Rapid In Situ SERS Analysis of Pesticide Residues on Plant Surfaces Based on Micelle Extraction of Targets and Stabilization of Ag Nanoparticle Aggregates

A structure of polyurethane micelle/Ag nanoparticle (Ag NP) cluster was fabricated as surface-enhanced Raman scattering (SERS) substrate for in situ extracting organic compounds on the surface of different matrixes, in which polyurethane micelles acted as the host material to capture target molecules and stabilize nanoparticle cluster. This method provided stable aqueous suspensions of Ag NP cluster due to the amphiphilic properties of polyurethane. We demonstrated SERS-based in situ detection of pesticides on vegetables and fruit skin, by simply dropping polyurethane micelle/Ag NPs substrate on the sample surface where the target molecules could be detected without a previous elution and extracting. The obtained results showed that this polyurethane micelle/Ag NP cluster substrate had excellent SERS performance for pesticide molecules with ideal stability and reproducibility. With further optimization, the limit of detection of 0.03 μg/mL acetamiprid, 0.08 μg/mL phosmet, and 0.002 μg/mL thiabendazole was obtained, respectively.     

Fast Preconcentration of Pesticide Residues in Oilseeds by Combination of QuEChERS with Dispersive Liquid–Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

A fast, efficient, and simple method for determination of pesticide residues in pumpkin seeds has been developed combining QuEChERS and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography and mass spectrometry (GC-MS). Parameters affecting the DLLME performance such as solvent selection and volume of extractive and dispersive solvent, salt effect, and extraction time were studied. Under the selected conditions (50 μL extractive solvent chloroform, 1 mL QuEChERS extract, and 3 mL water), the developed method was validated. Linearity was evaluated at nine concentrations in the broad range of 0.1–500 μg/kg with correlation coefficients from 0.9842 to 0.9972. The relative standard deviations at lowest calibration level varied from 0.3 to 22 %. Under the optimum conditions, an enrichment factor was 6–17-fold and detection limits 0.01–12.17 μg/kg were achieved. Finally, the developed and validated method was successfully applied for the extraction and determination of pesticide residues in 16 real samples with 2 positive findings below maximum residue limits (MRL). Limits of detection (LODs) of the proposed method are below the MRLs established by the European Union.     

高效液相色谱法检测粮油中黄曲霉毒素方法验证

该文报道验证同时检测粮食、植物油中黄曲霉毒素B1、B2、G1和G2的免疫亲和柱净化-柱后光化学衍生-高效液相色谱方法.样品经甲醇-水(体积比为70∶30)提取,通过免疫亲和柱富集和净化,采用Cloversil C18色谱柱(4.6mm×150 mm,粒度5μm),以甲醇:水(50∶50)溶液为流动相,柱后光化学衍生,利...     

Graphene Oxide-Reinforced Hollow Fiber Solid-Phase Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Cephalosporins in Milk Samples

An effective and sensitive method to determine six cephalosporins (cefadroxil, cephapirin sodium, cefixime, cefuroxime sodium, cefoxitin sodium, and ceftiofur hydrochloride) in milk samples was developed using graphene oxide-reinforced hollow fiber solid-phase microextraction (GO-HF-SPME). After extraction, analytes were desorbed and analyzed using high-performance liquid chromatography-photodiode array detection (HPLC-PDA). The graphene oxide (GO) was dispersed in N,N-dimethyl formamide by ultrasonication and then immobilized into the pores of a hollow fiber (HF). Several factors of GO-HF-SPME experiment, such as the pH of the sample solution, type of organic desorption solvent, pH of the desorption solvent, extraction time, and desorption time, were optimized to achieve the highest extraction efficiency. Under the optimized extraction conditions, the method showed good linear ranges (0.05–10 μg/mL) with correlation coefficients higher than 0.9950, low limits of determination (LODs, 0.01–0.02 μg/mL), and good recoveries (71–108 %) at three different spiked levels. The results demonstrated that GO-HF-SPME would be a promising method for the enrichment of cephalosporins in dairy products.     

Quantification of 5-Hydroxymethylfurfural in Coated Deep-Fried Products: Optimization of the Extraction Procedure by Using Statistical Design

This study describes for the first time the development and validation of an extraction procedure for the quantification of 5-hydroxymethylfurfural (HMF) in coated deep-fried products by liquid chromatography with photodiode array detection. The method entailed the extraction of HMF with ethyl acetate/hexane (4:1) followed by a concentration step with 40 mM sodium formate (pH?=?3)/methanol (1:1). The optimum combination of the extraction variables was achieved by response surface methodology. Sample amount and concentration solvent volume showed a notable influence on HMF yield, while the effect of extraction solvent volume seemed to be less marked. From experimental results, 5 g of sample, 10 ml of the extraction solvent, and 550 μl of the concentration solvent were selected as optimal combination. The consistency between predicted and experimented values as well as in the quality parameters was observed. Quantities of HMF in coated deep-fried fish products were 1.25?±?0.21 μg g^?1.     

Optimization of Antioxidant Compounds Extraction from Flesh of New Developed Apple Cultivar Using Response Surface Methodology

The response surface methodology (RSM) and the central composite rotatable design were used to optimize the antioxidant extraction from apple flesh of a new cultivar (Rural Issues and Agricultural Research Institute of Santa Catarina (EPAGRI) m-58/07). The extraction conditions were optimized by measured antioxidant capacities from the ferric-reducing power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, and by the determination of total phenol content. The results showed that the most significant variable in the extraction procedure was solvent concentration. The optimal condition found was of 60 %, 5 mL/g, 30 °C, and 61 min for acetone aqueous solution, solvent to solid ratio, temperature, and time, respectively, resulting in optimal antioxidant capacities of 2,152.96 μmol TE/100 g DW by DPPH and 6,491.39 μmol Fe²⁺/100 g DW by FRAP essays, and total phenol amount of 485.62 mg GAE/100 g DW. The antioxidant capacity of EPAGRI m-58/07 was verified to be substantially higher than other cultivars commercially available.     

Untargeted Metabolite Profiling of Abalone Using Gas Chromatography Mass Spectrometry

Abalone meat is a delicacy worldwide, fetching high prices and a valuable source of income for the many countries farming and exporting this commodity. The quality of abalone is based on its unique sensory properties and an analytical metabolomics method for determining the compounds related to this would serve as a valuable tool for ensuring quality and consumer satisfaction. Metabolomics is a promising “omics” tool which can be applied towards this goal; however, widely applicable parameters for the evaluation of an untargeted gas chromatography mass spectrometry (GC-MS) metabolomic approach is still lacking. GC-MS is a popular and suitable metabolomics method due to its high separation power, reproducible retention times, and selective mass detection. The aim of this study was to establish a reliable untargeted GC-MS method for analyzing firstly a standard compound mixture consisting of 10 compounds representing various compound classes and secondly applying the method in an untargeted manner to abalone muscle samples. Using a standard compound mixture with a concentration range of 1 to 100 μg/mL, the limit of detection (LOD) ranged between 0.01 and 3.30 μg/mL, the limit of quantification (LOQ) resulted in values between 0.02 and 9.49 μg/mL, the accuracy determined was <1.5 μg/mL, and the precision displayed a coefficient of variance (CV) <25 %. When evaluating the method in terms of biological samples harvested, the repeatability and intermediate precision showed CV values <50 % for most compounds measured, allowing application of this method for metabolite profiling of abalone to answer important biological questions.     

Chemical compositions,extraction technology,and antioxidant activity of petroleum ether extract from Abutilon theophrasti Medic. leaves

Petroleum ether extract from Abutilon theophrasti Medic. leaves was optimized by response surface methodology, and the optimal extraction conditions were as follows: ratio of solvent to material (20.12 mL/g), extraction time (5.45 h), and Soxhlet extraction temperature (61.32°C). And the yield of petroleum ether extract collected in August, September, and October was (2.05 ± 0.02)%, (2.39 ± 0.01)%, and (2.32 ± 0.02)%, respectively. The September and October extracts exhibited a better antioxidant activity, which was proved by DPPH·scavenging ability (IC₅₀ value of 327.5 and 331.5 μg/mL), ABTS^·+ scavenging ability (IC₅₀ value of 170.1 and 182.1 μg/mL), and reducing power (0.31 and 0.28 mmol Fe²⁺/100 μg/mL). Meanwhile, the gas chromatograph-mass spectrometry analysis revealed that the main antioxidant components contained 9, 12, 15-octadecatrienoic acid and 9, 12, 15-octadecatrienoic acid, ethyl ester (Z,Z,Z) in three petroleum ether extracts. Therefore, petroleum ether extract from Abutilon theophrasti Medic. leaves can be a potential resource of natural antioxidants in pharmaceutical, medicine, food, and chemical industries.     

Surfactant–Solvent-Based Quaternary Component Emulsification Microextraction Followed by High-Performance Liquid Chromatography for the Simultaneous Analysis of Benzimidazole Anthelmintics in Milk Samples

A simple surfactant-solvent-based quaternary component emulsification microextraction (SSEME) method combined with high-performance liquid chromatography–photodiode array detection has been developed for the extraction, preconcentration, and determination of four benzimidazole anthelmintic (i.e., oxfendazole, mebendazole, albendazole, and fenbendazole) residues in milk samples. The quaternary component solvent of SSEME carried out in 10 mL aqueous solution were Triton X-114 (emulsifier or carrier), acetonitrile (disperser solvent), and 1-octanol (extraction solvent). The surfactant has an important role in the enhancement of the extraction efficiency of the high polar analytes. For milk sample analyses, linearity was obtained in the range of 10–200 μg/L with the determination coefficients (R ²) higher than 0.996. Preconcentration factor was obtained in the range of 21–38, corresponding to limits of detection in the range of 2.6–9.9 μg/L. Intra-day (n?=?6) and inter-day (n?=?6?×?3) precisions in the sample studied were obtained with relative standard deviation below 8.8 %. The recoveries for the spiked target anthelmintics at different concentrations (25, 50, 100, and 150 μg/L) were obtained in the range 80.1–114.1 %. The proposed SSEME method has been demonstrated that is simple, effective, and reliable for the analysis of analytes in the samples studied and can be used as an alternative green analytical technique for benzimidazole analysis.     

Determination of 6-Benzylaminopurine and Hg<Superscript>2+</Superscript> in Bean Sprouts and Drinking Mineral Water by Surface-Enhanced Raman Spectroscopy

A novel method for the determination of 6-benzyladenine (6-BA) in bean sprouts and Hg²⁺ in drinking mineral water by surface-enhanced Raman spectroscopy (SERS) was described. 6-BA exhibits obvious SERS signal by using the substrate of silver nanoparticles (AgNPs), and the presence of Hg²⁺ could cause the decrease of SERS signal of 6-BA. The effects of type of aggregation agent, type and level of pH buffer solution, amount of AgNPs, mixing time, concentration of 6-BA, and reaction time on the SERS signals were investigated. Under the optimized experimental conditions, good linear responses were obtained for 6-BA and Hg²⁺ in the concentration ranges of 10–200 μg L^?1 and 5–200 μg L^?1, respectively. By the present method, the limits of detection (LODs) for the determination of 6-BA and Hg²⁺ are 3.3 and 0.20 μg L^?1, and the recoveries of 6-BA and Hg²⁺ in spiked samples are 85.5–113.0 % and 98.2–111.5 %, respectively.     

Simultaneous Determination of Seven Plant Growth Regulators in Melons and Fruits by Modified QuEChERS Coupled with Capillary Electrophoresis

A capillary electrophoresis method for the simultaneous determination of seven plant growth regulators including gibberellic acid, abscisic acid, 3-indole acetic acid, 3-indolepropionic acid, 3-indolebutyric acid, 2,4-dichlorophenoxyacetic acid, and 2-methyl-4-chlorophenoxyacetic acid in melons and fruits was established and validated. The samples were ultrasonically extracted with acidified acetonitrile and then dehydrated. The resulting solution was purified with modified QuEChERS method, and then dried-up under weak nitrogen flow, and the residue was redissolved with methanol-water (1:4, v/v) as sample solution. The electrophoretic separation was performed in an uncoated fused-silica capillary with borax buffer (pH 10.5) containing 29% of ethanol as the running buffer. The running voltage was 25 kV with the column temperature of 30 °C. The linear ranges of gibberellic acid, abscisic acid, and 2-methyl-4-chlorophenoxyacetic acid were from 0.10 to 8.0 μg/mL, while the others were from 0.05 to 4.0 μg/mL with the correlation coefficients greater than 0.997. The limits of detection and the limits of quantification of the method were in the range of 1.54–5.76 and 5.12–19.2 μg/kg, respectively. The recoveries of the method ranged from 69.0 to 109% with the relative standard deviations ranging from 2.01 to 15.4%. The proposed method has been successfully applied to the determination of plant growth regulator residues in 15 melon and fruit samples, and gibberellic acid and abscisic acid were detected in the samples.     

Development of a Dispersive Liquid–Liquid Microextraction Method for the Determination of α-Tocopherol in Pigmented Wheat by High-Performance Liquid Chromatography

A dispersive liquid–liquid microextraction (DLLME) method coupled to high-performance liquid chromatography was developed for the analysis of α-tocopherol in grain samples. The DLLME parameters including the type and volume of extractants, the volume of disperser and the addition of salt were examined. The optimized DLLME procedure consisted in the formation of a cloudy solution promoted by the fast addition to the sample (5 mL of saponified sample solution diluted with 5 mL of water) of a mixture of carbon tetrachloride (extraction solvent, 80 μL) and ethanol (dispersive solvent, 200 μL) without the addition of salt, followed by shaking for 5 min and centrifuging for 3 min at 5,000 rpm. Intra- and inter-day repeatability expressed as % RSD were 3.5 and 7.6 %, respectively. The limit of detection and the limit of quantification were 1.9 and 6.3 μg?L^?1. The comparison of this method with the national standardized extraction method, supercritical carbon dioxide extraction, accelerated solvent extraction, and conventional heat-reflux extraction indicates that the DLLME was accurate (no significant differences at the 0.05 % probability level), high efficient, low organic solvent-consuming, and low cost. This procedure was successfully applied to 42 samples of 14 types of purple wheat, for which the content of α-tocopherol exhibited a significantly negative correlation with the pigment content measured by a spectrophotometer. The recovery rates ranged from 90.5 to 103.7 %.     

HPLC Determination of Spectinomycin in Feed Premixes and Dosage Forms Using 1-Naphthyl Isocyanate Precolumn Derivatization with UV Detection

A new, simple, and sensitive HPLC method was developed for the determination of spectinomycin hydrochloride in dosage forms and feed premixes through derivatization with 1-naphthyl isocyanate. The separation was achieved on a C₁₈ column using a mobile phase consisting of acetonitrile/water (50:50 v/v, pH 3.2) in a flow rate of 1 mL/min with UV detection at 230 nm. The factors influencing the derivatization reaction yields were carefully studied and optimized. The method was linear over the concentration range of 10–100 μg/mL with a limit of detection 0.25 μg/mL and limit of quantitation 1.75 μg/mL. The developed method was successfully applied to the analysis the drug in the commercial dosage forms and spiked feed premix samples; the average recoveries were 99.79 and 99.56, respectively. The analytical performance of the method was fully validated and the results were satisfactory. A proposal of the reaction pathway was presented.     

Rapid Analysis of Multiple Sudan Dyes in Chili Flakes Using Surface-Enhanced Raman Spectroscopy Coupled with Au–Ag Core-Shell Nanospheres

Sudan dyes are often illegally added as colorants into a variety of foodstuffs and have been tied to many food safety issues. In this study, surface-enhanced Raman spectroscopy (SERS) coupled with Au–Ag core-shell nanospheres (Au@Ag) was applied to analyze standard solutions of Sudan I–IV and Sudan dyes in chili flakes. With the use of 90 ± 5 nm Au@Ag (Au seed 20 ± 2 nm) as SERS substrate, the lowest detectible concentrations for Sudan I and II were 0.10 mg/L, for Sudan III was 0.08 mg/L, and for Sudan IV was 0.2 mg/L. The use of principal component analysis (PCA) could successfully classify different Sudan dyes based upon the SERS spectra of their standard solutions. For chili flakes, the use of acetonitrile as extraction solvent led to an overall higher sensitivity for analysis of Sudan dyes with SERS method compared to that of methanol, ethanol, and n-hexane. The lowest detectible concentrations for Sudan I–III in chili flakes were 1 mg/kg and for Sudan IV was 2 mg/kg, which were about ten times as much as that for their standard solutions due to the interference of non-target compounds from sample matrices. Partial least squares (PLS) models developed for quantitative analyses showed relatively high linear correlation between the actual and predicted amounts of Sudan dyes in chili flakes (R ² _cv = 0.869–0.959). The results showed great potential of applying Au@Ag as SERS substrate for qualitative and quantitative analysis of Sudan I–IV with simplified sample preparation method.     

A Sensitive Immunoaffinity Column-Linked Indirect Competitive ELISA for Ochratoxin A in Cereal and Oil Products Based on a New Monoclonal Antibody

A new sensitive monoclonal antibody (mAb) 1H2 against ochratoxin A (OTA) was reported herein. This mAb belonged to the immunoglobulin G1 (k chain) isotype. In the optimized indirect competitive enzyme-linked immunosorbent assay (icELISA), 1H2 showed a 50 % inhibition concentration (IC₅₀) value of 0.058 ng/mL and a detection limit (IC₁₀) of 0.001 ng/mL. The cross-reactivity of 1H2 with ochratoxin B, aflatoxins, deoxynivalenol, zearalenone, T-2 toxin, or fumonisins was below 0.3 %. Based on this mAb, an immunoaffinity column (IAC)-linked icELISA was developed for OTA detection in the cereal and oil products. The working range of the assay for solid sample was 0.36–16 μg/kg. The recoveries from spiked samples of IAC-linked icELISA ranged from 83 to 101 %. These recoveries were much higher than those of icELISA (21–78 %) and in good agreement with those obtained by using the standard high-performance liquid chromatography method (87–110 %). The results indicated that the mAb 1H2 had the values for studies of OTA in the crude agricultural products.     

Establishment of rapid detection method of methamidophos in vegetables by surface enhanced Raman spectroscopy

Methamidophos (MAP) is a highly efficient and broad-spectrum organophosphate pesticide. In this study, a rapid method for detecting MAP in vegetables using surface enhanced Raman scattering (SERS) spectroscopy has been established. Density functional theory calculations were performed with Gaussian 03 at RB3LYP level and with the 6-311G (d) basis set. SERS, normal and theoretical Raman spectroscopy were compared to investigate the mechanism of Raman scattering enhancement. The SERS signal of MAP was improved in alkaline conditions with optimum scattering efficiency at pH of 13.46. Furthermore, MAP detection in vegetables by SERS method had a good linear relationship between 0.01 and 1,000?μg/mL. The concentration of MAP in vegetables was detected and chosen for recovery test with three levels: 4, 8, and 15?μg/mL. The results of three level tests were 86.7–96.6?% and their relative standard deviations were between 1.2 and 2.5?%, which shows the good repeatability of this method.     

Study on a Molecularly Imprinted Solid-Phase Extraction Coupled to Capillary Electrophoresis Method for the Determination of Trace Trichlorfon in Vegetables

How to determine the pesticide residues in vegetable is an urgent problem. In this study, we reported a new method of solid-phase extraction coupled to capillary electrophoresis (SPE–CE) based on a molecularly imprinted polymer (MIP) for determination of trace trichlorfon. The electrophoretic conditions and factors which affected the molecularly imprinted solid-phase extraction were optimized. Under optimal conditions, the linear ranges of the calibration graph were 0.1 μg/L to 10 mg/L. The limit of detection (LOD) and method quantitation limit (MQL) were 4.9 and 16.2 μg/kg, respectively. With a flow rate of 2.5 mL/min for 50 mL loading, an enrichment factor of 160 was obtained. The relative standard deviation (RSD) for five replicate extractions of 0.01 mg/L trichlorfon standard solution was 4.5 %. The blank cucumber, lettuce, and radish samples spiked with trichlorfon at three levels were extracted and determined by this presented method with recoveries ranging from 77.6 to 93.2 %. Moreover, this proposed methodology was successfully applied to the quantitative detection of the trichlorfon residues in the leek samples, and the results were in good agreement with that obtained by the gas chromatography method.     

Bioactive compounds and antioxidant activity of citrus juices produced from varieties cultivated in Calabria

Juices from 15 citrus varieties (six oranges, one lemon, two grapefruit, three bergamot, one cedar, one mandarin and one chinotto) from Calabria (Italy) were investigated mainly on quality parameters, total flavonoids, total phenolic compounds, total anthocyanin, ascorbic acid and antioxidant capacity (ABTS and DPPH assay). Total phenolic compounds had highest values, ranging from 1.54 mg/mL and 1.43 mg/mL respectively for pink grapefruit (PG) and yellow grapefruit (YG), to 0.92 and 0.96 mg/mL for cedar (C) and mandarin (Ma) respectively. Total anthocyanins ranged from 0.31 μg/mL yellow grapefruit (YG) to 3.51 μg/mL tarocco (T). Total flavonoids ranged from 0.09 mg/mL tarocco (T) to 0.24 mg/mL castagnaro (BC). In general the three cultivars of bergamot (BFe, BC and BF) have the greatest amount of flavonoids. All the analysed samples exhibit a good content of bioactive compounds.     

Electrophoretic Analysis of Natural Antioxidants in Plant and Beverage Samples Using Dynamically Coated Capillaries with Chitosan and Multiwall Carbon Nanotubes

Statically, chitosan-coated capillaries were simply dynamically coated with multiwall carbon nanotubes (MWNTs) coaggregated with sodium dodecyl sulfate (SDS). The capillary electrophoresis method was used to separate natural antioxidants in plant and beverage samples. In this way, a great improvement in the electrophoretic resolution was achieved when the running buffer was composed of 50 mM SDS and 10 mM sodium borate with 6.0 μg/mL of SDS-coated MWNTs, at pH 8.0, with an applied voltage of 30 kV. Under the optimal conditions, the limits of detection and quantitation for the target analytes were in the range of 0.14–0.82 μg/mL and of 0.47–2.75 μg/mL, respectively. The mean recovery values of 83.9–106.2 % were obtained for the spiked chrysanthemum samples. This proposed method was successfully applied for determining 12 phenolic compounds in complex chrysanthemum samples.     

Ultrasensitive Detection of Enrofloxacin in Chicken Muscles by Surface-Enhanced Raman Spectroscopy Using Amino-Modified Glycidyl Methacrylate-Ethylene Dimethacrylate (GMA-EDMA) Powdered Porous Material

Illegally use of enrofloxacin in chicken has raised serious concerns due to its negative effects on public health. In this study, surface-enhanced Raman spectroscopy (SERS) using amino-modified glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) powdered porous material was developed and validated to detect enrofloxacin in chicken muscles. By this method, enrofloxacin in chicken muscles was successfully detected at a concentration of 0.01 mg kg^?1, which was lower than the legal maximum residue limit. And the unique “fingerprint-like” spectral patterns of enrofloxacin obtained from SERS spectra could be used for identification and characterization. Compared with high-performance liquid chromatography, the assay of six samples with SERS was rapid in less than 40 min, and the detection was highly sensitive. The results demonstrate that SERS using GMA-EDMA powdered porous material can be potentially employed as a screening tool for rapid detection of residual drugs in a large amount of food samples.