidene difluoride) nanofibers at microfibrous scaffold were included among tested materials. Two different polycaprolactone-based materials were prepared and their effect on the extraction properties studied. Alternatively, dopamine-coated polycaprolactone fibers were also used. Poly(vinylidene difluoride) nanofibers/polycaprolactone microfibers composite was found as the most effective sorbent and utilized for the method validation. Resveratrol in red wine was determined using our validated on-line SPE HPLC method.

Introduction

Polyphenolic compounds present in grapes have significant health benefits [1] since they possess antioxidant activity, which plays a role in preventing and repairing damage caused by oxidative stress. Resveratrol and its effects on human body were widely reported [[2], [3], [4]]. It has anti-inflammatory and antioxidant [3] as well as anticancer effects [5]. It helps to cure neurodegenerative processes, ischema reperfusion, and metabolic diseases [6,7]. These health-related properties led to development of a broad spectrum of analytical methods enabling determination of resveratrol in various products such as wine, berries, and grapes [8,9]. For example, some of these methods used direct injection of wine in absence of extraction procedure [[10], [11], [12]]. However, this simple approach decreased the sensitivity and selectivity of resveratrol determination in wine matrix. Most of the alternative analytical methods included sample pretreatment for matrix removal, and increase in selectivity and sensitivity. Among them, conventional procedures such as solid phase extraction (SPE) [13,14] and liquid-liquid extraction (LLE) [14,15] were favored. These time-consuming methods required multiple steps and often consumed large volume of organic solvents. Modern approaches such as solid phase microextraction (SPME) were also used [9]. For example, the miniaturized solvent-free SPME method can be used as an alternative to conventional sample pretreatment methods [16]. Yet, SPME is time-consuming and demands high operator skills. Vinas et al. published a paper in 2008 describing the determination of resveratrol in wines, musts, and juices that included SPME followed by HPLC [17]. They compared two techniques, SPME and stir bar extraction. The complete procedure including extraction and desorption required more than 40 min. Aresta et al. tested different types of SPME fibers. Their extraction procedure was 45 min long [9].

Recent trends in sample pretreatment focus on saving solvents, time, and operator skills. The on-line extraction methods meet these requirements. Several alternative extraction sorbents coupled on-line to SPE-HPLC currently exist including molecularly imprinted polymers, different types of polymers, monolithic columns, and nanofibrous materials. Only one paper describing the determination of resveratrol using the on-line SPE HPLC method was published. Its authors used the molecularly imprinted polymers for the extraction of resveratrol from the Polygonum Cuspidatum, a plant used in the traditional Chinese medicine [18]. To our best knowledge, no method describing the on-line extraction of resveratrol from red wine has been published. Table 1 summarizes the reported methods for the determination of resveratrol in wine using HPLC and classical off-line extraction.

In this report, we present a new on-line SPE-UHPLC method using different types of nanofibrous materials as sorbents for the determination of resveratrol in wine. The fibrous materials applied were polyamide 6 (PA6) and polyacrylonitrile (PAN) nanofibers, composite polycaprolactone nanofibers placed on polycaprolactone microfibrous scaffold (nPCL/μPCL), and poly(vinylidene difluoride) nanofibers on polycaprolactone microfibrous scaffold (nPVDF/μPCL). We also introduced a novel sorbent, dopamine-coated nPCL/μPCL (PCL-D). Results obtained with these fibrous sorbents were compared with a commercial C18 monolithic sorbent. Method using the fibers was most effective for sample clean-up and recovery. Finally, our method using nPVDF/μPCL composite material for on-line SPE was validated and applied to real-life samples - wines.

Section snippets

Chemicals and materials

All used chemicals are summarized in the supplementary materials (Section S1 - Chemicals, materials).

Instrumentation and software

The meltblown system (Laboratory equipment J&M Laboratories, USA) equipped with small needleless electrospinning was used for the preparation of the composite fibers. Detailed description of the process was published elsewhere [19]. A scheme of device is presented in supplementary material (Fig. S1). Production of nanofibers using electrospinning is green-marked while production of microfibers

Stability of the fibrous polymers in solvents

Long-term stress stability of all our micro/nanofibrous materials was explored before their use. The long-term stability was tested for 24 h at a temperature of 25 °C while the stress stability was tested for 15 min in an ultrasonic bath at a temperature of 35 °C. Detailed description of the procedures was published elsewhere [19,21]. PCL based sorbents were not stable in organic solvents at higher temperature. Therefore, the column oven temperature for the analysis was set to 20 °C.

Conclusion

Five types of nanofibrous or microfibrous polymers were tested and compared as sorbents for the on-line SPE-UHPLC extraction of resveratrol from red wines. Two different versions of the PCL were among the tested materials and their extraction properties were evaluated. Compared to nPVDF/μPCL and nPCL/μPCL polymers, dopamine coated fibers featured an enhancement in retention of polar impurities present in the red wines. nPVDF/μPCL exhibited a similar clean-up potential as nPCL/μPCL. However,

Acknowledgements

Financial support of the GACR project no. 17-08738S and EFSA-CDN project (No. CZ.02.1.01/0.0/0.0/16_019/0000841) co-funded by ERDF is gratefully acknowledged. M. H. acknowledges the financial support of specific research of Charles University no. SVV 260 412. The result was obtained through the financial support of the Ministry of Education, Youth and Sports of the Czech Republic and the European Union (European Structural and Investment Funds - Operational Program Research, Development and

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