Lettuce Residues Research Articles

Development of a Portable Cell-Based Biosensor for the Ultra-Rapid Screening for Boscalid Residues in Lettuce.

Fungal plant pathogens have posed a significant threat to crop production. However, the large-scale application of pesticides is associated with possible risks for human health and the environment. Boscalid is a widely used fungicide, consistently implemented for the management of significant plant pathogens. Conventionally, the detection and determination of boscalid residues is based on chromatographic separations. In the present study, a Bioelectric Recognition Assay (BERA)-based experimental approach combined with MIME technology was used, where changes in the electric properties of the membrane-engineering cells with anti-boscalid antibodies were recorded in response to the presence of boscalid at different concentrations based on the maximum residue level (MRL) for lettuce. The membrane-engineering Vero cells with 0.5 μg/mL of antibody in their surface were selected as the best cell line in combination with the lowest antibody concentration. Furthermore, the biosensor was tested against another fungicide in order to prove its selectivity. Finally, the BERA cell-based biosensor was able to detect the boscalid residue, below and above the MRL, in spiked lettuce leaf extracts in an entirely distinct and reproducible manner. This study indicates that the BERA-based biosensor, after further development and optimization, could be used for the routine, high-throughput detection of boscalid residue in lettuce, and not only that.

Validation of modified QuEChERS extraction method for quantitative enrichment of seven multiclass antibiotic residues from vegetables followed by RP-LC-UV analysis

A modified rapid, simple quick, cheap, effective, robust and safe (QuEChERS) extraction method was developed for the simultaneous extraction and purification of seven antibiotic residues in lettuce, carrot and tomato using liquid chromatography UV detector. The method was validated for linearity, sensitivity, accuracy, repeatability, and reproducibility at six concentration levels for all matrices, according to the guidelines of UNODC. A matrix-matched calibration method was used for the quantitative analysis. Linear range of 0.01–250 μg kg−1 for target compounds with correlation coefficient (R2) 0.9978–0.9995 was obtained. The limits of detections (LODs) and quantifications (LOQs) were 0.02–2.48 μg kg−1 were 0.06–7.52 μg kg−1, respectively. The average recoveries of the seven antibiotics ranged from 74.5 to 105.9%, with relative standard deviation RSD (%) < 11, for all matrices and matrix effects were less than 20% for most of compounds. This comprehensive simple QuEChERS extraction method can be used for the investigation of multi-residue drugs belonging to different chemical families in vegetables.

Efficacy of some washing solutions for removal of pesticide residues in lettuce

BackgroundWhen previous studies were examined, it was reported that a wide variety of pesticide residues were detected in lettuce (Bakırcı et al. in Food Chem 160:379–392, 2014; Balkan and Yılmaz in Food Chem 384:132516, 2022; Qin et al. in Food Res Int 72:161–167, 2015; Selim et al. in Res J Environ Sci 5:248–258, 2011). In addition, pesticide-contaminated lettuce poses a risk to consumers as it is a fresh food that is eaten raw. Therefore, pesticide removal processes must be applied before consumption. Some pesticide removal process, such as storage and heat treatment cannot be applied to lettuce because of unshelled, no long shelf life and consuming as fresh. Different practical methods are needed for the removal of pesticides process. The recommendations of suitable methods for cleaning salad materials in ready-to-eat sector, hotels, restaurants and homes are very important. It is important to reduce pesticide residues in vegetables and fruits that are consumed raw by washing them with non-toxic solutions. These approaches aim to protect public health. The study conducted in 2021 determined the effect of various washing treatments. For this purpose, before the washing trials, QuEChERS method was validated for determination of 7 pesticides in lettuce, by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Lettuce plants were grown in the greenhouse for the study. Lettuces were brought to the laboratory 24 h after pesticides were applied in the greenhouse. The samples were kept in 2 L washing solution for pesticide analysis.ResultsThe processing factor values of all washing applications were found below 1. This result shows that the residue level was reduced by washing solutions. Among the washing solution treatments, the rice vinegar washing solution was found to be most effective in reducing the pesticide residues which was due to the high degree in the pesticide degradation. Washing with filtered rice water also exhibited equivalent reduction capability similar to rice vinegar.ConclusionsThe effectiveness of washing solutions was different for boscalid, deltamethrin, fluopcolide, fluopyram, pyrimethanil, pyraclostrobin and sulfoxaflor. However, when the average removal of these pesticides was evaluated, the most effective solutions were rice vinegar, filtered rice water, carbonated water, NaCl + grape vinegar, hot tap water (40 °C), grape vinegar (6% acetic acid), grape vinegar + water, cold tap water (20 °C), lemon juice, baking soda water, grape vinegar (8% acetic acid), filtered mint water and grape vinegar (4% acetic acid), respectively. It was concluded that some of the solutions used in this study can significantly reduce exposure to pesticides for consumers.

Human health risk assessment of pesticides in lettuce and spinach grown in urban backyard garden soils

Pesticide residues in lettuce and spinach could be a serious human health concern since the average per capita consumption per day of leafy salad vegetables is ∼60 g. Here, we determined the leftover residues (LoR) of dimethoate, 2,4-D, glyphosate, and chlorothalonil in lettuce and spinach grown in three urban backyard soils to assess their potential human health hazards. Pesticide residues were extracted by QuEChERS method and quantified through LC-MS and LC-DAD. In most cases, residue levels in the vegetable samples were above the EU-MRLs. Soil organic carbon, silt, oxides of iron and aluminium negatively correlated (P < 0.05) with LoR of the pesticides while LoR positively correlated (P < 0.05) with contents of sand and clay, and pH. The estimated short-term intake (ESTI) values (mg kg1 day1) for dimethoate, 2,4-D, glyphosate and chlorothalonil even at recommended doses in case of lettuce and spinach were 0.003–9.90 × 103 and 0.005–37.10 × 103 for adults and children, respectively, whereas the corresponding estimated daily intake (EDI) values were 0.007–9.58 × 103 and 0.03–35.90 × 103. Accordingly, the calculated values of non-cancer acute health hazard (aHI <100%) and hazard quotient (HQ <1) indicated that consumption of salad vegetables grown in soils spiked with pesticides at doses recommended in agriculture does not pose human health risks. On the other hand, both lettuce and spinach grown in soils at ten-fold higher concentrations of dimethoate or chlorothalonil exceeded the threshold limit of aHI (>100%) for children and HQ > 1 for both children and adults, suggesting their potential acute and chronic health hazards. The present study, for the first time, provides health awareness about the consumption of pesticide-contaminated leafy vegetables grown in urban backyard garden soils.

Green and Efficient Determination of Fluoroquinolone Residues in Edible Green Fruits and Leafy Vegetables by Ultrasound-Assisted Extraction Followed by HPLC-MS/MS.

In this work, a simple, quick and efficient analytical method for determination of human and veterinary fluoroquinolone antimicrobial residues in lettuce, cucumber and spinach is developed. The procedure entails a 6 min ultrasound-assisted extraction (UAE, 3 × 2 min) in an alkaline (2% v/v NH3) aqueous solution containing Mg2+ ions (3 × 6 mL), with no need for organic solvents. The extract is submitted to cleanup on the HLB™ cartridge and the fluoroquinolones are separated and quantified by HPLC-MS/MS in a 10 min chromatographic run, using a small amount of acetonitrile in the mobile phase. The method, entirely developed in real matrices, is validated according to the updated analytical guidelines and provided suitable recoveries in the range of 67–116% and precision (RSD ≤ 20%, n = 3) at different concentrations (15, 70 and 150 ng g−1), with method quantification limits of 2–10 ng g−1. Fluoroquinolones were detected and quantified at concentrations from few to hundreds of nanograms per gram in vegetables from supermarkets, demonstrating the applicability of the method for monitoring residues of these pharmaceuticals.

Residual characteristics and safety assessment of the insecticides spiromesifen and chromafenozide in lettuce and perilla

This study was performed to investigate the residual characteristics, safety assessment, and pre-harvest interval (PHI) of spiromesifen and chromafenozide in lettuce (Latuca sativa L.) and perilla (Perilla frutescens (L.) Britton) leaves. Samples were harvested periodically, extracted using QuEChERS method, and analyzed by LC-MS/MS. Average recoveries of spiromesifen and its metabolite BSN2060-enol and chromafenozide were ranged from 80.6 to 107.9%, with relative standard deviation < 10%. Spiromesifen and cromafenozide initial residues in lettuce were dissipated to 81.45 and 95.52% after 7 days, with half-lives of 2.89 and 1.69 days respectively. Values in perilla leaves were 76.68 and 61.27% after the same period, with half-lives of 4.25 and 6.30 days, respectively. Risk assessment results showed that %ADI (acceptable daily intake) of spiromesifen and chromafenozide was 6.83 and 0.56, in lettuce and 4.60 and 0.25% in perilla leaves, respectively. Theoretical maximum daily intakes of spiromesifen and chromafenozide were 67.49 and 3.43%, respectively, indicating that residues of both compounds pose no considerable health risks to consumers. This study provides data for setting maximum residue limits and PHIs for the safe use of spiromesifen and chromafenozide in lettuce and perilla.

Safety of foods sold in street fairs: analysis of pesticide residues in lettuce (Lactuca sativa L.)

Pesticides are chemical contaminants that can be found in food. Those with the greatest residual representation include insecticides, fungicides, and herbicides. The objective of this study was to analyze the presence of pesticide residues in lettuce (Lactuca sativa L.) sold at street fairs. This was a quantitative, cross-sectional study, carried out in street fairs in Chapecó, state of Santa Catarina, with producers of fresh vegetables, and consumers, and also analyzed pesticide residues in lettuce from conventional and organic cultivation. Data were collected using a semistructured questionnaire, administered to all producers, and a sample of consumers. Pesticide residues were analyzed in lettuce as it is the most purchased food by consumers. Pesticides surveyed included azoxystrobin, deltamethrin, imidacloprid, and glyphosate, as they are the most frequently applied on farms, and in cultivation of vegetables. Of the 67 vendors active in the seven street fairs, 30 were vegetable and fruit producers, and of these, 17 were conventional producers and 13 were organic farmers. The analysis of pesticide residues in lettuce from conventional production showed residues of azoxystrobin and imidacloprid, but below the maximum residue limits allowed by Anvisa. In samples of organic lettuce, residues of the analyzed pesticides were not detected. From the analysis of residues in lettuce, it is inferred that the food is safe in terms of the pesticides analyzed and that municipal public policies should prioritize systematic monitoring to ensure food safety and encourage the production of organic food.

Potential of Kale and Lettuce Residues as Natural Adsorbents of the Carcinogen Aflatoxin B1 in a Dynamic Gastrointestinal Tract-Simulated Model.

Adsorption of the carcinogen aflatoxin B1 (AFB1) onto agro-waste-based materials is a promising alternative over conventional inorganic binders. In the current study, two unmodified adsorbents were eco-friendly prepared from kale and lettuce agro-wastes. A dynamic gastrointestinal tract-simulated model was utilized to evaluate the removal efficiency of the sorptive materials (0.5%, w/w) when added to an AFB1-contaminated diet (100 µg AFB1/kg). Different characterization methodologies were employed to understand the interaction mechanisms between the AFB1 molecule and the biosorbents. Based on adsorption results, the biosorbent prepared from kale was the best; its maximum adsorption capacity was 93.6%, which was significantly higher than that of the lettuce biosorbent (83.7%). Characterization results indicate that different mechanisms may act simultaneously during adsorption. Non-electrostatic (hydrophobic interactions, dipole-dipole interactions, and hydrogen bonding) and electrostatic interactions (ionic attractions) together with the formation of AFB1-chlorophyll complexes appear to be the major influencing factors driving AFB1 biosorption.

The Impact of Organic Fertilizer Produced with Vegetable Residues in Lettuce (Lactuca sativa L.) Cultivation and Antioxidant Activity

Large amounts of organic waste are produced worldwide. This work aims to evaluate the influence of organic fertilizers, onion peel flour (OPF) and fruit and vegetable flour (FVF) on lettuce cultivation. Lettuce seeds were planted in pure soil (P), P with 10% OPF, and P with 3% FVF. Soil and lettuce leaves were analyzed. The addition of OPF and FVF improved soil quality but only in the soil with FVF was there significant lettuce growth and increase of antioxidant activity: Folin (8.89 mg EAG/g FM), FRAP (1.31 mg Fe2+/g FM), ABTS (4.09 mg TEAC/g−1 FM) and ORAC (0.52 mg TEac/g−1 FM). The present results show an improvement in lettuce nutritional quality and the potential of FVF as an organic fertilizer.

Development of a microwave-assisted extraction method for the recovery of bioactive inositols from lettuce (Lactuca sativa) byproducts.

A microwave-assisted extraction (MAE) method was developed for the extraction of bioactive inositols (D-chiro- and myo-inositols) from lettuce (Lactuca sativa) leaves as a strategy for the revalorization of these agrofood residues. Gas chromatography-mass spectrometry was selected for the simultaneous determination of inositols and sugars (glucose, fructose, and sucrose) in these samples. A Box-Behnken experimental design was used to maximize the extraction of inositols based on the results of single factor tests. Optimal conditions of the extraction process were as follows: liquid-to-solid ratio of 100:1 v/w, 40°C, 30min extraction time, 20:80 ethanol:water (v/v), and one extraction cycle. When compared with conventional solid-liquid extraction (SLE), MAE was found to be more effective for the extraction of target bioactive carbohydrates (MAE 5.42mg/g dry sample versus SLE 4.01mg/g dry sample). Then, MAE methodology was applied to the extraction of inositols from L. sativa leaves of different varieties (var. longifolia, var. capitata and var. crispa). D-chiro- and myo-inositol contents varied between 0.57-7.15 and 0.83-3.48mg/g dry sample, respectively. Interfering sugars were removed from the extracts using a biotechnological procedure based on the use of Saccharomyces cerevisiae for 24 h. The developed methodology was a good alternative to classical procedures to obtain extracts enriched in inositols from lettuce residues, which could be of interest for the agrofood industry.

Salmonella sensitivity to sodium hypochlorite and citric acid in washing water of lettuce residues

AbstractSalmonella spp. is one of the main lettuce pathogens and should be inactivated during the disinfection of these vegetables before consumption. In minimally processed vegetable industries, residues of organic matter can prevent the inactivation of this pathogen by disinfectants. The objective of the present work was to evaluate the inactivation of Salmonella isolated from organic lettuce to sodium hypochlorite (25 and 50 ppm) and citric acid (0.5 and 1%) in washing water added with lettuce residues. To do so, a washing water with lettuce residues was elaborated, and Salmonella was added in the order of 106 CFU/ml. Thereafter, each sanitizer was added separately to evaluate its effect on reducing Salmonella counts. After 1, 2, 3, 4, 5, 10, and 15 min of contact with the sanitizers, serial dilutions using neutralizer (0.5% sodium thiosulfate) were performed and each dilution was sown in Xylose‐Lysine‐Desoxycholate medium. Total aerobic mesophilic counts of wash water with lettuce residues before testing (without Salmonella) and after 15 min of exposure to each sanitizer (with Salmonella) were also performed. In addition, the free chlorine still present in the samples after the contact of sodium hypochlorite with lettuce residues for 15 min. The results demonstrated that 50 and 25 ppm sodium hypochlorite could reduce 6 log CFU/ml of Salmonella in 1 and 3 min of contact, respectively, while 0.5 and 1% citric acid was able to reduce 1.26 and 1.74 log CFU/ml respectively from the same microorganism within 15 min of contact. The total aerobic mesophilic counts of the wash water before being tested were, on average, 1.5 log CFU/ml. After addition of Salmonella, with 15 min of contact with the sanitizer, the results of total counts showed the same magnitude as the Salmonella counts. Organic matter may have reacted with the free chlorine present, reducing chlorine concentrations, since values of 30.4 ppm were observed when the initial concentration should be 50 and 17.1 ppm when the initial concentration should be 25 ppm. Based on the results, sodium hypochlorite demonstrated a greater microbial reduction capacity in wash water with lettuce residues, indicating that it is more appropriate to avoid cross‐contamination between batches during sanitation of lettuce in washing tanks.

Application of deep brief network in transmission spectroscopy detection of pesticide residues in lettuce leaves

AbstractTo realize the quick, nondestructive detection of pesticide residues in lettuce leaves, a new method based on deep brief network (DBN) combined with near‐infrared transmission spectroscopy, was studied in this article. Two kinds of pesticide residues (fenvalerate and triazoline) and distilled water were sprayed on the surface of lettuce leaves, respectively. In addition, near infrared transmission spectroscopy was used for collecting spectral data of 240 lettuce samples. Furthermore, Savitzky–Golay combined with multiplicative scatter correction was used to denoise the raw spectral data. Then, after preprocessing spectral data, DBN was used to extract features and identify kinds of pesticide residues in lettuce leaves. Moreover，successive projection algorithm (SPA) was used to select characteristic wavelengths. After all, support vector machine (SVM), PLS‐DA, and k‐nearest neighbor were carried out to establish classification models based on full spectral data, data extracted by DBN and data extracted by SPA. Consequently, DBN–SVM performed best and the accuracy of training set and test set reached 98.89 and 95.00%, respectively. Hence, the method of near infrared transmission spectroscopy combined with DBN–SVM is practical for the qualitative analysis of pesticide residues in lettuce leaves.Practical applicationsUsing near infrared spectroscopy could detect the kinds of pesticide residues in lettuce leaves quickly and effectively. A new method involving deep brief network (DBN) was proposed to extract the features of spectral data. Results in this study showed that the DBN is feasible and effective for building classification models of different pesticide residues.

Method Validation, Dissipation and Decontamination of Flubendiamide Residues in Lettuce using LC/MS/MS

A method for determining flubendiamide residues in lettuce using LCMS/MS with negative electron spray ionization was developed and used for its residue analysis. Samples were extracted in acetonitrile and cleaned up by dispersive solid phase extraction with recovery of 70 to 120 per cent at RSD < 20 per cent. The residues dissipated on 25 and 30 d of application of flubendiamide at 24 and 48 g a.i. ha−1 respectively on lettuce. Tamarind water washing was found very effective for decontamination of flubendiamide residues from iceberg lettuce. It removed 91.62 and 82.11 per cent of residues at the recommended and double the recommended doses.

Study on pesticide residues classification of lettuce leaves based on polarization spectroscopy

AbstractIn order to effectively implement the rapid and nondestructive testing of pesticide residues in lettuce leaves, polarization spectral detection technology was used in this article. There were 90 pieces of lettuce leaves from five different groups, as well as a total of 450 samples of lettuce were used to collect polarization spectral information. CARS, IRIV, and SPA were used to obtain optimal wavelengths. BP neural network, KNN, and SVM were used to establish classification models. The results showed that the significance of these parameters from primary factor to secondary factor were incident zenith angle A, detector polarization angle D, detecting zenith angle B, and sample stage azimuth E, respectively. Besides, optimal level of A, B, D, and E were 60°, 45°, 30°, and 270°, respectively. Furthermore, the best classification model different kinds of pesticide residues in lettuce leaves was CARS‐SVM model, with calibration identification rate of 100%, prediction identification rate of 97.78%. It confirms that polarization spectral detection technology is a feasible and effective method for classifying different pesticide residues in lettuce leaves.Practical applicationsIt is of great significance to understand the effects of pesticide residues on the biological structure and to reveal new biological functions and mechanisms of action. In order to effectively implement the rapid and nondestructive testing of pesticide residues in lettuce leaves, polarization spectral detection technology was used in this article. In addition, the order and superior level of polarization spectral factor were obtained through the calculation of the range using orthogonal test. It confirms that the polarization spectra is a feasible and effective method for discriminating different pesticide residues in lettuce leaves.

Identification of pesticide residues in lettuce leaves based on near infrared transmission spectroscopy

AbstractTo explore the nondestructive and accurate qualitative detection method of pesticide residues in vegetables, lettuce leaves were taken as carrier and pesticides (fenvalerate and chlorpyrifos) were taken as research object. The near infrared spectral data of lettuce leaves was collected by using near infrared spectrometer NIRez (950–1,650 nm), then it was preprocessed by SNV algorithm and SG‐SNV combination, respectively. The successive projections algorithm (SPA), competitive adaptive reweighted sampling (CARS), iteratively retaining informative variables (IRIV), and combination of two of them were used to select characteristic wavelengths from the preprocessed spectral data, respectively. In this study, support vector machine (SVM) was used to classify pesticide residues in lettuce leaves. Because the classification performance of SVM was influenced by parameters c (penalty coefficient) and g (kernel function parameter), so the parameters c and g of SVM were optimized by gravitational search algorithm (GSA). Finally, identification models were built on the full wavelengths and the selected characteristic wavelengths, respectively. Final result showed that CARS‐IRIV‐GSA‐SVM model had the best performance, and the classification accuracy of training set and predication set reached 100 and 98.33%. Therefore, near infrared transmission spectroscopy can be applied to the qualitative detection of pesticide residues in lettuce leaves.Practical applicationsLettuce leaves can be eaten raw, but pesticide residues in lettuce leaves are likely to do harm to human health. Near infrared transmission spectroscopy, a fast and nondestructive technology, can be used to detect pesticide residues in lettuce leaves. Furthermore, the small NIR spectrometer used in this study can also provide some idea for the production of portable pesticide residue detector. This study demonstrated that near infrared transmission spectroscopy can be applied to the qualitative detection of pesticide residues in lettuce leaves.

The Rapid Degradation of Lambda-Cyhalothrin Makes Treated Vegetables Relatively Safe for Consumption.

Lambda-cyhalothrin (λ-cyhalothrin) is the most commonly used pyrethroid insecticide for vegetable farming in Benin. This insecticide is misused and overused by farmers, and hence may pose health hazards to consumers. We monitored λ-cyhalothrin residues in lettuce and cabbage from farms at the market gates in Cotonou and Parakou using high performance liquid chromatography (HPLC) analysis techniques. These residues were also monitored on samples directly from farms (on-farm sampling) for 14 days post-treatment. Potential factors such as photolysis and hydrolysis involved in λ-cyhalothrin degradation were also screened. Results revealed that the level of λ-cyhalothrin residue concentrations in lettuce from Houeyiho decreased from 4.2 mg/kg on Day 1 to about 0.2 mg/kg on Day 7. On Day 9, analyzed lettuces were all λ-cyhalothrin free. In contrast, even 14 days after treatment of cabbage from Bawera (Parakou), we still recorded the presence of λ-cyhalothrin residues in analyzed samples. For samples from market gates, λ-cyhalothrin residues were found in lettuce from two markets out of the nine surveyed in Cotonou. Interestingly, none of these contaminated samples had residues above the maximum residue limit for lettuce (MRL = 0.5 mg/kg). Similarly, in Parakou, samples from all five surveyed vegetable markets were contaminated with λ-cyhalothrin residues at concentrations below the MRL for cabbage (MRL = 0.2 mg/kg). We conclude that λ-cyhalothrin residues in lettuce and cabbage from farms and markets in Parakou and Cotonou are within the MRL, and hence are relatively safe for consumption.

Uptake and Accumulation of Pharmaceuticals in Overhead- and Surface-Irrigated Greenhouse Lettuce.

Understanding the uptake and accumulation of pharmaceuticals in vegetables under typical irrigation practices is critical to risk assessment of crop irrigation with reclaimed water. This study investigated the pharmaceutical residues in greenhouse lettuce under overhead and soil-surface irrigations using pharmaceutical-contaminated water. Compared to soil-surface irrigation, overhead irrigation substantially increased the pharmaceutical residues in lettuce shoots. The increased residue levels persisted even after washing for trimethoprim, monensin sodium, and tylosin, indicating their strong sorption to the shoots. The postwashing concentrations in fresh shoots varied from 0.05 ± 0.04 μg/kg for sulfadiazine to 345 ± 139 μg/kg for carbamazepine. Root concentration factors ranged from 0.04 ± 0.14 for tylosin to 19.2 ± 15.7 for sulfamethoxazole. Translocation factors in surface-irrigated lettuce were low for sulfamethoxalzole, trimethoprim, monensin sodium, and tylosin (0.07-0.15), but high for caffeine (4.28 ± 3.01) and carbamazepine (8.15 ± 2.87). Carbamazepine was persistent in soil and hyperaccumulated in shoots.

Temporal change in N2O emission derived from cabbage and lettuce residues

Temporal change in N₂O emission derived from cabbage and lettuce residues

DETERMINATION OF CHLORPYRIFOS IN LETTUCE (LACTUCA SATIVA L.) BY MICROWAVE-ASSISTED EXTRACTION COUPLED WITH HEADSPACE SINGLE DROP MICROEXTRACTION

Objective: The objective of this research was to improve the method of extracting pesticide residue from vegetable by using microwave-assisted extraction, headspace single drop microextraction (MAE-HS-SDME) and analysed by gas chromatograph-mass spectrometer (GC-MS).Methods: Microwave-assisted extraction (MAE) coupled with headspace single drop microextraction (HS-SDME) was used for extraction of chlorpyrifos insecticide residues in lettuce. The optimum conditions for obtaining efficient extraction have been tried; kind and quantity of solvent, extraction time, microwave irradiation power, pH value and the amount of salt added in the sample followed the method of Plackett–Burman. Optimum conditions for efficient analysis were evaluated by using a central composite design (CCD) combined with a response surface methodology (RSM).Results: The optimum extract conditions from CCD for the MAE-HS-SDME method were: using 1.5 µl of n-butyl acetate, 460 W of the microwave power, 4.5 min of the extraction time, no pH adjustment and no salt addition. Verification of the optimized experimental conditions showed that validation of the determination coefficient ranges from the concentrations of 0.01 to 0.10 mg/l, equal to 0.999; the percentages of variation coefficient were ranges from 4.6 to 7.7%; the recoveries ranges from 70.0 to 79.5%; limit of detection was 0.003 mg/kg and limit of quantitation was 0.01 mg/kg.Conclusion: In this study, the MAE-HS-SDME method coupled with GC-MS was found most suitable for chlorpyrifos analysis. The results obtained from analyzing chlorpyrifos in lettuce samples indicated that this method is rapid, simple, sensitive, reducible cost and safety for the analyst and the environment.

Discrimination of pesticide residues in lettuce based on chemical molecular structure coupled with wavelet transform and near infrared hyperspectra

AbstractTo facilitate more quickly and effectively detect the types of pesticide residues on the surface of lettuce, a method involving the chemical molecular structure coupled with wavelet transform (CMS‐WT) was proposed to extract the characteristic wavelength. Five different kinds of pesticide residues were sprayed on the surface of lettuce, respectively, dimethoate, acephate, phoxim, dichlorvos, avermectin (the ratio of pesticides and water were 1:1000). In addition, the near infrared hyperspectral image information of 200 samples in five different kinds of pesticides residue in lettuce were achieved by the NIR hyperspectral imaging system (870–1780 nm). The region of interest (ROI) in hyperspectral image of samples was selected to get the near infrared spectral data by the software of ENVI. Furthermore, CMS‐WT was used to extract the most influential wavelengths. Four characteristic intervals were extracted by comparing the different of pesticides in chemical molecular structures, respectively, 875—1050 nm, 1050—1250 nm, 1350—1550 nm, 1650—1780 nm. Further, the best combination of eight features were selected according to the reorder of the size of the singular value by wavelet transform algorithm using db6 as wavelet basis function, respectively, 919.18, 944.25, 972.25, 1194.20, 1363.81, 1426.69, 1673.29, 1680.74 nm. Finally, SVM model was established according to the extracted characteristic spectral data. The results showed that the calibration and prediction accuracy of SVM model established by the best combination of eight features were all achieved 100%. It confirms that the CMS‐WT feature extraction algorithm is feasible and effective for building models of different pesticide residues in lettuce.Practical applicationsWell understanding the effect of pesticide residues to biological structure is very important for revelation of novel biological function and mechanism of action of the protein. To facilitate more quickly and effectively detect the types of pesticide residues on the surface of lettuce, a method involving the chemical molecular structure coupled with wavelet transform (CMS‐WT) was proposed to extract the characteristic wavelength in this article. It confirms that the CMS‐WT feature extraction algorithm is feasible and effective for building models of different pesticide residues in lettuce.