Research article Received: 10 September 2014,
Revised: 18 November 2014,
Accepted: 30 November 2014
Published online in Wiley Online Library: 21 January 2015
(wileyonlinelibrary.com) DOI 10.1002/bio.2835
Rapid determination of trace thiabendazole in apple juice utilizing dispersive liquid–liquid microextraction combined with fluorescence spectrophotometry Wei Li, Yuning Wang, Limin Huang, Ting Wu, Huilian Hu and Yiping Du* ABSTRACT: Food safety has become a large concern and prompts an urgent need for the development of rapid, simple and sensitive analytical methods that can monitor pesticide residues in foods. This study aimed to provide a method for quantitative determination of trace thiabendazole in apple juice. Due to its high sensitivity and selectivity, fluorescence spectrophotometry was utilized as a front end to dispersive liquid–liquid microextraction (DLLME). The experimental parameters that influenced the extraction were systematically investigated. Under optimum conditions, the whole procedure, including DLLME and analysis of one sample, was carried out within 5 min, and linearity was found in the 5–50 μg/L range with a correlation coefficient (r) of 0.9987. The limit of detection value was 2.2 μg/L. Good reproducibility was achieved based with a less than 4.5% relative standard deviation (RSD) for five replicates at different sample concentrations. This method was shown to be suitable for rapid and sensitive quantification of thiabendazole in apple juice. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: dispersive liquid–liquid microextraction (DLLME); fluorescence spectrophotometry; thiabendazole; quantitative analysis; rapid determination
Introduction
872
Thiabendazole (TBZ) is widely employed benzimidazole fungicide in agriculture for protection against, and eradication of, fungi that affect fruits and vegetables. European Union legislation has established the maximum residue limits (MRLs) for TBZ in raw fruits and vegetables in the 0.05–15 mg/kg range, depending upon the type of crop. Fruits and vegetables play important roles in a healthy diet, thus pesticide residues in these products may present a potential threat to human health and safety. Food safety has become a large concern and prompts an urgent need to develop rapid, simple and sensitive analytical methods to monitor trace pesticide residues in foods. The commonly used analytical methods for the analysis of TBZ are chromatographic techniques (1–4), immunochemical techniques (2,5,6) and spectrophotometric methods (2,7–9). However, the low concentration levels of TBZ in some samples and their complex matrix often increase the difficulty of direct determination with conventional methods. Sample preparation is needed to reduce or remove compounds initially present in samples that interfere with detection method and to concentrate low levels of analytes to facilitate their determination. Various pre-treatment methods, such as liquid–liquid extraction (LLE) (10), hollow-fiber liquid-phase microextraction (HF-LPME) (11,12), cloud point extraction (CPE) (13,14), single-drop microextraction (SDME) (15), solid-phase extraction (SPE) and solid-phase microextraction (SPME) (16–19) have been used for separation and preconcentration of TBZ from different samples. Regrettably, some of these methods are often time-consuming, and some are costly or complicated to some extent.
Luminescence 2015; 30: 872–877
Dispersive liquid–liquid microextraction (DLLME) was introduced as an efficient separation and enrichment technique in 2006 by Rezaee et al. (20). This method is based on the ternary-component solvent system that consists of extraction solvent, disperser solvent and an aqueous phase that contains analytes. In DLLME, the appropriate mixture of extraction solvent and disperser solvent is injected rapidly by syringe into the aqueous sample solution to disperse the extraction solvent as fine droplets. In this way, a cloudy solution is formed and the analytes transfer promptly from the aqueous solution into the extractant droplets. The dispersion is removed with the help of centrifugation. The major benefits of the DLLME method are simplicity of operation, rapidity, low extraction solvent volume, low cost, and high enrichment factor, all of which have made this technique widely adopted in various fields in recent years (21,22). As a simple and fast sample pre-treatment technique, DLLME has proved to be a suitable pre-concentration procedure for gas chromatography (GC) (20,23), high-pressure liquid
* Correspondence to: Yiping Du, Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, People’s Republic of China. E-mail: [email protected] Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, People’s Republic of China Abbreviations: MRL, maximum residue limits; RSD, relative standard deviations; SPE, solid-phase extraction.
Copyright © 2015 John Wiley & Sons, Ltd.
Rapid determination of TBZ in juice with DLLE-FL spectrophotometry chromatography (HPLC) (24–26), and atomic absorption spectrometry (AAS) (27,28) because of the small volume of the extraction phase. Conversely, DLLME combined with spectrophotometry as a subsequent detection method has potential difficulty, as
Revised: 18 November 2014,
Accepted: 30 November 2014
Published online in Wiley Online Library: 21 January 2015
(wileyonlinelibrary.com) DOI 10.1002/bio.2835
Rapid determination of trace thiabendazole in apple juice utilizing dispersive liquid–liquid microextraction combined with fluorescence spectrophotometry Wei Li, Yuning Wang, Limin Huang, Ting Wu, Huilian Hu and Yiping Du* ABSTRACT: Food safety has become a large concern and prompts an urgent need for the development of rapid, simple and sensitive analytical methods that can monitor pesticide residues in foods. This study aimed to provide a method for quantitative determination of trace thiabendazole in apple juice. Due to its high sensitivity and selectivity, fluorescence spectrophotometry was utilized as a front end to dispersive liquid–liquid microextraction (DLLME). The experimental parameters that influenced the extraction were systematically investigated. Under optimum conditions, the whole procedure, including DLLME and analysis of one sample, was carried out within 5 min, and linearity was found in the 5–50 μg/L range with a correlation coefficient (r) of 0.9987. The limit of detection value was 2.2 μg/L. Good reproducibility was achieved based with a less than 4.5% relative standard deviation (RSD) for five replicates at different sample concentrations. This method was shown to be suitable for rapid and sensitive quantification of thiabendazole in apple juice. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: dispersive liquid–liquid microextraction (DLLME); fluorescence spectrophotometry; thiabendazole; quantitative analysis; rapid determination
Introduction
872
Thiabendazole (TBZ) is widely employed benzimidazole fungicide in agriculture for protection against, and eradication of, fungi that affect fruits and vegetables. European Union legislation has established the maximum residue limits (MRLs) for TBZ in raw fruits and vegetables in the 0.05–15 mg/kg range, depending upon the type of crop. Fruits and vegetables play important roles in a healthy diet, thus pesticide residues in these products may present a potential threat to human health and safety. Food safety has become a large concern and prompts an urgent need to develop rapid, simple and sensitive analytical methods to monitor trace pesticide residues in foods. The commonly used analytical methods for the analysis of TBZ are chromatographic techniques (1–4), immunochemical techniques (2,5,6) and spectrophotometric methods (2,7–9). However, the low concentration levels of TBZ in some samples and their complex matrix often increase the difficulty of direct determination with conventional methods. Sample preparation is needed to reduce or remove compounds initially present in samples that interfere with detection method and to concentrate low levels of analytes to facilitate their determination. Various pre-treatment methods, such as liquid–liquid extraction (LLE) (10), hollow-fiber liquid-phase microextraction (HF-LPME) (11,12), cloud point extraction (CPE) (13,14), single-drop microextraction (SDME) (15), solid-phase extraction (SPE) and solid-phase microextraction (SPME) (16–19) have been used for separation and preconcentration of TBZ from different samples. Regrettably, some of these methods are often time-consuming, and some are costly or complicated to some extent.
Luminescence 2015; 30: 872–877
Dispersive liquid–liquid microextraction (DLLME) was introduced as an efficient separation and enrichment technique in 2006 by Rezaee et al. (20). This method is based on the ternary-component solvent system that consists of extraction solvent, disperser solvent and an aqueous phase that contains analytes. In DLLME, the appropriate mixture of extraction solvent and disperser solvent is injected rapidly by syringe into the aqueous sample solution to disperse the extraction solvent as fine droplets. In this way, a cloudy solution is formed and the analytes transfer promptly from the aqueous solution into the extractant droplets. The dispersion is removed with the help of centrifugation. The major benefits of the DLLME method are simplicity of operation, rapidity, low extraction solvent volume, low cost, and high enrichment factor, all of which have made this technique widely adopted in various fields in recent years (21,22). As a simple and fast sample pre-treatment technique, DLLME has proved to be a suitable pre-concentration procedure for gas chromatography (GC) (20,23), high-pressure liquid
* Correspondence to: Yiping Du, Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, People’s Republic of China. E-mail: [email protected] Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, People’s Republic of China Abbreviations: MRL, maximum residue limits; RSD, relative standard deviations; SPE, solid-phase extraction.
Copyright © 2015 John Wiley & Sons, Ltd.
Rapid determination of TBZ in juice with DLLE-FL spectrophotometry chromatography (HPLC) (24–26), and atomic absorption spectrometry (AAS) (27,28) because of the small volume of the extraction phase. Conversely, DLLME combined with spectrophotometry as a subsequent detection method has potential difficulty, as
