•DTNS-based ratiometric immunosensor is brought for vegetables phoxim detection.•Three-dimensional DTNS is self-assembled with flexibly-designed ssDNA sequences.•DTNS-based functionalization is ...certified as a better MB carrier than other rivals.•Active m-Ab is vertically and evenly bonded on DTNS vertex, improving phoxim signal.•This method is confidently proven with real-analysis and certified HPLC.
A ratiometric electrochemical immunosensor, based on DNA tetrahedron nanostructure (DTNS), is introduced for vegetable phoxim determination. DTNS spontaneously adheres onto gold-nanoparticle-modified electrode and forms stable three-dimensional structure, providing plenty of binding sites to the built-in reference, methylene blue (MB). Monoclonal antibody (m-Ab) is vertically linked onto DTNS vertex, selectively responses antigenic phoxim, and promotes the target signal of IPHO. Thus, a ratiometric indicator, IPHO/IMB, is sensibly established with the target signal (IPHO) and the reference signal (IMB). Modifications, mechanisms and advances of the proposed method are subsequently examined with morphological methods and electrochemical experiments. This method brings considerable advances in analytical behaviors. The ratiometric signal presents better performance than solo system in repeatability and long-time stability. As-fabricated sensor presents wide dynamic range as 0.1∼30 μg/L, and limit of detection is well defined as 0.003 μg/L (S/N = 3). Finally, this method is verified with real-vegetable-sample analysis, certified HPLC and recovery test.
In this work, a new microextraction approach termed as vortex-assisted liquid phase microextraction based on deep eutectic solvent (VALPME-DES) combined with graphite furnace atomic absorption ...spectrometry (GFAAS) has been developed for the extraction, preconcentration and determination of potentially toxic elements (PTEs) in vegetables and soil samples irrigated with treated sewage from two different regions of Iran. The new DES was prepared by mixing a 1:1 molar ratio of choline chloride and citric acid monohydrate. Some effective parameters on extraction were studied and optimised. Under the optimum conditions, the repeatability and reproducibility of the VALPME-DES coupled with ETAAS for 5.0 µg L
−1
of As(III) and 0.50 µg L
−1
of Pb and Cd were determined to be 2.7-4.3 and 3.8-6.2%, respectively. The correlation coefficient (r
2
) of the calibration curves was in the range of 0.995-0.998. The limit of detections was in the range of 0.03 and 0.1 µg kg
−1
for different metal ions. Linear range of 0.3 − 100 µg kg
−1
for As(III) and, 0.03-200 µg kg
−1
for Cd and Pb were obtained. The results showed among the target metals, the highest impact on the total value of non-carcinogenic risk was related to arsenic. Furthermore, the non-carcinogenic risk value for all vegetable types was lower than the permitted level. We also found that the risk of arsenic carcinogenicity was higher than the acceptable levels in all four types of vegetables. According to the findings, interventions to reduce arsenic should be used, especially in cultivated soils.
•A GC–(APCI) MS/MS quantitative method has been developed for 142 pesticides.•Validation was performed using orange, tomato and carrot samples.•SRM method includes the quasi-molecular ion as ...precursor for most compounds.•The new APCI source coupled to GC allowed reaching high sensitivity and selectivity.•LODs in the range 0.01–1μg/kg were obtained for most compounds.
A multi-residue method for the determination of 142 pesticide residues in fruits and vegetables has been developed using a new atmospheric pressure chemical ionization (APCI) source for coupling gas chromatography (GC) to tandem mass spectrometry (MS). Selected reaction monitoring (SRM) mode has been applied, acquiring three transitions for each compound. In contrast to the extensive fragmentation typically obtained in classical electron ionization (EI), the soft APCI ionization allowed the selection of highly abundant protonated molecules (M+H+) as precursor ions for most compounds. This was favorable for both sensitivity and selectivity. Validation of the method was performed in which both quantitative and qualitative parameters were assessed using orange, tomato and carrot samples spiked at two levels, 0.01 and 0.1mg/kg. The QuEChERS method was used for sample preparation, followed by a 10-fold dilution of the final acetonitrile extract with a mixture of hexane and acetone. Recovery and precision were satisfactory in the three matrices, at both concentration levels. Very low limits of detection (down 0.01μg/kg for the most sensitive compounds) were achieved. Ion ratios were consistent and identification according to EU criteria was possible in 80% (0.01mg/kg) to 96% (0.1mg/kg) of the pesticide/matrix combinations. The method was applied to the analysis of various fruits and vegetables from the Mediterranean region of Spain.
A zirconium(IV)‐based metal organic framework, composed of 4,4′‐biphenyldicarboxylic acid ligands and Zr6O4(OH)4 clusters, was successfully fabricated. Characterizations were performed on fourier ...transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller, and thermogravimetric analysis, which confirmed that it possessed large specific surface area, high pore volume, and strong acid resistant stability. Furthermore, the prepared material containing biphenyl skeleton and a large number of Zr‐O bonds, can grasp acid herbicides especially phenoxyacetic acid herbicides with aromatic structures through π‐π interaction, hydrophobic interaction and Zr‐O‐H+ bonds. Based on these advantages, a method was developed for the determination of four phenoxyacetic acid herbicides from vegetable samples. Under the optimal conditions, wide linearities from 0.3 to 250 μg/L and low limits of detection from 0.1 to 0.5 μg/L were obtained. The intra‐ and interday relative standard deviations were 1.56‐3.92 and 5.01‐7.65%, respectively. The proposed method was applied to analyze phenoxyacetic acid herbicides residues in the tomato, cucumber, and white gourd samples. The satisfactory recoveries (86.12–103.44%) for the spiked samples in vegetable samples were achieved which demonstrated the method was an efficient pretreatment procedure and has a potential application for the trace determination of phenoxyacetic acids from a complex matrix.
Fruits and vegetables play an important role in human nutrition. Study of the contamination sources which result from farming activities is of importance. For this reason, a chitosan-graphene oxide ...nanocomposite film was prepared and implemented as the extractive phase in thin film microextraction of six organophosphate residues (OPPs) in the samples using high-performance liquid chromatography. The optimized method was validated and the limits of detection (0.7-1.2 µg l
), limits of quantification (2.3-4.0 µg l
) and linear dynamic range (2.0-1000.0 µg l
) were obtained. Principal component analysis revealed clustering of the fruit and vegetable samples based on the selected (OPPs) into two groups of unwashed-unpeeled and peeled-washed. This mapping was further investigated using descriptive method of boxplot. Washing and peeling of the samples, reduced the presence of OPPs to half or one third of interquartile range found in the unpeeled and unwashed samples.
Folate deficiency is a prevalent phenomenon worldwide especially in underprivileged countries. Polyglutamyl 5-methyltetrahydrofolate (5MTHF) species are the naturally occurring principle folate in ...store-bought vegetables. Here we report a simple and complete extraction method for the determination of native polyglutamyl 5-methyltetrahydrofolate in vegetables using high performance liquid chromatography with tandem mass spectrometric detection (HPLC–MS/MS). Coarsely chopped samples (18 different vegetables) were steamed to inactivate glutamylase enzymes and liberate folate from binding proteins and extracted in a reducing buffer with
13C
5 5MTHF stable isotope added as internal standard. The polyglutamyl 5-methyltetrahydrofolate species were separated in 9
min on a C
18 column using a reversed phase system. HPLC eluate was interfaced with a triple quadrupole mass spectrometer operated in electrospray positive mode. The respective pseudomolecular cation of each polyglutamyl 5-methyltetrahydrofolate species was selected for fragmentation to a common daughter ion for detection. We quantitated polyglutamyl 5-methyltetrahydrofolate in store-bought vegetables from families
Brassicaceae,
Asteraceae and
Amaranthaceae (including mustard greens, romaine lettuce and Swiss chard) of which most have not been quantitated previously. Most vegetables from
Asteraceae and those from
Amaranthaceae contained similar amounts of monoglutamyl 5MTHF and polyglutamyl 5MTHF while
Brassicaceae were dominated by polyglutamyls and endive species (
Asteraceae) contained mainly monoglutamyl 5MTHF. The precision of the method for the various polyglutamyl 5-methyltetrahydrofolate forms was 1–9% RSD, recovery 84–91%, limit of detection 64–658
fmol and limit of quantitation 193–1994
fmol. Herein we describe a rapid, sensitive and selective HPLC–MS/MS technique to quantitate polyglutamyl 5-methyltetrahydrofolate species. This method may be suitable for analyzing the polyglutamyl 5-methyltetrahydrofolate profile of inherent folates in a wide range of leafy green vegetables.
In this article, homogeneous liquid-liquid extraction (HOLLE), combined with HPLC-fluorescence detector (HPLC-FLD), has been developed for the extraction and determination of polycyclic aromatic ...hydrocarbons (PAHs) in vegetables. ACN was used as extraction solvent for the extraction of target analytes from vegetables. When the previous extraction process was over, the ACN extract was transferred to the water-immiscible organic phase, tetrachloroethane, used as extraction solvent in HOLLE procedures. Under the optimum conditions, repeatability was carried out by spiking PAHs at concentration level of 12.5 μg/kg, the RSDs varied between 1.1 and 8.5% (n = 3). The LODs, based on S/N of 3, ranged from 0.025 to 0.25 μg/kg. Relative recoveries of PAHs from cucumber and long crooked squash samples were in the range of 72.4-104.9% and 65.5-119.3%, respectively. Compared with the conventional extraction method, the proposed method has the advantage of being quick, easy to operate, and having low consumption of organic solvent.
This manual, to be published in two volumes, provides a condensed overview of the analytical investigation of 80 Chinese Herbal Drugs which are most frequently in use. Thin layer chromatographic-, ...high pressure liquid chromatographic- and gas chromatographic-fingerprint analytical techniques allow the detection of all main low-molecular constituents of a plant drug and even single constituents can be visualized. Analytical results thereof are shown in numerous color figures. The quality proof of the investigation meets the standard of the European Drug Regulatory Authority.Furthermore, this volume gives a detailed description of the analytical methods used for several drugs. Bioactive constituents, pharmacological and biological activities of several single herbal drugs as well as their therapeutic applications are discussed.
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