High-throughput gas chromatography-mass spectrometry analysis of pesticide residues in spices by using the enhanced matrix removal-lipid and the sample dilution approach
Introduction
Spices are natural food additives which contribute to add flavor, color and aroma to processed or non-processed food. Volatile oils give the aroma and oleoresins impart the taste. In addition, spices have medicinal, pharmacological and nutritional properties. Spices are also excellent sources of phenolic compounds with good antioxidant activities. Because of the trend for a healthy living, the global demand for spices and herbs by the end-consumer and by the industries, that use spices as food additives for their processed product, is increasing. Asia-pacific region led by China and India are the main producers and exporters of spices and herbs. The USA market, followed by Europe, represents the largest trade markets of spice worldwide.
Like other agricultural products, spices and herbs may be contaminated by chemicals and pesticides. The use of pesticides is often a key requirement in ensuring safety and economic benefits. Pesticides should be applied in accordance with manufacturer’s recommendation and good agricultural practices, and their application must comply with existing national and/or EU legislations. The MRLs established by the EU for spices cover 190 pesticides. For pesticides with no established MRLs, a default limit of 0.01 mg kg− [1] is considered. Fig. 1 summarizes the MRLs set for spices. MRLs are equal or higher than 0.05 mg kg-1 for 75% of the compounds 1 (Fig. 1). The European Spice Association (ESA) has published a dehydration factor (DF) list for herbs and spices and is working to ensure that this principle is incorporated into the legislation. The DF of some foodstuffs have been established, e.g. basil (DF: 7), celery leaves (DF: 10), coriander leave (DF: 13). Accordingly, taking into consideration the concentration caused by the drying process for pesticide residue assessment, MRLs fixed by the regulation in case of dried spices, are multiplied by the dehydration factor [2]. By that, the final MRLs sound less rigorous.
Spices are classified as difficult or unique commodities according to DG SANTE/11813/2017 [3], due to the complex composition of the matrix. The most difficult matrices among spices are black pepper and cayenne pepper [4]. The main constituents of black pepper are volatile essential oils, oleoresin and piperine [5]. Piperine compounds are naturally occurring chemical compounds that contain mostly basic nitrogen atoms. Oleoresins are a naturally occurring combination of oil and resin. Therefore, for the analysis of pesticide residues in black pepper and other spices, the aim is the removal of oils, piperine, phenols, free amino-acids and starch from the final extract to avoid interferences of the analyte with the co-extractives compounds.
The reported extraction methods for pesticide residue analysis in spices were mainly based on modified QuEChERS with PSA [6,7] or excluding PSA [8,9], or even without a clean-up step [4,10] resulting in acceptable recoveries, but also resulting in moderate to strong signal suppression especially for black pepper. The removal of oils and piperine was also reported by SPE using Carb/NH2 cartridges [11], silica gel based cartridges [12], and Hydrophilic-Lipophilic Balance (HLB) cartridges [13]. Ethyl acetate method was also studied for the analysis of pesticide residues in spices, showing good performance regarding clean extracts and matrix effect, but the experiment was accompanied with lower recovery values compared to QuEChERS method [6]. Recently, a study assessing the possibility of adding a freezing out step to a modified QuEChERS extraction has been developed 10], resulting in low recoveries for some non-polar compounds (dodine, famoxadone, isoprocarb, isocarbophos, and trifloxystrobin). Another aspect to be considered in spices is the dryness of the commodity. Some of the studies included a 30 min soaking time in water before sample preparation facilitating pesticides´ extraction and allowing the obtaining of a finely homogenized sample [6,7], or just a quick water addition 10] or the addition of water saturated with acetonitrile [12].
Most of the studies reported were performed by LC–MS/MS [[7], [8], [9], [10],14], but recently due to the complexity of the matrix and with the availability of High Resolution Mass Spectrometry (HRMS), two of the studies were reported using LC-Orbitrap-MS 10,13]. The main advantage of accurate mass measurement is in displaying significantly lower background signals and consequently, higher signal to noise ratios (S/N) for the analytes of interest, reducing the amount of interference of background ions.
The aim of this work is to highlight the importance of reducing matrix interferences generated from co-extractive components of spices based on sample dilution approach for the analysis of pesticide residues by GC–MS/MS. Several aspects were considered for this aim, such as the sorbents used in the clean-up step, the dilution factor and the freezing-out step. For this purpose, several clean-up approaches were applied and compared: Z-Sep, enhanced matrix removal lipid (EMR-Lipid), HLB oasis prime cartridges, and Supelclean cartridges. The optimized extraction method was validated by GC–MS/MS and was applied to 50 real samples.
Section snippets
Reagents and materials
All pesticide standards of high purity were purchased from Sigma-Aldrich and LGC Standards and were stored at - 30 °C in dark conditions. Stock solutions were prepared in a suitable solvent (ethyl acetate or acetonitrile) at a concentration in the range of 1000–2000 mg L−1.
Ultra-gradient HPLC-grade acetonitrile was obtained from Merck. Anhydrous magnesium sulphate, sodium chloride and disodium hydrogencitrate sesquihydrate were supplied by Sigma-Aldrich. Trisodium citrate dihydrate was obtained
Extraction method selection
All the extracts had a yellowish color, but the intensity and the transparency of this color was less with the Supelclean SPE and the EMR-Lipid dispersive sorbent.
The TIC and recoveries were evaluated with Z-Sep, HLB, EMR-Lipid and Supelclean cartridges. PSA in not recommended for compounds that contain high oily compounds content. Recoveries weren’t studied with PSA, but only the TIC was evaluated. Moreover, EMR-Lipid was previously demonstrated to be effective when applied on fatty matrices
Conclusions
EMR-Lipid showed the best results among the tested clean-up methods. However, for the analysis of pesticide residues in complex matrices such as spices, despite the sorbent advantage, an additional sample dilution approach is a must. Sample dilution allows the reduction of the background signal and allows the improvement of the method performance in terms of recoveries and matrix effect. Additionally, the 25 times dilution of the final extract allows the decrease of instrument maintenance´s
Conflicts of interest
The authors declare no conflict of interest with any of the instruments or materials referred to in this work.
Acknowledgments
The authors acknowledge funding support from the European Commission, DG SANTE (Grant decision SI2.726352).
References (22)
- et al.
Optimization of multi-residue method for targeted screening and quantitation of 243 pesticide residues in cardamom (Elettaria cardamomum) by gas chromatography tandem mass spectrometry (GC-MS/MS) analysis
Chemosphere
(2018) - et al.
QuEChERS-based method for the determination of carbamate residues in aromatic herbs by UHPLC-MS/MS
Food Chem.
(2017) - et al.
A reliable screening of mycotoxins and pesticide residues in paprika using ultra-high performance liquid chromatography coupled to high resolution Orbitrap mass spectrometry
Food Control
(2016) - et al.
A rapid multi-residue method for pesticide residues determination in white and black pepper (Piper nigrum L.)
Food Control
(2013) - et al.
A simultaneous screening and quantitative method for the multiresidue analysis of pesticides in spices using ultra-high performance liquid chromatography-high resolution (Orbitrap) mass spectrometry
J. Chromatogr. A
(2018) - et al.
Evaluation of different cleanup sorbents for multiresidue pesticide analysis in fatty vegetable matrices by liquid chromatography tandem mass spectrometry
J. Chromatogr. A
(2016) - et al.
Large multiresidue analysis of pesticides in edible vegetable oils by using efficient solid-phase extraction sorbents based on quick, easy, cheap, effective, rugged and safe methodology followed by gas chromatography-tandem mass spectrometry
J. Chromatogr. A
(2016) - et al.
Determination of pesticides in edible oils by liquid chromatography-tandem mass spectrometry employing new generation materials for dispersive solid phase extraction clean-up
J. Chromatogr. A
(2016) - et al.
Evaluation of a recent product to remove lipids and other matrix co-extractives in the analysis of pesticide residues and environmental contaminants in foods
J. Chromatogr. A
(2016) EU Pesticides
(2018)
Report on dehydration factors recommendation for pesticide residues assessment on products of the spice industry
J. Consum Prot Food Saf
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